Optimization of the solid phase microextraction procedure for the ultra-trace determination of organotin compounds by gas chromatography-inductively coupled plasma-mass spectrometry

A chemometric approach based on experimental design and desirability functions was used to develop and validate a SPME-GC-ICP-MS method for the determination of the organotin compounds dimethyltin, tributyltin and dibuthyltin. Three different SPME coatings were evaluated, obtaining the best results by using the divinylbenzene/carboxen/polydimethylsiloxane 2 cm 50/30 mm fibre. The optimal extraction conditions were found to be the following: T ¼ 30 1C, t ¼ 40 min and pH ¼ 4. Method validation was performed by determining the most relevant quality parameters such as detection limit, quantitation limit, repeatability and intermediate precision. LOD values in the 0.2–8 ng L_1 were obtained.