SUPERCRITICAL-FLUID EXTRACTION OF TRIBUTYLTIN AND ITS DEGRADATION PRODUCTS FROM SEAWATER VIA LIQUID-SOLID PHASE EXTRACTION

Quantitative extraction of di- and tributyltin compounds from aqueous matrices using C-18 liquid-solid extraction (LSE) discs, followed by in situ Grignard ethylation and supercritical fluid extraction of derivatized LSE discs, is demonstrated for the first time. The optimum extraction efficiency of dibutyltin and tributyltin from synthetic seawater at pH 2 was achieved by using a combination of static and dynamic extraction procedures with supercritical carbon dioxide (10 MPa, 40 degrees C). The extraction efficiency for dibutyltin and tributyltin ranged from 92 to 102%, and the R.S.D.s (n = 5) were 6.6 and 8.2%, respectively. The limit of detection of tributyltin (1 l of seawater) using a capillary gas chromatograph coupled to a single-flame tin-selective flame photometric detector was 6 ng/l, while the limit of quantitation of harbour seawater was 9 ng/l. Furthermore, analysis time and solvent usage are reduced by 50 and 90%, respectively, in comparison with classical methods involving liquid-liquid extraction in the presence of complexing agents.