Design of automated solid-phase microextraction for trace analysis of organic compounds in aqueous samples

The evaluation of static at,sorption and three different agitation modes including magnetic stirring, fibre vibration method, and a self constructed flow-through extraction cell for solid-phase microextraction (SPME) of trace organics is presented in this study. A mixture of analytes which contained five pesticides: ametryn, parathion, prometryn, simetryn, and terbutryn was selected for direct absorption from aqueous samples using a 100 mu m poly(dimethylsiloxane) fibre. The absorption-time profiles and precisions were studied under different conditions using spiked aqueous samples. A commercially available autosampler was investigated for static absorption and the fibre vibration method. The efficiency of the automated SPME analysis methods developed was compared to the classical extraction of magnetically stirred samples and on-line SPME using the recently developed flow-through cell concept. Besides the kinetic aspect of a fast absorption characterizing the efficiency of the absorption mode selected, the precision was studied for all systems investigated to estimate the analytical accuracy which could be achieved by using these absorption techniques. In general, all agitation modes showed a precision for most of the compounds below 5% R.S.D. The fibre vibration technique significantly increases the precision and sample output of the automated SPME-GC method for the analysis of semi-volatile compounds. (C) 1997 Elsevier Science B.V.