Complete Elimination of Interferences in the Organotin Determination by Oxidation with Dimethyldioxirane Combined with Alumina Cleanup

Abstract

Most of the analytical procedures used in organotin (OT) speciation from sediment involves the Grignard derivatization reaction followed by a cleanup step and a desulfuration reaction since sulfur and/or sulfur species interfere with OT determination by GC/MS or GC-FPD. However, alkyl sulfides are generated from the coextracted elemental sulfur, and they are not removed by conventional desulfurization procedures. We propose here a method based on the oxidation of all the sulfur species with dimethyldioxirane (DMD) to sulfones or sulfur oxides. While sulfones are easily eliminated by alumina adsorption chromatography because they have higher polarity than OTs, the sulfur oxides are spontaneously evaporated. The DMD chemoselectivity favors the oxidation of sulfur compounds to sulfones in a few minutes, whereas OTs remain unreacted. In addition, the excess DMD is easily removed by evaporation under a nitrogen stream before the Al(2)O(3) cleanup step. The effectiveness of the desulfurization reaction combined with the cleanup step is demonstrated for a variety of sediment samples containing up to 3.1% of elemental sulfur, which is completely removed by adding 0.6 molar equiv of DMD. No statistical differences in the OT distribution pattern throughout the DMD intermediate oxidation steps were observed.

Speciation of organotin compounds in sediment cores from Guanabara Bay, Rio de Janeiro (Brazil) by gas chromatography–pulsed flame photometric detection

“…In this study the sulfur interference was reduced by oxidation with DMD, as it was imperative to use the filter providing the best detection limit. Fernández-Escobar et al 19 found that a large sulfone peak appearing just after the MBT peak could interfere with the quantification, and so introduced a cleanup by alumina adsorption chromatography after the oxidation step to eliminate the sulfone. In this study, a similar peak was observed, but this was not completely eliminated by the second cleanup step.…”

“…The methodology adopted was modified from Baijona and co-workers 19,29,30 as appropriate to the sediments' characteristics and to the detection by pulsed flame photometric detection (PFPD). 31 Sediment (2 g, dry mass) was transferred to a glass centrifuge tube.…”

Butyltin speciation in sediments from Todos os Santos Bay (Bahia, Brazil) by GC-PFPD

“…The adopted extraction methodology ( Figure 2) was modified from Abalos et al and Fernández-Escobar et al as appropriate to the sediments characteristics and to the detection by PFPD [17][18][19][20] . Two grams of sediment (dry mass) were transferred to a glass centrifuge tube.…”

Speciation of mercury, tin, and lead compounds by gas chromatography with microwave-induced plasma and atomic-emission detection (GC–MIP–AED)

“…Methods based on hydride generation have been shown to be poorly efficient for extracts with high sulfur, hydrocarbon, or inorganic metal content, and are therefore not advisable for sediment analysis [72]. The element selectivity of GC-MIP-AED makes it unnecessary to perform the time-consuming desulfuration procedures described in the literature for the determination of organotin species in sediments by GC-FPD [90,91]. In general, no clean-up procedures are necessary with GC-MIP-AED, although Ceulemans et al [89] have recommended that if tropolone is used as complexing reagent the final organic extract should be passed over basic alumina, or excess tropolone can contaminate the head of the column.…”