Evaluation of dynamic headspace and purge-and-trap techniques for the high-resolution gas chromatography analysis of nitrous oxide in seawater

The present study focuses on the effectiveness of dynamic headspace (DH) an d purge-and-trap (PT), which are two commonly used techniques for determini ng volatile organic compounds in environmental samples, on the extraction a nd trace analysis of nitrous oxide in seawater. With the aim of obtaining r eliable quantitative data in the DH and in the PT techniques, kinetics of t hese processes were studied; a first-order kinetic-like function is found t o be followed for the extraction of nitrous oxide in both the DH and PT sam pling methods. A three-way analysis of variance was carried out to evaluate the effect of the water sample composition on DH and PT analysis in order to systematically and accurately examine the effect of different factors on the chromatographic response of N2O; a significant matrix effect proportio nal to the nitrous oxide concentration was observed when bidistilled water, synthetic and natural seawater were considered. The effects of different s ampling procedures were evaluated in terms of linearity range, limit of det ection, capability of detection, precision, extraction recovery and accurac y. Better results in terms of extraction recovery, sensitivity and detectio n limit were obtained when applying the purge-and-trap technique combined w ith GC-electron-capture detection; detection limits at very low pmol ml(-1) levels were achieved, making this procedure suitable for trace nitrous oxi de analysis in marine samples, (C) 1999 Elsevier Science B.V. All rights re served.