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  • Column liquid chromatography  (86)
  • stability  (40)
  • Springer  (126)
  • Annual Reviews
  • Blackwell Publishing Ltd
  • 2005-2009
  • 1990-1994  (126)
  • 1980-1984
  • 1955-1959
  • 1992  (126)
Collection
Keywords
Publisher
Years
  • 2005-2009
  • 1990-1994  (126)
  • 1980-1984
  • 1955-1959
Year
  • 1
    Electronic Resource
    Electronic Resource
    Characterization of stable matchings as extreme points of a polytope (1992)
    Springer
    Mathematical programming 54 (1992), S. 57-67 
    Details
    ISSN: 1436-4646
    Keywords: Matchings ; stability ; extreme points ; polytope
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract The purpose of this paper is to extend a modified version of a recent result of Vande Vate (1989) which characterizes stable matchings as the extreme points of a certain polytope. Our proofs are simpler and more transparent than those of Vande Vate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01586041
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  • 2
    Electronic Resource
    Electronic Resource
    Phthalocyanine-containing polymers (1992)
    Springer
    Journal of inorganic and organometallic polymers and materials 2 (1992), S. 79-85 
    Details
    ISSN: 1572-8870
    Keywords: Phthalocyanines ; polymers ; siloxanes ; conductivity ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The author's work on the incorporation of phthalocyanines into inorganic polymers is reviewed. The synthesis of poly(siloxane phthalocyanines) and the synthesis and characterization of fluoro(phthalocyanine) Group III compounds and their conducting derivatives are described.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00696537
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  • 3
    Electronic Resource
    Electronic Resource
    Analytical relationships between the ionization of 1,3-dicarbonylic ligands and stability of their Cr(III), Ni(II), Co(II) and Cu(II) 1∶1 chelates (1992)
    Springer
    Journal of solution chemistry 21 (1992), S. 1145-1152 
    Details
    ISSN: 1572-8927
    Keywords: Chromium(III) ; β-diketones ; β-diketonates ; chelation ; complexation ; correlation ; stability ; equilibrium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract It has been demonstrated that the logarithm of the stability constant of some monochelated chromium(III) compounds, with structurally similar 1,3-dicarbonylic species, is linearly related to the negative logarithm of the acid ionization constant of the ligand. Graphical and analytical correlations which could be useful in predicting equilibrium constants of chromium(III)-β-diketonates, as well as other first-row transition metal derivatives, have been developed. A quantitative evaluation of the complexes stability has been carried out, providing information about the effects of ligand substituents on the equilibrium constants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00651860
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  • 4
    Electronic Resource
    Electronic Resource
    Interval stability and interval covering property in finite posets (1992)
    Springer
    Order 9 (1992), S. 163-175 
    Details
    ISSN: 1572-9273
    Keywords: Primary 06A07 ; secondary 05C70 ; Partial order ; interval ; stability ; covering ; Sperner property ; symmetric chains ; NP-completeness
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract Given a finite ranked posetP, let α(P) be the maximum size of a subset ofP such that no two elements of it belong simultaneously to some interval ofP and let ϱ(P) be the minimum number of intervals covering all elements ofP. We say thatP has the strong interval stability property (resp. the strong interval covering property) if for each subposetP′ induced by consecutive levels ofP, i.e.,P′=P (l)∪...∪P (u), one has α(P′)=max{|P (l)|, |P (u)|} (resp. ϱ(P′)=max{|P (l)|, |P (u)|}). We prove these properties for several classes of posets and discuss some general facts concerning the numbers α(P) and ϱ(P), e.g., NP-completeness and min-max relations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00814408
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  • 5
    Electronic Resource
    Electronic Resource
    Stationary waiting time derivatives (1992)
    Springer
    Queueing systems 12 (1992), S. 369-389 
    Details
    ISSN: 1572-9443
    Keywords: Perturbation analysis ; stability ; stochastic difference equations ; simulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract We investigate the stability of waiting-time derivatives when inputs to a queueing system-service times and interarrival times-depend on a parameter. We give conditions under which the sequence of waiting-time derivatives admits a stationary distribution, and under which the derivatives converge to the stationary regime from all initial conditions. Further hypotheses ensure that the expectation of a stationary waiting-time derivative is, in fact, the derivative of the expected stationary waiting time. This validates the use of simulation-based infinitesimal perturbation analysis estimates with a variety of queueing processes. We examine waiting-time sequences satisfying recursive equations. Our basic assumption is that the input and its derivatives are stationary and ergodic. Under monotonicity conditions, the method of Loynes establishes the convergence of the derivatives. Even without such conditions, the derivatives obey a linear difference equation with random coefficients, and we exploit this fact to find stability conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01158809
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  • 6
    Electronic Resource
    Electronic Resource
    Stability of token passing rings (1992)
    Springer
    Queueing systems 11 (1992), S. 7-33 
    Details
    ISSN: 1572-9443
    Keywords: Token passing rings ; stability ; substability ; ergodicity ; Markov chains ; Loynes' scheme ; stochastically dominant ; Little's formula ; regenerative processes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract A sufficient stability condition for the standard token passing ring has been “known” since the seminal paper by Kuehn in 1979. However, this condition was derived without formal proof, and the proof seems to be of considerable interest to the research community. In fact, Watson observed that in the performance evaluation of token passing rings, “it is convenient to derive stability conditions ... (without proof)”. Our intention is to fill this gap, and to provide a formal proof of thesufficient and necessary stability condition for the token passing ring. In this paper, we present the case when the arrival process to each queue is Poisson but service times and switchover times are generally distributed. We consider in depth a gatedl-limited (l≤ ∞) service discipline for each station. We also indicate that the basic steps of our technique can be used to study the stability of some other multiqueue systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01159285
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  • 7
    Electronic Resource
    Electronic Resource
    Stable steady state of some population models (1992)
    Springer
    Journal of dynamics and differential equations 4 (1992), S. 161-190 
    Details
    ISSN: 1572-9222
    Keywords: Delay differential equations ; equilibrium ; stability ; limiting equations ; population dynamics ; 34K20 ; 34K25 ; 92A15
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract Applying an analytical method and several limiting equations arguments, some sufficient conditions are provided for the existence of a unique positive equilibriumK for the delay differential equationx=−γx+D(x t ), which is the general form of many population models. The results are concerned with the global attractivity, uniform stability, and uniform asymptotic stability ofK. Application of the results to some known population models, which shows the effectiveness of the methods applied here, is also presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01048159
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  • 8
    Electronic Resource
    Electronic Resource
    Stability estimates in inverse scattering (1992)
    Springer
    Acta applicandae mathematicae 28 (1992), S. 1-42 
    Details
    ISSN: 1572-9036
    Keywords: 35R30 ; Inverse scattering ; stability ; noisy data
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract An algorithm is given for calculating the solution to the 3D inverse scattering problem with noisy discrete fixed energy data. The error estimates for the calculated solution are derived. The methods developed are of a general nature and can be used in many applications: in nondestructive evaluation and remote sensing, in geophysical exploration, medical diagnostics, and technology.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00047029
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  • 9
    Electronic Resource
    Electronic Resource
    A new interpolation procedure for adapting Runge-Kutta methods to delay differential equations (1992)
    Springer
    BIT 32 (1992), S. 634-649 
    Details
    ISSN: 1572-9125
    Keywords: AMS(MOS): 65L20 ; CR: 5.17 ; delay differential equations ; numerical solution ; Runge-Kutta methods ; interpolation procedures ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract This paper deals with adapting Runge-Kutta methods to differential equations with a lagging argument. A new interpolation procedure is introduced which leads to numerical processes that satisfy an important asymptotic stability condition related to the class of testproblemsU′(t)=λU(t)+μU(t−τ) with λ, μ ε C, Re(λ)〈−|μ|, and τ〉0. Ifc i denotes theith abscissa of a given Runge-Kutta method, then in thenth stept n−1→t n :=t n−1+h of the numerical process our interpolation procedure computes an approximation toU(t n−1+c i h−τ) from approximations that have already been generated by the process at pointst j−1+c i h(j=1,2,3,...). For two of these new processes and a standard process we shall consider the convergence behaviour in an actual application to a given, stiff problem.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01994847
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  • 10
    Electronic Resource
    Electronic Resource
    On a class of variational equations transformable to the Gauss hypergeometric equation (1992)
    Springer
    Celestial mechanics and dynamical astronomy 53 (1992), S. 145-150 
    Details
    ISSN: 1572-9478
    Keywords: Monodromy matrix ; Gauss hypergeometric equation ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A new class of linear ordinary differential equations with periodic coefficients is found which can be transformed to the Gauss hypergeometric equation, and therefore the monodromy matrices are computable explicitly. These equations appear as the variational equations around a straight-line solution in Hamiltonian systems of the form H = T(p) + V(q), where T(p) and V(q) are homogeneous functions of p and q, respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00049462
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  • 11
    Electronic Resource
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    Effects of small external forces on the planar oscillation of a cable connected satellites system (1992)
    Springer
    Celestial mechanics and dynamical astronomy 53 (1992), S. 219-226 
    Details
    ISSN: 1572-9478
    Keywords: Artificial satellite ; dissipative forces ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The effects of small external dissipative and disturbing forces on the non-linear planar oscillation of a cable connected satellites system in the central gravitational field of earth have been studied. Typical non-linear oscillation's phenomena arizing from the aforesaid external forces are shown to take place. The presence of these forces enables the application of asymptotic methods of the theory of non-linear oscillations due to Bogoliubov and Mitropolsky to the equation characterizing the non-linear oscillation of the system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00052610
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  • 12
    Electronic Resource
    Electronic Resource
    Real-time feedback scheduling of flexible manufacturing systems (1992)
    Springer
    Journal of intelligent and robotic systems 6 (1992), S. 51-63 
    Details
    ISSN: 1573-0409
    Keywords: Scheduling ; flexible manufacturing systems ; stability ; feedback
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A genetic manufacturing environment is considered. The emphasis is on small-lot, discrete, and asynchronous type of manufacturing systems rather than high volume and continuous type. Two classes of scheduling policies are proposed to render the machine stable. The policies are of feedback type. The decision is made in real-time and on-line.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00314697
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  • 13
    Electronic Resource
    Electronic Resource
    Force control of robots with nonlinearities (1992)
    Springer
    Journal of intelligent and robotic systems 6 (1992), S. 219-240 
    Details
    ISSN: 1573-0409
    Keywords: Force control ; slip-stick friction ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract This paper explores two practical issues related to the force control of manipulators. The first issue examined is how system stability is effected by commonly occurring manipulator nonlinearities, such as sampled-data, control signal saturation and slip-stick friction. It is shown that discretely implemented force control algorithms can drive the feedback force controlled manipulator into a limit cycle, even for a very small sampling period that by far satisfies Shannon's sampling theorem. The bounds of stability are enhanced by the presence of control signal saturation and slip stick friction. The second issue investigated is the inclusion of a high gain inner position loop as a means to minimize the unpredictability in the steady state error due to slip-stick friction. In order to support the theoretical conclusions, experiments were performed with the PUMP 560 industrial robot testbed facility developed at Colorado State University.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00248017
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  • 14
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    A structural approach to robust stability of polynomials (1992)
    Springer
    Multidimensional systems and signal processing 3 (1992), S. 421-425 
    Details
    ISSN: 1573-0824
    Keywords: Convex combination ; polynomial ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract A sufficient condition for Hurwitz stability of a convex combination of two stable polynomials is obtained.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01940234
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  • 15
    Electronic Resource
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    Fertilizer value of pig slurries processed by the Promest procedure (1992)
    Springer
    Nutrient cycling in agroecosystems 32 (1992), S. 61-70 
    Details
    ISSN: 1573-0867
    Keywords: Pig slurry ; processing ; relative efficiency index ; N ; P ; K ; organic carbon ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract In the Netherlands, pig slurries are processed to improve their fertilizer value as well as handling and application. The relative efficiency index (REI) of N, P and K and the stability of organic carbon (C) in test products of processed pig slurries (PPS) were determined in pot and incubation experiments. The dry and easily manageable PPS were produced according to the Promest procedure. The mineral fraction of total N varied from 60 to 88%. It consisted mainly of nitrate. About 25% of the organic N was rapidly mineralized. The REI of N varied from 66 to 92%. After application REI of P from pelletized PPS varied from 41 to 62% in the first half year. The REI of P in ground but non-pelletized PPS varied from 81 to 100%. The REI of K was estimated to be 100%. PPS contained less easily decomposable organic C than untreated pig slurry due to the anaerobic digestion step in the processing procedure. About 34% of the organic C disappeared as methane and carbon dioxide during processing. It was concluded that processing improved the fertilizer value of PPS compared with that of untreated pig slurry.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01054395
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  • 16
    Electronic Resource
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    A reinforcement connectionist approach to robot path finding in non-maze-like environments (1992)
    Springer
    Machine learning 8 (1992), S. 363-395 
    Details
    ISSN: 0885-6125
    Keywords: Connectionism ; reinforcement learning ; robot path finding ; stability ; reactive systems
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract This paper presents a reinforcement connectionist system which finds and learns the suitable situation-action rules so as to generate feasible paths for a point robot in a 2D environment with circular obstacles. The basic reinforcement algorithm is extended with a strategy for discovering stable solution paths. Equipped with this strategy and a powerful codification scheme, the path-finder (i) learns quickly, (ii) deals with continuous-valued inputs and outputs, (iii) exhibits good noise-tolerance and generalization capabilities, (iv) copes with dynamic environments, and (v) solves an instance of the path finding problem with strong performance demands.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00992702
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  • 17
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    A Reinforcement Connectionist Approach to Robot Path Finding in Non-Maze-Like Environments (1992)
    Springer
    Machine learning 8 (1992), S. 363-395 
    Details
    ISSN: 0885-6125
    Keywords: Connectionism ; reinforcement learning ; robot path finding ; stability ; reactive systems
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract This paper presents a reinforcement connectionist system which finds and learns the suitable situation-action rules so as to generate feasible paths for a point robot in a 2D environment with circular obstacles. The basic reinforcement algorithm is extended with a strategy for discovering stable solution paths. Equipped with this strategy and a powerful codification scheme, the path-finder (i) learns quickly, (ii) deals with continuous-valued inputs and outputs, (iii) exhibits good noise-tolerance and generalization capabilities, (iv) copes with dynamic environments, and (v) solves an instance of the path finding problem with strong performance demands.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022684924132
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  • 18
    Electronic Resource
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    The structure of the SF6 molecule and the SF 6 − anion excited states (1992)
    Springer
    Russian chemical bulletin 41 (1992), S. 504-510 
    Details
    ISSN: 1573-9171
    Keywords: electronic structure ; geometry optimization ; electron affinity ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The electronic and geometric structures of the ground state and a number of excited states of the SF6 molecule and the SF 6 − anion have been calculated by the discrete-variation method of the local density-functionals. The anion was found to possess a number of states stable toward the outer electron detachment, and at least one excited state stable toward dissociation. The adiabatic electron affinity (EA) was determined as 3.46 eV at the highest level of theory. This result is correlated to the high EAs of the isovalent compound SeF6 and TeF6; however, it does not agree with the presently accepted experimental estimate of 1.0 ± 0.2 eV for the SF6EA value. The basic anion configuration is octahedral with a S-F bond length of 1.717 Å. The calculated limit for the highest dissociation channel of the ground state SF 6 − → SF 5 − + F is ≈ 1.5 eV lower than the minimum of the total energy of the neutral molecule; this is in good agreement with experimental estimates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00863073
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  • 19
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    2-Bromoacetyl-6-methoxynaphthalene: A useful fluorescent labelling reagent for HPLC analysis of carboxylic acids (1992)
    Springer
    Chromatographia 33 (1992), S. 13-18 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Fatty acids and bile acids ; Fluorogenic precolumn derivatization ; 2-Bromoacetyl-6-methoxynaphthalene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The use of 2-bromoacetyl-6-methoxynaphthalene as a fluorogenic labelling reagent in pre-column derivatization for the HPLC separation of biologically active carboxylic acids (fatty acids and bile acids) has been investigated. The compound reacts (30 min. at 70°C) with carboxylic acids to give fluorescent esters that can be separated by reversedphase HPLC and detected at λ ex. 300 nm, λ em. 460 nm. The experimental conditions for the derivatization and chromatographic separation are discussed. Applications to the determination of valproic acid and chenodeoxycholic acid in pharmaceutical formulations are described.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02276844
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  • 20
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    HPLC method for the simultaneous analysis of valproic acid and other common anticonvulsant drugs in human plasma or serum (1992)
    Springer
    Chromatographia 33 (1992), S. 37-40 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Valproic acid ; Simultaneous determination of anticonvulsants
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The derivatizing procedure of Moody et al. [20] for valproic acid has been simplified and applied to the simultaneous HPLC determination of valproic acid (VPA), barbital (B), primidone (PRM), phenobarbital (PB) and carbamazepine (CBZ) in serum or plasma of epileptic patients. The sample is deproteinized with acetonitrile containing esterification agents and an aliquot of the supernatant is heated to 70°C for 15 min with 4-bromophenacyl bromide. The reaction mixture is analysed on a C18 column at ambient temperature, with gradient elution and with detection at 205 nm. The time required for the chromatographic analysis is 13 min; identification is based on retention time and quantification is by peak area determination with an internal standard. The calibration curves show good linearity in the range 6.25 to 100 mg/L. The detection limits at a signal: noise ratio ≥3, ranged from 1 mg/L for B and CBZ to 2–3 mg/L for PRM, PB and VPA. The method described for the simultaneous determination of the five drugs in the same plasma pool, correlated well with isocratic HPLC methods specific for each drug. The simultaneous procedure described allows a reproducible (CVs≤6.5% within run) and rapid (25 min for sample preparation: 13 min for chromatographic run) therapeutic monitoring of patients treated with VPA and two or more antiepileptic drugs.
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    URL: http://dx.doi.org/10.1007/BF02276848
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  • 21
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    Porous polymer packings from vinyl ether derivatives for reversed-phase liquid chromatography (1992)
    Springer
    Chromatographia 33 (1992), S. 19-24 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Porous polymer spherical packings ; Vinyl ether ; Alkali resistance ; No abnormal adsorption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Spherical, porous-polymer particles for column packing in high-performance liquid chromatography were prepared by suspension copolymerization of alkylvinyl ether with triethyleneglycol divinyl ether. The hydrophobicity of the packings was easily adjusted by changing the monomer ratio. The packings showed the usual reversed-phase liquid chromatographic properties, but did not sho abnormal retention, tailing and broadening of peaks and irreversible adsorption of ionic and aromatic substances, owing to the lack of ionic or aromatic groups. In addition, the packings were stable in alkaline solutions because of the relative alkali stability of C−O−C bonds as compared with CO−O and Si−O−C bonds in conventional packings.
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    URL: http://dx.doi.org/10.1007/BF02276845
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  • 22
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    Comparison study between indirect photometric and direct conductivity detection for anion exchange chromatography using naphthalenesulfonate derivatives as mobile phases (1992)
    Springer
    Chromatographia 33 (1992), S. 25-31 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Anion exchange ; Indirect photometric and direct conductivity detection ; Naphthalenesulfonate ; Inorganic anions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Indirect photometric and unsuppressed direct conductivity detection modes are examined using naphthalene mono-, di-, and tri-sulfonate as mobile phases for the separation of several anions such as F−, Cl−, NO2 −, Br−, NO3 −, SO4=,I−, and SCN− using a commercial anion exchange column. With all three mobile phases, conductivity detection shows better sensitivities and detection limits than indirect photometry. Conductivity detection is 5 to 16 times more sensitive than indirect photometry for all analytes. Detection limits achieved using these mobile phases are, for example, 0.04 ng and 0.1 ng for chloride ion with conductivity and indirect photometry, respectively. Both detection modes give wide linear ranges extending from at least 100 ppm to the detection limit of each anion which is generally about 0.02 ppm. Sulfur oxide anions such as dithionate and tetrathionate are separated using flow programming with naphthalenetrisulfonate as the mobile phase in less than 20 minutes. With both detection modes, desired chromatographic performance of these three eluents is achieved without pH adjustment of the mobile phase.
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    URL: http://dx.doi.org/10.1007/BF02276846
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  • 23
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    An enhanced liquid chromatographic method for 5-hydroxymethylfurfural determination in UHT milk (1992)
    Springer
    Chromatographia 33 (1992), S. 45-48 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Heat-treated milk ; Milk quality indicators ; 5-Hydroxymethyl-2-furfuraldehyde
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An enhanced method of HPLC for the determination of 5-Hydroxymethyl-2-furfuraldehyde (HMF) in fluid milk was perfected. Its resolving capacity permitted the specific separation of this compound. The real concentration (μmol/l) of HMF was determined and not the HMF value, as in the colorimetric analysis, where an intermediary coloured compound (HMF-TBA) is utilised. The optimum pH condition (pH=4.0–4.2) for the mobile phase to prevent overlapping between the HMF peak and the peaks of the other compound (α and β) that coeluted with the HMF and also the optimum organic solvent content (3% or 7%) were established. This is a sensitive, quick and safe method for the determination of HMF in fluid milk.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02276850
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  • 24
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    Ion-pair reversed-phase liquid chromatography of arsenic species on polymeric styrene-divinylbenzene packed columns with an alkaline aqueous mobile phase (1992)
    Springer
    Chromatographia 33 (1992), S. 581-585 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Arsenic compounds ; Polymeric styrene divinylbenzene phase ; Ion-pairing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The resolving power of an ion-pair reversed-phase liquid chromatography method, on a polymeric stationary phase (PRP-1) with an alkaline aqueous mobile phase (pH=9) containing tetrabutylammonium cation as ion-pairing agent, is compared with a traditional ion-pairing system using an octadecyl-modified silica column and a neutral aqueous mobile phase (pH=7.3). This chromatographic system (PRP-1 column) provides a rapid means for the determination of two of the most important arsenic species, arsenobetaine and arsenite. Addition of methanol (5%) to the aqueous mobile phase allows the differentation of arsenobetaine from the system peak when using UV detection.
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    URL: http://dx.doi.org/10.1007/BF02262252
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    Comparison of provitamin A determination by normal-phase gravity-flow column chromatography and reversed-phase high performance liquid chromatography (1992)
    Springer
    Chromatographia 33 (1992), S. 133-137 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Gravity-flow column chromatography ; Provitamin A determination
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The provitamin A content of some food samples was determined by methods involving MgO: Hyflosupercel gravityflow column chromatography (GFCC) and reversed phase high performance liquid chromatography (HPLC), the quantitation being done by external standardization (HPLC-ES) or internal standardization (HPLC-IS) with Sudan. The results obtained with α- and β-carotene in carrots, β-carotene and β-cryptoxanthin in papaya and β-carotene in tomato and kale agreed well, showing that any of the these techniques can be used, provided the analysis is done under optimum conditions. Good separation of the different provitamins using GFCC depends on the analyst's skill and visual acuity. HPLC-ES required a constant supply of provitamin standards, thus the varying purity of commercially available standards and the high instability of these compounds could pose grave problems. Due to the stability of Sudan, HPLC-IS appeared to be the method of choice although passage of the extract through a MgO: Hyflosupercel minicolumn was required prior to injection to separate chlorophylls, dihydroxy- and polyoxycarotenoids which would otherwise elute with Sudan. Nonconformity of the Sudan structure to those of the provitamins did not effect the quantitative results. The chromatographic separation, identity and quantification of the provitamins could be more easily established by using HPLC-IS, complemented with GFCC.
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    URL: http://dx.doi.org/10.1007/BF02275893
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    Diastereoselective and enantioselective chromatography of the pyrethroid insecticides allethrin and cypermethrin (1992)
    Springer
    Chromatographia 33 (1992), S. 103-112 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Gas chromatography ; Chiral separations ; Allethrin ; Cypermethrin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Liquid and gas chromatographic separations of the pyrethroid insecticides allethrin and cypermethrin have been investigated with various achiral and chiral stationary phases. Diastercomeric and enantiomeric selectivity was observed for cypermethrin on a Pirkle-type chiral LC stationary phase, but very strong interactions and therefore long retention times prevented the separation of allethrin on this phase. Trans-allethrin isomers were separated on a chiral β-cyclodextrin RP-HPLC column while cypermethrin showed some difficulties on this phase due to isomerization. Diastereomeric but no enantiomeric selectivity by GC was achieved for cypermethrin with an apolar DB 5 capillary. GC separation of the diastereomers was used to study the selective photodegradation of cypermethrin isomers after forestry applications. Chiral β-cyclodextrin-based GC phases showed some enantioselectivity for cis- and trans-allethrin isomers. A separation of the eight isomers into six partially resolved peaks was achieved by GC with a coupled column consisting of chiral permethylated β-cyclodextrin and DB 1701 as stationary phases. This combination was used to characterize allethrin formulations intended for indoor use and to investigate allethrin products formed by ozonolysis of thin films of the insecticide.
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    Estimation of diuretic drugs in biological fluids by HPLC (1992)
    Springer
    Chromatographia 33 (1992), S. 177-185 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Diuretics ; Screening and determination of diuretics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary This critical review of different methods proposed for the determination and screening of diuretics is directed mainly, because of its potential application, towards highperformance liquid chromatography.
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    URL: http://dx.doi.org/10.1007/BF02275902
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    Peak recognition technique by a computer program copying the human judgement (1992)
    Springer
    Chromatographia 33 (1992), S. 218-224 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Peak ; Pattern recognition ; Prediction interval
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary It is still difficult to determine peaks and peak boundaries properly, though peak recognition is very important for the precision of quantitative data. A new computer program overcomes these problems using a method which is adapted from human judgements. The algorithm was developed for HPLC but can also be used in other fields of analytical chemistry.
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    URL: http://dx.doi.org/10.1007/BF02276186
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    High performance liquid chromatography of raw sugars and polyols using bonded silica gels (1992)
    Springer
    Chromatographia 33 (1992), S. 325-330 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Diol silica gels ; Carbohydrates ; Evaporative light scattering detection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Bonded silica columns have been evaluated for their ability to separate carbohydrates and polyols. Mobile phases consisting of dichloromethane/methanol produced the best separations in comparison with the acetonitrile/water mixtures commonly used with amino columns. Of all the bonded phases tested, LiChrospher Diol silica provided the best separations, and selectivities were not very different from those obtained on the most popular system using an amino bonded phase and acetonitrile/water as eluent. In addition, diol columns with a dichloromethane/methanol eluent offer excellent stability with no Schiff’s base formation of reducing sugars. Using an evaporative light scattering detector, low limit detection is obtainable (20 ng of glucose from a column) and gradient elution is quite feasible.
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    Retention of some ring-substituted aniline derivatives by porous graphitized carbon. Dependence on physico-chemical parameters (1992)
    Springer
    Chromatographia 33 (1992), S. 356-360 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Porous graphitized carbon ; Ring-substituted aniline derivatives ; Electronic interactions ; Principal component analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The retention characteristics of 22 aniline derivatives were determined on a porous, graphitized-carbon column in unbuffered acetonitrile-water and methanol-water mixtures. Each aniline derivative gave symmetrical peaks in each eluent without buffers. Good linear correlations were found between the log k′ and the concentration of the organic component in the eluent. The slope and intercept values differed according to the type of organic modifier and the charcter, number and position of substituents, indicating the different selectivities of methanol and acetonitrile and the good separating power of the column. Multivariate mathematical-statistical calculations proved that the retention of ring-substituted aniline derivatives is mainly governed by electronic parameters and the hydrogen acceptor capacity of substituents.
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    Determination of furosine in milk samples by ion-pair reversed phase liquid chromatography (1992)
    Springer
    Chromatographia 33 (1992), S. 374-376 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Ion-pairing ; Furosine ; Pyridosine ; Milk
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An ion-pair, reversed-phase, liquid chromatographic procedure using UV detection for quantitation of furosine is described. The standard plot was linear (r〉0.999) over a 5 ng range. An authentic synthesised sample of furosine was used for calibration. Commerical milk samples were analyzed by the described procedure.
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    Optimisation of data handling and detection conditions for automated chromatographic assay software (1992)
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    Chromatographia 33 (1992), S. 361-368 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Automated peak detection ; Discrete Fourier transform ; Frequency acquisition and filtering ; Peak detection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The principle of automated chromatographic peak detection and analysis software is summarized, and critical steps are systematically studied. As the only parameter to be entered is the acquisition frequency, evaluation of its effect on software performance is discussed. In the case of relatively noisy chromatograms, it is shown experimentally that numerous points per peak have to be taken, leading to quite fast computer acquisition procedures. The use of discrete Fourier transform filtration techniques can modify peak shapes and a comparative study evaluates the relative errors induced in the shapes and characteristics of the chromatographic profiles. Optimisation of filtering conditions is achieved and it is shown that for a filter position only 2% of the Nyquist frequency no deformation occurs in the chromatographic profile. Detection of the start and finish of chromatographic peaks is optimized according to a simple four step iterative procedure. In the case of simulations, the difference between the values used to simulate peaks and those calculated by the software are less than 1%.
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    URL: http://dx.doi.org/10.1007/BF02275919
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    Simultaneous determination of 5′-deoxy-5-fluorouridine, 5-fluorouracil and its main metabolites in body fluids by HPLC (1992)
    Springer
    Chromatographia 33 (1992), S. 413-417 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Fluoropyrimidine drugs ; Pharmacokinetics of doxifluridine ; Chemotherapy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A reversed phase high performance liquid chromatographic method has been developed for the simultaneous determination of the pro-drug 5′-deoxy-5-fluorouridine (5′-dFUR), its metabolite 5-fluorouracil (5-FU) and some fluorinated pyrimidines involved in the metabolic activation process of 5-FU. The method has been used to monitor the bioavailability of 5′-dFUR and 5-FU in patients undergoing anticancer chemotherapy. Serum sample treatment involves addition of internal standard (5-bromouracil), protein precipitation with saturated ammonium sulphate solution and liquid-liquid extraction with ethyl acetate-isopropanol (90 ∶ 10 v/v). Urine is simply diluted with mobile phase and injected. The average recovery from serum (at 0.5 μg/mL level) was 95.0%±1.4 for 5′-dFUR and 86.3%±3.5 for 5-FU. A linear response extending over four decades of concentration was observed. Detection limits in the low ng/ mL range were obtained using a 250 μL sample size and a 20 μL injection volume. Within-day and between-day coefficients of variation were below 4 and 10%, respectively.
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    Total and individual determination of carbamate pesticides by use of an integrated flow-injection/HPLC system (1992)
    Springer
    Chromatographia 33 (1992), S. 449-453 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Flow injection analysis ; Combined flow injection/HPLC ; Carbamate pesticides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An integrated flow injection (FI)/HPLC system for the total and individual determination of carbamate pesticides (propoxur, carbofuran and carbaryl) is proposed. The determination is based on the alkaline hydrolysis of the analytes and subsequent coupling with diazotized sulphanilic acid to yield the monitored dyes with or without a prior separation step by HPLC in a C18 column. The calibration curves obtained are linear in the μg/ml range and r.s.d. values are between 0.5 and 3.7% in all instances. Injection of the sample into the FI manifold allows the total pesticide content in the sample to be screened. The manifold thus acts as a post-column reactor/detector of the chromatograph for samples with high overall carbamate content, which are also injected into the HPLC instrument. The performance was checked with contaminated water samples.
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    Evaluation of the enantioselectivity towards β-blocking agents of the α1 glycoprotein type chiral stationary phase: Chiral AGP®glycoprotein type chiral stationary phase: Chiral AGP® (1992)
    Springer
    Chromatographia 33 (1992), S. 454-462 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; α1 glycoprotein ; Enantioseparation ; β-blocking agents
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The enantioselectivity of the α1 glycoprotein chiral stationary phase, Chiral AGP® has been evaluated for a number of β-blocking agents. A correlation has been found between the retention behaviour on this stationary phase and the hydrophobicity of the compounds. The separation factor α is higher for compounds that are well retained. Retention, and thus α, are also controlled by pH and the percentage of organic modifier in the mobile phase.
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    Isocratic HPLC separation of aromatic hydrocarbons and fluorine-containing compounds using perfluoroalkyl polymer packings (1992)
    Springer
    Chromatographia 33 (1992), S. 473-477 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Perfluoroalkylated polymer-gel packings ; Aromatic and fluorine-containing compounds
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Porous, perfluoroalkylated polymer-gels for column packings in high-performance liquid chromatography (HPLC) were prepared by suspension polymerization of heptadecafluorodecyl arcylate and ethylene glycol dimethacrylate. The packings showed no abnormal retention for ionic or aromatic compounds, due to the lack of ionic or aromatic groups. In addition, the packings showed no excessive retention for strongly hydrophobic compounds which is often the case with long-chain, alkylated silica gels and polymer gels. This is due to the extremely low surface energy of perfluoroalkyl groups. Therefore, perfluoroalkylated polymer gels enable isocratic HPLC separation of solutes with significantly different hydrophobicity.
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    URL: http://dx.doi.org/10.1007/BF02262330
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    Comments on the paper “correlation between retention in liquid chromatography and the adsorption energy” by J. Kloubek (1992)
    Springer
    Chromatographia 33 (1992), S. 485-486 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Porous glass ; Surface free energy ; Film pressure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
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    URL: http://dx.doi.org/10.1007/BF02262332
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    Correlation between retention in liquid chromatography and the adsorption energy (1992)
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    Chromatographia 33 (1992), S. 478-484 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Porous glass adsorbents ; Surface free energy ; Oriented adsorption of hydrocarbons
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The relationship between the specific capacity factor (k/S, where k is the capacity and S is the surface area of the sorbent, in m2) in the liquid chromatography of aromatic hydrocarbons and the adsorption energy (-°GA) has been investigated. The previously published results, based on the calculation of the work of adhesion (WSA) from contact angles, were re-examined and a new hypothesis on interactions at interfaces was employed. Direct proportionality has been found between k/S and-°GA, which allows prediction of the chromatographic behavior of adsorbates on sorbents. The surface free energy components were calculated in order to determine-°GA in terms of the work of adhesion. The dispersion component of the surface free energy of glass was obtained from the adsorption isotherm of n-octane and it was found that the hydrocarbon molecules are adsorbed in an oriented position. The contact angles of liquids on the outer surface of porous solids do not yield reliable values of WSA and of the surface free energy components. A higher intermolecular attraction increases WSA and decreases the contact angle in pores.
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    A high-performance liquid chromatographic method for the analysis of adenosine and some metabolites in the brain tissue of rats (1992)
    Springer
    Chromatographia 34 (1992), S. 563-567 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Adenosine and some metabolites ; Extraction from brain tissue ; Quantitative determination
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An analytical procedure has been developed for the assay of adenosine and some metabolites in brain tissue extracts of rats. This paper reports the extraction method, the technique adopted to avoid enzymatic transformations and the chromatographic conditions for the identification and quantitation of these nucleosides and bases. Peaks in the chromatograms of brain tissue extracts were identified by retention times, absorbance ratios of reference compounds and by enzymatic peak-shift.
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    Influence of silica gel surface purity on the coverage density of chemically bonded phases (1992)
    Springer
    Chromatographia 34 (1992), S. 573-580 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Chemically bonded phases (CBP) ; Surface heterogenity ; Surface purification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The surface chemistry of eight silica-gels with different siliceous matrix structures have been described. The influence of surface impurities on the chemical modification process (coverage density) with monooctadecylsilane has been studied. The surfaces of the adsorbents, before chemical modification, were cleaned by extraction with 20% HCl. Bare and modified materials were characterized using different physico-chemical methods e.g.: SIMS, CP/MAS NMR, porosimetry, pH measurement, elemental analysis and chromatography (GC & HPLC). The presence of trace amounts of different metallic elements creating new adsorption centers on the surfaces of the packings, have been demonstrated. Moreover, it has been shown that washing of silica gel adsorbents increases the coverage density of alkylsilyl ligands and improves the chromatographic properties of prepared packings.
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    Zone electrophoretic sample treatment coupled on-line with column liquid chromatography for the determination of basic and acidic compounds in biological samples (1992)
    Springer
    Chromatographia 34 (1992), S. 581-588 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Zone-electrophoretic sample treatment ; Basic and acidic compounds ; Biological samples
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A modified valve arrangement for zone-electrophoretic sample treatment (ZEST)-which is coupled on-line with column liquid chromatography — is used to pretreat biological (plasma) samples. Carry-over of plasma proteins depends on the pH of the electrophoresis buffer. The determination of propranolol, metoprolol, cromolyn and salicylic acid demonstrates that both basic and acidic analytes can be isolated from the plasma matrix with high selectivity. Analogous piperazines, with different protein binding properties, were used to study the influence of protein binding on the recovery. It is shown that high protein can cause a decreased recovery.
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    HPLC analysis of the main oxindole alkaloids fromUncaria tomentosa (1992)
    Springer
    Chromatographia 34 (1992), S. 597-600 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Oxindole alkaloids ; Uncaria tomentosa
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The main oxindole alkaloids from the root bark ofUncaria tomentosa were separated by reversed phase HPLC with an acetonitrile/methanol/phosphate buffer solvent gradient. UV detection was carried out at 245 nm. The chromatographic parameters for the separation of the alkaloids were optimized by studying the impact of the pH value of the mobile phase and the column temperature on the separation efficiency of the analytical system. The best separation was achieved with a mobile phase pH of 6.6 and a column temperature of 15°C. The method developed is suitable for the qualitative characterisation and quantitative determination of oxindole alkaloids in crudeUncaria tomentosa extracts and phytopharmaceuticals.
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    Indirect stereoselective determination of enantiomers of furprofen in human plasma by high-performance liquid chromatography (1992)
    Springer
    Chromatographia 34 (1992), S. 618-620 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Enantiomers of furprofen ; Human plasma
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A sensitive and stereoselective liquid chromatographic (HPLC) assay for the S and R enantiomers of furprofen in human plasma has been developed. The assay is based on derivatization with S(−)-1-phenylethylamine with formation of two diastereoisomeric derivatives and on their separation and quantitation using HPLC with uv detection. The method is linear from 25 to 600 ng ml−1 of both enantiomers, with a variation coefficient below 10.8%, and a detection limit of 20 ng ml−1. This procedure is suitable for pharmacokinetic studies.
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    Solute-micelle association constants and correlation of octanol-water coefficients with hydrophobicity for polycyclic aromatic hydrocarbons by micellar chromatography (1992)
    Springer
    Chromatographia 34 (1992), S. 627-635 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Micelle-solute association constants ; Polynuclear aromatic hydrocarbons ; Octanol/water partition coefficients
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Sodium dodecyl sulphate, hexadecyltrimethylammonium bromide and polyoxyethylene(23) lauryl ether were investigated as mobile phases in the micellar liquid chromatography of polycyclic aromatic hydrocarbons of environmental concern. A wide range of surfactant concentrations were used and the retention parameters and distribution coefficients calculated. The trends in the retention data for the PAHs are discussed and several conclusions are presented concerning the partition coefficients when these surfactants are present in the mobile phase. Comparisons are made between the structural features of the compounds and their capacity factors, and the octanol/water partition coefficients are correlated with hydrophobicity for the PAHs studied.
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    Retention characteristics of chlorinated polycyclic aromatic hydrocarbons in normal phase HPLC. II. Chloro-substituted PAHs (1992)
    Springer
    Chromatographia 34 (1992), S. 115-120 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Normal phase separations ; Chloro-substituted polycyclic aromatic hydrocarbons ; Coupled column system ; Environmental samples
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The retention behaviour of chloro-substituted PAHs on several commercial normal bonded phase HPLC columns has been investigated. Chloro-substitution was shown to generally decrease the retention on stationary phases like amino-, diol- and nitrophenylpropyl-modified silica. Dimethylaminosilica exhibited more complex retention characteristics towards chloro-substituted PAHs. On this stationary phase, the position of the chlorine substituents on the aromatic solute seemed to be of greater importance for retention than on the amino-, nitro- and diolsilica. For some chloro-PAHs, the retention was shown to increase with the number of chloro-substitutions, probably due to the large affinity of the electron-rich nitrogen in the stationary phase for the electron deficient π-system of the chloro-PAHs. Chloro-substituted PAHs were strongly retarded on the electron donating 2-(1-pyrenyl)-ethylsilica (PYE) stationary phase. However, the molecular shape of the chloro-derivatives had a large influence on retention, which was considerably decreased for some nonplanar chloro-derivatives of chrysene and benz(a)anthracene. A two-dimensional back-flush HPLC method, consisting of a combination of a nitrophenylsilica column and a PYE column of matched lengths, was shown to be useful for clean-up of chloro-substituted PAHs in environmental samples.
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    A column switching technique for the determination of lidocaine and its metabolites in horse urine (1992)
    Springer
    Chromatographia 34 (1992), S. 143-145 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Column switching ; Lidocaine ; Horse urine analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A rapid method is described for the determination of lidocaine and its metabolites in horse urine using a column switching technique and HPLC analysis. This procedure offers a sensitive assay without the need for time consuming extractions.
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    URL: http://dx.doi.org/10.1007/BF02276127
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    Cystine and cysteine analysis as the same phenylthiocarbamyl derivatives by HPLC in protein hydrolyzates (1992)
    Springer
    Chromatographia 34 (1992), S. 132-136 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Cysteine, cystine ; Phenylthiocarbamyl derivatives ; Protein hydrolyzates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A new approach is described, and a novel explanation presented, for the high performance liquid chromatographic analysis of cystine and cysteine as their phenylthiocarbamyl derivatives. PTC cystine and cysteine have been eluted with the same retention times and molar responses, most probably due to electrophilic attack of phenylisothiocyanate on cystine resulting in the scission of the disulfide bond yielding two moles of cysteine. Further, total PTC cystine and cysteine have been measured both in model solutions and in standard protein hydrolyzates (lysozyme, bovine albumin, ribonuclease) with the same linearity as the other ineteen amino acids. The reproducibility of the measurements, at the 250–750 pmole level, proved to be 4.1% (Relative Standard Deviation %) or less.
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    URL: http://dx.doi.org/10.1007/BF02276125
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    Retention behaviour of crown ethers and actinomycin D in reversed-phase HPLC (1992)
    Springer
    Chromatographia 34 (1992), S. 155-158 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Retention ; Crown ethers ; Actinomycin D ; Metal cation complexation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Retention of crown ethers in reverse-phase HPLC has been determined by their bonding ability with cations present in the eluent. The dependence of retention of crown ethers on cation concentration exhibits an inflection and makes it possible to calculate stability constant for the crown ether-cation complex. It is shown that in 75% MeOH retention of antitumor antibiotic, actinomycin D, depends on [Na+] and not on [K+] at concentrations of K+ from 5×10−7 to 10−1 mol l−1. Hence, actinomycin D may be classified as an ionophore-antibiotic.
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    URL: http://dx.doi.org/10.1007/BF02276129
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    Liquid chromatographic retention and separation of phenols and related aromatic compounds on reversed phase columns (1992)
    Springer
    Chromatographia 34 (1992), S. 146-154 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Phenolic compounds ; Optimisation of isocratic separations ; River water samples
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Isocratic column liquid chromatographic systems with UV absorbance detection at 280 nm have been developed for the separation of 29 phenolics and related compounds. The selectivity was investigated on silica-, carbon- and polymer-based separation columns for the separation of phenolic type of components. The effects of various acetonitrile/buffer mixtures, and pH of the mobile phase, and their impact on the retention of the phenols was assessed. Tables of retention times on the four columns for the 29 phenols with two different acetonitrile/buffer mixtures, together with the retention times at three pHs from 6.5 to 2.3 with varying levels of organic modifier on the LiChrospher RP 18 column are presented. As an application, the analysis of real river water samples from the Ebro river is described using a solid phase extraction step prior to injection into the chromatographic system.
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    URL: http://dx.doi.org/10.1007/BF02276128
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    Microcolumn liquid chromatography on carbon sorbents (1992)
    Springer
    Chromatographia 34 (1992), S. 173-176 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Carbon packing materials ; Aromatic compound separation ; Eluent effect
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The retention volume dependences on the molar volume were found for aromatic compounds using liquid microcolumn chromatography. The contributions of the functional groups in molecules of these compounds to the total retention value were calculated from the capacity factor values. The comparison of capacity factor values for carbon sorbents and octadecyl-silicagel has shown that for several microcolumn separations the carbon sorbent column has a better selectivity and resolution than the octadecyl-silicagel column.
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    URL: http://dx.doi.org/10.1007/BF02276133
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    Synthesis of acceptor bonded phases for donor-acceptor liquid chromatography (1992)
    Springer
    Chromatographia 34 (1992), S. 177-181 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Synthesis of bonded stationary phases ; Acceptor ligands ; Normal phases ; PAHs
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The synthesis of several electron-acceptor stationary phases has been reviewed the materials evaluated for their capacity to separate polyaromatic hydrocarbons (PAHs). Chemically bonded phases were obtained by the same procedure; the organosilane moiety is monofunctional and the HPLC behaviour is compared under identical conditions. Examples of PAHs separations are given.
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    URL: http://dx.doi.org/10.1007/BF02276134
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    Silanol group effect in C18 bonded phases in HPLC (1992)
    Springer
    Chromatographia 34 (1992), S. 182-184 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; C18 bonded phase ; Residual silanol groups ; Metal 5-Br-PADAP complexes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary If any residual (free) silanol groups remain at the surface of silica gel after bonding treatment, they may affect the retention of solutes since the dissociated groups (≡SiO−) will attract cations. The silanol group effect on the retention of cationic solutes will increase with increasing pH of the mobile phase but the effect will decrease with increasing hydrophobic-ion concentration at the C18 surface because such ions can mask the residual silanol groups. A method for the separation of metal complexes with 2-(5-bromo-2-pyridylazo)-diethylaminephenol (5-Br-PADAP) has been developed. The hydrophobic ion in the MeOH/H2O mobile phase was tetrabutylammonium (TBA).
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    URL: http://dx.doi.org/10.1007/BF02276135
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    Michael Tswett's columns: Facts and speculations (1992)
    Springer
    Chromatographia 34 (1992), S. 342-346 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; History of chromatography ; Calcium carbonate stationary phase ; Chlorophyll
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Although Michael Tswett is the originator of chromatography, little is known about the performance of his chromatographic systems. His descriptions of the separation of plant pigments are detailed but nevertheless difficult to interprete by today's chromatographic theory. By our own experiments with the system calcium carbonate/benzene it was found that the separation factor of chlorophyll a and b is approx. 1.6 which means that less than 100 theoretical plates are necessary for separation. Tswett's columns with 50 μm particles and 2–3 cm of bed height presumably exceeded this plate number. His separations could have been impaired by mass overload and by a volume flow rate which was two orders of magnitude faster than the optimum.
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    Factors influencing retention and resolution of substituted alkylbenzenes in reversed-phase liquid chromatography (1992)
    Springer
    Chromatographia 34 (1992), S. 347-356 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Isomeric substituted alkylbenzenes ; Retention and resolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The retention data of isomeric xylenes, ethyltoluenes and diethylbenzenes, and of mesitylene, benzene, toluene and ethylbenzene were obtained on a reversedphase column using methanol-water and ethanol-water mobile phases at four different temperatures. This database was used to relate the dependence of solute retention and resolution on the polarity of the mobile phase, solute dipole moment, and column temperature. The additivity of the free energy of the transfer of solute molecules or solute segments from the stationary phase to the mobile phase, was examined for the isomeric compounds. For this, the logarithm of the net retention volume was substituted for the free energy. Deviations from the additivity of free energies indicate that the separation of isomeric substituted alkylbenzenes is governed by their differential interactions with both the polar mobile phase and nonpolar stationary phase. Among the disubstituted alkylbenzenes,ortho-isomers favor the mobile phase more andpara-isomers tend to prefer the stationary phase more. Themeta-isomers are found to follow the additivity rule closely. These trends are amplified as the polarity of the mobile phase is increased indicating that these isomers are resolved better in water-rich mobile phases. These findings are substantiated by analogous results from gas-liquid chromatographic retention data, estimation of dipole moment effects, and examination of the entropic and enthalpic contributions to the net retention volume.
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    URL: http://dx.doi.org/10.1007/BF02268367
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    Direct determination of Benzo[a]pyrene in oil distillates by on-line two-dimensional HPLC with column switching (1992)
    Springer
    Chromatographia 34 (1992), S. 376-380 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Column switching ; Polycyclic aromatics ; Oil distillates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A selective and sensitive HPLC method for the determination of Benzo[a]pyrene (B[a]p) in oil fractions by means of column switching is described. The diluted oil samples were injected directly onto a silica column with isooctane as eluent. After fast elution of the main part of the sample matrix, the B[a]p containing fraction was transferred on-line to a dinitro-aryl-modified silica column for final separation with isooctane/tetrahydrofuran. A detection limit of 50 ppt B[a]p was found when using fluorescence detection.
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    URL: http://dx.doi.org/10.1007/BF02268371
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    Gradient high performance liquid chromatography of block copolymers of styrene andt-butyl methacrylate II. Association phenomena in mixtures of block copolymer with polystyrene (1992)
    Springer
    Chromatographia 34 (1992), S. 363-368 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Precipitation chromatography of polymers ; Block copolymers of styrene-butyl methacrylate ; Association phenomena
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Block copolymers of styrene andt-butyl methacrylate can be analysed by methanol/tetrahydrofuran gradients on C18 or phenyl bonded phase columns. On both of these columns, retention increases with styrene content of the samples. At 50°C, the retention of PS or a block copolymer containing 45% styrene was longer on the phenyl than the C18 columns. This indicates the contribution of adsorption to retention on phenyl bonded phase columns. Lowering the temperature from 50 to 30°C caused earlier elution of part of the sample from the phenyl phase. On a C18 phase the same drop in temperature improved the shape of the peak, which also started later than at 50°C. This effect of temperature is generally observed in polymer retention due to an adsorption mechanism, whereas increasing retention with decrease in temperature is characteristic of a precipitation mechanism. The block copolymer investigated contained 15% free polystyrene precursor which could not be separated from the block copolymer under the conditions employed. The addition of 20% PS homopolymer with a molecular weight similar to that of the styrene block in the copolymer showed that the polystyrene eluted together with the block copolymer, whereas the addition of PS homopolymer with a much higher molecular weight caused an extra peak at the expected elution time.
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    URL: http://dx.doi.org/10.1007/BF02268369
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    Multidentate phenyl-bonded phases in high-performance liquid chromatography (1992)
    Springer
    Chromatographia 34 (1992), S. 381-385 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Molecular recognition ; Multidentate phenyl-bonded phases ; PAHs
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary New multidentate phenyl-bonded phases (MPBPs) were synthesized and evaluated the chromatographic retention behaviour with polycyclic aromatic hydrocarbons as sample probes in high-performance liquid chromatography. The new MPBPs show different retention characteristics from the previously synthesized MPBP, designated TP. Nevertheless, the results indicate that the retention mechanism is still the same as the TP phase: the size and shape of the solute molecule can be recognized by a cavity-like space formed by the methyl groups and phenyl rings of MPBPs.
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    Comparison and evaluation of HIC columns of different hydrophobicity (1992)
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    Chromatographia 34 (1992), S. 391-397 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Hydrophobic interaction ; Stationary phases ; Salt effect ; Proteins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Retention and selectivity in hydrophobic interaction chromatography (HIC) depend both on the type of stationary phase and on the mobile phase. In the last few years various high performance packing materials and columns have been introduced for HIC resulting in a range of different retentions and selectivity. We have investigated the effect of the stationary phase on the retention of various proteins. The retention of some solutes of different hydrophobicities were measured on three commercial HIC columns (TSK-Phenyl, Synchropack-Propyl, CAA-HIC) under isocratic conditions using water-methanol mixtures as eluent. The log kw values determined according to the literature were devalues determined according to the literature were dependent on the type and structure of the stationary phase and indicated a much less hydrophobic character for these columns than that obtained for reversed phase columns. Gradient separations were then carried out on a standard protein mixture using ammonium sulfate and sodium citrate to change the gradient time. In order to compare the effect of the stationary phase and the two salts investigated apparent capacity factors (kg) were determined and plotted against the gradient time obtained for the three columns in the two eluent system. It was shown that the type of stationary phase had a significant effect on the retention of proteins. In addition, the effect of the mobile phase composition, i.e. salt type, was considerably different on the various stationary phases. In order to exploit the potential of HIC to modulate selectivity for the separation of proteins, the combined effect of the stationary phase and the type of salt should be taken into account.
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    Chromatographic characteristics of porphyrine ether glycerides (1992)
    Springer
    Chromatographia 34 (1992), S. 431-432 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Thin-layer chromatography ; Porphyrine ether glycerides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Efficient TLC and HPLC conditions for the separation of a newly synthesized class of compounds, porphyrine ether glycerides, have been established. Supplementary physico-chemical characteristics are given for this group of solutes.
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    Integrated FIA/HPLC method for preconcentration and determination of transition metal ions (1992)
    Springer
    Chromatographia 34 (1992), S. 445-449 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Flow injection analysis ; Combined methods ; Transition metal ions ; Aqueous samples
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An automatic method based on the combination of a flow injection (FI) manifold with a liquid chromatograph has been developed for the enrichment and determination of transition metal ions in water samples. Alternatively, the FI configuration can be used as a screening system for the determination of the total concentration of heavy metals. Two-parameter expressions for calibration graphs involving preconcentration time and concentration of the analytes were established for both the FIA and the integrated FIA/HPLC methods. The preconcentration time depends on the concentration level of the analytes in the samples. The method is linear in the range 2–200 ng/ml, with r.s.d. values between 1.5 and 5.0. It has been applied to the determination of copper, lead, zinc, nickel, cobalt, cadmium and manganese in synthetic water samples.
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    URL: http://dx.doi.org/10.1007/BF02290233
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    Comparison of HPLC and solid phase clean-up methods for identification of PCBs in cod-liver oil by HRGC/MS-SIM technique (1992)
    Springer
    Chromatographia 34 (1992), S. 421-430 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Solid phase extraction ; PCBs in cod-liver oil ; GC/MS identification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A group of non-planar PCBs (IUPAC nos. 28, 52, 101, 118, 138, 153, and 180) was identified in a cod-liver oil product by using high resolution gas chromatography-mass spectrometry (HRGC/MS) in electron impact (EI) and negative chemical ionization (NCI) modes. The cod-liver oil samples were prepared either in a cyano column by high performance liquid chromatography (HPLC) or by a solid phase extraction (SPE) clean-up procedure that included e.g. purified charcoal treatment. The two methods of sample preparation were evaluated on the basis of the detectabilities of the congeners. The GC/MS-SIM method allowed quantitative monitoring of congeners nos. 52, 101, 118, 138, 153, and 180 at low concentration levels. Detection limits were 1.2 pg and 130 fg (m/z 292.00) in EI and NCI modes, respectively. The determination levels in EI and NCI were 1.8 pg and 290 fg in HPLC followed by HRGC/MS and 170 pg and 27 pg in SPE followed by HRGC/MS. The linear range was from 5.0 pg/μl to 1.0 ng/μl and from 1.0 pg/μl to 1.0 ng/μl in EI and NCI modes, respectively. In addition, the co-planar PCBs, PCDDs, and PCDFs were also screened and two of the chlorinated furanes were identified by HRGC/MS-NCI after separation from non-planar PCBs by SPE. In this case the only congeners that could be quantified were 2,3,4,7,8-PCDF and 1,2,3,4,6,7,8-HCDF, the detection limit for them being 740 fg (m/z 351.90) with NCI. SPE allows the separation of the planar and non-planar compounds, but LC separation is more effective for separation of the compounds of interest from the matrix. LC clean-up is easier and faster to perform than SPE clean-up.
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    Separation of stereoisomers of tetramethylcalix[4]arenoctol and derivatives by high-performance liquid chromatography (1992)
    Springer
    Chromatographia 34 (1992), S. 453-456 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Calix[4]arenes ; Host-guest chemistry ; Separation of stereoisomers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A high performance liquid chromatographic procedure on 5 μm RP-18 was developed for the separation of the four possible cis-trans isomers of tetramethyl-calix[4]arenoctol, and of their octaacetates, and their octamethyl ethers.
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    HPLC separation of molecular species of intact sphingomyelin, utilizing multivariate design and optimization (1992)
    Springer
    Chromatographia 34 (1992), S. 529-533 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Sphingomyelin ; Molecular species separation ; Experimental design and optimization ; Chemometrics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An improved method has been developed for the separation of molecular species of intact sphingomyelins from natural sources (chicken egg yolk, bovine brain, and bovine milk) by high performance liquid chromatography with light-scattering detection. The method was developed and optimized using a novel multivariate optimization strategy.
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    High-performance liquid chromatography of carbohydrates in enzymic hydrolysate of waste paper (1992)
    Springer
    Chromatographia 34 (1992), S. 534-536 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Carbohydrates ; Enzymic hydrolysate ; Waste paper
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Waste paper was pretreated with 5M sulfuric acid at 28°C to give a gel-like solution which was then hydrolyzed with cellulase, purified fromTrichoderma viride, to form carbohydrates. The determination of the carbohydrates was accomplished using an aminopropylbonded silica HPLC column and an RI detector. The detection limits were 20 ppm; xylose, glucose, and cellobiose were the major components. Salts from the buffer solution may affect the activity of cellulase. The analysis of carbohydrates can be performed under acid conditions. HPLC analysis of carbohydrates from enzymatic hydrolysis is reliable and successful.
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    The vibration and stability analysis of moderate thick plates by the method of lines (1992)
    Springer
    Applied mathematics and mechanics 13 (1992), S. 523-531 
    Details
    ISSN: 1573-2754
    Keywords: moderate thick plate ; vibration ; stability ; method of lines
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Mathematics , Physics
    Notes: Abstract The method of lines based on Hu Hai-chang's theory for the vibration and stability of moderate thick plates is developed. The standard nonlinear ordinary differential equation (ODE) system for natural frequencies and critical load is given by use of ODE techniques, and then any indicated eigenvalue could be obtained directly from ODE solver by employing the so-called initial eigenfunction technique instead of the mode orthogonality condition. Numerical examples show that the present method is very effective and reliable.
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    Adaptive foraging by predators as a cause of predator-prey cycles (1992)
    Springer
    Evolutionary ecology 6 (1992), S. 56-72 
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    ISSN: 1573-8477
    Keywords: dynamics of adaptation ; optimal foraging ; predator-prey cycles ; stability ; type-2 functional response
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary When foraging has costs, it is generally adaptive for foragers to adjust their foraging effort in response to changes in the population density of their food. If effort decreases in response to increased food density, this can result in a ‘type-2’ functional response; intake rate increases in a negatively accelerated manner as prey density increases. Unlike other mechanisms for type-2 responses, adaptive foraging usually involves a timelag, because foraging behaviours do not often change instantaneously with changes in food density or risks. This paper investigates predator-prey models in which there are explicit dynamics for the rate of adaptive change. Models appropriate to both behavioural and evolutionary change are considered. Both types of change can produce cycles under similar circumstances, but under some evolutionary models there is not sufficient genetic variability for evolutionary change to produce cycles. If there is sufficient variability, the remaining conditions required for cycles are surprisingly insensitive to the nature of the adaptive process. A predator population that approaches the optimum foraging strategy very slowly usually produces cycles under similar conditions as does a very rapidly adapting population.
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    Adaptation of barley (Hordeum vulgare L.) to harsh Mediterranean environments (1992)
    Springer
    Euphytica 62 (1992), S. 29-38 
    Details
    ISSN: 1573-5060
    Keywords: adaptation ; barley ; drought ; heading date ; plant ideotype ; principal component analysis ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Barley adapted to the combined stresses of low winter temperatures and terminal drought requires a medium carly heading date, little affected by environmental fluctuations. Two plant ideotypes that are adapted to terminal drought in Mediterranean environments can be distinguished. The first combines early heading with good early vigour, erect winter growth habit, light plant colour, and ability to recover from cold damage. The second combines medium early heading, prostrate winter growth habit, dark winter plant colour which changes to pale green in spring, and cold tolerance. This study was conducted to determine the relationship between consistency in heading date and plant ideotype, and to identify the usefulness of earliness and plant ideotype as criteria for indirect selection for grain yield under drought. Thirty-six two-rowed entries of barley (Hordeum vulgare L.) were sown at 15 environments in northern Syria. Average grain yields ranged from 7 to 331 g/m2; the range in average heading date was 20 days. Consistency in date of heading was related to the second ideotype through vernalization requirement. Early heading was positively correlated with grain yield in most of the environments, but especially in low-yielding environments. After eliminating the effect of heading date, the second plant ideotype was advantageous only under harsh conditions. In early generations, selection under favourable conditions for earliness, prostrate winter growth habit, dark winter plant colour, and cold tolerance is a useful alternative for yield testing, to identify material well adapted to environments experiencing low winter temperatures and terminal drought stress. Selection for the first plant ideotype is proposed for Mediterranean environments with mild winters.
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    Effects of pre-storage conditions on storage of in vitro cultures of Nephrolepis exaltata (L.) Schott and Cordyline fruticosa (L.) A. Chev. (1992)
    Springer
    Plant cell, tissue and organ culture 28 (1992), S. 167-174 
    Details
    ISSN: 1573-5044
    Keywords: dark ; in vitro storage ; light ; stability ; temperature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In vitro cultures of Nephrolepis exaltata and Cordyline fruticosa were stored at 5°, 9° or 13°C, at a low irradiance (3–5 μmol m−2 s−1) or in darkness. Prior to storage the cultures were subjected to 18°, 21°, 24° or 27°C and 15, 30 or 45 μmol m−2 s−1 in a factorial combination. The optimal storage conditions for Nephrolepis were 9°C in complete darkness. These cultures were still transferable to a peat/perlite mixture at the end of the experimental period of 36 months. The optimal storage conditions for Cordyline were 13°C and a low light level (±3–5 μmol m-2 s-1). When the pre-storage conditions were normal growth room conditions (24°C and 30 μmol m-2 s-1), in vitro cultures could be stored for 18 months. With the most favourable pre-storage treatment (18°C and 15 μmol m-2 s-1) some cultures still had green shoots after 36 months of storage, but did not survive transfer to peat/perlite. Pre-conditioning before storage was most favourable for Nephrolepis, and not that important, but still favourable, for Cordyline. There was an interaction between pre-storage temperature and pre-storage irradiance. For both species a high irradiance level was less favourable than a low irradiance level when combined with high growth room temperatures.
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    Predictability of streamflow and particulate organic matter concentration as indicators of stability in prairie streams (1992)
    Springer
    Hydrobiologia 242 (1992), S. 7-18 
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    ISSN: 1573-5117
    Keywords: POM ; prairie streams ; predictability ; stability ; stream flow
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Predictability of stream discharge and particulate organic matter (POM) in the water column was estimated, using Colwell's indices of constancy and contingency, for 6 Texas prairie streams (1 each of 2nd, 3rd, and 4th order with intermittent or perennial discharge). Stream discharge in these 6 prairie streams varied between 0 and 36000 1 s−1, depending on the stream and season. Predictability (P) of discharge in these streams ranged from 0.45 to 0.62, within the range of values expected for North American streams. Predictability of stream discharge was not significantly different between streams. Particulate organic matter concentrations in these prairie streams are relatively low, ranging from 0.25 to 4.00 mg AFDM 1−1. Predictability of POM concentration in these streams was high, ranging from 0.75 to 0.85, and was largely the result of constancy of POM concentrations. Within the different POM size classes, Fine POM (FPOM) had the highest predictability (P = 0.89−0.96). In spite of relatively unpredictable stream discharge, POM remained fairly constant providing a measure of habitat predictability and stability.
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    Lyapunov's direct method in the estimation of the Hausdorff dimension of attractors (1992)
    Springer
    Acta applicandae mathematicae 26 (1992), S. 1-60 
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    ISSN: 1572-9036
    Keywords: 58F13 ; Hausdorff measure ; Hausdorff dimension ; strange attractor ; Lorenz system ; Rössler system ; Lyapunov function ; stability ; chaos ; weakly contracting system ; monostability ; frequency theorem
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract This paper surveys results of the authors and others conceming estimates for the Hausdorff dimension of strange attractors, particularly in the case of (generalized) Lorenz systems and Rössler systems. A key idea is the interpretation of Hausdorff measure as an analogue of a Lyapunov function.
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    URL: http://dx.doi.org/10.1007/BF00046607
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    Chemical reactions as dynamical systems on the interval (1992)
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    Journal of statistical physics 66 (1992), S. 1557-1574 
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    ISSN: 1572-9613
    Keywords: Boltzmann ; chemical kinetics ; stability ; chaos ; entropy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We consider the most general chemical reaction of the typen 1 A 1+...+n N A N ⇌m 1 B 1+...+m M B M whereN,M⩾1,n 1,...,n N andm 1,...,m M are positive integers defining the stoichiometry, andA 1,...,A N andB 1,...,B M are the names of chemicals or ions. We assume that ∑ i=1 N ni=∑ j=1 M mj. The time evolution of the concentrations is given by the law of mass action and leads to a dynamical system (with discrete or continuous time) which is governed by a polynomial map of the interval [B, C], where B⩾0 and C⩽1. We define the physically meaningful range for the parameters of the map, and we show that, within such a range, the map has a unique fixed point, which is stable and a global attractor, with the exception of one particular case, where bifurcation is observed.
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    URL: http://dx.doi.org/10.1007/BF01054433
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    Reconsidering the green revolution: Diversity and stability in cradle areas of crop domestication (1992)
    Springer
    Human ecology 20 (1992), S. 145-167 
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    ISSN: 1572-9915
    Keywords: agriculture ; development ; diversity ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Ethnic Sciences
    Notes: Abstract This paper reconsiders two widely held hypotheses about the effects of the green revolution, that it led to biological simplification and instability. The hypothesis of biological simplification (genetic erosion) is tested with evidence from Andean agriculture, where farmers maintain a significant degree of crop diversity even as they adopt modern crop varieties. The hypothesis of increased instability is tested with evidence from Asia where wheat and rice yields show no general pattern of increased instability. Neither of these hypotheses is confirmed. The conventional wisdom about the green revolution should be reconsidered with emphasis on resilience and variation in modernizing farming systems.
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    URL: http://dx.doi.org/10.1007/BF00889077
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    Spatial and temporal trends in stream macroinvertebrate communities: the influence of catchment disturbance (1992)
    Springer
    Hydrobiologia 241 (1992), S. 173-194 
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    ISSN: 1573-5117
    Keywords: disturbance ; recovery ; fire ; streams ; stability ; macroinvertebrates ; watershed
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Macroinvertebrate communities of five headwater streams in catchments disturbed by wildfire were compared with five similar streams with no catchment disturbance. Over the five years of observation, communities in disturbed streams were more similar to one another than they were to reference streams. Communities in disturbed streams exhibited more year-to-year variation than reference streams, although some indication of decreasing variation was evident through time, and species richness was greater in reference streams than disturbed streams. No increasing trend in richness over time was observed in disturbed streams. Stability of the relative abundance structure and persistence of dominant taxa through time may be characteristic of temperate streams over moderate time intervals. Local effects of catchment-wide disturbance have persistent effects that alter these trends.
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    URL: http://dx.doi.org/10.1007/BF00028640
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    Alteration of the structural attributes of a compact clay loam soil by growth of a perennial grass crop (1992)
    Springer
    Plant and soil 139 (1992), S. 195-202 
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    ISSN: 1573-5036
    Keywords: bulk density ; epoxy resin impregnation ; image analysis ; macroporosity ; nitrogen ; stability ; strength ; structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Soil aggregate stability, organic matter content, pH, bulk density, strength, and macropore attributes were assessed in order to evaluate the influence of grass root growth in a field sward. The amount of grass grown was varied by varying the quantity of applied nitrogen fertilizer: following one year with a uniform application rate, nitrogen fertilizer was applied over the subsequent three years to a compact soil at zero (N0), moderate (N1) and high (N2) rates. Differences in herbage production were evident in the three years of the contrasting nitrogen treatments. An index of soil aggregate stability increased in response to the increased grass growth promoted by heavier applications of nitrogen, but both bulk density and vane shear strength were unchanged. Binary images of the soil solid and pore space showed that for each treatment the largest volume of macropores occurred close to the surface, particularly in N0 where there was more pore space than in either N1 or N2. Analysis of the pore structure attributes of the binary images revealed further differences between treatments, in particular, at 40–80 mm depth, the soil in treatment N0 had fewer and smaller pores, and greater distance between pores, than the soil in the N1 and N2 treatments. The larger macropore volume in N1 and N2 constituted a major portion of the air-filled porosity when the soil was relatively wet. It was concluded that the root growth in the intensively cropped grassland was conducive to maintenance of a relatively stable and porous soil structure. An attendant increase in soil acidity close to the soil surface was a disadvantage of the larger nitrogen inputs.
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    URL: http://dx.doi.org/10.1007/BF00009310
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    The impact of genotype x soil texture interaction on the efficiency of selection for yield in maize (Zea mays L.) (1992)
    Springer
    Euphytica 61 (1992), S. 61-65 
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    ISSN: 1573-5060
    Keywords: population improvement ; maize ; Zea mays ; honeycumb selection ; adaptability ; stability ; yield
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary This study was undertaken to investigate the implications of genotype x soil texture interaction on response to selection in maize. Mass honeycomb selection for yield was applied for 11 cycles from the F2 of the single cross maize hybrid F68×NE2 in a field B with silty-clay-loam soil texture. Response to selection compared to the original single cross hybrid was estimated both in absence of competition and under solid stand in the selection field B and in a nearby field A differing in soil texture (clay-loam). A strong crossover type of interaction occurred both under solid stand and in the absence of competition in the two tests the improved population outyielded the hybrid in field B in the two densities, but lagged behing the hybrid in field A. The results suggest that interaction between genotype and soil texture might affect efficiency of selection detrimentally unless provision is taken for parallel selection early in the crop improvement program in fields differing in soil texture.
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    Adaptation and yield stability of selected lines of Lathyrus spp. under rainfed conditions in West Asia (1992)
    Springer
    Euphytica 66 (1992), S. 89-97 
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    ISSN: 1573-5060
    Keywords: chickling ; Lathyrus ; G×E interactions ; adaptation ; stability ; heritability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Sixteen promising lines (selections) of Lathyrus spp. (chicklings), comprising 11 L. sativus, four L. ochrus, and one L. cicera, were evaluated under rainfed conditions in Syria. Two locations in each of four years were treated as separate environments, to give eight environments altogether. Genotype x environment (G×E) interactions were analysed using linear regression. There was considerable variation in herbage and seed yields within both lines and environments. Genotype x environment interactions were present for both herbage and seed yields; a little over half was accounted for by the linear regression. The non-linear component was also significant, although it was smaller than that of the linear component. The most stable herbage and seed yields were obtained from L. sativus. Two selections, 347 and 311, origmating from Syria and Turkey respectively, combined both high herbage and seed yields with wide adaptation and stability, and could be considered the most widely adapted lines. Other lines were identified as suitable for favourable and unfavourable environments; in particular, all four lines of L. ochrus have great potential in frost-free climates. The importance of genotype x environment interactions in future breeding strategies is discussed.
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    URL: http://dx.doi.org/10.1007/BF00023512
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    HPLC separation of catecholamines after derivatization with 9-fluorenylmethyl chloroformate (1992)
    Springer
    Chromatographia 33 (1992), S. 83-86 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Pre-derivatization ; Catecholamines ; 9-fluorenylmethyl chloroformate (FMOC-Cl)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Optimum conditions for the separation of 9-fluorenylmethyl chloroformate derivatized catecholamines by HPLC are described; three catecholamines (noradrenaline, adrenaline and dopamine) and an internal standard (epinine) were separated in less than 20 minutes under isocratic conditions. This method is 17 to 350 times more sensitive than electrochemical detection, depending on the test compounds. It has been applied to the analysis of catecholamines in urine. The sample was extracted by a metal-loaded silica prior to separation.
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    Preparation and determination of manganese(III) chlorophylls by reversed-phase high performance liquid chromatography (1992)
    Springer
    Chromatographia 33 (1992), S. 567-570 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Chlorophylls ; Manganese(III) chlorophylls
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Manganese chlorophylls have been synthesized by refluxing a mixture of pheophytins dissolved in acetone and manganese(II) acetate anhydride dissolved in glacial acetic acid. A good separation of manganese(III) chlorophylls has been attained by RP-HPLC using chemically bonded C18 silica as a stationary phase and methanol with 3% acetic acid as a mobile phase. An accurate and rapid HPLC method is described for the simultaneous determination of manganese(III) chlorophyll-a [Mn(III)-chl-a] and manganese(III) chlorophyll-b [Mn(III)-chl-b]. Tailing arising from dissociation of acetate ions is improved by addition of sodium acetate (5×10−3 M) to the mobile phase (acetone: methanol=90∶10, vol/vol). The analytical values obtained by the HPLC method are very close to the calculated contents in all samples, but those obtained by spectrophotometry are high because of the interferences from overlapping of absorption bands. In the proposed HPLC method the calibration graphs of Mn(III)-chl-a and Mn(III)-chl-b are linear in the concentration range 0–20 μg cm−3 with relative standard deviations (n=10) of 3.46% and 4.54%, respectively.
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    Liquid chromatographic separation of the anomers and isomers of 2′-deoxyuridine (1992)
    Springer
    Chromatographia 33 (1992), S. 571-574 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; 2′-Deoxyuridine ; Anomer separation ; Isomer separation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A liquid chromatographic assay method was developed to separate 2′-deoxyuridine from its anomer and pentopyranosyl isomers. The influence of the pH of the mobile phase, the type of organic modifier and the column temperature on the chromatographic parameters was systematically investigated. Using a Hypersil C18 (5 μm) column at 10°C, the following mobile phase was found suitable: tetrahydrofuran −0.2 M potassium phosphate buffer pH 4.0-water (0.1∶5∶94.9, v/v).
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    Controlled-porosity glasses as alternative adsorbents to silica gel for HPLC (1992)
    Springer
    Chromatographia 33 (1992), S. 122-126 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Controlled-porosity glasses ; Correlation between silica and porous glass ; Hydrocarbons separations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The paper deals with the use of controlled-porosity glasses (CPGs) as adsorbents for HPLC. The physicochemical and chromatographic properties of small-pore CPGs are compared to the analogous properties of silica gels. The results show good correlation between them and suggest the possibility of application of CPGs as adsorbents for liquid chromatography.
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    URL: http://dx.doi.org/10.1007/BF02275891
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    Retention, enantioselectivity and enantiomeric elution order of propranolol and its ester derivatives on an alpha1-acid glycoprotein-bonded column (1992)
    Springer
    Chromatographia 33 (1992), S. 127-132 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Chiral separation ; Alpha 1-acid glycoprotein-bonded column ; Propranolol ; Propranolol ester derivatives
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The retention, enantionselectivity and enantiomeric elution order of racemic propranolol (PP) and its ester derivatives (O-acetyl,-propionyl,-butyrul and-valeryl PP) on an α1-acid glycoprotein (AGP)-bonded column have been investigated by changing eluent composition (eluent pH, buffer concentration, type and content of organic modifier). The retention of these cationic solutes, PP and its ester derivatives, was influenced by eluent pH, ionic strength and organic modifier content. The enantioselectivity was dependent on eluent pH and type of organic modifier. Reversal of the enantiomeric elution order of ester derivatives of PP (O-propionyl-butyryl) and-valeryl PP) occurred around eluent pH 6–7. These results suggst that chiral recognition or binding properties may be altered by the change in eluent composition, espeically eluent pH and type of organic modifier.
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    The development and validation of a solid phase extraction/HPLC method for the determination of aflatoxins in groundnut meal (1992)
    Springer
    Chromatographia 33 (1992), S. 208-212 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Solid phase extraction ; Validation ; Aflatoxins in groundnut meal ; CB method
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The efficiency of an analytical method for the determination of aflatoxins in groundnut meal has been statistically examined. The procedure consists of a phenyl bonded phase (PH) clean-up of an acetone: water (85∶15) extract followed by HPLC quantification. Average recoveries from spiked groundnut meal extracts were calculated to be 101.3% and 101.8%, with limits of detection of 7.4 and 2.62 μg/kg for aflatoxins-B1 and-B2 respectively. Higher recoveries of aflatoxin-B1 from naturally contaminated samples were recorded using the proposed procedure than those recorded using the official AOAC (CB) method although the precisions of the two methods were not found to differ at the 5% significance level. Similar recoveries of aflatoxin-B2 were recorded for both methods but the proposed procedure was found to be more precise. The proposed PH-HPLC method was far less time consuming and more economical on solvents than the CB procedure.
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    URL: http://dx.doi.org/10.1007/BF02276184
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    Preparation of octadecyl modified column gels using heat-treated silicas and their retention behaviour in high-performance liquid chromatography (1992)
    Springer
    Chromatographia 33 (1992), S. 203-207 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Octadecyl modified silica ; Hexamethyldisilazane treated silica ; Calcination ; Heat-treated silica
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The effect of silanol groups on three types of octadecylmodified column gels using heat-treated silicas by calcination has been studied by high-performance liquid chromatography. After heat-treating at 180°C, 500°C and 950°C, the silicas treated with octadecyldimethylchlorosilane were used for the measurement of physical and chemical analysis. From elemental carbon analysis data, the reactive silanol group concentrations, αOH(s), were determined to be 2.0 in the 180°C treated silica, 2.1 in the 500°C treated silica and 1.6 in the 950°C treated silica, respectively (original silica: mean pore diameter 116 Å, specific surface area 298 m2/g, pore volume 1.22 ml/g, particle size 5.0 μm). The separation factors, α, of pyridine versus phenol were measured to be 0.79 on 180°C treated silica, 0.91 on 500°C treated silica and 1.98 on 950°C treated silica, using acetonitrile-water mixtures as the eluent. And then, on the basis of the physico-chemical and chromatographic data, the three types of octadecyl modified column gels using heat-treated silicas by calcination have been compared.
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    Determination of chloride in biological fluids as pentafluorobenzylchloride by reversed-phase high-performance liquid chromatography and UV detection (1992)
    Springer
    Chromatographia 33 (1992), S. 317-320 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; UV detection ; Pentafluorobenzyl chloride by UV detection ; Chloride in biological fluids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A reversed-phase high-performance liquid chromatographic method for the determination of chloride in plasma, urine, saliva, sweat and aqueous solution is described. Chloride, in solution in aqueous acetone, is converted by means of pentafluorobenzyl bromide into pentafluorobenzyl chloride. This derivative is separated on a ODS-5 μm reversed-phase column using isocratic elution with acctonitrile/water, 50/50, v/v, at a flow rate of 2.0 ml/min, and detected by a UV detector at 264 nm. The method is rapid, accurate and sufficiently sensitive for the determination of chloride in less than 10 μl sample volume of a biological fluid.
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    Liquid chromatography of carbon clusters (1992)
    Springer
    Chromatographia 33 (1992), S. 344-346 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Charge-transfer chromatography ; Carbon clusters ; Fullerenes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A comparison of three binary mobile phases in LC separation of C60 and C70 fullerences on chemically bonded 2,4-dinitroanilinopropyl (DNAP) stationary phase was carried out, n-Hexane-benzene has been found to be the best mobile phase for efficient separation of the all-carbon molecules permitting high loads in preparative LC.
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    Determination of trichlormethiazide in human plasma and urine by high-performance liquid chromatography (1992)
    Springer
    Chromatographia 33 (1992), S. 339-343 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Trichlormethiazide ; Electrochemical detection ; Diuretics in plasma and urine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary This paper describes a high-performance liquid chromatographic (HPLC) assay method for the determination of trichlormethiazide (TCM) in human plasma and urine. After extraction and separation on an ODS column TCM from plasma was detected by oxidation in an electrochemical detector (ECD) by a porous graphite electrode. The sensitivity was better than HPLC with UV detection, enabling the determination of 2 ng ml−1 TCM in human plasma. This method also allows determination of TCM at higher concentrations by exchanging the UV for the electrochemical detector. To study the pharmacokinetics, TCM in plasma and urine was assayed with coefficients of variation in the range 2–3%. The method has the advantages of high sensitivity for plasma assay and high precision with a simple procedure for both plasma and urine samples. Small samples of 0.5 ml plasma per assay also reduced the total volume of plasma needed.
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    Partial separation of lactic acid enantiomers by HPLC using (S)-(+)mandelic acid as chiral mobile-phase additive (1992)
    Springer
    Chromatographia 34 (1992), S. 31-34 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Chiral mobile-phase additive ; Inductive adsorption ; Enantiomer resolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Separation of lactic acid enantiomers by inductive adsorption has been studied on silica columns using (S)-(+)mandelic acid as the chiral mobile-phase additive. The lactic acid peak is not very strongly retained, broad, strongly tailing and splits in two at loadings lower than 60 μmol cm−2 column cross-section and at mandelic acid concentrations higher than 10−4M. The splitting indicates partial separation of enantiomers: enantiomerically enriched fractions are obtained but not enantiomerically pure. Lactic acid retention strongly decreases with increasing concentration of both hydroxy-acids; mandelic acid acts by displacement and lactic acid acts by an overloading effect.
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    Chromatographic resolution of racemic amines, carboxylic acids, and alcohols by a new homochiral reagent derived fromendo-borneol (1992)
    Springer
    Chromatographia 34 (1992), S. 48-50 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Diastereomer separation ; Chiral derivatizing agent ; Chiral oxazolidin-2-one
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Chromatographic separation of racemic amines, carboxylic acids and alcohols can be achieved with excellent resolution as measured in terms of the chromatographic separation factor α by derivatization with a homochiral oxazolidin-2-one easily prepared in three steps fromendo-borneol. The resolved materials can be isolated in excellent yields by cleavage of the resultant diastereomers using conventional methods, which also allow recovery of the chiral resolving agent for re-use.
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    Combined Kalman filtering and steepest descent minimization for quantitative analysis of unresolved misaligned chromatographic peaks. The resolution of alternariol and altenuisol mycotoxins in mixtures by HPLC (1992)
    Springer
    Chromatographia 34 (1992), S. 56-62 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Kalman filter ; Deconvolution ; Mycotoxins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The potential of a computational approach for the quantitative resolution of seriously overlapping chromatographic peaks when there is loss of collinearity between the pure component peaks and the mixture peak has been explored. The program makes iterative use of the Kalman filter algorithm for resolving the mixture peak with the component peaks aligned according to some values of the position parameters, and of a steepest descent minimization procedure to find the optimal alignment. This combined procedure has been applied to the quantitive resolution of the HPLC chromatograms of alternariol and altenuisol mycotoxins in synthetic mixtures and in real samples.
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    Direct injection analysis of hexamethylene bisacetamide in biological fluids by an HPLC column switching technique with a micellar mobile phase (1992)
    Springer
    Chromatographia 34 (1992), S. 63-66 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Micellar mobile phase ; Direct injection of biological fluids ; Hexamethylene bisacetamide (HMBA)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary This paper describes the direct injection analysis of the anti-cancer drug hexamethylene bisacetamide (HMBA) in biological fluids by an HPLC column switching technique. The first chromatographic column, which provides for sample extraction and cleanup, employs a micellar mobile phase with SDS as the modifier. The second column, coupled on-line to the first, utilizes reversed-phase conditions for analysis. UV detection is employed at 210 nm. 282 samples from 12 cancer patients were analysed and good pharmacokinetics curves obtained. The drug gives recoveries of 94.0–100.9% with a relative standard deviation of 1.88%. A sample analysis is completed within 15 minutes. This method should be satisfactory not only for the analysis of HMBA but also, probably for other drugs in biological fluids.
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    Eluent composition effect on ion chromatographic determination of oxyanions in solutions equilibrated with soils (1992)
    Springer
    Chromatographia 34 (1992), S. 643-647 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Suppressed ion chromatography ; Eluent composition and concentration ; Oxyanions in soils
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Methods based on simultaneous determination of oxy-anions in soil extracts are needed for studies of competitive adsorption of oxyanions by soils. We studied the effect of NaHCO3/Na2CO3 and NaOH/Na2CO3 concentrations on ion chromatographic (IC) determination of PO 4 3− , AsO 4 3− , SeO 4 2− , SeO 3 2− , WO 4 2− , and MoO 4 2− in a 10-mM NaCl matrix equilibrated with soils by using a Dionex 2002i IC unit. The eluent, 6.0 mM NaOH+4.5 mM Na2CO3, resolved the 10 mM Cl− from the six oxyanions. Elution times for Cl−, SeO 3 2− , SO 4 2− , NO 3 − , SeO 4 2− , PO 4 3− , WO 4 2− , MoO 4 2− , and AsO 4 3− were 1.7, 2.7, 5.2, 6.1, 7.8, 10.5, 14.3, 17.7, and 21.2, respectively. The recovery of 0.2-mM oxyanion standards added to the soil solutions ranged from 93.0 to 106.8%, with coefficients of variation ranging from 0 to 14.3%. The detection limits of the oxyanions studied ranged from 0.3 μM for SeO 3 2− to 9.0 μM for AsO 4 3− .
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02269877
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  • 92
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    Comparison of post-column fluorescence derivatization and evaporative light-scattering detection to analyse saccharides selectively by LC (1992)
    Springer
    Chromatographia 34 (1992), S. 651-654 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Post-column derivatization ; Light-scattering detection ; Carbohydrates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The use of post-column fluorescence derivatization and evaporative light-scattering detection to analyse saccharides selectively by LC was investigated. In order to compare the performances of these two detection systems, factors such as reproducibility, detection limits and linear calibrations were determined. Despite the derivatization reaction step, post-column derivatization is superior from the standpoint of sensitivity. The detection of saccharides in beverages is also described.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02269879
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  • 93
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    A study of diastereoisomerism of oxovanadium schiff base chelates by gas chromatography-atomic emission spectroscopy, and high performance liquid chromatography (1992)
    Springer
    Chromatographia 34 (1992), S. 269-275 
    Details
    ISSN: 1612-1112
    Keywords: Gas chromatography — atomic emission spectroscopy ; Column liquid chromatography ; Metal chelate chromatography ; Diastereoisomer separation ; Vanadium complexes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Capillary gas chromatography with atomic emission detection (GC-AED), and high performance liquid chromatography (HPLC) have been employed to characterize isomerism of oxovanadium N,N'-propylenebis(trifluoroacetylacetoniminate). Other tetradentate Schiff base chelates of nickel, copper and palladium are also included in this study. Element-specific detection for metal and nonmetal elements in the chelates provides a means of identifying eluted peaks. Picogram detection limits for metals by GC-AED facilitated study of kinetic behavior at low concentration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02268357
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  • 94
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    Retention behaviour of binaphthyl compounds in enantiomeric separation by microcolumn liquid chromatography with micellar bile-salt mobile phases (1992)
    Springer
    Chromatographia 33 (1992), S. 58-62 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Enantiomeric separation ; Micellar bile-salt mobile phase ; Binaphthyl compounds
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Optical isomers of substituted binaphthyl, compounds such as 2,2′-dihydroxy-1,1′-dinaphthyl and 1,1′-binaphthyl-2,2′-diyl hydrogenphosphate are, separated by HPLC using micellar bile-salt mobile phases. Operating conditions which affect the optical resolution of these enantiomers are examined. The largest separation factor achieved for these enantiomers is 2.74. The elution order of the latter enantiomers changes with mobile phase composition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02276853
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  • 95
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    Retention mechanism of enantiomeric separation by liquid chromatography with micellar bile-salt mobile phases (1992)
    Springer
    Chromatographia 33 (1992), S. 63-66 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Micellar bile-salt mobile phase ; Enantiomeric resolution ; Retention model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The retention mechanism involved in enantiomeric separation of binaphthyl compounds by HPLC with micellar bilesalt mobile phases is discussed. A new model for the equilibrium is proposed, in which a heterogeneous stationary phase comprising solvated and micelle-adsorbed portions is considered. The experimental data supported the adsorption of the bile salt micelles on the octadecylsilica stationary phase which could recognize the chirality of binaphthyl compounds.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02276854
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  • 96
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    Purification of the glycosylated beta subunit of (Na,K)-ATPase by lectin affinity chromatography (1992)
    Springer
    Chromatographia 33 (1992), S. 521-524 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Affinity chromatography ; (Na,K)-ATPase β-subunit ; Wheat germ agglutinin ; Protein purification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Wheat germ agglutinin (WGA) affinity chromatography was examined as a method for the purification of the glycosylated beta subunit from SDS solubilized (Na,K)-ATPase. This lectin, WGA, bound quantitatively all of the beta subunit from SDS solubilized (Na,K)-ATPase whether or not the sample was reduced and/r alkylated. The combination of affinity and high performance size exclusion chromatography purified the beta subunit to a single band on SDS-PAGE electrophoresis. Compared to other methods of isolation this two step procedure utilizing wheat germ agglutinin was superior in terms of yield and purity for the beta subunit of (Na,K)-ATPase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02262242
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  • 97
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    Quantitative structure-enationselective retention relationships for the chromatography of 1,4-benzodiazepines on a human serum albumin based HPLC chiral stationary phase: An approach to the computational prediction of retention and enantioselectivity (1992)
    Springer
    Chromatographia 33 (1992), S. 546-550 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Benzodiazepines ; Human serum albumin chiral stationary phase (HSA-CSP) ; Quantitative structure-enantiospecific retention relationships (QSERR) ; Structural descriptors ; Submolecular polarity parameter
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Quantitative structure-enantiospecific retention relation-ships (QSERR) have been derived for a series of 1,4-benzodiazepines. The compounds were chromatographed on a human serum albumin based HPLC chiral stationary phase (HSA-CSP). Molecular modeling of the solutes allowed the determiantion of various structural descriptors. Among these descriptors, a submolecular polarity parameter, PSM, was identified which was able to characterize enantiospecific interactions of benzodiazepines with the HSA-CSP. Combining PSM with the retention parameter of the less retained enantiomer permitted precise prediction of the retention of the second eluting enantiomer. Highly statistically significant regression equations were also derived which described the retentions of both enantiomers in terms of nonempirical molecular descriptors. The calculated enantioselectivity correlated well with the experimentally observed values. A significant conclusion from this study is support for the existence of two different binding sites for chiral benzodiazepines on HSA.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02262246
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  • 98
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    Evaluation of analytical methods. Analysis of minocycline by liquid chromatography (1992)
    Springer
    Chromatographia 33 (1992), S. 560-566 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Official methods of analysis ; Method evaluation ; Minocycline
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The liquid chromatographic methods laid out for the analysis of minocycline hydrochloride in the British Pharmacopoeia 1988, the United States Pharmacopeia XXII and the Pharmacopée Française 10 were examined. The major difference between these methods lies in the adjustment of the pH of the mobile phase. The analyst has to obtain the right pH of the mobile phase for his available column. This was found to be a less than easy task for the occasional analyst. Other disadvantages observed were poor solubility of the components of the mobile phase, reduced sensitivity due to UV absorbance by the mobile phase, rather high back pressure, the elution order for 9-minocycline depending on the brand of stationary phase, and above all, poor stability of the stationary phase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02262248
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  • 99
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    Ion-pair, liquid chromatographic analysis of total gossypol in chicken liver (1992)
    Springer
    Chromatographia 33 (1992), S. 174-176 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Ion-pair system ; Gossypol analysis ; Chicken liver ; Plant toxin residues
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An ion-pair, liquid chromatographic method for the determination of total gossypol in chicken liver has been developed. It involves hydrolysis of bound gossypol in the presence of ascorbic acid, partitioning into chloroform and isocratic separation on Spherisorb ODS2, 10 μm, column with a methanol-water mobile phase containing octane-1-sulfonate. Precision data based on within-day and between-days variation suggested an overall relative standard deviation of 8.1%, while overall recovery was 81.1%±3.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02275901
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  • 100
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    Energetics of hydrophobic solute retention on reversed-phase chromatography supports: Effects of solute, solvent, and sorbent properties (1992)
    Springer
    Chromatographia 33 (1992), S. 403-412 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Hydrophobic solutes ; Enthalpy and entropy changes ; Eluent composition effects ; Surface area effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Chromatographic retention of several nonpolar solutes by three reversed-phase liquid chromatography (RPLC) supports was measured at several temperatures with binary mixtures of methanol/water and acetonitrile/water as the mobile phase. These data were used to estimate enthalpy and entropy changes (ΔH sorp o and ΔS sorp o ) associated with solute retention. The dependence of these two thermodynamic parameters on organic solvent content (θ) in the mobile phase, solute hydrophobic surface area (HSA), and bonded n-alkyl chain length (Nc) of the RPLC support was evaluated. The differences noted in the two solvent mixtures were attributed to: (1) the manner in which solvent surface tension changes with increasing θ, and (2) the differences in the interaction of methanol and acetonitrile with the bonded alkyl chains.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02262319
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