A magnetic nanocomposite based on amine‑functionalized pH‑sensitive functional poly(styrene‑co‑maleic anhydride) copolymer for selective extraction, pre‑concentration and determination of sub‑trace Ag+ and Cu2+ ions from edible vegetable oils by a combination of spectrophotometry and ultrasound‑assisted cloud point extraction

Abstract

In this study, a new magnetic nanocomposite based on amine-functionalized pH-sensitive poly(styrene-co-maleic anhydride) copolymer derived from the tris(2-hydroxymethyl)aminomethane and Fe3O4 nanoparticles was designed, characterized and used in selective extraction and pre-concentration of sub-trace Ag+/ Cu2+ ions from aqueous solutions by ultrasoundassisted cloud point extraction. The method is based on the formation of charge transfer complexes among Ag+/ Cu2+ ions and weak basic amidic copolymer matrix at pH 4.0/5.0, respectively, in the presence of pH-sensitive anionic surfactant, and their detection by spectrophotometry at 346 nm. The variables affecting extraction efficiency were optimized in detail. Under the optimized conditions, the good linear relationships were obtained in ranges of 0.8–110/1.0–120 μg L− 1 for Ag+ and 1–125/2.0–140 μg L− 1 for Cu2+ by two calibration curves with a better determination coefficient than 0.992. The limits of detection, repeatability/intermediate precision (as RSDs%, 5, 25 and 100 μg L− 1, n: 5) and the percent recoveries were 0.25/0.41 μg L− 1, 3.0–7.1% and 90.4–98.5%, respectively. From pre-concentration of 25 mL sample solution, a pre-concentration factor was found to be of 62.5 with sensitivity enhancements of 35.2- and 28.3-fold in calibration for each ion. A matrix effect was not observed (n: 3, for 50 μg L− 1 of each ion). The accuracy was validated by analysis of the two certified samples. The standard addition method after two sample pre-treatment procedures was successfully applied to determination of total Ag/Cu contents of edible vegetable oils, and the quantitative recoveries were obtained in the ranges of 87–94% with lower RSD than 6.8% after spiking with 10 μg L− 1.