Reduction of the column diameter has proved to be a highly efficient tool to increase the speed of analysis. Unfortunately, the requirements for instrumental design with respect to sample input band width, low dead volume interfacing, and time constants of detection and registration systems are the more critical the smaller the inside diameter. Recently we reported input band widths as low as 1 ms [1] for gaseous samples at ppm concentration levels, without any preconcentration, in a study with narrow bore columns and thermal conductivity detection. In this study a simple versatile micro on‐column cold trap/thermodesorption enrichment system for narrow bore columns is introduced and evaluated. The combination of considerable sample enrichment and preservation of the compatibility of the required input band width with column dimensions is critically examined. The process of thermodesorption (reinjection) which is the most critical step, is particularly emphasized. The system consists of a short aluminum coated fused silica or metal capillary with a low mass and a low cost electrical heating. Input band widths down to 1 ms are obtained without extreme demands on electrical power (300 watt). The potential of the system is illustrated with some extremely fast separations.

The speed of analysis in capillary gas chromatography can be substantially increased by reduction of the column inner diameter. However, special demands are then posed upon instrumental design. In particular, the sampling system is highly critical because it has to be capable of delivering extremely small injection band widths which must be compatible with the column inside diameter. This study focuses on the evaluation of two potentially suitable sample introduction systems with respect to input band width and detection limits and their compatibilitywith small bore (5 100 pm)columnsincapillarygas chromatography. One of them allows liquid on-column injection, based on liquid splitting, of only a few nl onto small bore (5 100 4m) fused silica columns. Forgases, input band widthsas low as 1 ms are obtained with this system. The other one is part of a miniaturized gas chromatograph with extremely low dead volume interfaces and detector volumes. It allows input band widths for gases of a few ms. Without any preconcentration ppm concentrations are measured in gaseous samples with a 80 4m thick film capillary column. It will be shown that a further reduction of the minimum detectable amount and analysis time is possible with this equipment.

SummaryThe design and features of an on-line purge and cold-trap preconcentration device for rapid analysis of volatile organic compounds in aqueous samples are discussed. Excessive water is removed from the purge gas by a condenser or a water permeable membrane in order to avoid blocking of the capillary cold-trap. Synthetic mixtures covering concentrations ranging from tenths to tens of ppb's and different chemical classes are used to study the effect of various process factors on the efficiency and selectivity of water removal as well as on the purging recovery. The importance of the concentration of the solutes, the flow rateinconjunction with thevolumeof the purge gas, and the temperatureof thecondenser, thecold-trapand the sample is emphasized. Theoretical models describing the purge process and the blocking of the cold-trap agree fairly well with the highlyreproducibleexperimental results (o = 2-4'10). Both the condenserand the Nafion membrane successfullyremove water, although some compounds, dependent on volatility and polarity, are partly or completely lost. It is shown that non-polar volatile organic compounds are efficiently enriched so that recoveries between 80-100% and a detection limit of 1 ppt can be obtained. The applicability of the system is illustrated on some examples.

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SummaryExpressIons for the minimum detectabie amount 0 0 and the minimum analyte concentration Co as functlons of the chromatographic parameters are derlved for both mass and concentratlon sensltlve detectors. The effects of pressure drop, column inner diameter, and film thickness are given.The minimum analyte concentration for mass flow sensitlve detectors, Cam, can be reduced conslderably by selecting the carrier gas velocity weil above lts optimum value (related to Hml n ), however, at the cost of long columns and long analysis times. For 0 0 the improvements can be neglected, and 80 the analysis can best be performed at Uopt.When the flow rate In the detector, F d, is equal to the column flow rate F c, the maximum permissible detector volume of concentration sensitlve detectors is proportional to d c 2 up to d c 3 , and so narrow bore columns requlre detectors of extremely sm all volume. Make-up gas has to be added when the actual volume is too large, th us worsening the detectability. Another approaCh, vacuum operation of the detector cell, appears to be very attractive. On the other hand, when wide bore columns are used in comblnation with smaU volume concentration sensltive detectors, very smaU values of Qoc and Coc are obtalnable when the abundant carrier gas can be removed betare entering the detector cell.Digital nolse filtering can furtherreducethe obtalnable 0 0 and Co values, especially for broad peaks and thus for wide bore columns.