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  • 1
    Electronic Resource
    Electronic Resource
    Light transmittance as a measure of interfacial area in liquid-liquid dispersions (1956)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 2 (1956), S. 205-210 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Interfacial area in liquid-liquid systems has been measured photographically. Precision and accuracy of the method have been shown to be better than 10%. To avoid tedium of counting drops, a simple light probe of easily reproducible design has been developed to measure the light transmission through the dispersions formed. A correlation of light transmittance with interfacial area is presented and its usefulness and limitations are discussed.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690020215
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  • 2
    Electronic Resource
    Electronic Resource
    Lattice relaxation in type I gas hydrates (1991)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 37 (1991), S. 1511-1516 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Computer simulations have been used to examine the approximations upon which the van der Waals-Platteeuw theory of hydrate stability is based, and in particular, the extent to which the water lattice relaxes about the guest molecules. It is found that the behavior of the water lattice depends significantly on both the nature and number of guest molecules present - an effect that is neglected in the van der Waals-Platteeuw theory. The simulations also indicate an important role for the repulsive guest-host interactions in generating the mechanical stability of gas hydrates in the bulk. On the basis of these simulations, it is conjectured that surface interactions (particularly at a water/guest interface) are fundamental to the phase behavior of gas hydrates.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690371008
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  • 3
    Electronic Resource
    Electronic Resource
    Relationship between resolution and analysis time in chiral subcritical fluid chromatography (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 8 (1996), S. 249-257 
    Details
    ISSN: 0899-0042
    Keywords: chiral SubFC resolution ; analysis time ; column efficiency ; library of chiral columns ; selectivity ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A model is presented that predicts a defined relationship between chiral SubFC resolution and analysis time. This model is based upon ideal chromatographic behavior and requires column efficiency and selectivity to be independent of mobile phase modifier level and flow rate. The validity of these assumptions was found to be imperfect but acceptable for two model compounds on two commonly used chiral columns.A major implication of the model is that the maximum resolution obtainable with a particular column and mobile phase modifier may be predicted from one injection. The retention time required to obtain a desired resolution is also calculable. This information enables the practitioner to discern quickly the futility of method development efforts. Insufficient maximum resolution predicted from the first injection would require an increase in selectivity to achieve a useful separation. Selectivity may then be altered by temperature, modifier, or stationary phase. The increased column efficiency of SubFC at typical flow rates rescues separations that fail by HPLC, thus shrinking the practitioner's required library of chiral columns. This work demonstrates that SubFC also allows the practitioner to skim through that library very quickly. © 1996 Wiley-Liss, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Temperature effects for chiral separations using various bulk fluids in near-critical mobile phases (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 693-698 
    Details
    ISSN: 0899-0042
    Keywords: supercritical fluid chromatography ; subcritical fluid chromatography ; HFC-134a ; 1,1,1,2-tetrafluoroethane ; carbon dioxide ; chiral selectivity ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: As supercritical fluid chromatography becomes more accepted as a facile means for the separation of chiral compounds, the need for mobile phases that can readily solubilize these polar compounds grows. Prior studies suggest that HFC-134a may prove suitable due to its very high eluotropic strength compared to carbon dioxide-based mobile phases. A comparison is made between ethanol-modified carbon dioxide, HFC-134a, and decafluoropentane as to their relative eluotropic strength, selectivity, and efficiency for three chiral compounds using a Whelk O-1 chiral bonded phase. The bulk component of the mobile phase was found to have relatively little effect on chiral selectivity over the range of 5° to 95°C. Chirality 9:693-698, 1997. © 1997 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Differentiation of α- from γ-glutamyl dipeptides by chemical ionization mass spectrometry (1982)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 9 (1982), S. 252-256 
    Details
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Chemical ionization mass spectrometry has been shown to be a useful method for the differentiation of α- and γ-glutamyl dipeptides where the C-terminal amino acids are simple α-amino or α-imino acids without additional functional groups. The α-glutamyl dipeptides lost one and two molecules of H2O from the protonated molecular ion to give fragment ions at [MH—H2O]+ and [MH—2H2O]+. With the γ-glutamyl dipeptides, the characteristic fragment ions of highest intensities were the protonated pyroglutamic acid (pyrrolidone-5-carboxylic acid) ion at m/z 130, and a fragment ion corresponding to the protonated C-terminal amino acid. The procedure does not require derivatization of the dipeptide, and because only small sample sizes are needed it could prove useful for the characterization of synthetic samples and glutamyl dipeptides isolated and purified from biological sources.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200090606
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  • 6
    Electronic Resource
    Electronic Resource
    Quantitative measurement of Δ9-tetrahydrocannabinol and two major metabolites in physiological specimens using capillary column gas chromatography negative ion chemical ionization mass spectrometry (1983)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 10 (1983), S. 316-323 
    Details
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Δ9-Tetrahydrocannabinol and two of its metabolites, 11-hydroxy-Δ9-tetrahydrocannabinol and 11-nor-9-carboxy-Δ9-tetrahydrocannabinol, can be measured in a single 1-ml sample of blood, plasma, or urine by a new assay which combines a relatively rapid extraction procedure with capillary column gas chromatography and negative ion chemical ionization mass spectrometry. Deuterium-labeled analogs of each cannabinoid are added to the physiological specimen as internal standards. Two extracts are obtained from each sample: a neutral fraction containing Δ9-tetrahydrocannabinol and 11-hydroxy-Δ9-tetrahydrocannabinol, and an acid fraction containing 11-nor-9-carboxy-Δ9-tetrahydrocannabinol. The neutral fraction is derivatized by treatment with trifluoroacetic anhydride; the acid fraction is first treated with BF3-methanol followed by reaction with trifluoroacetic anhydride. Under electron-capture chemical ionization conditions the derivatized Δ9-tetrahydrocannabinol and 11-nor-9-carboxy-Δ9-tetrahydrocannabinol give abundant molecular anions ideally suited for selected ion monitoring. The negative ion chemical ionization spectrum of the HO-THC-trifluoroacetate shows no molecular anion. Consequently, quantitation of the hydroxy metabolite is achieved by monitoring a fragment ion formed by loss of CF3CO2 from its molecular anion. The limits of reliable measurement are judged to be 0.1 ng ml-1 for 11-nor-9-carboxy-Δ9-tetrahydrocannabinol, 0.2 ng ml-1 for Δ9-tetrahydrocannabinol and 0.5 ng ml-1 for 11-hydroxy-Δ9-tetrahydrocannabinol. Four examples are given of the application of the assay to the analysis of specimens of medico-legal importance.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200100503
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  • 7
    Electronic Resource
    Electronic Resource
    Effect of available volumes on radial distribution functions (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 19 (1998), S. 363-367 
    Details
    ISSN: 0192-8651
    Keywords: solution structuring ; radial distribution functions ; available volume ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The traditional method of analyzing solution structuring properties of solutes using atom-atom radial distribution functions (rdfs) can give rise to misleading interpretations when the volume occupied by the solute is ignored. It is shown by using the examples of O(4) in α- and β-D-allose that a more reliable interpretation of rdfs can be obtained by normalising the rdf using the available volume, rather than the traditional volume of a spherical shell.   © 1998 John Wiley & Sons, Inc.   J Comput Chem 19: 363-367, 1998
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Dielectric and viscoelastic properties of some meta-tetramethyl xylene diisocyanate-based polyurethanes as a function of sample composition (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 45 (1992), S. 1175-1188 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A series of linear segmented polyurethanes were synthesized, based on soft segments of polycaprolactone having an average number molecular weight of 2100, or hydroxy-terminated polybutadiene having an approximate molecular weight of 2800. Hara segments were made of meta-tetramethyl xylene diisocyanate and diethyl toluene diamine. The dynamic Young's modulus and loss tangent, relative permittivity, and dielectric loss, were found to be significantly affected by soft segment polarity and hard segment content. These results are discussed in terms of polymer morphology, such as degree of phase separation and soft segment phase state.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1992.070450706
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  • 9
    Electronic Resource
    Electronic Resource
    Chemical ionization mass spectrometry of dimethyl acetals and diethyl dithioacetals of aldopentoses and aldohexoses, and the influence of stereochemical configuration (1980)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 15 (1980), S. 317-325 
    Details
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Chemical ionization mass spectra have been recorded for the title compounds having the four pentose configurations and the eight hexose configurations, with ammonia and isobutane as the reagent gases. The ammonia mediated spectra display [NH4]+ capture ions with successive loss of one or two molecules of methanol (acetals) or ethanethiol (dithioacetals), whereas when isobutane was the reagent gas, loss from the protonated acetals of one or two molecules of methanol and of water, and loss from the protonated dithioacetals of one or two molecules of ethanethiol and of water were featured. Significant differences in the ion intensities as a function of stereochemistry in the precursor are noted, and are discussed in terms of the ease of formation of cyclic fragment ions.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/oms.1210150610
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  • 10
    Electronic Resource
    Electronic Resource
    Effect of Mobile Phase Components on the Separation of Polypeptides Using Carbon Dioxide-Based Mobile Phases (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 74-78 
    Details
    ISSN: 0935-6304
    Keywords: Polypeptides ; subcritical fluid chromatography ; supercritical fluid chromatography ; carbon dioxide ; additives ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The effect of mobile phase modifier and additive on the chromatographic properties of various small polypeptides was explored under subcritical conditions. A polymeric column was used to separate various enkephalin analogs, bradykinin, and oxytocin using a carbon dioxide-based mobile phase with either an ethanol or a 2-methoxyethanol modifier. The role of the modifier was found to be secondary to that of the mobile phase additive. As progressively stronger acidic mobile phase additives were used, the peak profiles of the various polypeptides improved and retention decreased. Heptadecafluorooctanesulfonic acid was found to be the most useful additive for these types of solutes under near-critical conditions, while the potassium salt of heptadecafluorooctanesulfonic acid failed to elute any of the polypeptides. At low temperatures, pressure gradients with a carbon dioxide/ethanol/heptadecafluorooctanesulfonic acid ternary mobile phase produced reasonably good peak profiles with the polymeric column.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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