Determination of butyltin and phenyltin analogues in sea products by Grignard derivatization and gas chromatography-triple quadrupole tandem mass spectrometry

A robust method for the determination of six organotin compounds (OTs), monobutyltin (MBT), dibutyltin (DBT), tributyltin (TBT), monophenyltin (MPhT), diphenyltin (DPhT) and triphenyltin (TPhT), in sea products was developed using gas chromatography-triple quadrupole tandem mass spectrometry (GC-MS/MS). The target compounds were extracted by hexane containing 0.01% tropolone, derivatizated by Grignard reagent n-PrMgBr, purified on a serial connection of silica and florisil solid-phase extraction (SPE) columns, and finally analyzed by GC-MS/MS. Improved sensitivity and selectivity were achieved using tandem MS/MS rather than single MS, especially in reducing complex interferences in biotic matrices. The limits of detection (LODs) for the six OTs were all below 0.1 mu g Sn per kg in the case of wet samples, and were no higher than 0.5 mu g Sn per kg for dry samples. The linearity coefficients (r(2)) for the six OTs were all above 0.999 within the linear range from 0.4 to 200 mu g Sn per kg. The accuracy of the method was thoroughly validated using the certified reference material Mytilus edulis (ERM-CE477) and a spiked recovery test in four different biotic matrices, including tonguefishes, sea snails (Neverita didyma), scallops (Patinopecten yessoensis) and the Asian moon scallop. The butyltin concentrations determined for CE477 agreed well with the certified values, and the relative standard deviations (RSDs) for the six OTs were all below 12.1%. The spiked recoveries in four biotic matrices were within the range 70.5-105.3% for MBT, DBT, TBT, DPhT and TPhT, and 82.2-133.5% for MPhT, and the RSDs ranged from 0.5% to 12.5%. The proposed methodology was applied to the determination of butyltin and phenyltin compounds in nine different sea products sampled from the Bohai coast, China, with total OTs ranging from 1.36 to 20.54 mu g Sn per kg wet weight.