摘要:

AbstractThis report describes an on‐line capillary GC injection system which enables on‐column injection of a hundred or more microliters, and yields separations comparable with those obtained from on‐column injection of 1–2 microliters of solutions a hundred times more concentrated. Precision, carry‐over, linearity, and discrimination are comparable with those of classical sample‐introduction techniques. A selection of polar and high boiling compounds has been examined, and excellent peak shapes obtained for hundreds of injections. Initial results indicate that maintenance and long‐term reproducibility will also be comparable with those of classical techniques.The instrument utilizes a version of the large volume on‐column injector with solvent diversion described in an earlier communication, with the addition of a method for independent heating of the retention gap. This modification reduces the effects of activity in the retention gap and improves the capability of the technology to handle complex mixtures. It also increases reliability and system lifetime, fits readily into most GC ovens, is easily automated, and should be compatible with all capilla

ISSN:0935-6304    

DOI:10.1002/jhrc.1240160102

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

年代:1993

数据来源: WILEY

摘要:

AbstractThe identification and quantification of sulfur‐containing compounds in gasoline has become an area of interest because of impending legislation regulating total sulfur levels in these fuels. To study the effects of catalyst type and catalytic conditions on gasoline sulfur distribution, a method has been developed employing both the compound‐independent and element‐specific response of the atomic emission detector (AED). Calibration and quantification can be accomplished even where standards are not available, owing to the nature of the AED response.Compounds were separated on a thick film polydimethylsiloxane column. An external calibration curve was applied to the area responses of individual sulfur components in the sulfur chromatogram, and the concentrations of each were calculated. Summation of these sulfur concentrations over the gasoline range yields the total sulfur content of the gasoline.The method is applicable to the determination of these compounds in raw crude oils, finished gasolines, fluid cracking catalyst (FCC) unit gasolines, and fluid catalytic cracking “model” compound studies. A prefractionating column was employed to remove heavy (>C13) materials; prefractionation is not, however, necessary for distilled or commercial gasoline samples. Detection limits, linearity, detector stability, and accuracy are

ISSN:0935-6304    

DOI:10.1002/jhrc.1240160103

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

年代:1993

数据来源: WILEY

摘要:

AbstractThe tuning of selectivity by changing the flow rate has been investigated in HPLC: two columns with different retention characteristics were coupled in seriesviaa T‐piece and the relative retention of components chromatographed on the system were changed by varying the individual flow rates in the coupled columns. The flow rate alteration was performed by adding a second flow after the first column. The flow rate ratio necessary for optimum resolution can be easily calculated on the basis of the capacity factors measured on the individual columns. The performance of this method for adjusting selectivity has been demonstrated by using different column combinations to separate several mixtures containing chlorophenols, nitroaromatic compounds, and aromatic hydrocarbon

ISSN:0935-6304    

DOI:10.1002/jhrc.1240160104

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

年代:1993

数据来源: WILEY

摘要:

AbstractA simple and quick gas chromatographic method has been developed for the determination of up to six commonly used antiepileptic drugs in human serum. The antiepileptics are isolated from serum by solid phase extraction on to a reversed phase sorbent and recovered with ethyl acetate as eluent. The ethyl acetate eluate is suitable for direct on‐column injection on to a phenyl methyl siloxane capillary column; hydrogen is used as carrier gas and the compounds are separated with a two‐ramp temperature program. Detection is by FID.The reproducibility of the method varies between 2 and 6% RSD, depending on the drug and the level analyzed; limits of detection were found to be 14–51 pg and minimum assayed concentrations in serum were between 14 and 51

ISSN:0935-6304    

DOI:10.1002/jhrc.1240160105

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

年代:1993

数据来源: WILEY

摘要:

AbstractIn linear chromatography (i.e.chromatography performed in the absence of sample overloading), when the plate height of a column is roughly uniform along its length, variations in the velocities of solutes are the only possible causes of erosion of efficiency. The sources of these variations (variations in capacity ratio and in the density of the mobile phase,etc.) play no direct role in the erosion of efficiency except through their effect on solute velocities. In other words, what eventually causes the erosion of efficiency is merelyvariationin the time required for solutes to traverse equally small segments of a column. Significant erosion can only arise from abrupt and deep deceleration of solutes in one or several relatively small segments of a column.If erosion of efficiency caused by pressure gradients in linear SFC is to be large, the depth and the sharpness of the deceleration of a solute must go beyond that hitherto confirmed experimentally. Many relevant examples are analyzed graphically.

ISSN:0935-6304    

DOI:10.1002/jhrc.1240160106

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

年代:1993

数据来源: WILEY

摘要:

AbstractImportant considerations are discussed for analytical SFE method development employing methanol–modified carbon dioxide and solid‐phase trapping. The focus of this study was to break the method development procedure into distinct steps so that the origins of low recoveries could be determined conclusively. Sulfonyl urea herbicides were used as probe analytes. Analyte solubility, analyte trapping, analyte trap removal (solid‐phase), and extract analysis were all shown to be equally important in achieving quantitative SFE recov

ISSN:0935-6304    

DOI:10.1002/jhrc.1240160107

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

年代:1993

数据来源: WILEY

摘要:

AbstractRetention times in linear temperature programmed gas chromatography on narrow bore and megabore capillary columns have been calculated from experimental retention times measured at three isothermal temperatures: an iterative procedure performed by BASIC programs was used to obtain the values of the constants enabling the calculation of the programmed temperature retention times. Different methods of calculation have been compared.

ISSN:0935-6304    

DOI:10.1002/jhrc.1240160108

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

年代:1993

数据来源: WILEY

ISSN:0935-6304    

DOI:10.1002/jhrc.1240160110

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

年代:1993

数据来源: WILEY

ISSN:0935-6304    

DOI:10.1002/jhrc.1240160111

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

年代:1993

数据来源: WILEY

ISSN:0935-6304    

DOI:10.1002/jhrc.1240160112

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

年代:1993

数据来源: WILEY