Performance of restricted access copper-imprinted poly(allylthiourea) in an on-line preconcentration and sample clean-up FIA-FAAS system for copper determination in milk samples

• Published in: Talanta (Oxford) 2019-09, Vol.202, p.460-468
• Main Authors: Suquila, Fabio Antonio Cajamarca, Tarley, César Ricardo Teixeira
• Format: Article
• Language: English
• Subjects: Allylthiourea; Animals; Bovine serum albumin; Copper - analysis; Flame atomic absorption spectrometry; Flow injection analysis; Graphite - chemistry; Hydroxyethyl methacrylate; IIP-RAM; Milk - chemistry; Molecular Imprinting; Polymers - chemistry; Spectrophotometry, Atomic; Thiourea - analogs & derivatives; Thiourea - chemistry
• ISSN: 0039-9140; 1873-3573
• DOI: 10.1016/j.talanta.2019.05.023

A new on-line solid phase preconcentration method using an ion-imprinted polymer with restrict access material based on copper-imprinted poly(allylthiourea) modified with 2-hydroxyethyl methacrylate and bovine serum (IIP-HEMA-BSA) to preconcentrate Cu2+ ions and exclude protein from milk samples via FIA-FAAS was developed. The samples were on-line preconcentrated at pH 4.5 through a mini-column packed with 50.0 mg of IIP-HEMA-BSA at a flow rate of 7.6 mL min−1 followed by a counter-current elution with 1.00 mol L−1 HCl towards the FAAS detector. The interference of ions commonly found in milk samples and the presence of BSA were investigated in the Cu2+ ions preconcentration. The method provided an analytical curve ranging from 3.6 to 100.0 μg L−1, preconcentration factor of 24-fold, limit of detection of 1.1 μg L−1 and sample throughput of 20 h−1. The accuracy of the method was attested by Cu2+ ions addition/recovery tests as well as by using GFAAS of samples microwave-assisted digested. The proposed method was successfully applied to the copper determination in milk samples, requiring only pH adjustment followed by preconcentration step as sample pretreatment. Copper content in bovine milk sample was 0.635 ± 0.042 mg kg−1, while to soybean milk samples were between 0.048 ± 0.008 and 0.094 ± 0.005 mg kg−1. To the best of our knowledge, the potential of IIP-HEMA-BSA for Cu2+ ions extraction from biological samples and simultaneous removal of macromolecules employing minimal sample pretreatment was demonstrated for the first time. The proposed extraction method stands out by being simple, fast and a low-cost analytical strategy when compared to the conventional microwave-assisted acid digestion. [Display omitted] •The new proposed method allows the Cu2+ preconcentration and the exclusion of protein.•IIP-HEMA-BSA was employed in SPE for the Cu2+ preconcentration in milk samples.•The proteins were excluded using the HEMA and the BSA protein as surface modifiers.•The polymer can be reused for 450 cycles without a decrease in the recovery of Cu2+.