A home – made purge and trap – thermos desorption - gas chromatograph coupled with atomic fluorescence detector for the determination of ultra – trace methylmercury

Abstract

A hyphenated system for methylmercury based on a gas chromatograph (GC) coupled with an atomic fluorescence spectrometric (AFS) detector equipped with an online purge and trap as a preconcentrator was made. Operating parameters for the whole system were optimized and analytical performances of the system are verified by quality control chart for stability. Organomercurial compounds in an aqueous sample were in-situ ethylated and purged to a trap in-line with a separation device instead of conventional off-line solvent extraction. A 100 mL aqueous sample containing methylmercury in an impinger was mixed with sodium tetraethylborate at pH 5.0. The forming volatile ethylmethylmercury was purged for 30 minutes with the assistance of an Ar flow and trapped into a Tenax sorbent. The trap was then heated to release volatile compounds including ethylmethylmercury into a GC-AFS for separation and detection. The instrumental detection limit was 4.8 pg Hg/L. The method can therefore be applied for the determination of methylmercury in water samples at ultra – trace.