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

Abstract

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 À1 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 À1 , with a linear range of 0.05-50 mg L À1 . 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.

Trends in the analysis and monitoring of organotins in the aquatic environment

“…ICP-MS) to GC and LC is complex to set-up and expensive to operate. For example, LC-ICP-MS requires additional oxygen to the nebuliser argon gas flow (for higher temperature combustion of organic solvents), increased power to the plasma, de-solvating equipment and a refrigerated spray chamber to avoid blockages of the interface [48]. LC applications can suffer reduced sensitivity (Table 4); typically being two orders of magnitude higher than GC-ICP-MS.…”

“…The most recent LPME procedures used with organotins include dispersive liquid-liquid microextraction (DLLME) [46], headspace-single drop micro-extraction (HS-SDME) [47] and direct immersionsingle drop microextraction (DI-SDME) [44]; with LODs using tandem mass spectrometry (MS-MS) and inductively coupled plasma-mass spectrometry (ICP-MS) ranging between 0.4 and 3.0 ng L À1 [44,47]. Stir-bar sorptive extraction (SBSE) is similar to SPME with both solvent less direct immersion or headspace sampling applications [7,48,49]. SBSE provides an increased preconcentration capacity of 50-250 times over SPME [47], however, uptake and elution conditions (e.g.…”

“…Commercially available SBSE sorbent coatings were previously limited to PDMS; however, bespoke adaptations (e.g. C 18 ) are emerging [48].…”

“…sample pH, stirring speed, and temperature) must also be optimised for the target analytes. Recovery of extracted organotins is by liquid desorption [48] or online thermal desorption [49] (using a specialised unit). Using PDMS stir bars and 2D gas chromatography-tandem mass-spectrometry (GC-GC-MS-MS) or LC-MS-MS, LODs of 0.01-0.8 ng L À1 for butyltins in sea water have been reported [7,50].…”