ISSN:0935-6304    

DOI:10.1002/jhrc.1240180902

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

年代:1995

数据来源: WILEY

摘要:

AbstractIn this work the application of high‐speed narrow‐bore capillary GC in combination with a fast scanning double focusing magnetic sector mass spectrometer is evaluated. Special emphasis is placed upon detection limits and scan speed in the full scan mode and in the selected ion monitoring mode (SIM). In the full scan mode, up to 20 scans per second could be obtained. The detection limits are in the low picogram range in the full scan mode and improve even to 5 to 50 fg in the SIM mode, depending on the sample complexity and mass resolving power. It will be illustrated that by increasing the resolution in the SIM mode, interferences from ions of the same nominal mass‐to‐charge ratio as the ions of interest are significantly reduced. Chemical background noise can therefore be largely eliminated, thus enhancing the signal‐to‐

ISSN:0935-6304    

DOI:10.1002/jhrc.1240180903

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

年代:1995

数据来源: WILEY

摘要:

AbstractDetermination of trace concentrations of sulfur components in natural gas is a true analytical challenge. Only analytical procedures based on gas chromatography can meet the sensitivity and accuracy requirements dictated by environmental regulation institutions and modern chemical industry. In the present contribution the sample pretreatment and chromatographic separation steps have been evaluated and optimized based on the use of a flamebased sulfur chemiluminescence detector (SCD) for target compound detection.The proposed instrument consists of a programmed temperature vaporizing (PTV) injector employing a liner packed with Chromosorb 104, a 4 μm thick film apolar column and a flame‐based SCD. Using a 13 mL sample loop the detection limit achievable with the new method is 3 μg S/m3. The precision of replicate measure. ments is generally in the range of 5–15% relative standard deviation. Lower detection limits can be achieved by preconcentrating larger sample volumes,e.g.1

ISSN:0935-6304    

DOI:10.1002/jhrc.1240180904

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

年代:1995

数据来源: WILEY

摘要:

AbstractIn order to meet the requirements of analyzing very low concentrations of pesticides in water (typically at 0.1 μg/l or less), samples have to be concentrated prior to GC‐analysis. Samplie pre‐concentration by off‐line methods based on solid phase extraction (SPE) or liquid‐liquid extraction are very time consuming and cumbersome. Moreover, the quantitative performance of the analytical method as a whole in terms of accuracy and reliability is seriously hindered by elaborate, manually performed sample pre‐treatment steps. This paper describes an automated method based on solid phase extraction and capillary gas chromatography. The technique was applied for the analysis of 31 polar organophosphorus and organonitrogen pesticides. A commercially available HPLC/GC instrument is modified, using the LC‐part for solid phase extraction. The sample, of which only a few ml's is required to obtain sufficiently low detection limits, is delivered by a robotic large volume autosampler. After solid phase extraction and elution, the eluate is transferred into the GC via a so called “loop type interface”. In this paper the instrumentation and analytical methodology is described, as well as the main validation results. The quantitative performance (i.e.recovery and repeatability) of the most polar solutes like metamitron and dimethoate appears to be better than obtained with off‐line SPE as a result of the more beneficial ratio between the amount of sorbent and the sample volume. As the loop‐type interface causes losses of the most volatile compounds, a co‐solvent is added. This co‐solvent provides sufficient trapping capacity in the capillary pre‐columns to allow quantitative analysis of even the most volatile pesticides. Moreover a better separation of early eluting com

ISSN:0935-6304    

DOI:10.1002/jhrc.1240180905

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

年代:1995

数据来源: WILEY

摘要:

AbstractRetention factors in capillary electrochromatography (CEC) were calculated by means of theoretically derived equations and experimentally determined parameters in microcolumn liquid chromatography and capillary zone electrophoresis. It was found that the retention factor of uncharged components in CEC was about 20% higher than was calculated. The derived equations do not take into account alteration of the nature of the stationary phase or distribution constant by the applied electric field. However, the influence of the electric field on the retention in CEC can be estimated. Individual field contributions could not be determined.

ISSN:0935-6304    

DOI:10.1002/jhrc.1240180906

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

年代:1995

数据来源: WILEY

摘要:

AbstractSome triazines and metabolities have been analyzed in water and soil samples, at the 0.1 and 10 ppb level, respectively, by CGC‐MS and CGC‐MS‐MS using an ion trap detector (ITD). The sample preparation consisted of SPE on LiChrolut EN cartridges for water samples, and of ultrasonic treatment followed by SPE for soil samples. Recoveries were in the order of 90%. The advantage of MS‐MS compared to MS operation of the ITD, is the enhanced selectivity resulting in more precise determinations. The metabolites of atrazine and metribuzin have also been studied. Desethylatrazine and desamino‐metribuzin are the main me

ISSN:0935-6304    

DOI:10.1002/jhrc.1240180907

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

年代:1995

数据来源: WILEY

摘要:

AbstractAn iterative regression design has been used in the optimization of selectivity in capillary zone electrophoresis and micellar electrokinetic capillary chromatography. This strategy, initially developed for HPLC, is modified in respect of the choice of the parameter(s) and the parameter space and the description of the migration behavior of (charged) solutes in capillary electrophoresis. The six test solutes could not be fully resolved by adjusting the pH in a free zone system but the simultaneous two‐parameter optimization of the pH and the concentration of surfactant resulted in baseline separation of all the solutes. Further improvement may be obtained when distorted peak shapes are also considered at the level of the parameter choice and the criterio

ISSN:0935-6304    

DOI:10.1002/jhrc.1240180908

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

年代:1995

数据来源: WILEY

摘要:

AbstractA new method to accurately deliver small amounts (0.5 to 20 mol%) of modifier into CO2was used to study the effects of three different modifiers (methanol, water, and formic acid) in packed capillary column SFC. The method allows the use of different modifiers, with minimal instrument modification. The effects of the different modifiers at different concentrations on retention and peak shape are shown by analyzing a polarity test mixture and a sample of free fatty acids.

ISSN:0935-6304    

DOI:10.1002/jhrc.1240180909

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

年代:1995

数据来源: WILEY

摘要:

AbstractA method for the determination of anionic solutes such as phenol, cresols, and xylenols present in industrial effluents has been developed. It is based on microextraction using two miscible phases followed by demixing of the phases by the addition of ammonium sulfate. The extraction properties of 2‐propanol were examined and the procedures were optimized. High resolution gas chromatography–mass spectrometry in the selected ion monitoring mode was used as a separation and quantitation technique. This method is rapid and precise and allows detection limits of 1 μg L−1to be easily obtainable employing a 50 mL water

ISSN:0935-6304    

DOI:10.1002/jhrc.1240180910

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

年代:1995

数据来源: WILEY

摘要:

AbstractA chemically bonded C60silica phase was synthesized as a stationary phase for liquid chromatography (LC) and its retention behavior evaluated for various polycyclic aromatic hydrocarbons (PAHs) using microcolumn LC. The results indicate that the C60bonded phase offers selectivity different from that of octadecylsilica (ODS) bonded phases in the separation of isomeric PAHs. With the C60phase, PAH molecules having a partial structure similar to that of the C60molecule,e.g.triphenylene and perylene, were retained longer than with ordinary ODS stationary phases. The results also show that good correlation exists between the retention data with this C60bonded phase and with C60itself as the stationary phase.

ISSN:0935-6304    

DOI:10.1002/jhrc.1240180911

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

年代:1995

数据来源: WILEY