Headspace solid-phase microextraction-capillary gas chromatography-ICP mass spectrometry for the determination of the organotin pesticide fentin in environmental samples

The extraction and preconcentration capabilities of headspace solid-phase m icroextraction (headspace SPME) were combined with the separation power of capillary gas chromatography (CGC) and the low limits of detection (LODs) o f inductively coupled plasma mass spectrometry (ICP-MS) for the determinati on of the organotin compound triphenyltin (TPhT or fentin) in aqueous stand ard solutions and in potatoes and mussels after digestion with tetramethyla mmonium hydroxide (TMAH) or KOH-EtOH. Throughout, tricyclohexyltin (cyhexat in, TCT) was used as internal standard. Derivatization to transform TPhT an d TCT into sufficiently volatile compounds was carried out with sodium tetr aethylborate (NaBEt4), at pH 8 (0.2 mol L-1 ammonium buffer). Headspace ext raction was performed for 10-20 min at 75 or 85 degrees C (depending on the type of sample) with a 100 mu m polydimethylsiloxane (PDMS) fiber. Absorpt ion curves showed that even at high temperature (75 degrees C) no equilibri um conditions were obtained for either compound. Direct aqueous SPME was al so studied, but the sensitivity was 11 times lower at 25 degrees C than tha t observed when using headspace SPME at 75 degrees C. After 2 min desorptio n of the SPME fiber at 270 degrees C in the GC inlet, the organotin compoun ds were separated on a capillary column with a polydimethylsiloxane coating and transported into the ICP by means of a home-made heated (270 degrees C ) transfer line. Monitoring of the Sn-120(+) signal by ICP-MS during the ru n of the GC provided extremely low LODs for fentin in water: 2 pg L-1 (inst rumental) and 125 pg L-1 (procedure) as well as a good repeatability of 8% RSD (n = 10). For mussels and potatoes, concentrations in the range 3-10 an d 0.9-3 ng g(-1) (dry weight, as Sn), respectively, were found.