Novel amide- and imide-co-polymers modified with sulfathiazole as efficient chelator for selective extraction, pre-concentration and determination of trace inorganic antimony (as Sb(III)) from edible vegetable oils by ultrasound assisted-cloud point extraction coupled to micro-volume UV-spectrophotometry

The study described the synthesis, characterization, and application of newly prepared sulfathiazole-modified amide/imide co-polymers for the extraction of trace Sb(III) from edible vegetable oils. The method was based on the pH-dependent complexation between Sb(III) and chelators as a result of charge transfer via tautomeri-zation in presence of the mixed ionic surfactants in 5%(v/v) 2-propanol, 1:1, v/v) at pH 2.0 and 8.0, respectively for amide and imide copolymers and then selectively ultrasound assisted-cloud point extraction of the Sb(III)-complexes into the micellar phase of extractant. The separated micellar phase by centrifugation was diluted to 0.4 mL with tetrahydrofuran, and detected at 269 nm by micro-volume UV-spectrophotometry. The parameters affecting extraction efficiency were optimized. The optimal extraction conditions were found to be: 0.6/0.8 mmol L-1 of McIlvaine buffer, 30 mu mol L-1 of the mixed-ionic surfactant mixture, 120 mu mol L-1 KCl, 0.1/0.06% (v/v) of the nonionic surfactant and (0.4/0.2)x 10-3%(w/v) of sulfathiazole-modified amide/imide copolymers at pH 2.0 and 8.0 for 7 min at 40 degrees C in an ultrasonic bath (40 kHz, 300 W). From preconcentration of 20-mL sample, the good linear relationships (r2 >= 0.995) between absorbance and Sb(III) concentration were ob-tained from calibration curves prepared in solvent in range of 1-40 and 1-62.5 mu g L-1 with the method detection limits of 0.30/0.47 and 0.51/0.51 mu g L-1 at 269 nm by spectrophotometer after 50-fold pre-concentration. The accuracy was statistically verified by analysis of a non-certified sample with and without spiking where the precision and relative recoveries are within 5-12% and 83-92%, respectively. Also, the matrix effect was evaluated by triplicate measurements of 25 mu g L-1 Sb(III) (n: 3) under optimal conditions. The method was successfully applied into the analysis of total iSb levels of edible vegetable oils. The results shown that the STZ-modified amide/imide co-polymers were efficient selective chelators even in presence of 50-fold excess Sb(V), and exhibited great potential as alternative binding chelators for the extraction of Sb(III) from edible vegetable oils.

Automated summary

This study described the synthesis, characterization, and application of newly prepared sulfathiazole-modified amide/imide co-polymers for the extraction of trace Sb(III) from edible vegetable oils. The method involves pH-dependent complexation and ultrasound-assisted cloud point extraction. The results showed good linear relationships and low detection limits. The method was successfully applied for the analysis of Sb levels in edible vegetable oils.