Ion-imprinted polymers (IIPs) have been widely used in different fields of Analytical Sciences due to their intrinsic selective properties. However, the success of chemical imprinting in terms of selectivity, as well as the stability, specific surface area, and absence of swelling effect depends on fully understanding the preparation process. Therefore, the proposal of this review is to describe the influence of relevant parameters on the production processes of ion-imprinted polymers, including the nature (organic, inorganic, or hybrid materials), structure, properties of the salt (source of the metal ion), ligand, crosslinking agent, porogenic solvent, and initiator. Additionally, different polymerization methods are discussed, the classification of IIPs as well as the applications of these adsorbent materials in the last years (2017–2022).

For years, researchers have focused on the determination of metal ions at trace levels in environmental and food samples using analytical methods that employ techniques with low cost acquisition and maintenance and without microwave-assisted acid digestion procedures or aggressive reagents. Therefore, the present study deals with the synthesis and application of a novel, restricted-access poly(protoporphyrin-co-vinyl pyridine) adsorbent to preconcentrate copper in water samples and bovine milk that have only been subjected to pH adjusting (pH 6.0) and filtration using posterior on-line determination by FAAS. Regarding macromolecules, the restricted-access property of the adsorbent was achieved using the hydrophilic compound 2-hydroxyethyl methacrylate (HEMA). This method is based on the preconcentration of Cu²⁺ ions using a flow-injection system which is buffered with 0.05 mol L⁻¹ of Britton–Robinson (BR) at a pH of 6.0 and has a flow rate of 14.0 mL min⁻¹ through a mini-column packed with 50.0 mg of adsorbent. The elution was carried out using 0.40 mol L⁻¹ of HCl toward the FAAS detector. The developed method provided a preconcentration factor of 44.7-fold, low limits of detection (LOD) (0.90 µg L⁻¹) and quantification (LOQ) (2.90 µg L⁻¹), tolerance to interfering ions (95.0 and 103.0%), and intra-day and inter-day precision assessed as the RSD (percentage of relative standard deviation), which ranged from 3.08 to 4.80%. The restricted-access poly(protoporphyrin-co-vinyl pyridine) adsorbent demonstrated outstanding features to exclude macromolecules, bovine serum albumin (BSA), and humic acid (HA) from an aqueous medium. Lake water and bovine milk samples were analyzed by the proposed preconcentration method with minimal sample pretreatment (which was based mainly on pH adjusting and filtration using an analytical curve with external calibration), yielding recovery values from addition and recovery tests ranging from 91.7 to 101.9%. The developed method shows great advantages over previously published methods, avoiding the time-consuming use of concentrated acids in a microwave-assisted acid digestion procedure.

The performance of three conventional treatments, including microwave-assisted acid digestion (MWAD), ultrasoundassisted extraction (UAE) and dry method (DAM) for determination of Cu²⁺ and Zn²⁺ in flaxseed meal, was evaluated. Quantification was performed by flame atomic absorption spectrometry (FAAS) and differential pulse anode stripping voltammetry (DPASV). TheMWAD treatment was performed with both concentrated HNO₃ (CA) and diluted acid (DA). The concentration of Cu²⁺ was determined by FAAS and DPASV, by different treatments, ranging from 14.4-26.0 μg g⁻¹ and 8.5-17.9 μg g⁻¹, respectively. The concentration of Zn²⁺ was possible only by FAAS (28.7-77.4 μg g⁻¹). The highest concentrations were obtained using MWAD. The DAM showed values similar to MWAD for Cu²⁺, however, for Zn²⁺ it showed the lowest concentrations. UAE, in turn, showed low concentrations of Zn²⁺ in relation to MWAD, but similar results to MWAD-DA for Cu²⁺ in a sample with low fat content. Therefore, both the choice of treatment and the quantification technique play a crucial role in metal determination.