ISSN:0935-6304    

DOI:10.1002/jhrc.1240130702

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1990

数据来源: WILEY

摘要:

AbstractA sensitive and reproducible residue method is described for the determination of cypermethrin and deltamethrin in fish eggs. The limit of determination of 0.0005 mg kg−1is achieved using only a very small sample size; typical sample weights lie in the range of 0.1‐1 g of fathead minnow or trout eggs. The method involves tissue homogenization (tube homogenizer) followed by hot acetonitrile extraction, then sequential C8, aluminum oxide, and silica gel clean‐up. The clean‐up is carried out in glass columns using cotton wool plugs in order to minimize potential sample contamination by plasticizers. Residues are determined by capillary chromatography using automated on‐column injection with electron‐capture detection. Confirmation of residues by gas chromatography‐mass spectrometry using selected ion monitoring (SIM), is a

ISSN:0935-6304    

DOI:10.1002/jhrc.1240130703

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1990

数据来源: WILEY

摘要:

AbstractThe present paper describes constructional details and evaluations of an at‐column injector for capillary GC. Injections were madeviaa sample loop on a 0.32 mm i.d. capillary column. Two rotary valves were employed to allow a wash of the sample loop and a backflush of the transfer line. Repeatability, calculated from absolute area counts forn‐alkanes was between 0.3–1%RSD, for injected sample volumes between 5 and 100 μl. Promising results were also obtained with syringe‐based injections on narrow bore (100 μ i.d.) columns. Repeatability on the basis of normalized area counts was in the order of 0.1–0.2%RSD, while solvent tailing was practic

ISSN:0935-6304    

DOI:10.1002/jhrc.1240130704

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1990

数据来源: WILEY

摘要:

AbstractThis paper describes the use of coupled LC‐GC for the determination of organochlorine pesticide residues in fat samples. Organochlorine pesticide residues are preseparated from fat by LC on a short C‐18 column using an organic solvent as the mobile phase. Evaporation of the LC eluent is achieved by a modified on‐column interface, introducing an on‐line vaporizer module using the fully concurrent evaporation te

ISSN:0935-6304    

DOI:10.1002/jhrc.1240130705

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1990

数据来源: WILEY

摘要:

AbstractHigh‐resolution capillary gas chromatographic separation of enantiomers, belonging to different classes of compounds on cyclodextrin derivatives is described. The solutions of heptakis (2,3,6‐O‐trimethyl)‐β‐cyclodextrin (Phase I), heptakis (2,6‐O‐dimethyl‐3‐O‐trifluoro‐acetyl)‐β‐cyclodextrin (Phase II) and heptakis (2,6‐O‐dimethyl‐3‐O‐heptafluorobutyryl)‐β‐cyclodextrin (Phase III) in the moderately polar polysiioxane OV‐1701 were coated onto deactivated fused silica capillaries furnishing columns of high efficiency. The three phases show different enant

ISSN:0935-6304    

DOI:10.1002/jhrc.1240130706

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1990

数据来源: WILEY

摘要:

AbstractThe possibility of enhancing radial mass transfer in capillary SFC by tightly coiling the column is discussed. The influence of coiling‐induced secondary flow on the plate height and the speed of analysis in capillary SFC is investigated. It is shown that the experimental plate height in tightly coiled metal or fused silica columns departs from the Golay theory for laminar flow. The effect of the pressure drop associated with the use of higher mobile phase linear velocities is studied. The capacity factors of retained components are used as sensitive probes for pressure drop over the column. Experimental plate heights in coiled columns are compared with values calculated fromTijssen'stheory for coiling induced secondary flow. At low velocities a good quantitative agreement was observed between the theory and the experimental results. At intermediate velocities only a qualitative agreement is found. The speed of analysis in coiled columns was found to be up to 5 times higher than in straight capillaries. The largest gain in analysis speed was obtained for solutes with low capacity factors. It is shown that coiling the column can have a positive influence on the detectability. For tightly coiled 210 μm i.d. columns the advantages of coiling‐induced secondary flow could be fully exploited without adverse effects of the column pressure drop. For 50 μm columns the possibility to increase the speed of analysis by coiling was limited due to the high pressure

ISSN:0935-6304    

DOI:10.1002/jhrc.1240130707

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1990

数据来源: WILEY

摘要:

AbstractReversed phase LC is coupled to capillary GC by means of an on‐line extraction of the LC eluent. The extract is transferred to a loop‐type LC‐GC interface equipped with an early vapor exit. Using a phase switch from an aqueous reversed‐phase (RP)LC solvent to an organic solvent facilitates the introduction of the analyte in the GC system, since organic solvents such as hexane, pentane, and dichloromethane are more appropriate for the GC‐injection technique used in this study. As the partition coefficient of an organic solvent/aqueous system is correlated to the retention mechanism of reversed phase LC, the method has a general potential in LC/GC interfacing,viz.the extractability a component from the LC mobile phase eluting above a certain capacity factor from a RPLC column can be expected to be efficient. The method is applied to the determination of residues of the fungicide fenpropimorph in barley, oats, rye, and wheat. Another application of the interface which is feasible is the on‐line extraction of aqueous samples prior to large volume injection on GC‐NPD. The potential of the interface for the determination of residues nitrogen containing herbicides

ISSN:0935-6304    

DOI:10.1002/jhrc.1240130708

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1990

数据来源: WILEY

摘要:

AbstractThe FPD and the new SCD have been examined for their respective performance characteristics as sulfur selective detectors for HRGC in the determination of atmospheric sulfur gases. Overall, the SCD was an extremely selective and sensitive sulfur gas detector with lower MDLs than the FPD and fewer problems with interferences and noise stability, thus allowing the SCD more flexibility in capillary column selection. Modification of the FPD, however, provided more symmetrical peaks and greater resolution than the Sievers Model 350 SCD.

ISSN:0935-6304    

DOI:10.1002/jhrc.1240130709

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1990

数据来源: WILEY

摘要:

AbstractIn this paper we show that wine free amino acids derivatized as isopropylN‐heptafluorobutyryl esters can be used as a tool for wine characterization. Elementary wines of eightVitis viniferavarieties were studied during a seven year period. The characteristic wine amino acids for each variety were assessed by means of pattern recognition techniques. A “star symbol plot” was used for graphic represent

ISSN:0935-6304    

DOI:10.1002/jhrc.1240130710

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1990

数据来源: WILEY

摘要:

AbstractThe atomic emission detector (AED) is a valuable tool for the identification of unknowns in complex mixtures. To the extent that elemental response factors are independent of compound structure, gas chromatographic results allow calculation of atomic ratios for unknown compounds. In favorable cases, empirical formulas can be found. An algorithm for automated calculation of empirical formulas for all the peaks in a chromatogram has been developed. When finite accuracy prevents an exact determination of empirical formulas, the algorithm gives a list of all formulas for each compound which are compatible with the user‐defined limits.Examples are given of calculations for fatty acid methyl esters, substituted phenols, and pesticides. Analyses of volatile pollutants and polychlorinated biphenyls reveal a nonlinearity for hydrogen response, and an interference of chlorine on hydrogen. A lubricating oil analysis is used to illustrate the identification of unknown

ISSN:0935-6304    

DOI:10.1002/jhrc.1240130711

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1990

数据来源: WILEY