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  • Articles  (191)
  • Gas chromatography  (181)
  • wheat
  • Springer  (191)
  • 1990-1994  (170)
  • 1975-1979  (21)
  • Chemistry and Pharmacology  (191)
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  • Articles  (191)
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  • 1
    Electronic Resource
    Electronic Resource
    Bromierte Diphenylether — eine entscheidende Zwischenstufe auf dem Weg zu synthetischen Schmierstoffen (1992)
    Springer
    Monatshefte für Chemie 123 (1992), S. 1153-1161 
    Details
    ISSN: 1434-4475
    Keywords: Gas chromatography ; Polyphenyl ethers ; Lubricants, synthetic
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The described synthesis of synthetic lubricants based on polyphenyl ethers requires an analytical characterization of the isomerization step, which is important to the process optimization. The separation of the intermediates succeeds with gas chromatography; the isomers are determined using a retention index system. The obtained results are compared with the composition of the final product, which was investigated by HPLC analysis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00808278
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  • 2
    Electronic Resource
    Electronic Resource
    Location of chromosomal control of GA-induced enzyme release by distal half-grains of wheat (1977)
    Springer
    Biochemical genetics 15 (1977), S. 47-57 
    Details
    ISSN: 1573-4927
    Keywords: wheat ; chromosomes ; gibberellin ; enzymes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The three enzymes, α-amylase, peroxidase, and acid phosphatase, are among those released by the aleurone of bread wheat, Triticum aestivum, as a direct response to gibberellins (GA) from the embryo during germination. Aneuploid genotypes are used to investigate the chromosomal location, nature, and extent of genetic control of the release of these enzymes in endosperms after induction by exogenous GA. Ditelosomics demonstrate the effect of removal of known chromosome arms, and tetrasomics show the effect of duplication of chromosome pairs. Quantitative analysis demonstrates complex control systems over and above those previously found using zymogram techniques. For α-amylase, chromosome arms with net promoter effects and chromosomes with net inhibitor effects were found. These effects were not chromosome-dosage responsive, unlike the promoter-inhibitor system found for acid phosphatase control. Peroxidase levels in the endosperms were generally high in both types of aneuploids. With one exception, all chromosomes showing involvement as ditelosomics showed a similar effect as tetrasomics, indicating that in the euploid a balanced state restricting, rather than promoting, peroxidase levels existed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00484547
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  • 3
    Electronic Resource
    Electronic Resource
    Allelochemicals in soil from no-tillage versus conventional-tillage wheat (Triticum aestivum) fields (1990)
    Springer
    Journal of chemical ecology 16 (1990), S. 2277-2289 
    Details
    ISSN: 1573-1561
    Keywords: Allelochemicals ; no-tillage ; conventional-tillage ; soils ; wheat ; Triticum aestivum ; mass spectrometry ; Petri-dish bioassay ; fatty acids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Putative allelochemicals found in the soil of no-tillage and conventional-tillage wheat plots near Stillwater, Oklahoma, were obtained by a mild alkaline aqueous extraction procedure, bioassayed to determine their biological activity, purified, and analyzed with a capillary gas chromatography-mass spectrometry-data analysis system. The most significant inhibition was found in bioassays of extracts from soil collected immediately after harvest in June, July, and August. No-tillage soils produced significant inhibition during the rest of the year also. Mass spectrometry showed fatty acids as the most abundant compounds. However, when bioassayed authentic samples of the five free fatty acids showed no significant biological activity toward wheat.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01026937
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  • 4
    Electronic Resource
    Electronic Resource
    Allelopathic activity in wheat-conventional and wheat-no-till soils: Development of soil extract bioassays (1992)
    Springer
    Journal of chemical ecology 18 (1992), S. 2191-2221 
    Details
    ISSN: 1573-1561
    Keywords: Cover crops ; wheat ; Triticum aestivum ; soybean ; Glycine max ; soil extracts ; germination bioassays ; phenolic acids ; hydroxamic acids ; allelopathy ; slope analysis ; ivy-leaved morning glory ; Ipomoea hederacea ; crimson clover ; Trifolium incarnalum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The primary objective of this research was to determine if soil extracts could be used directly in bioassays for the detection of allelopathic activity. Here we describe: (1) a way to estimate levels of allelopathic compounds in soil; (2) how pH, solute potential, and/or ion content of extracts may modify the action of allelopathic compounds on germination and radicle and hypocotyl length of crimson clover (Trifolium incarnatum L.) and ivyleaved morning glory (Ipomoea hederacea L. Jacquin.); and (3) how biological activity of soil extracts may be determined. A water-autoclave extraction procedure was chosen over the immediate-water and 5-hr EDTA extraction procedures, because the autoclave procedure was effective in extracting solution and reversibly bound ferulic acid as well as phenolic acids from wheat debris. The resulting soil extracts were used directly in germination bioassays. A mixture of phenolic acids similar to that obtained from wheat-no-till soils did not affect germination of clover or morning glory and radicle and hypocotyl length of morning glory. The mixture did, however, reduce radicle and hypocotyl length of clover. Individual phenolic acids also did not inhibit germination, but did reduce radicle and hypocotyl length of both species. 6-MBOA (6-methoxy-2,3-benzoxazolinone), a conversion product of 2-o-glucosyl-7-methoxy-1,4-benzoxazin-3-one, a hydroxamic acid in living wheat plants, inhibited germination and radicle and hypocotyl length of clover and morning glory. 6-MBOA, however, was not detected in wheat debris, stubble, or soil extracts. Total phenolic acids (FC) in extracts were determined with Folin and Ciocalteu's phenol reagent. Levels of FC in wheat-conventionaltill soil extracts were not related to germination or radicle and hypocotyl length of either species. Levels of FC in wheat-no-till soil extracts were also not related to germination of clover or morning glory, but were inversely related to radicle and hypocotyl length of clover and morning glory. FC values, solute potential, and acidity of wheat-no-till soil extracts appeared to be independent (additive) in action on clover radicle and hypocotyl length. Radicle and hypocotyl length of clover was inversely related to increasing FC and solute potential and directly related to decreasing acidity. Biological activity of extracts was determined best from slopes of radicle and hypocotyl length obtained from bioassays of extract dilutions. Thus, data derived from the water-autoclave extraction procedure, FC analysis, and slope analysis for extract activity in conjunction with data on extract pH and solute potential can be used to estimate allelopathic activity of wheat-no-till soils
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00984946
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  • 5
    Electronic Resource
    Electronic Resource
    Genetic aspects of wheat gliadin proteins (1978)
    Springer
    Biochemical genetics 16 (1978), S. 831-853 
    Details
    ISSN: 1573-4927
    Keywords: Triticum aestivum L. ; wheat ; storage proteins ; gliadins ; gel electrophoresis ; endosperm ; dominant genes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Inheritance of gliadin components unique to three different varieties of common wheat (Triticum aestivum L.) was studied in F1 and F2 seeds of intervarietal crosses using protein patterns obtained by polyacrylamide gel electrophoresis in aluminum lactate buffer (pH 3.2). The patterns of F1 seeds of the crosses Cheyenne × Justin and INIA 66R × Justin evidenced all the bands present in the patterns of the parents; band intensities reflected gene dosage levels dependent on whether the contributing parent was maternal or paternal in accordance with the triploid nature of endosperm tissue. Most of the gliadin components examined segregated in accordance with control by a single dominant gene, but in two instances single bands in the one-dimensional electrophoretic patterns segregated in the F2 as expected if controlled by two genes. A method of two-dimensional electrophoresis was developed that resolved these apparently single bands into two components each, which could segregate independently. Linkage analysis provided evidence of codominant alleles and closely linked genes coding for gliadin protein components in both coupling and repulsion situations. The gliadin protein components seem to be coded for by clusters of genes located on chromosomes of homoeologous groups 1 and 6 in hexaploid wheats.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00484739
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  • 6
    Electronic Resource
    Electronic Resource
    The amino acid sequence of a protein from wheat kernel closely related to proteins involved in the mechanisms of plant defence (1993)
    Springer
    The protein journal 12 (1993), S. 379-386 
    Details
    ISSN: 1573-4943
    Keywords: Amino acid sequence ; wheat ; wounding ; plant defence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The amino acid sequence of wheatwin1, a monomeric protein of 125 residues isolated from wheat kernel (variety S. Pastore), is reported. Wheatwin1 is highly homologous (95%) to barwin, a protein from barley seed, which was shown to be related to the C-terminal domain of two proteins encoded by the wound-induced geneswin1 andwin2 in potato and to a protein encoded by the same domain of the hevein gene (hev1) in rubber tree. Similarly to barwin, wheatwin1 contains six cysteine residues all linked in disulfide bridges and the N-terminal residue is pyroglutamate. Moreover, structural studies performed on wheatwin1 andwin1 protein by predictive methods demonstrated that these proteins and barwin are closely related in the secondary structure also. The high level of homology found with the product ofwin1,win2, andhev1 genes strongly suggests that barwin and wheatwin1 play a common role in the mechanism of plant defence.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01025037
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  • 7
    Electronic Resource
    Electronic Resource
    The amino acid sequence and reactive site of a single-headed trypsin inhibitor from wheat endosperm (1994)
    Springer
    The protein journal 13 (1994), S. 187-194 
    Details
    ISSN: 1573-4943
    Keywords: Trypsin inhibitor ; wheat ; primary structure ; reactive site ; Bowman-Birk
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The sequence of a trypsin inhibitor, isolated from wheat endosperm, is reported. The primary structure was obtained by automatic sequence analysis of the S-alkylated protein and of purified peptides derived from chemical cleavage by cyanogen bromide and digestion withStaphylococcus aureus V8 protease. This protein, named wheat trypsin inhibitor (WTI), which is comprised of a total of 71 amino acid residues, has 12 cysteines, all involved in disulfide bridges. The primary site of interaction (reactive site) with bovine trypsin has been identified as the dipeptide arginyl-methionyl at positions 19 and 20. WTI has a high degree of sequence identity with a number of serine proteinase inhibitors isolated from both cereal and leguminous plants. On the basis of the findings presented, this protein has been classified as a single-headed trypsin inhibitor of Bowman-Birk type.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01891977
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  • 8
    Electronic Resource
    Electronic Resource
    Kubische Berechnung der Retentionsindices ohne Kenntnis der Totzeit tm (1979)
    Springer
    Chromatographia 12 (1979), S. 790-798 
    Details
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Dead-time ; log ts=f(C) ; Retention index calculation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung In der vorliegenden Arbeit wird eine Methode zur Retentionsindex-Bestimmung beschrieben, die von einem kubischen Zusammenhang zwischen Bruttoretentionszeit-Differenzen der Referenzhomologen und der Kohlenstoffzahl ausgeht. Hieraus ergeben sich direkt die Nettoretentionszeiten. Der Fehler der Totzeitbestimmung entfällt bei dieser Methode. Mit den so gewonnenen Nettoretentionszeiten erhält man über einen kubischen Zusammenhang zwischen 1g ts=f(C) die Retentionsindices. Extrapolationen und Interpolationen sind über 300 Retentionsindexeinheiten mit einem mittleren Fehler von ±0,02 Retentionsindexeinheiten möglich. Das Verfahren bietet sich für eine automatische Berechnung der I-Werte mittels on-line-Datenverarbeitung an.
    Notes: Summary The method for the calculation of retention indices described here is based on a third order relationship between the logarithm of differences of unadjusted retention times of homologues and the carbon number. From this adjusted retention times are directly calculated. A determination of the dead-time is not necessary thus avoiding the errors connected with this factor. A cubic equation for the logarithm of the adjusted retention time lg ts as a function of carbon number Cn is used for the retention index calculation. Extrapolations and interpolations can be done over a range of 300 index units with an average deviation of ±0.02 i.u.. The method offers the possibility of an automated on-line calculation of retention indices by computer merely on the basis of unadjusted retention times.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02260660
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  • 9
    Electronic Resource
    Electronic Resource
    GC-MS-SIM quantitation of amantadine in biological samples (1979)
    Springer
    Chromatographia 12 (1979), S. 523-526 
    Details
    ISSN: 1612-1112
    Keywords: Amantadine ; Gas chromatography ; Gas chromatography-mass spectrometry ; Biochemical analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A simple, selective and sensitive method for the quantitation of amantadine in biological samples is described. After extraction from biological samples using a two-step procedure, amantadine is quantitatively converted into its isothiocyanate (NCS) derivative by treatment with carbon disulfide and then determined quantitatively using isobaric compounds, p-methoxyphenyl-ethylamine-NCS or N-acetylamantadine as external standards. The applicability of this method is illustrated by determining plasma levels of amantadine for pharmacokinetic studies and levels in dialysate samples of amantadine treated patients who were on dialysis machines.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02265466
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  • 10
    Electronic Resource
    Electronic Resource
    A relationship between the retention indices on nematic and isotropic phases and the shape of polycyclic aromatic hydrocarbons (1979)
    Springer
    Chromatographia 12 (1979), S. 595-599 
    Details
    ISSN: 1612-1112
    Keywords: Polynuclear aromatic hydrocarbons ; Retention index ; Gas chromatography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An equation has been derived allowing to predict retention index values on nematic phases from computable parameters and sizes of the molecules of polycyclic aromatic hydrocarbons. Another equation, which has also been derived, allows to determine the shape parameter of a molecule from chromatographic data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02265531
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  • 11
    Electronic Resource
    Electronic Resource
    Abnormalities in spinal fluid detected by gas liquid chromatography in meningitis patients (1979)
    Springer
    Chromatographia 12 (1979), S. 583-586 
    Details
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Clinical analysis ; Meningitis detection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Gas liquid chromatography was performed on cerebrospinal fluid from cases of purulent meningitis, and control subject. A relatively constant pattern of peaks was obtained in all samples. Four constant peaks in the chromatogram frequently showed a significant increase in purulent meningitis but not in aseptic meningitis or control cases. There was a gradual return to normal levels during clinical improvement, usually within 5–6 days of appropriate therapy. In one case of recurrent meningitis, an increase in the peaks was noted with relapse. Identification of the compounds represented by these peaks may provide further information regarding diagnosis, prognosis and pathogenesis of meningitis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02265529
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  • 12
    Electronic Resource
    Electronic Resource
    Capillary gas chromatography of some triglycerides in cheese using programmed-temperature injection (1993)
    Springer
    Chromatographia 35 (1993), S. 649-652 
    Details
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Triglycerides in cheese ; Programme temperature (PTV) injection ; Silica capillary columns
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A rapid gas chromatographic method for the analysis of triglycerides in cheese on a capillary column with a programmed temperature vaporizer has been developed. Fat were extracted with hexane to dryness. The reproducibility of the method was assessed and the coefficient of variation for the total triglycerides was 2.50%. Recovery of individual triglycerides ranged between 87 to 105%.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02267931
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  • 13
    Electronic Resource
    Electronic Resource
    Determination of sodium dodecylbenzene sulfonate using several internal standards by multivariate analysis of curiepoint, pyrolysis gas chromatography (1993)
    Springer
    Chromatographia 35 (1993), S. 643-648 
    Details
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Curie-point pyrolysis ; Multivariate analysis ; Sodium dodecylbenzene sulfonate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Multivariate analysis can be applied to quantitative analysis of sodium dodecylbenzene sulfonate (DBS) by pyrolysis gas chromatography. The pyrograms obtained from mixtures of DBS and polyoxyethylene lauryl ether (PEG) were normalized for the peak heights and areas of several internal standards which appeared in every pyrogram, against the characteristics peaks for DBS and PEG. This normalization method gave smaller experimental errors than when using one internal standard. The normalization values were used for cluster analysis unchanged. The values were calculated correlation coefficients and principal component analysis was performed using 11 data base and a set of sample data simultaneously. One calibration curve was calculated from the principal component scores. The DBS content of a sample was obtained from the calibration curve. Calculated values were in fair agreement with theoretical values.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02267930
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  • 14
    Electronic Resource
    Electronic Resource
    Determination of pesticides in soil samples by solid phase extraction disks (1993)
    Springer
    Chromatographia 36 (1993), S. 187-190 
    Details
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Solid-phase extraction disks ; Pesticides ; Soil analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A systematic study comparing the methodology and analytical results obtained in an investigation of seven pesticide residues (Molinate, Atrazine, Carbofuran, Pirimicarb, Prometryn, Malathion and Tetrachlorvinphos) in soil samples is reported. Solid-phase extraction (SPE) using glass columns and 47 mm disks of octyl and octadecyl-bonded silica was used in the pesticide analysis. The best extraction efficiency and clearest extracts are obtained with C8 disks. The analyses were carried out by capillary gas chromatography with nitrogen and phosphorus detection. Recovery experiments were performed at ppb levels in spiked soil samples. The average recoveries of the compounds were 53–77%. Detection limits are between 5 and 30 ng g−1 based on 5 g moist soil sample. The method was validated by comparing it with conventional liquid-liquid extraction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02263860
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  • 15
    Electronic Resource
    Electronic Resource
    Thermodynamic properties at infinite dilution of several solutes in ethers by gas-liquid chromatography (1992)
    Springer
    Chromatographia 33 (1992), S. 41-44 
    Details
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Activity coefficients ; 18-Crown-6-ether and tetraethyleneglycol dimethyl ether ; Thermodynamic properties
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The thermodynamic properties of different solutes at infinite dilution have been determined at 323.15 K. Deviations from ideality are discussed in terms of different contributions. The activity coefficients are compared with the calculated values by the one group contribution method.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02276849
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  • 16
    Electronic Resource
    Electronic Resource
    Diesel fuel derived from vegetable oils, V [1]: Gas chromatographic determination of free glycerol in transesterified vegetable oils (1993)
    Springer
    Chromatographia 37 (1993), S. 623-626 
    Details
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Fatty acid methyl esters ; Diesel fuel substitute ; Glycerol
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A GC method for the determination of free glycerol in vegetable oil methyl esters used as diesel fuel is described. The sample preparation includes dissolving in dimethylformamide, silylation with bistrimethylsilyltrifluoroacetamide (BSTFA) and separation on a methyl silicone capillary column using either FID or MS detection. The recovery was tested using standard samples containing known amounts of glycerol. The results of the analysis of different samples were compared with those obtained by enzymatic determination. The method described offers a far more sensitive and quick determination of free glycerol compared to other methods.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02274113
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  • 17
    Electronic Resource
    Electronic Resource
    Analysis of trace levels of trichothecene mycotoxins in Austrian cereals by gas chromatography with electron capture detection (1993)
    Springer
    Chromatographia 37 (1993), S. 191-201 
    Details
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Electron capture detection ; Trichothecenes ; Cereal grain
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Various analytical methods developed for trichothecene determination, including TLC, HPLC, GC, supercritical fluid chromatography (SFC) and enzyme immuno assay (EIA) are reviewed. In addition a new method is described for the simultaneous determination of the trichothecene mycotoxins deoxynivalenol (DON), nivalenol (NIV), 3-acetyldeoxynivalenol (3-ADON), diacetoxyscirpenol (DAS), T-2 toxin (T-2), HT-2 toxin (HT-2) and T-2 triol (TRIOL), in Austrian wheat and corn samples by GC-ECD. A clean-up procedure has been developed using a combination of liquid-liquid and liquid-solid extraction. Trichothecenes were detected as their heptafluorobuturyl esters or alternatively as trimethylsilyl ethers (only sensitive for deoxynivalenol and nivalenol) using nandrolone or chloramphenicol as internal standard. Four derivatization techniques using HFBI, HFBA+DMAP on polystyrene, TMSI and TMSI+BSA+TMCS have been studied and the advantages and disadvantages of each are discussed. Quantification of trichothecenes from 10 to 1000 ppb in cereals could be accomplished routinely.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02275860
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  • 18
    Electronic Resource
    Electronic Resource
    Unified retention indices of alkylbenzenes on OV-101 and SE-30 (1993)
    Springer
    Chromatographia 37 (1993), S. 215-217 
    Details
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Unified retention indices ; Dimethylsiloxane stationary phases
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Gas chromatographic, unified retention-indices of 56 alkylbenzenes up to C15 on dimethylsiloxane OV-101 and SE-30 stationary phases are given. These values agree well with the corresponding experimental values used in the statistical treatment of the experimental data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02275863
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  • 19
    Electronic Resource
    Electronic Resource
    Analysis of reaction by-products in ethylene oligomers by capillary gas chromatography (1993)
    Springer
    Chromatographia 37 (1993), S. 259-263 
    Details
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Quantitative analysis ; Ethylene oligomer by-products ; n-Alkanes, n-alkenes and 2-alkyl-1-alkenes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A gas chromatographic method using temperature-programmed poly-dimethylsiloxane OV-101 and poly(pheny ether) (5 rings) capillary columns was developed to separate and quantify the reaction by-products in ethylene oligomers. It was found that the content of 2-alkyl-1-alkenes, 2-alkenes and n-alkanes in the C8−C18 α-olefin fractions amounts to 29, 10 and 2.6% respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02278630
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  • 20
    Electronic Resource
    Electronic Resource
    Gas chromatographic analysis of organic solvent mixtures on capillary columns of different polarity (1993)
    Springer
    Chromatographia 37 (1993), S. 211-214 
    Details
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Organic solvents ; Routine analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A gas chromatographic method for the analysis of organic solvents in chemical products is described. The analysis is performed by the use of a polar column, Supelcowax 10, and a non-polar column CP-Sil-5CB. Samples containing a non-volatile matrix or water were analysed by headspace analysis. The identification of the solvents in a sample, based on GC retention times on one column, is confirmed by GC of the sample on the second column. The method has been found to be suitable for the routine analysis of solvent mixtures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02275862
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  • 21
    Electronic Resource
    Electronic Resource
    Calculation of retention indices and peak widths in temperature programmed gas-liquid chromatography (1993)
    Springer
    Chromatographia 37 (1993), S. 264-270 
    Details
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Temperature programmed ; Peak widths ; Polynomial interpolation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Isothermal chromatographic measurements lead directly to ΔH v o and A (entropy term) of solutes, and three constants of an empirical relationship between peak width and column temperature. From the thermodynamic parameters ΔH v o and A retention temperatures have been computed by means of a theoretical model including temperature dependence of carrier gas viscosity, and subsequently retention times; programmed retention indices have been determined by linear and polynomial interpolations. By substituting the value of the calculated retention temperature in the above-mentioned relationship, peak width at half-height for a linear temperature may be estimated. Predicted retentions correlate with observed data, with a P-value ≤0.01; simulation accuracy is generally 6–10% for peak widths. Retention indices of some organochlorine species, separated on an OV-101 capillary column, may differ by as much as 26 units depending on the method of calculation. Polynomial-calculated indices are more consistent with the retention index scheme, and have smaller standard deviations and better constancy at different heating rates.
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    URL: http://dx.doi.org/10.1007/BF02278631
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  • 22
    Electronic Resource
    Electronic Resource
    The structure and chromatographic properties of poly(ethylene glycol) 20M layer on the surface of a diatomaceous earth type support (1993)
    Springer
    Chromatographia 37 (1993), S. 444-450 
    Details
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Inverse gas chromatography ; Poly(ethylene glycol) 20M ; Retention mechanisms
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The properties of poly(ethylene glycol) 20M (PEG 20M) coated on the hydroxylated surface of Chromaton N AW were investigated by inverse gas chromatography. It was found that the solid form of PEG 20M exhibits partition as the retention mechanism even below its melting range. The contribution of adsorption to the specific retention volume was also determined. It was demonstrated that inverse gas chromatography establishes the existence of a polymer surface layer but precise determination of its thickness is difficult. The limitation of the applicability of inverse gas chromatography results from the structure of the investigated surface layer which is thin and not coherent so that solute molecules can penetrate it.
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    URL: http://dx.doi.org/10.1007/BF02272262
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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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    URL: http://dx.doi.org/10.1007/BF02275888
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  • 24
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    2,6-Di-O-pentyl-3-O-propionyl-γ-cyclodextrin as an enantiomeric stationary phase for capillary gas chromatography (1994)
    Springer
    Chromatographia 38 (1994), S. 22-28 
    Details
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Chiral separation ; Capillary column ; 2,6-Di-O-pentyl-3-O-propionyl-γ-cyclodextrin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary 2,6-Di-O-pentyl-3-O-propionyl-γ-cyclodextrin has been synthesized and used for enantiomer separation in capillary gas chromatography. Experimental results showed that the stationary phase has good enantiomer selectivity toward amino acids, amines, alcohols, diols, epoxides, and lactones,etc. 2,6-Di-O-pentyl-3-O-propionyl-γ-cyclodextrin has good thermal stability: the highest recommended temperature isca 170°C.
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    URL: http://dx.doi.org/10.1007/BF02275722
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    Determination of pentachlorophenol residues in wine and corks by solvent extraction methodology and specific gas chromatography detection (1994)
    Springer
    Chromatographia 38 (1994), S. 147-150 
    Details
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Pentachlorophenol residues ; Off-flavours ; Wines and corks ; Electrolytic conductivity detector/mass spectrometry ; detectors
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A gas chromatographic methodology with selective detection is presented for the analysis in wines and corks of pentachlorophenol residues, which are suspected to be the most likely precursors of some off-flavours described in several wine samples. After derivatisation, pentachlorophenol acetate residues were monitored by electrolytic conductivity detection and/or mass spectrometric detection in the selective ion mode at m/z 264 and 266. Recoveries varied from 80 to 96% for wine samples fortified with 5 to 100 μg l−1 and from 83 to 91% for corks (fortified at 25 to 100 μg kg−1). The proposed methodology allowed for a determination limit of μg l−1 for wine and 10 μg kg−1 for corks.
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    URL: http://dx.doi.org/10.1007/BF02290327
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    Capillary gas chromatography of plant tissues and soil phenolic acids (1994)
    Springer
    Chromatographia 38 (1994), S. 475-478 
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    ISSN: 1612-1112
    Keywords: Gas chromatography ; Phenolic acids ; Olive and elm tree tissues ; Soil phenolics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A method for the separation of phenolic acids along with shikimic and quinic acids by means of capillary gas chromatography is described and discussed. The method involves the previous derivatization of the acids to trimethylsilyl derivatives and it has been applied to the separation of acids extracted from olive leaves and roots, elm leaves and a soil A horizon. Quite good results were achieved both from qualitative and quantitative points of view. Qualitative differences have been pointed out in the phenolic acid composition of two olive cultivars and between leaves and roots of the same cultivar; also two elm species can be discriminated on the basis of the phenolic acid content.
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    URL: http://dx.doi.org/10.1007/BF02269839
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    Characterization of methacrylic ester of p, p′-dihydroxydiphenylpropane diglicydyl ether-divinylbenzene porous copolymers for GC (1994)
    Springer
    Chromatographia 38 (1994), S. 643-648 
    Details
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Porous polymer stationary phase ; Selectivity studies
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The behaviour of GC columns packed with the copolymer of methacrylic ester of p,p'-dihydroxydiphenylpropane diglicydyl ether and divinylbenzene was studied. Selectivity studies were made for three polymer samples of different molar ratio of monomers. To determine the selectivities of these copolymers retention indices for seven test compounds in comparison to those obtained on Porapak Q are calculated. Additionally, the efficiency of porous polymer purification was studied by a SFE-GC-MS technique.
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    URL: http://dx.doi.org/10.1007/BF02277169
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    Enantiomeric separation of amphetamine and methamphetamine by capillary gas chromatography (1994)
    Springer
    Chromatographia 38 (1994), S. 595-598 
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    ISSN: 1612-1112
    Keywords: Gas chromatography ; Chiral / enantiomeric separation ; Amphetamine ; Methamphetamine ; Cyclodextrin-derivatized phases
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Enantiomeric separation of amphetamine and methamphetamine as achiral derivatives on 2,6-di-O-pentyl-3-O-trifluoroacetyl-β-cyclodextrin, 2,6-di-O-pentyl-3-O-trifluoroacetyl-γ-cyclodextrin and 2,6-di-O-pentyl-3-O-propionyl-γ-cyclodextrin stationary phase in capillary gas chromatography is described. Trifluoroacetic anhydride and acetic anhydride were used as derivatizing reagents. Excellent precision was obtained for concentrations down to 0.1% / e.e. On 2,6-di-O-pentyl-3-O-propionyl-γ-cyclodextrin the elution order of R,S-amphetamine was reversed when the derivatizing reagent was changed but could not be reversed on any of the other phase types.
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    URL: http://dx.doi.org/10.1007/BF02277160
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    Rapid magnetic particle-based ELISA assay compared with gas chromatography-nitrogen phosphorus detection for determining atrazine in freeze-dried water samples (1994)
    Springer
    Chromatographia 38 (1994), S. 633-636 
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    ISSN: 1612-1112
    Keywords: Gas chromatography ; Nitrogen phosphorus detection ; Atrazine and simazine ; Freeze-dried water analysis ; ELISA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The determination of atrazine in freeze-dried water samples containing simazine, 0.6% glycine as stabilizer and other pesticides has been compared using three different techniques: (i) direct rapid-magnetic particlebased ELISA, (ii) dichloromethane liquid-liquid extraction (LLE) and Florisil column clean-up prior to ELISA determination and (iii) LLE, Florisil column clean-up and gas chroamtography with nitrogen phosphorus detection (GC-NPD). The methodology developed in this paper has shown the advantages of the introduction of a clean-up step prior to ELISA determination and its correlation with GC-NPD determinations. Atrazine could be determined at levels between 0.1 to 5 μg l−1 in water smaples using the different methods described in this paper. The crossreactivity problems found in the ELISA test associated with the presence of simazine are also discussed.
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    An improved gas chromatographic assay for spectinomycin hydrochloride (1994)
    Springer
    Chromatographia 39 (1994), S. 71-73 
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    ISSN: 1612-1112
    Keywords: Gas chromatography ; Spectinomycin ; Silylation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A gas chromatographic assay for spectinomycin hydrochloride is described. The method is based on that prescribed by the United States Pharmacopeia (USP XXII). The method involves silylation of spectinomycin hydrochloride; phenazone is used as an internal standard. Spectinomycin and phenazone have adequate stability under the prescribed conditions. The stationary phase is 3% OV-17 on Gaschrom Q 100–120 mesh. The selectivity of the proposed method is better than that of the GLC method described in the USP XXII.
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    Improved gas chromatographic method for the determination of the individual free fatty acids in cheese using a capillary column and a PTV injector (1992)
    Springer
    Chromatographia 33 (1992), S. 351-355 
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    ISSN: 1612-1112
    Keywords: Gas chromatography ; Free fatty acids ; Cheese ; Programmed temperature vaporizer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A gas chromatographic method with a capillary column and a programmed temperature vaporizer injector has been used to analyze the individual free fatty acids in cheese. The lipids were extracted from an acidified cheese slurry with diethyl ether and treated with tetramethylamonium hydroxide (TMAH) to convert the free fatty acids to tetramethylammonium soaps (TMA-soaps), which were subsequently pyrolyzed to methyl esters in the injector. Carrying out injection at the initial column temperature resulted in lower dispersion of the results, but the solvent front prevented quantitative determination of butyric and caproic acids, and an injector temperature of 300°C was therefore employed. Under the conditions tested, trimethylamine (tma) flash-off did not affect the determinations. The accuracy of the method improved at higher free fatty acid contents (coefficient of variation of 0.53% for a total free fatty acid content of 9000 mg/kg as opposed to 7.0% for a total free fatty acid content of 1400 mg/kg). The recovery rate for individual free fatty acids ranged between 91 and 103%.
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    URL: http://dx.doi.org/10.1007/BF02275917
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    Enantiomer separation of side-chain fluorinated alkylbenzenes by capillary gas chromatography on cyclodextrin phases (1994)
    Springer
    Chromatographia 39 (1994), S. 192-199 
    Details
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Enantiomer separation ; Permethylated cyclodextrin stationary phases ; Side-chain fluorinated alkylbenzenes ; Thermodynamic data
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The separation of racemic side-chain fluorinated alkylbenzenes and bromofluorinated analogues by capillary gas chromatography using permethylated α, β and γ-cyclodextrins dissolved in polysiloxanes of different polarity as stationary phases is described. The influence of the achiral polysiloxane matrices on the separation of enantiomers is discussed in the light of the results obtained with the different phases. For a part of the tested compounds thermodynamic data are determined which describe the interaction of enantiomers with the stationary phase. The mechanism of separation is discussed on this basis and by comparison with data for structurally similar compounds.
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    Ruggedness testing of gas chromatographic method for residual solvents in pharmaceutical substances (1994)
    Springer
    Chromatographia 39 (1994), S. 355-362 
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    ISSN: 1612-1112
    Keywords: Gas chromatography ; Method validation ; Reggedness test ; Residual solvents
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Ruggedness testing is performed on a gas chromatographic method for the quantitative determination of residual solvents in steroids. Eight experimental variables or factors which were expected to influence the quantitative results were selected. These factors were divided into two independent groups, i.e. four factors related to the injection process and four factors related to separation and detection. In order to determine interaction between factors and quadratic effects, a central composite design was selected for the set-up of the experiments. Because in the method an internal standard is used, relative peak area was used as response. A deviation of up to 2.5% per factor for the quantitative results was regarded as acceptable. Other responses studied are related to the system suitability. Observed main, quadratic and interaction effects were translated into rugged intervals of the experimental variables by graphical presentation. It was found that besides main effects significant interaction effects were present, for example between the temperature of the injector and the split-flow. Interaction effects can easily result in the reduction of the rugged intervals by a factor of 2. The calculated rugged intervals were compared with the precision of the instrument or factor settings in order to estimate the ruggedness of the factors. Eventually, the maximum effect of the variation in the instrument settings on the quantitative results regarding the precision of the factor settings was found to be only 2.2%. Overall, the method proved to be rugged for most factors, except for the split-flow of the injector for which the method was only rugged to a limited extent.
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    Effect of ester molecular structure and column temperature on the retention of eight esters in gas chromatography (1994)
    Springer
    Chromatographia 39 (1994), S. 438-442 
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    ISSN: 1612-1112
    Keywords: Gas chromatography ; Retention/structure and retention/temperature ; relationships ; Experimental design ; Enthalpy-entropy compensation ; para-Hydroxy benzoic esters
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An experimental design has been used to study the effect of column temperature on the gas chromatographic retention of eightpara-hydroxy benzoic esters. A rapid procedure has been developed to reduce the number of experiments compared with traditional methods. Capacity factors were determined and the enthalpy and entropy of transfer from the mobile phase to the stationary phase, ΔHo and ΔSo, respectively, were calculated using the linear Van't Hoff equation (dependence of ln k′ on 1/T). A retention prediction system (RPS) for these compounds in GC was investigated. The molecular connectivity index was used to describe the quantitative structure relationships. Enthalpy — entropy compensation revealed that the mechanism was similar for all the compounds studied.
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    Optimization of selectivity by tuning column temperatures of identical capillary columns in series in a dual-oven GC system (1992)
    Springer
    Chromatographia 33 (1992), S. 463-466 
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    ISSN: 1612-1112
    Keywords: Gas chromatography ; coupling capillary columns ; Selectivity optimization ; Dual oven tuning
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A computer-assisted procedure is presented for optimization of selectivity of tandem capillary columns with the same apolar (SE-54) stationary phase by varying column temperatures. The procedure is based on a threshold criterion calculated from the required resolution factor in which the separating power of the columns as a function of temperature is incorporated. The validity of the procedure has been verified by the analysis of a sample containing 33 hydrocarbons on two 31 m×0.3 mm i.d. SE-54 capillary columns coupled in series and by varying the temperatures of both columns in the range 60–100°C. At the optimum temperatures (70°C for the first and 92°C for the second column) 26 compounds were resolved equal to or better than Rji=1.00 in 22.8 min.
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    Gas chromatographic study of the adsorption of methyl iodide on several types of carbons (1992)
    Springer
    Chromatographia 34 (1992), S. 568-572 
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    ISSN: 1612-1112
    Keywords: Gas chromatography ; Carbon adsorbents ; Methyliodide ; Effect of KI on adsorption ; Thermodynamics of adsorption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Gas chromatography has been used to measure the adsorption at zero surface coverage of methyl iodide on different types of carbon. The effect on the adsorption of methyl iodide of adding potassium iodide to the carbon samples was also studied. The differences observed in the behaviour of these samples for the adsorption of methyl iodide are explained on the basis of the textural characteristics of the samples. Thermodynamic functions of adsorption of methyl iodide at zero surface coverage are obtained.
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    Direct determination of partition coefficients of volatile liquids between oil and gas by gas chromatography and its use in QSAR analysis (1992)
    Springer
    Chromatographia 34 (1992), S. 601-606 
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    ISSN: 1612-1112
    Keywords: Gas chromatography ; Partition coefficients ; Olive oil-nitrogen partition ; QSAR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A gas-liquid chromatographic method has been used for direct determination of the partition coefficients (KD) of alcohols, ethers and ketones between olive oil and nitrogen. Olive oil was characterised as a stationary phase for gas chromatography. The differential molar enthalpies of solution were also calculated from retention data. Correlations between log KD for olive oil — nitrogen and molecular connectivity indices, differential molar enthalpies of solution, biological activity and partition coefficients for blood-air were obtained.
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    Fast derivatization and GC analysis of phenolic acids (1992)
    Springer
    Chromatographia 34 (1992), S. 621-626 
    Details
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Methyl and ethyl chloroformate ; Derivatization in the presence of water ; Alkyl and alkoxycarbonyl esters
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Phenolic acids, i.e. benzoic, phenylacetic, phenylpropenoic (cinnamic), phenylglycolic (mandelic), phenylpropionic and their variously substituted forms can be converted almost instantly to derivatives amenable to GC by treatment with methyl or ethyl chloroformate. The reaction, catalyzed by pyridine, proceeds even in the presence of water. The carboxylic group is esterified to the corresponding alkyl ester but even the alkoxycarbonyl ester (mixed anhydride) can be produced by altering the reaction conditions. Hydroxyl groups on the benzene ring or adjacent to the carboxylic group are converted to the alkoxycarbonyl ethers. Benzoic acid and some of its substitutents, unlike the other aromatic acids, shows a tendency to mixed anhydride formation even under conditions used for alkyl esters. A well deactivated capillary column with a thin film of stationary phase of low polarity enables even the mixed anhydrides to be analyzed successfully.
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    The GC separation of C2-naphthalene isomers using cyclodextrins and crown ethers (1992)
    Springer
    Chromatographia 34 (1992), S. 163-165 
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    ISSN: 1612-1112
    Keywords: Gas chromatography ; Cyclodextrins ; Crown ethers ; Dimethylnaphthalene isomer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The twelve structural C2 isomers of naphthalene are resolved on a single capillary column using α, β, or γ cyclodextrin as the stationary phase. A change in elution order is seen upon going from α to β and then γ cyclodextrin which can be related to the size of the cyclodextrin cavity and the stereochemical fit of the isomer. A crown-ether column and a liquid-crystal column were found to be unable to separate all of the isomers.
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    Determination of partition coefficients by automatic equilibrium headspace gas chromatography by vapor phase calibration (1992)
    Springer
    Chromatographia 34 (1992), S. 235-240 
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    ISSN: 1612-1112
    Keywords: Gas chromatography ; Headspace sampling ; Partition coefficients ; Multiple headspace extraction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Equilibrium headspace gas chromatography has been applied to the determination of the partition coefficients of volatile compounds in water-air systems. Only techniques that are suited to a fully automatic headspace procedure using the pneumatic headspace sampling-technique have been considered. Particularly simple is the technique of “vapor phase calibration —VPC” where an external vapor standard is used to calibrate the concentration of the volatile analyte in the headspace, while the concentration in the sample is found from the difference in the total amount in the vial. This technique is described in detail for 2-butanone in water. Finally, the water-air partition coefficients of several selected volatile compounds at different temperatures are listed together with their temperature functions.
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    Isolation of volatiles with insecticidal properties from the genusTagetes (Marigold) (1992)
    Springer
    Chromatographia 34 (1992), S. 241-248 
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    ISSN: 1612-1112
    Keywords: Gas chromatography ; Natural insecticides ; Marigolds ; Isolation of volatiles
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The results of optimizing Soxhlet and Simultaneous Distillation-Extraction (SSDE) procedures for the isolation of natural insecticides fromTagetes erecta, Tagetes patula, andTagetes minuta, members of theCompositae family, are presented. Extraction procedures were developed and validated that produced the extract with the highest degree of biocidal activity. The highest activity was obtained with extracts isolated by SSDE using methylene chloride. Initial work was carried out on a micro-SSDE. Preparative SSDE was used to provide large quantities of extracts for bioassays. Bioassays were used to govern optimization procedures usingAedes aegypti andAnopheles stephensi adults and larvae as target organisms.Tagetes minuta was determined to be the most active of the three species studied. Evaluation of activity and recovery versus extraction time was investigated. It was determined that an extraction time of ten hours resulted in the highest activity and over 90% recovery of the oils. Finally, supercritical fluid extraction of the flowers with CO2 was compared to SSDE.
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    Pair-wise interactions by gas chromatography. Part II: Sociation free enthalpies of some hydrogen bonding solutes with non-associated primary alcohol groups (1992)
    Springer
    Chromatographia 34 (1992), S. 249-252 
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    ISSN: 1612-1112
    Keywords: Gas chromatography ; Sociation constants ; Hydrogen bonding solutes ; Nearly ideal binary solvent theory ; Isosteric solvents
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Gas chromatographic data measured on mixtures of 19,24-dioctadecyldotetracontane, A≡C78, and 18,23-dioctadecyl-1-hentetracontanol, POH, allow the determination of the standard chemical potential of a solute on an ideal stationary phase with primary alcohol groups at ideal dilution. The Nearly Ideal Binary Solvent Theory provides the link between these data and the sociation constant of the solute with the primary alcohol. The method was applied to calculate sociation constants of a series of hydrogen bonding solutes. Results are compared with those determined by spectroscopy and calorimetry.
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    Hhdrodenitrogenation catalysis studied by reversed-flow gas chromatography (1992)
    Springer
    Chromatographia 34 (1992), S. 398-410 
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    ISSN: 1612-1112
    Keywords: Gas chromatography ; Reversed-flow technique ; Catalysis ; Hydrodenitrogenation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Many important parameters of surface catalysed reactions can be determined simultaneously, under nonsteady state conditions using Reversed-Flow Gas Chromatography. A simple, slightly modified gas chromatograph is required. The distorted diffusion bands, obtained experimentally for reactant and product(s), can be analysed mathematically, using simple PC programs, to give the pre-exponential factors and the exponential coefficients of a function consisting of the sum of two-four exponential functions of time. From these, and some geometrical and diffusional characteristics of the reaction cell, the values of adsorption, desorption and reaction rate constants, the overall mass transfer coefficients in the gas and in the solid catalyst, and the adsorption equilibrium constant, for both reactant and product(s) can be calculated. The above parameters were determined at various temperatures and over three catalysts for the hydrodenitrogenation of piperidine ton-pentane, an industrially important hydrotreating process. The results obtained can help to understand the mechanism of reactions on solid surfaces and to confirm experimentally theoretical calculations on adsorption and surface reactions.
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    Use of a high-pressure Soxhlet extractor for the determination of organochlorine residues by gas chromatography (1992)
    Springer
    Chromatographia 34 (1992), S. 468-474 
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    ISSN: 1612-1112
    Keywords: Gas chromatography ; High-pressure Soxhlet extraction ; Organochlorine residue analysis ; Supercritical fluid extraction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The operational conditions of a high-pressure Soxhlet extractor (pressure, temperature, time and amount of sample) have been optimized, using carbon dioxide as extractant for the determination of organochlorine pesticides and polychlorinated biphenyls (PCBs) in certified potato, carrot, olive oil and lyophilized fish tissue samples. Good recoveries were obtained.
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    URL: http://dx.doi.org/10.1007/BF02290238
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    Capillary gas chromatography of some telomeric fluoroalkanols (1992)
    Springer
    Chromatographia 34 (1992), S. 475-478 
    Details
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Telomeric fluoroalkanols ; Retention index ; Regression equation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The separation of fluoroalkanols with the general formula H(CF2CF2)nCH2OH (n=1–8) on fused-silica capillary columns coated with dimethylsilicone and cyanopropylmethylsilicone stationary phases was investigated. Retention indices were determined at three temperatures. A correlation between the retention index values, the molecular weights and the number of C and F atoms in the solute molecules was found.
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    URL: http://dx.doi.org/10.1007/BF02290239
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    Allyl thiocyanate — Natural product or artifact in Crucifer extracts? (1992)
    Springer
    Chromatographia 34 (1992), S. 461-467 
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    ISSN: 1612-1112
    Keywords: Gas chromatography ; Allyl thiocyanate and isothiocyanate ; Plant extract ; Analytical artifacts ; Isomerization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Allyl thiocyanate and isothiocyanate were synthesized and could be analysed by gas chromatography without isomerization by keeping the injector at, or below, 50°C. Synthetic allyl isothiocyanate contained none of the isomeric thiocyanate but allyl thiocyanate contained 0.5% of isothiocyanate. The NMR spectra indicated both compounds to be free of the corresponding isomer. Analysis of extracts of stinkweed, mustard and horseradish by GC using non-isomerizing conditions showed that only the stinkweed extract contained allyl thiocyanate. Mustard and horseradish extracts contained allyl, and other, isothiocyanates but no allyl thiocyanate. Allyl thiocyanate previously reported in extracts of mustard and horseradish was most likely an artifact caused by partial isomerization of allyl isothiocyanate under the conditions of isolation and/or analysis.
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    URL: http://dx.doi.org/10.1007/BF02290237
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    Open-tubular columns: Past, present and future (1992)
    Springer
    Chromatographia 34 (1992), S. 513-528 
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    ISSN: 1612-1112
    Keywords: Gas chromatography ; Open-tubular (capillary) columns ; History of chromatography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
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    URL: http://dx.doi.org/10.1007/BF02290246
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    The selectivity of crown ether polysiloxane stationary phases (1993)
    Springer
    Chromatographia 35 (1993), S. 33-37 
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    ISSN: 1612-1112
    Keywords: Gas chromatography ; Crown ether polysiloxane phases ; Selectivity mechanisms
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The phase recognition mechanism of nine groups of position isomers on four crown ether polysiloxanes, OV-1701 and PEG 20M has been investigsated by measuring various thermodynamic parameters. The high selectivity of crown ether polysiloxane phases is due to hydrogen bonding and the extent of fitting between the analytes and the crown ethe cavity. The effects on selectivity of cavity size, heteroatoms and substituent groups on the crown ether are discussed.
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    URL: http://dx.doi.org/10.1007/BF02278553
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    Determination of gas-liquid partition coefficients by automatic equilibrium headspace-gas chromatography utilizing the phase ratio variation method (1993)
    Springer
    Chromatographia 35 (1993), S. 73-84 
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    ISSN: 1612-1112
    Keywords: Gas chromatography ; Equilibrium headspace sampling ; Partition coefficient determination ; Theory of chromatography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The new phase ratio variation method is described which represents a convenient way for the determination of gas-liquid partition coefficients for practical purposes, utilizing equilibrium headspace-gas chromatography (EHS-GC). This method is based on the relationship between reciprocal peak area and the phase ratio in the vial containing the sample solution; it involves regression analysis of the EHS-GC measurements of a number of sample vials containing the same sample solution but with a wide variation of phase ratios. Examples are given for both aqueous systems and systems consisting of a stationary (liquid) phase used as the solvent; comparison of the measured values with results obtained by other methods shows satisfactory agreement. A critical discussion of the conditions influencing the accuracy of the analytical results is given.
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    Correlation of unified retention indices for OV-101 and squalane (1993)
    Springer
    Chromatographia 35 (1993), S. 109-110 
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    ISSN: 1612-1112
    Keywords: Gas chromatography ; Unified retention index ; Correlation of data ; Hydrocarbons
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Gas chromatographic unified retention indices for 43 hydrocarbons (alkanes and cycloalkanes) are given for squalane and OV-101. Comparison of these values and unified retention index increments are presented as linear regression equations with high correlation coefficients and acceptable standard deviations.
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    URL: http://dx.doi.org/10.1007/BF02278566
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    Use of artificial neural networks for the classification of vegetable oils after GC analysis (1993)
    Springer
    Chromatographia 35 (1993), S. 160-166 
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    ISSN: 1612-1112
    Keywords: Gas chromatography ; Neural networks ; Classification ; Pattern recognition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Artificial Neural Networks are proposed for the classification of vegetable oils submitted to gas chromatography analysis through their FAME profiles. Three important neural networks are evaluated here: the Hopfield model as a content-addressable memory (CAM), the Hamming model and the multi-layer perceptron. A brief description of these nets is first presented and further implemented for the classification of known vegetable oils. After the learning step, unknown samples are presented to the nets and the identification step performed. The performances of these nets are compared for the recognition of popular vegetable oils, including several edible oils.
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    URL: http://dx.doi.org/10.1007/BF02269696
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    Identification of chlorinated sulfur compounds in pulp mill effluents by GC-MS and GC-AED (1993)
    Springer
    Chromatographia 35 (1993), S. 193-198 
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    ISSN: 1612-1112
    Keywords: Gas chromatography ; Mass spectrometry ; Atomic emission spectroscopy ; Pulp mill effluents
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Three chlorinated dimethyl sulfones and five chlorinated thiophenes have been identified in the alkaline extraction liquor from a bleach plant by gas chromatography with atomic emission detection (GC-AED) and with mass spectrometry (GC-MS). The information on elemental content obtained by GC-AED enabled a rapid screening of the sulfur compounds and provided important structural information complementary to the mass spectral data. Quantitation was accomplished by GC-AED based on universal calibration.
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    URL: http://dx.doi.org/10.1007/BF02269702
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    Insecticidal volatiles from the marigold plant (genustagetes). Effect of species and sample manipulation (1993)
    Springer
    Chromatographia 35 (1993), S. 209-215 
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    ISSN: 1612-1112
    Keywords: Gas chromatography ; Gas chromatography-mass spectrometry ; Tagetes ; Plant volatiles ; Extractions ; Natural insecticides ; Mosquitos
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Volatiles from three species of the genustagetes, commonly called marigold have been isolated and characterized. Simultaneous steam distillation extractions (SSDE) produced consistently extracts of higher insecticidal activity than Soxhlet extractions. Methylene chloride was the best solvent. Volatiles isolated from theminutae species showed higher activity than those frompatula anderecta. Comparison of extracts from the flower, foliage and roots of the plant showed that most of the activity is located in the flower. The volatiles are highly effective toward both larvae and adult mosquitoes.
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    URL: http://dx.doi.org/10.1007/BF02269705
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    Enantiomer separation on amylose tris(n-butylcarbamate) by gas chromatography (1993)
    Springer
    Chromatographia 35 (1993), S. 237-240 
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    ISSN: 1612-1112
    Keywords: Gas chromatography ; Enantioselectivity ; Polysaccharide chiral stationary phase ; Amylose tris(n-butylcarbamate) ; Grob test
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Seven aromatic and alkyl amylose and cellulose carbamates have been tested as chiral stationary phases in gas chromatography. One of them, amylose tris(n-butylcarbamate) can be used for enantiomer separation.
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    URL: http://dx.doi.org/10.1007/BF02269709
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    Rapid determination of chlorinated pesticides using CN-bonded cartridges followed by GC-ECD (1993)
    Springer
    Chromatographia 35 (1993), S. 290-294 
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    ISSN: 1612-1112
    Keywords: Gas chromatography ; Solid phase extraction ; Organochloride pesticides ; Water analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Gas chromatography of chlorinated pesticides in water is carried out after adsorption of a 50 mL sample using a cartridge containing 100 mg CN-bonded porous silica and extraction with 500 μL pentane. The average recovery for eight organochloride pesticides at 1 ppb was 〉95%. The procedure described is simple, selective and reproducible.
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    URL: http://dx.doi.org/10.1007/BF02277512
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    Improvements in preconcentration methods for determining trace impurities in ultra-pure gases by gas chromatography (1993)
    Springer
    Chromatographia 35 (1993), S. 339-343 
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    ISSN: 1612-1112
    Keywords: Gas chromatography ; Preconcentration techniques ; Trace gas analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The blanks in preconcentration methods for determining trace amounts of impurities in ultra-pure gases, which include the preconcentration volume of sample gases, carrier gas impurities and atmospheric contamination are discussed and three concentration methods for eliminating blank errors are proposed. These are, the differential volume method by concentrating at the same flow-rate but different times (DVMSF), the differential time method by concentrating the same volumes at different flow-rates (DTMSV) and the differential volume method by concentrating for the same times but different flow-rates (DVMST). DVMST is proposed as the best method for its ability to eliminate all blank errors described. The methods are used to determine trace amounts of Ar+O2 and N2 in ultra-pure hydrogen. Calculations demonstrate that the methods can effectively improve analytical accuracy.
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    URL: http://dx.doi.org/10.1007/BF02277521
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    Estimation of silanol groups in silica-based packings for liquid chromatography from gas chromatographic retention of cyclohexane and benzene (1993)
    Springer
    Chromatographia 35 (1993), S. 375-380 
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    ISSN: 1612-1112
    Keywords: Gas chromatography ; Micropacked columns ; Retention behavior ; LC silica packing materials ; Silanol groups
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Gas chromatographic retention of cyclohexane and benzene on microcolumns packed with silica-based materials for liquid chromatography has been investigated to elucidate the relationship with the surface properties of the packing materials. Differences in capacity factors (Δk′) for these two hydrocarbons were related to the surface area of the packing materials. For untreated silica gels, the Δk′ value increased with increasing total surface area of the column employed and measurement of Δk′ for chemically-bonded stationary phases allowed estimation of accessible residual silanol groups.
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    Multi-residue procedure for the analysis of pesticides in groundwater: Application to samples from the comunidad Valenciana, Spain (1993)
    Springer
    Chromatographia 37 (1993), S. 303-312 
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    ISSN: 1612-1112
    Keywords: Gas chromatography ; Pesticides in groundwater ; Solvent extraction ; Multiresidue analysis ; Selective detection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A simple multi-residue procedure has been developed and applied to the analysis of pesticides in groundwater samples from the Comunidad Valenciana, a predominantly agricultural area on the Mediterranean coast of Spain. The procedure includes a liquid-liquid extraction, after addition of NaCl on the samples, and a subsequent analysis by capillary gas chromatography using a dual detection system with electron capture and nitrogen-phosphorous detectors. This allows the determination of more than 30 compounds (organophosphorous, organochlorine and pyrethroid pesticides) at the low ppb (μg l−1) levels. Detection limits obtained varied between 0.01 μg l−1 (lindane, fonofos) and 0.5 μg l−1 (cypermethrin). An additional injection of the sample extracts into a gas chromatograph equipped with a column of different polarity and electron capture detector is used for the confirmation of chromatographic peaks. The recommended procedure has been applied to 66 ground water samples. Pesticides, including organophosphorus and organochlorine compounds were detected in 31 of them, in levels ranging from 0.02 to 0.7 μg l−1.
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    Indirect GC determination of ethephon in drinking water by a combination of reactive headspace sampling with adsorptive enrichment/thermal desorption (1993)
    Springer
    Chromatographia 37 (1993), S. 361-364 
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    ISSN: 1612-1112
    Keywords: Gas chromatography ; Headspace sampling ; PTV-System ; Ethephon in drinking water
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An indirect GC method is described for the determination of Ethephon in drinking water on the basis of the headspace analysis of the ethylene formed from Ethephon. In order to reach the necessary detection limit, the entire volume of the static headspace distribution is transferred into a cold injection system (CIS). There, the ethylene is adsorbed on Carbosieve SIII at 10°C and, subsequently, desorbed at 300 °C. The water vapour included in the headspace is completely eliminated through the splitting system. By means of this technique, a detection limit of 0.05 μg/l water was reached.
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    Viscosities of carrier gases at gas chromatograph temperatures and pressures (1993)
    Springer
    Chromatographia 37 (1993), S. 399-401 
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    ISSN: 1612-1112
    Keywords: Gas chromatography ; Viscosity ; Carrier gases
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Equations are derived for viscosities of H2, He, N2 and Ar for use at chromatographic temperatures which are accurate to within 0.3% for H2, and 0.1% for the other gases. The effect of pressure is usually negligible but may increase the viscosity of N2 or Ar by as much as 0.5% at 25°C or lower and 5 atm or higher.
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    A very efficent column for the separation of 60 volatile organochlorine priority pollutants and for other environmental problems (1994)
    Springer
    Chromatographia 38 (1994), S. 114-117 
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    ISSN: 1612-1112
    Keywords: Gas chromatography ; Priority pollutants ; EPA methods ; Unleaded gasoline ; Volatile organochlorine compounds
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The complete separation of the sixty volatile organochlorine (VOC) priority pollutants has been achieved by coupling two different liquid-modified adsorption chromatography columns. Two temperature programs were used to obtain the complete separation in a relatively short analysis time. Detection was by FID alone
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    Influence of adsorption effects on retention indices of selected C10-hydroxy compounds at various temperatures (1994)
    Springer
    Chromatographia 38 (1994), S. 93-97 
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    ISSN: 1612-1112
    Keywords: Gas chromatography ; Retention index ; Adsorption effects ; Terpene alcohols ; Fused-silica capillary columns
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Retention indices of 6 selected hydroxy compounds (aliphatic and bicyclic alcohols, phenols) were determined on 2 HP-5 fused-silica, capillary columns with different film thicknesses (0.11 μm and 0.33 μm) at 8 different oven temperatures between 80 and 150°C. For some substances the I-T plot was found to show a minimum which cannot be explained by the common retention-index temperature-dependence in gas-liquid chromatography. This result is discussed in terms of adsorption at the liquid-solid interface of the capillary column.
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    Molecular structural coefficients of Takács. Their dependence on column temperature, stationary phase polarity and solute chemical nature (1994)
    Springer
    Chromatographia 38 (1994), S. 701-708 
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    ISSN: 1612-1112
    Keywords: Gas chromatography ; Stationary Phase and solute polarity ; Molecular structural coefficients ; Retention index ; Takács equation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Molecular structural coefficients, Sc, for one hundred solutes have been calculated by means of the Takács equation using retention data obtained with over fifty stationary phases, SP. Employing data of seven SP's (characterized in our laboratories) it was found that the variation of Sc with column temperature was linear for most solutes. With data of n-decane and the ten McReynolds probes on up to fifty SP's of polarity less than RP=72, at 120°C, it was found that the Sc of n-decane and cis-hydrindane decreased slightly with increasing SP polarity, while the Sc of non-alkanes remained constant or increased very little as the SP polarity increased. The points for n-decane fit well to a second order polynomial. Again using a temperature of 120°C, the increments of Sc for solutes belonging to an homologous series were correlated with the polarity of SP's. Reasonably straight lines were obtained for all the chemical functions studied, Sc increasing with increasing SP polarity.
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    Characterization of some new polysiloxane stationary phases by principal component analysis (1994)
    Springer
    Chromatographia 38 (1994), S. 227-231 
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    ISSN: 1612-1112
    Keywords: Gas chromatography ; Stationary phase characterization ; Principal component analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary In this study, several new stationary phases were characterized by principal component analysis. Fourteen new stationary phases, including substituted phenyl and oligoethyleneoxide functionalities on polysiloxane polymers, were tested and compared to three well known stationary phases. The main features of these phases were studied using a series of test solutes of varying chemical characteristics representing the data set for principal component analysis. Two principal compounds were found to account for 99.20% of the variance (the first accounted for 94.96% and the second for 4.24%). The data were represented as a two-dimensional map for visual representation of the characteristics of these stationary phases. The first principal component represented a selectivity based on polarity (r2=0.998), while the second showed Lewis acid-base characteristics of the phases. Polarizable and amphoteric characteristics of these phases also became evident using this evaluation method.
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    Comparison of supercritical fluid extraction and liquid-liquid extraction for isolation of selected pesticides stored in freeze-dried water samples (1994)
    Springer
    Chromatographia 38 (1994), S. 502-508 
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    ISSN: 1612-1112
    Keywords: Gas chromatography ; Liquid-liquid extraction ; Supercritical fluid extraction ; Pesticides ; Freeze-dried water
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The stability of freeze-dried water samples spiked with eight agrochemicals (atrazine, simazine, linuron, carbaryl, propanil, fenitrothion, parathion and fenamiphos) were examined to evaluate their suitability as candidate reference materials for their determination in water samples. In addition, two different extraction procedures, liquid-liquid and supercritical fluid extraction, were compared for the isolation and trace enrichment of target analytes from freeze-dried water samples. Final analytical determinations were by gas chromatography-nitrogen phosphorus detection and electronic impact mass spectrometry, and by liquid chromatography-diode array detection. The whole methodology developed in this paper permitted the determination of pesticides spiked in water at levels varying from 0.03 to 6.9 μg L−1.
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    Determination of bromoxynil and ioxynil residues in cereals and soil by GC-ITD (1994)
    Springer
    Chromatographia 38 (1994), S. 624-628 
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    ISSN: 1612-1112
    Keywords: Gas chromatography ; Ion-trap detection ; Nitriles ; Cerelas ; Perfluoroacylation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Bromoxynil and ioxynil have been determined inplants and soil by gas chromatography. These herbicides are extracted from soil samples with methylene chloride at acidic pH. Plant samples are extracted with a basic acqueous solution and extracts purified by solvent partitioning. Herbicide residues are submitted to perfluoroacylation prior to GC separation. These compoiunds are determined by ion-trap detection with single ion monitoring; N-(3-chloro-4 methyl-phenyl_ perfluoropropyl amide is used as internal standard. The detection limit of the method is near 0.001 μg g−1 for the samples studied. The proposed methods are sensitive and reproducible enough to allow determination of these herbicides at residue levels in plants and soil.
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    Supercritical fluid extraction of oxadixyl from food crops (1994)
    Springer
    Chromatographia 39 (1994), S. 11-14 
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    ISSN: 1612-1112
    Keywords: Supercritical fluid extraction (SFE) ; Gas chromatography ; Pesticide residues ; Oxadixyl
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary This work describes the study of a degradation curve of Oxadixyl in field-treated potato and tomato samples. The residues were extracted using classical and supercritical fluid (SFE) extraction methods and analyzed by HRGC/ECD. The extraction techniques were compared and the results indicate the advantages of using SFE as an alternative method for pesticide analyses in these samples.
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    Analysis of short chain fatty acids from different intestinal samples. I: By packed column gas chromatography (1994)
    Springer
    Chromatographia 39 (1994), S. 706-712 
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    ISSN: 1612-1112
    Keywords: Gas chromatography ; Short chain fatty acids ; Intestinal fluids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The quantification of short chain fatty acids in their free form, by gas chromatography, is the method of choice provided that the underivatized acids elute with good peak shape and reproducibility. In biological samples not only the highly polar acids themselves but also deposits of nonvolatile sample components may interact with the column or the packing material. As a result, the peak symmetry of the fatty acids and their reproducibility can become increasingly poor. Reduction of the nonvolatile matrix components by filtration of the sample has been examined in order to achieve direct analysis of the short chain fatty acids in intestinal samples by packed column GC. Membrane filter units (0.8 μm) allow a quick and simple filtration of the samples. This pretreatment reduces the peak tailing and the broadening of the peaks. The method, when applied to different intestinal samples, allowed the quantification of short chain fatty acids in hundreds of samples without derivatization. Good results are obtained at sample concentrations higher than 0.2 mmol l−1 for each acid.
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    Capillary gas chromatography of C1−C4 alkyl tert-butyl ethers (1994)
    Springer
    Chromatographia 39 (1994), S. 224-227 
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    ISSN: 1612-1112
    Keywords: Gas chromatography ; C1−C4 alkyl tert-butyl ethers ; Retention index
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The separation of C1−C4 alkyl tert-butyl ethers with the general formula (CH3)3C−O−R (R-alkyl substituent) on fused-silica capillary columns coated with dimethylsilicone and cyanopropylmethylsilicone stationary phases was investigated. Retention indices were determined at two temperatures in order to understand their chromatographic behaviour. The respective standard deviations were 0.3 and 0.5 i.u.
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    GC-NPD investigation of the recovery of organonitrogen and organophosphorus pesticides from apple samples: The effect of the extraction solvent (1994)
    Springer
    Chromatographia 39 (1994), S. 320-324 
    Details
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Organonitrogen pesticides ; Organophosphorus pesticides ; Apples ; Solvent extraction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A gas chromatographic method employing a capillary column and a selective nitrogen/phosphorus detector (NPD) has been developed for the determination of organophosphorus (OP) and organonitrogen (NP) pesticides in horticultural samples (apples). The separation of sixteen pesticides and the internal standard was performed in thirteen minutes. The analytical characteristics of the method, including linear response ranges, detection limits, and reproducibility, have been studied using a 1∶1 mixture of ethyl acetate and xylene as extraction solvent. The possibility of mutual interference between pesticides has also been studied. A procedure for the quantitative extraction of the sixteen pesticides from apple samples has also been developed; for fifteen of the pesticides recoveries 〉85% were obtained after 90 minutes extraction. The effect of different solvents both on recovery and on the sensitivity of the subsequent chromatography were also investigated. It was found that the sensitivity required must be considered when the solvent for sample treatment is selected.
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    URL: http://dx.doi.org/10.1007/BF02274520
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    Chromatographic determination of D-amino acids as native constituents of vegetables and fruits (1994)
    Springer
    Chromatographia 39 (1994), S. 419-426 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Gas chromatography ; Chirasil-Val ; Amino acid enantiomers ; N-Isobutyryl-cysteine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Free D-amino acids (D-AA) were detected as native constituents in juices of vegetables (cultivars of cabbage, tomato, carrot, garlic) and fruits (organes, clementine, grapefruit, lemon, apples, pear, grapes) using gas chromatography (GC) or high-performance liquid chromatography (LC). For investigation by GC, AA enantiomers were converted into theirN(O)-pentafluoropropionyl 2-propyl esters and resolved on a Chirasil-L-Val capillary column. For determination by LC, precolumn derivatization of AA enantiomers usingo-phthaldialdehyde together with the chiral thiolsN-isobutyryl-L-cysteine orN-isobutyryl-D-cysteine and fluorescence detection of the diastereomeric isoindole derivatives, resolvable on an octadecylsilyl stationary phase, were used. D-Ala (0.6–3.8%) was detected in all freshly pressed plant juices usually in the highest relative amounts. Other D-AA detected were D-Asx (0.1–1.9%), D-Glx (0–1.3%), D-Ser (0–1.7%), D-Arg (0.4–1.2%, in grapes, orange, grapefruit, and clementine) and D-Leu and D-Val (1% in cabbage). Absolute amounts of native D-AA were totally 28–57 μmol L−1 in fruit juices, 14.5 μmol L−1 in a tomato juice and 8.5 μmol L−1 in a carrot juice.
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    URL: http://dx.doi.org/10.1007/BF02278756
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    Soil transformation of wheat and corn metabolites mboa and DIM2BOA into aminophenoxazinones (1993)
    Springer
    Journal of chemical ecology 19 (1993), S. 2453-2461 
    Details
    ISSN: 1573-1561
    Keywords: DIMBOA ; MBOA ; DIM2BOA ; M2BOA ; 2-amino-7-methoxy-3H-phenoxazin-3-one ; 2-amino-4,6,7-trimethoxy-3H-phenoxazin-3-one ; corn ; wheat ; soil microbial transformation ; phytotoxicity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The defensive cyclic hydroxamates 7-methoxy-2,4-dihydroxy-1,4(2H)-benzoxazin-3-one (DIMBOA) and 7,8-dimethoxy-2,4-dihydroxy-1,4(2H)-benzoxazin-3-one (DIM2BOA) of wheat and corn are transformed in nonsterile soil, via 6-methoxy-2(3H)-benzoxazolone (MBOA) and 6,7-dimethoxy-2(3H)-benzoxazolone (M2BOA) respectively, into 2-amino-7-methoxy-3H-phenoxazin-3-one and 2-amino-4,6,7-trimethoxy-3H-phenoxazin-3-one. The soil transformation is similar of that undergone by the rye metabolite 2(3H)-benzoxazolone (BOA) into 2-amino-3H-phenoxazin-3-one. The transformations to phenoxazinones are not observed in sterile soil. The 2-amino-3H-phenoxazin-3-one inhibits barnyard grass radicle elongation, but the methoxylated aminophenoxazinones are not significantly inhibitory.
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    Foliar chemicals of wheat and related grasses influencing oviposition by Hessian fly,Mayetiola destructor (Say) (Diptera: Cecidomyiidae) (1992)
    Springer
    Journal of chemical ecology 18 (1992), S. 1965-1980 
    Details
    ISSN: 1573-1561
    Keywords: Hessian fly ; Mayetiola destructor ; Diptera ; Cecidomyiidae ; oviposition stimulants ; wheat ; rye ; barley ; oat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract More than twice the number of mated female Hessian flies,Mayetiola destructor (Say) entered a zone within 1 cm of a paper strip treated with one plant equivalent (PE) of a chloroform extract of wheat foliar waxes compared to a strip treated with solvent only; females also stayed six times longer and laid 10 times more eggs on the strip treated with the wheat extract. Column chromatographic fractionation of the wheat extract and application of these fractions onto filter paper strips showed four fractions elicited significant numbers of eggs to be laid. Single, binary, and tertiary combinations of three of these fractions (two of the four fractions apparently contained similar compounds) were tested. The greatest numbers of eggs were laid on strips treated with the tertiary combination or the binary combination conaining the two most active fractions (3 and 6); three times the number of eggs were laid on strips treated with this binary combination than the sum of eggs laid on strips treated with these two fractions separately. A comparison of grasses and their extracts showed female Hessian flies laid greater numbers of eggs on wheat or rye than on barley or oat. Fractionated barley and oat extracts were tested for activity as for wheat, and a similar pattern was observed, i.e., the greatest numbers of eggs were laid on fractions 3 and 6. Dose-response tests, using these two fractions of wheat, barley, or oat showed the same threshold of activity for fraction 3 for all three extracts, i.e., 2 PE. In contrast, fraction 6 of wheat was active at the lowest dosage tested, 0.25 PE, while the same fraction of either barley or oat was not active until tested at a dosage of 2 PE. It appears that (at least) two chemicals in the foliar waxes of these grasses influence ovipositional behavior of female Hessian flies. Furthermore, given the similar foliar chemistry of these grasses and the strong synergistic interaction between fractions 3 and 6 shown for wheat extract, it is likely that the ovipositional preferences exhibited by female Hessian flies towards these grasses may be explained by quantitative differences in the amount(s) of the active chemical(s) in their respective fraction 6 (most polar fraction tested).
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    Hydroxamic acid glucosides in honeydew of aphids feeding on wheat (1992)
    Springer
    Journal of chemical ecology 18 (1992), S. 841-846 
    Details
    ISSN: 1573-1561
    Keywords: Rhopalosiphum padi ; Homoptera ; Aphididae ; wheat ; maize ; DIMBOA ; hydroxamic acids ; aphid honeydew
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract DIMBOA glucoside (2-O-/gb-D-glucopyranosyl-4-hydroxy-7-meth-oxy-1,4-benzoxazin-3-one), the main hydroxamic acid (Hx) in intact wheat plants, was detected in the honey dew ofRhopalosiphum padi feeding on seedlings of six wheat cultivars that differed in their concentration of Hx, suggesting that the chemical circulates in the phloem. Neither the aglucone (DIMBOA) nor its main breakdown product were found in any of the honeydew samples. Honey dew production by aphids caged on seedlings of the wheat cultivars and DIMBOA glucoside concentrations in the honeydew followed biphasic curves when plotted against Hx concentration, suggesting passive ingestion of the chemical from the phloem at low Hx concentrations and limited ingestion due to feeding deterrency by Hx in mesophyll cells at high Hx concentrations. The presence of plant toxins such as Hx glucosides in the phloem sap, the main ingesta of aphids, and in the mesophyll cells, has major implications for plant defense, through a feeding deterrent effect during stylet penetration, and deterrency (antixenosis) along with antibiosis during feeding.
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    A modified procedure for acid-catalyzed esterification with isopropanol (1979)
    Springer
    Chromatographia 12 (1979), S. 168-170 
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    ISSN: 1612-1112
    Keywords: Acid catalyzed esterification ; Amino acids ; Fatty acids ; Gas chromatography ; Isopropyl esters
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Acid-catalyzed esterification of carboxyl groups with acetyl chloride in isopropanol is investigated. Yields are equivalent to those obtained with reagent prepared conventionally by bubbling gaseous hydrogen chloride into isopropanol. The preparation of the former reagent is less time consuming and no special equipment is needed. The procedure is applicable for other alcohols as well.
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    Universal system for liquid stationary phase classification on the basis of thermodynamical data (1979)
    Springer
    Chromatographia 12 (1979), S. 533-538 
    Details
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Sorbents: liquid phases, supports, adsorbents ; Thermodynamical classification ; Polarity and selectivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Equations modifying Rohrschneider's relationship between ΔI and thermodynamical characteristics values are derived. Polarity in chromatography is discussed as a possibility of stationary phases or absorbents to enter into intermolecular interactions and is determined on the basis of the partial molar free energies of solution (ΔG) of six test substances. A simple method for the calculation of stationary phase polarity in terms of ΔG from retention indices and McReynolds constants is given. Equations are presented for the calculation of stationary phase selectivity utilizing ΔG data tabulated for selected test substances. The thermodynamical basis of selecting a reference phase for a unified system expressing the selectivity of stationary phases which can also be applied for adsorbents is suggested. The energy equivalent to an index unit, ΔGi.u., is discussed.
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    Détection Spécifique par lonisation Haute Fréquence (1979)
    Springer
    Chromatographia 12 (1979), S. 803-807 
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    ISSN: 1612-1112
    Keywords: Gas chromatography ; Ionization detector ; High frequency discharge ; Specific or no specific detection ; Gas adsorption (by flues)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The response of a high frequency ionization detector according to various parameters: voltage, tuning capacitance, feed-back capacitance, space between the electrodes and direct flux-plasma distance is studied. The characteristic measure of v in accordance to high voltage for various mixtures of carrier gas argon-nitrogen gives a maximum which demonstrates that specific automatic analyses of oxygen, krypton and methane are possible with concentrations in the order of ppb. Complete adsorption of 0.8 ppb of methane by a flue of 120 cm in tube 2×4 mm at 50°C after twentieth recycling is essential.
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    On-column interactions in the direct GLC assay of hexetidine (1979)
    Springer
    Chromatographia 12 (1979), S. 530-532 
    Details
    ISSN: 1612-1112
    Keywords: Hexetidine ; Triamine ; Gas chromatography ; On-column interactions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Gas chromatography was used for the direct assay of hexetidine and triamine in a pharmaceutical formulation. During this work we came across a strong oncolumn interaction, in such a way that the GLC retention, selectivity and response parameters were seriously modified relative to the injections of hexetidine and triamine standard solutions. The interaction was traced to the coinjected hydrochloride form of a major component of the sample and in practical terms points to the potential quantitation errors that may be associated to similar systems.
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    A routine gas chromatographic method for the analysis of chlorofluorocarbons in aerosol cans (1990)
    Springer
    Chromatographia 29 (1990), S. 13-15 
    Details
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Mass spectrometery ; Aerosol cans ; Chlorofluorocarbons
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A gas chromatographic (GC) method for the routine analysis of fully halogenated chlorofluorocarbons (CFCs) in aerosol cans is described. The identification of CFCs by GC was found to be in full agreement with those by GC-mass-spectrometery. The method has been applied to the analysis of CFCs in 448 aerosol products. The most commonly used fully halogenated CFC propellants in aerosol cans were found to be CFC11, CFC12 and CFC114.
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    Improved gas chromatographic separation of C6 epoxides (1990)
    Springer
    Chromatographia 29 (1990), S. 322-324 
    Details
    ISSN: 1612-1112
    Keywords: Gas chromatography ; C6 epoxides ; Retention indices
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The separation of C6 epoxides on a fused-silica capillary column coated with Permaphase DMS (dimethylsilicone) was investigated. Retention indices were determined at 50 and 60°C. We demonstrate that this stationary phase provides a better resolving power than OV-101.
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    The glass insert in stop-flow split injection (1990)
    Springer
    Chromatographia 29 (1990), S. 385-388 
    Details
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Capillary columns ; Split injector design ; Glass inserts
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary In stop-flow split injection the careful choice of the experimental conditions is of great importance for accurate quantitation, the size of the gaseous sample plug and its position with respect to the column inlet and to the top of the insert during the evaporation period are critical to prohibit sample vapour overflow and aerosol splitting. The proper insert design is established. A sample volume of 0.5 μl is recommended in the practical application of the stop-flow method.
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    A comparative study of different multiresidue methods for the determination of pesticides in fruit samples by gas chromatography (1990)
    Springer
    Chromatographia 29 (1990), S. 459-466 
    Details
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Pesticide analysis ; Multiresidue methods ; Solvent extraction schemes ; Fruit samples
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A comparative study of different multiresidue methods for the determination of organochlorine and organophosphorus pesticides in fruit samples has been carried out. Recoveries for each pesticide added to a peach sample were obtained after applying different extraction systems. The study was performed with the following pesticides: dimethoate, chlorpyrifos, fenitrothion, lindane, malathion, methidathion, phentoate and tetradifon. Extraction systems induded: acetonitrile+anhydrous sodium sulphate, acetonitrile-water+Celite acetone and acetone-methanol. Determination of pesticides was performed by gas capillary chromatography with ECD and NPD. GC/FPD and GC/MS were also used for confirmation and identification purposes.
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    Quality control and classification of camomilla oils with the oxygen-sensitive flame-ionization detector (1990)
    Springer
    Chromatographia 30 (1990), S. 47-50 
    Details
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Selective detection ; Oxygen flame ionization detector ; Camomilla oils
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The application of the Oxygenate Analyzer (O-FID) developed for the selective determination of oxygenated compounds has been studied for the quality control and classification of camomilla oils. In comparison to FID detection the O-FID results in a simpler chromatogram and a much higher sensitivity for the characteristic oxygenated compounds. On the basis of the O-FID chromatograms, by measuring the relative peak areas of the characteristic compounds, the camomilla oils can be classified and the oils of unacceptable quality unambigously distinguished.
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    The retention mechanism in poly(ethylene glycol) 20M layer on the surface of a silanized support (1990)
    Springer
    Chromatographia 30 (1990), S. 630-634 
    Details
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Poly(ethylene glycol) 20M ; Silanized supports ; Retention mechanisms
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The properties of poly(ethylene glycol) 20M (PEG 20M) on the silanized surface of Chromosorb W HMDS were investigated. It was found that the surface layer of PEG 20M is in a liquid form below its melting temperature. It the stationary phase loading ratio is above 0.105 the main retention mechanism is partition in both the liquid and solid forms of PEG 20M. The contribution of adsorption to the retention volume was also determined. It is suggested that in the case of methanol this contribution is caused by adsorption on the residual silanol groups present on the support surface whereas for n-octane this is rather adsorption on the gas-liquid interface.
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    Dependence of solution data at ideal dilution on solvent molecular size (1990)
    Springer
    Chromatographia 30 (1990), S. 493-499 
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    ISSN: 1612-1112
    Keywords: Gas chromatography ; Chemical potential of solutes ; Ideal dilute solutions ; Effect of size of solvent molecule
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Gas-liquid chromatography allows the rapid experimental determination of the Henry coefficient of molecular probes if a number of precautions are taken. From a knowledge of the temperature dependence of the related standard chemical potential, the standard partial molar enthalpy, entropy and the mean heat capacity difference can be calculated. These functions determine the retention behaviour of the probe over a temperature range of more than 100 K with a precision better than 1%. They also give the necessary information to verify and to develop models for ideal dilute solutions and for the calculation of interaction forces. The choice of specific solvents is examined and justified and the experimental determination of retention data is discussed especially with reference to the precautions to observe in order to measure retention governed by gas-liquid partition only. Calculation of the standard chemical potential related to the molal Henry coefficient is advocated and the dependence of the standard chemical potential on size and shape of the solvent molecule based on data collected on paraffinic stationary phases is examined. This latter function is shown to depend linearly on the inverse of the molar mass of the solvent. Comparison with literature data demonstrates the general validity of this finding and that the shape of the solvent molecule is of less importance.
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    Determination of carbofuran in a nutrient solution by GLC/NPD and HPLC (1990)
    Springer
    Chromatographia 30 (1990), S. 421-423 
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    ISSN: 1612-1112
    Keywords: Gas chromatography ; Column liquid chromatography ; Carbofuran ; Hydroponics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Two analytical methods using GC/NPD and HPLC to analyse carbofuran in a nutrient solution used in hydroponic culture are described. Both methods show a high recovery, (greater than 90%), and their limits of detection are low.
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    Wide-bore capillary column for the direct analysis of ethanolamines and ethylene glycols (1991)
    Springer
    Chromatographia 31 (1991), S. 171-172 
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    ISSN: 1612-1112
    Keywords: Gas chromatography ; Ethanolamines ; Ethylene glycols ; Wide-bore capillary column
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The GC separation of a mixture of three ethanolamines and four ethylene glycols without any preliminary derivatization, on a wide-bore capillary column coated with Carbowax 20M is described. These high-boiling and polar compounds elute giving simmetrical peaks and show good resolution. The analysis is completed in less than 14 minutes.
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    Computer-assisted multifactor optimization of selectivity in gas chromatography (1991)
    Springer
    Chromatographia 31 (1991), S. 173-176 
    Details
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Stationary phase optimization ; Mobile phase optimization ; Column temperature optimization ; Multifactor optimization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A computer-assisted method is presented for the simultaneous multifactor optimization (stationary phase loading, column temperature and carrier gas flow rate) of the analytical conditions for the optimum separation of multicomponent samples in gas chromatography. The optimization of the separation over the experimental region is based on a special polynomial from twelve preliminary experiments using the resolution as the selection criterion. Computer scanning technique was used for optimum selection in three dimensions. Excellent agreement was obtained between the predicted data and the experimental results.
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    Silica surface controversies, strong adsorption sites, their blockage and removal. Part II (1991)
    Springer
    Chromatographia 31 (1991), S. 193-205 
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    ISSN: 1612-1112
    Keywords: Gas chromatography ; Column liquid chromatography ; Silanol adsorption centres ; Strongly interacting adsorption sites ; Suppression of adsorption activity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary In this second part of the review heterogeneity of the silica surface is described and evidence is presented for the existence of a low population of strong adsorption sites. Methods of detection and determination of these strongly interacting sites are discussed. The last part of the review is devoted to the suppression of unwanted adsorption activity. Methods of blockage and special methods for the preparation of HPLC packings are described.
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    Gas chromatographic evaluation of wool wax alcohols supported by principal component analysis (1991)
    Springer
    Chromatographia 31 (1991), S. 243-246 
    Details
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Principal component analysis ; Wool wax alcohols ; Sterols
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Capillary gas chromatography with flame ionization detection has been applied to the separation of the components of wool wax alcohols. Twenty-six commercial and non-commercial (laboratory) samples were investigated. Twenty-eight components found in the samples were used as variables for further characterization by a chemometric procedure. Principal component analysis was applied to the differentiation of samples from different sources and obtained by different technologies.
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    Fluorine-induced chemiluminescence detection of phosphine, alkyl phosphines and monophosphinate esters (1991)
    Springer
    Chromatographia 31 (1991), S. 342-346 
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    ISSN: 1612-1112
    Keywords: Gas chromatography ; Chemiluminescence detection ; Phosphine derivatives ; Headspace analysis ; Fluorine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Phosphine, alkylated phosphines and monophosphinate esters are detected with high sensitivity in capillary gas chromatography (GC) by their chemiluminescent reactions with molecular fluorine. Detection limits are estimated to be 1.3 pg, 0.5 pg, 8 pg, and 17 pg for phosphine, trimethyl phosphine, trimethyl phosphinate ester, and triethyl phosphine, respectively. As found earlier with alkylated sulfur, selenium and tellurium compounds, the detector exhibits a linear response. For triethyl phosphine, a linear range of greater than three orders of magnitude was demonstrated. Emission spectra were obtained for the trimethyl phosphine and triethyl phosphine systems. Chemiluminescence emitters include electronically excited HCF, vibrationally excited HF, and an unknown species in the trimethyl phosphine system. Banded emission from vibrationally excited HF and a broad continuum were observed for both trimethyl phosphine and triethyl phosphine; however, HCF emission was observed only for TMP. Under the conditions employed, the principal emitter is HCF for trimethyl phosphine and HF and the unknown emitter for triethyl phosphine. This detector may have important applications in investigations of the biogeochemical cycling of phosphorus.
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    A spark modulator for correlation chromatography (1991)
    Springer
    Chromatographia 31 (1991), S. 393-397 
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    ISSN: 1612-1112
    Keywords: Gas chromatography ; Correlation chromatography ; Spark modulator injector
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A spark modulator has been tested as an injection system for correlation gas chromatography. An air/hydrocarbon vapour mixture was used as the carrier gas. Single negative sample injections were performed using a single spark period. The experiments resulted in negative sample peaks and a positive product peak. The intensity of all peaks showed a characteristic dependence on the spark frequency and power used. Ghostpeaks were absent when a correlation experiment was performed with a high concentration of a test compound in pure air. The signal to noise ratio enhancement however, was lower than the theoretical value. More experiments are necessary to expalain this phenomenon.
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    Evaluation of new organoclay stationary phases for the separation of ethylbenzene and xylene isomers (1991)
    Springer
    Chromatographia 31 (1991), S. 457-464 
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    ISSN: 1612-1112
    Keywords: Gas chromatography ; Organoclay stationary phase ; Bentone ; Ethylbenzene and xylene isomers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Several kinds of Bentones which have structures similar to Bentone 34 have been tested and compared for the purpose of improving the resolution of ethylbenzene and xylene isomers by gas chromatography. Bentone SD-3 was found to have higher selectivity toward these close-boiling compounds than the well known stationary phase Bentone 34. Modification effects of some conventional stationary phases which represent the whole range of polarity on the chromatographic property of Bentone SD-3 have been investigated and discussed. A number of new organoclays which have different structures of the organic cation in complexes have been synthesized and their properties evaluated for the separation of positional isomers. A simultaneously high selective organoclay for each component in the aromatic mixture of ethylbenzene and xylene isomers, without assistance of conventional stationary phases, has been described.
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  • 94
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    A GC method for chlorinated pesticides and PCB's in mussels (1991)
    Springer
    Chromatographia 31 (1991), S. 453-456 
    Details
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Organochlorine pesticides ; Polychlorinated biphenyls ; Solid phase extraction ; Mussels
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A multi-residue method for the determination of organochlorine pesticides and polychlorinated biphenyls (PCB's) in mussels (Mytilus sp.) is presented. After extraction with acetonitrile, pesticides and PCB's are separated from coextractives by liquid-liquid partition between acetonitrile and water/hexane. Further clean-up is performed using Sep-Pak Florisil cartridges eluting PCB's in the first eluate with hexane and organochlorine pesticides in the second eluate with 15% ethyl ether in hexane. Final determination is carried out by capillary gas chromatography with ECD. Detection limits for different pesticides and PCB's range from 0.02 to 0.3 μg kg−1 and recoveries from standards solutions treated in the same way as the samples averaged 91.5%.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02262388
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  • 95
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    Non-linear calibration of a nitrogen-phosphorus detector for the GC determination of amino acids (1991)
    Springer
    Chromatographia 31 (1991), S. 500-504 
    Details
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Amino acids ; Linearity ; Nitrogen-phosphorus detector
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A significant curvature of the detector response was observed when a Nitrogen-Phosphorus Detector (NPD) was used for the gas chromatographic determination of amino acids. Five calibration standards, over a 16 fold concentration range, were used to calibrate the NPD. A calibration curve of form y=axb was found to be suitable, with coerelation coefficients (r)〉0,997 for all 17 amino acids. A t-test was used to prove that b≠1, i.e. there was significant curvature. This calibration curve reduced calibration errors to less than 6%, compared to more than 40% for linear calibration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02262396
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  • 96
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    Headspace-gas chromatography: The influence of sample volume on analytical results (1991)
    Springer
    Chromatographia 32 (1991), S. 5-12 
    Details
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Headspace sampling ; GC theory ; Influence of sample volume
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The role of the volume of the sample and the sample vial in equilibrium headspace-gas chromatography is discussed. A new term, thesample phase fraction (ΦS) is introduced. It is shown that if the value of ΦS is kept constant, the vial's volume has no influence on the “sensitivity” of the headspace analysis (which is proportional to the concentration of the analyte in the headspace). In a given headspace sampling system, concentration of the compound of interest in the headspace (c G * ) at equilibrium is related to the value of ΦS: a higher ΦS will increase c G * . However, the influence is important only in the case of low distribution coefficients: in the case of higher distribution coefficients this influence is negligible. This conclusion is also true for small changes in the sample volume in duplicate analyses: exact reproducibility of the sample volume is important only in the case of low distribution coefficient values.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02262458
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  • 97
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    Purity of carbon dioxide as limiting factor in trace-level analysis by on-line supercritical fluid extraction/capillary gas chromatography (1991)
    Springer
    Chromatographia 32 (1991), S. 543-545 
    Details
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Supercritical fluid extraction ; GC detectors ; Purity of gases
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The usefulness of several grades of carbon dioxide for online supercritical fluid extraction/capillary gas chromatography has been studied. If trace-level work has to be performed, no single grade can be recommended for all modes of detection studied. Good-quality carbon dioxide is available for use with flame ionization and thermionic detectors. With electron-capture detection, however, distinct problems still exist.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02327900
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  • 98
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    Gas syringe sampling at very low pressure (1991)
    Springer
    Chromatographia 32 (1991), S. 579-582 
    Details
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Flame gas analysis ; Low pressure sampling ; Gas syringes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A new sampling technique is developed for flame samples taken at very low pressure (50 Torr absolute). This technique uses gas syringes. Analysis is by gas chromatography and the compounds of interest are the fixed gases and selected C1 and C2 hydrocarbons and chlorinated hydrocarbons. Linear response factors are obtained for all compounds. This is highly unusual for gas-phase chlorinated hydrocarbon sampling, which is very prone to sample absorption. The sources of experimental error unique to gas syringe use are identified and quantified. One error source is exacerbated by the very low sample pressure and requires special treatment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02327907
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  • 99
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    Cubic splines compared with other methods for the calculation of programmed temperature retention indices (1991)
    Springer
    Chromatographia 32 (1991), S. 116-124 
    Details
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Linear temperature programming ; Calculation of retention indices
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Program temperature retention indices for fifteen nonalkane solutes have been determined by cubic splines, by other procedures found in the literature and by interpolation of the n-alkanes retention time logarithm for eleven temperature programs. A comparison in terms of variance of the differences between PTRI calculated by CS and each of the remaining methods is made for each of the eleven program runs, for each of the three stationary phases used and for many of the programs. The smallest variances obtained result when the Zenkevich, van den Dool & Kratz and Chen et al. methods are tested. The stationary phase polarity is of no relevance since it has no effect on the specific PTRI found by the different methods employed in this work.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02325013
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  • 100
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    Anomalies in homologous relationships: When to suspect extrapolations (1991)
    Springer
    Chromatographia 32 (1991), S. 211-214 
    Details
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Retention index of homologous series ; Chain rigidity ; Stationary phase polarity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The rule that addition of a CH2 group to a molecule increases the retention index by 100±3 is subject to a greater uncertainty than ±3 when (a) the stationary phase has very strong intermolecular attractions comparable to the nitriles and the analyte has a polar group in the 1-position, (b) the alkyl chain to which the CH2 is added has 3 or fewer carbons and (c) when a group that is remote from the end of the chain, such as an ester group or a double bond, introduces rigidity in that part of the chain. In cases (a) and (c), it is still true that the retention index increases linearly in a specific homologous series, but it may deviate from 100 units per carbon by as much as 10 or, in the case of nitrile stationary phases, may be as low as 70.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02276242
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