Optimization of an analytical method for determining organotin compounds in fish tissue by base-hydrolysis pretreatment and simultaneous ethylation–extraction procedures

To determine butyl- and phenyl-tins in fish muscle, a method including base digestion pretreatment, followed by a simultaneous ethylation–extraction procedure and gas chromatograph-flame photometric detector (GC-FPD) analysis is outlined. Key parameters that influence analyte recovery were investigated and optimized. A solution of 3% (w/v) potassium hydroxide (KOH) and 1 h digestion time at 60 °C were chosen in the base digestion step, to ensure complete solubilization of fish muscle and the decomposition of organotins was found to be insignificant. We found that the ratio of fish muscle/reaction solution should not exceed 0.2 g (dry weight) per 100 mL in order to avoid the matrix effect caused by the binding of hydrolyzed fish tissue with organotin ions. Ethylation of organotins were conducted at pH 6–7 with a 1% (w/v) sodium tetraethylborate (NaBEt4) solution for 1 h. This simple and timesaving procedure should be able to be applied to the routine analysis of organotins in other bio-tissues.