Abstract A method has been developed for species-se- lective analysis of organotin compounds in solid, biologi- cal samples. The procedure is based on accelerated sol- vent extraction (ASE) of analytes and includes extraction of the tin species with a methanol–water (90% methanol) solution of acetic acid/sodium acetate containing tropolone (0.03% w/v), their ethylation with NaBEt 4 , and separation and detection by GC–FPD. The analytical procedure was optimized with an unspiked sample of harbor porpoise (Phocoena phocoena) liver. Effects of ASE operational variables (extraction temperature and pressure, solvent composition, number of static extraction steps) are dis- cussed. Method detection limits (MDL) were in the range 6–10 ng(Sn) g –1 dry weight and 7–17 ng(Sn) g –1 dry weight for butyl- and phenyltin compounds, respectively. Recov- eries were comparable with or better than those obtained by use of other procedures reported in the literature. The analytical procedure was validated by analysis of NIES No. 11 (fish tissue) certified reference material. Keywords Biological samples · Organotin compounds · Extraction · Multicapillary gas chromatography Introduction Organotin compounds are widely used in agriculture and industry. Butyl- and phenyltin compounds are employed mainly as biocides for protection of vessels and crops, re- spectively. Recently their use, especially in marine indus- try, has been restricted or even forbidden due to their non- specific and detrimental impact on the aquatic environ- ment [1]. To evaluate the fate of organotin compounds in the en- vironment and the effectiveness of legal provisions con- trolling their use, many analytical methods have been de- veloped. Although different separation, derivatization, and detection techniques have been employed, the major prob- lem still confronting us is quantitative extraction of analytes from complex sample matrices. Twelve extraction proce- dures for determination of butyl- and phenyltin compounds were recently evaluated [2]. Only one method was found to be suitable for the samples tested and gave satisfactory results for all six compounds under study. It is obvious that the extraction routine should match subsequent steps of whole analytical procedure to minimize the number of operations which are potential sources of erratic results. Considering the large number of derivatization, separation and detection techniques used in speciation studies one can expect a whole variety of extraction procedures reflecting the diversity of analytical methods and types of samples. Accelerated solvent extraction (ASE) is a relatively new extraction technique enabling control of important extrac- tion conditions such as solvent composition, applied pres- sure, temperature, and duration of the procedure, in order to achieve more quantitative extraction. Great advantages of this technique are the high degree of automation of the procedure and the possibility of processing several sam- ples in one run [3]. Literature search reveals that ASE has been successfully employed for extraction of different or- ganic compounds including polynuclear aromatic hydrocar- bons (PAH), polychlorinated biphenyls (PCB), polychlori- nated dibenzo-p-dioxins (PCDD), organochlorine pesticides (OCP) [4], and bioactive compounds from plant material [5]. On the other hand, there are, as far as we are aware, few papers dealing with application of this technique to the speciation of organometallic compounds [6, 7, 8, 9]. The aim of this study was to develop an analytical pro- cedure based on accelerated solvent extraction of butyl- and phenyltin compounds from biological material with their subsequent aqueous-phase ethylation and GC–FPD detection. Andrzej Wasik · Tomasz Ciesielski Determination of organotin compounds in biological samples using accelerated solvent extraction, sodium tetraethylborate ethylation, and multicapillary gas chromatography–flame photometric detection Anal Bioanal Chem (2004) 378 : 1357–1363 DOI 10.1007/s00216-003-2423-y Received: 29 July 2003 / Revised: 5 November 2003 / Accepted: 13 November 2003 / Published online: 30 January 2004 ORIGINAL PAPER A. Wasik (✉) Department of Analytical Chemistry, Chemical Faculty, Gdańsk University of Technology, 11/12 G. Narutowicza St, 80-952 Gdańsk, Poland e-mail: wasia@chem.pg.gda.pl T. Ciesielski Department of Food Sciences, Medical University of Gdańsk, 107 Hallera St, 80-416 Gdańsk, Poland © Springer-Verlag 2004