Pressurized liquid extraction using the accelerated solvent extractor (Dionex ASE 200) has been evaluated for the determination of mono-, di- and tributyltin (MBT, DBT, and TBT, respectively) in PACS-2 certified reference material. A double-enriched spike containing 119Sn-enriched MBT and TBT and 118Sn-enriched DBT allowed for the simultaneous determination of the three butyltin species and the factors governing species interconversion. The stability of the spike was evaluated by reverse isotope dilution experiments covering more than one year with satisfactory results. Quantitative recoveries using ASE for TBT and DBT were obtained at temperatures above 110 degrees C. The effect of the extraction time and number of static cycles was evaluated. Results suggest that extraction efficiency was quantitative with extraction times as low as 10 min for all butyltin species at 110 degrees C. Decomposition reactions were only detected at the higher temperatures assayed (140 and 175 degrees C) and that was only for the degradation of DBT to MBT (approximately 4%). The results found for MBT were approximately 25% higher than the certified value for the PACS-2 sediment reference material in agreement with previous results obtained by ultrasonic and microwave assisted extraction.