pH-controlled charge transfer sensitive 2-aminobenzimidazole modified poly(styrene-co-maleic anhydride) copolymer for selective extraction, pre-concentration and determination of trace Hg2+ and CH3Hg+ in vinegar by combination of ultrasound assisted-cloud point extraction with UV-VIS spectrophotometry

In this study, a separation/pre-concentration procedure, ultrasound assisted-cloud point extraction with modi-fied 2-aminobenzimidazole (2-ABzI), was developed for the extraction of trace Hg2+ and CH3Hg+ and from vinegar samples-modified copolymer coupled with Hg-binding chelator, 2-ABzI. The imidic copolymer was characterized, and used for detection of the enriched Hg species by spectrophotometer at 332 nm. The method is based on their pH-induced charge transfer sensitive complexation with copolymer matrix via 2-AmBzI moiety at pH 6.0 and 4.5, and their extraction into the mixed micellar phase of the mixed non-ionic/ionic surfactants as extractant/sensitivity enhancer. The variables influencing the extraction efficiency were optimized. From pre -concentration of 25-mL sample, with a changing calibration sensitivity and pre-concentration factor of 62.5, a good rectilinear relationship between absorbance and concentrations of Hg species in ranges of 1-15, 15-150 mu g L-1 was obtained. The detection limits are 0.30 and 0.31 mu g L-1, respectively. Its precision/accuracy were in range of 3.1-7.6 % and 90.5-96 % after spiking (n: 5, for measurements of 5, 25 and 100 mu g L-1 in same day and three consecutive days). The matrix effect was also studied (n: 3, 100 mu g L-1). The method is simple, cost-effective, fast, accurate, safe, highly stable and selective, which has successfully been applied to the speciation of mercury in vinegar.