C18-coated stir bar sorptive extraction combined with HPLC-ICP-MS for the speciation of butyltins in environmental samples

In this paper, a new approach of C-18-coated stir bar sorptive extraction (SBSE) coupled with high performance liquid chromatography-inductively coupled plasma mass spectrometry (HPLC-ICP-MS) was developed for the speciation of butyltins in environmental samples. The butyltin compounds, including monobutyltin trichloride (MBT), dibutyltin dichloride (DBT) and tributyltin chloride (TBT), were first extracted with a C-18-coated stir bar, and then desorbed with 40% (v/v) methanol for subsequent HPLC-ICP-MS analysis. The factors affecting C-18-SBSE were systematically studied. To reduce the percentage of organic solvents in the mobile phase loaded on the plasma and to improve the separation resolution, a CN column with carboxylic acids as the mobile phase additives was used for butyltin separation. Quick separation (<8 min) was accomplished using a methanol-formic acid-water (16 : 8 : 76, v/v/v) mobile phase containing 5 mmol L-1 mercaptoacetic acid, and the mobile phase was compatible with the conventional quadrupole ICP-MS detector without addition of oxygen gas or desolvation and post-column dilution systems. Under the optimal conditions, the limits of detection for three target butyltins ranged from 15.6 to 29.4 ng L-1, with a linear range of 0.05-50 mu g L-1. The enrichment factors (EFs) were 85- to 127-fold (the theoretical EF is 200-fold). The developed method is simple and rapid, with no derivatization involved, and is successfully applied to the speciation of butyltins in the Certified Reference Material of PACS-2 sediment and real water as well as sediment samples from the East Lake, Yangtze River and Bohai Sea in China.