Rapid and Convenient Potentiometric Method for Determining Fluorosulfate, a Byproduct of the Fumigant and Greenhouse Gas Sulfuryl Fluoride.

Abstract

A fluorosulfate ion (FSO3-) is a hydrolysis product of sulfuryl fluoride (SO2F2), which is widely used to fumigate buildings, soil, construction materials, and postharvest commodities, and is a potent greenhouse gas. It is a potential marker for biological exposure to SO2F2 and for monitoring the progress of reactions used to scrub SO2F2 from fumigation vent gases. Here, we report a simple and inexpensive potentiometric method for determining FSO3- using a commercial nitrate-selective electrode and discuss its application. The method is suitable for solutions between 0.0025 mM and 660 mM FSO3- at initial pH between 5 and 9. Halide interference depends on its molar ratio to FSO3- and follows the sequence, F- < Cl- < Br- ≪ I-. Halide interference can be eliminated by adding silver sulfate. Interference by bicarbonate can be eliminated by H2SO4 pretreatment, and interference by phosphate or pyrophosphate by MgSO4 addition. Sulfate does not interfere, as it does in ion chromatography. Satisfactory method detection limits for FSO3- in spiked aqueous extracts of 11 fruits were obtained. The method accurately quantified the yield of FSO3- relative to that of F- in base hydrolysis of SO2F2. This study demonstrates that the developed method is highly selective, convenient, and sensitive and thus can be of great value in practice.