Speciation of butyltins by dispersive liquid-liquid microextraction and gas chromatography-mass spectrometry

Dispersive liquid-liquid microextraction in combination with an in situ derivatization is suggested for butyltin compounds sampling and preconcentration from water solutions. The derivatization was carried out with sodium tetraethylborate at pH 4.5. The effects of extraction and disperser solvents type, volume, extraction time and ionic strength of the solution on the extraction efficiency were investigated. Tetrachloromethane containing n-hexadecane as an internal standard was used as an extracting solvent and methanol was used as a disperser solvent. The calibration graphs were linear from 2.8, 4.2 and 9.8 ng L–1 up to 10 μg L–1 for monobutyltin, dibutyltin and tributyltin, respectively, correlation coefficients were 0.996–0.999, detection limits were 1.7, 2.5 and 5.9 ng L–1 for monobutyltin, dibutyltin and tributyltin, respectively. Repeatabilities of the results were acceptable with relative standard deviations up to 17%. A possibility to apply the proposed method for butyltin compounds determination in water samples was demonstrated.