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

Abstract

A fluorosulfate ion (FSO 3 − ) is a hydrolysis product of sulfuryl fluoride (SO 2 F 2 ), 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 SO 2 F 2 and for monitoring the progress of reactions used to scrub SO 2 F 2 from fumigation vent gases. Here, we report a simple and inexpensive potentiometric method for determining FSO 3 − using a commercial nitrate-selective electrode and discuss its application. The method is suitable for solutions between 0.0025 mM and 660 mM FSO 3− at initial pH between 5 and 9. Halide interference depends on its molar ratio to FSO 3 − and follows the sequence, F − < Cl − < Br − ≪ I − . Halide interference can be eliminated by adding silver sulfate. Interference by bicarbonate can be eliminated by H 2 SO 4 pretreatment, and interference by phosphate or pyrophosphate by MgSO 4 addition. Sulfate does not interfere, as it does in ion chromatography. Satisfactory method detection limits for FSO 3 − in spiked aqueous extracts of 11 fruits were obtained. The method accurately quantified the yield of FSO 3 − relative to that of F − in base hydrolysis of SO 2 F 2 . This study demonstrates that the developed method is highly selective, convenient, and sensitive and thus can be of great value in practice.