Use of new polymeric composites for preconcentration of trace Ag+ ions from the selected mushroom/vegetables by ultrasound-assisted cloud-point extraction coupled to microvolume UV-Vis spectrophotometry

The magnetic nano-composites based on the tris(hydroxymethlmethyl)aminomethane-modified maleic anhydride-co-styrene copolymers and Fe3O4 nano-particles were prepared as new potential chelating agents for ultrasound-assisted-cloud point extraction (UA-CPE) and pre-concentration of trace levels of Ag+ ions from aqueous solutions. The structures of the nano-composites were characterised via FT-IR, H-1-NMR and XRD analysis. After structural characterisation of composites, Ag+ ions were detected by micro-volume UV-vis spectrophotometry at 347 nm. The variables affecting complex formation and extraction efficiency for separation/pre-concentration of the Ag+ ions from various food matrices were evaluated and optimised in detail. Under the optimised conditions, the method shows a good sensitivity with linearity range from 10 to 350 mu g L-1 and 4 to 160 mu g L-1 for amidic and imidic composites, respectively, with a better correlation coefficient than 0.9825. The limits of detection, intra- and inter-day precision (as RSDs%) and recovery rates for six replicate determinations of Ag+ ions at levels of 25 and 100 mu g L-1 were 4.28/1.21 mu g L-1, 2.4-4.1% and 92-98% for the modified copolymers, respectively. The pre-concentration factor for Ag+ ion from pre-concentration of 35-mL sample was 70. A significant matrix effect was not observed for the triplicate measurements of 100 mu g L-1 Ag+ in the presence of various interfering species below their maximum concentrations allowed in this method, for Ag+ ions. The accuracy of the method was confirmed by analysis of the two certified samples. The method was successfully applied to determine low levels of Ag+ ions in mushroom and vegetable samples, and satisfactory recoveries were obtained in the range of 91-97% with lower RSD than 5.1% for the spiked samples.