Tailored-designed material for the preconcentration of Cd(II) on glycidyl methacrylate-based ion-imprinted polymer for flame atomic absorption for trace determination in real samples: multivariate optimization

A new Cd(II)-imprinting polymer was synthesised based on glycidyl methacrylate (Fe₃O₄@GMA@IIP) and employed to develop a dispersive magnetic solid-phase extraction method for the preconcentration prior to the determination of Cd(II) from the environmental samples. A central composite design (CCD) based on response surface methodology was used for optimization of the process variables and the material shows the promising saturation adsorption capacity of 28.21 mg g^-1 under the optimum pH of 4.9 within 15.2 min at saturation concentration 914 μg mL^-1. The experimental data were well described by Sips isotherm model and Brouers-Sotolongo fractal kinetic model that indicated the surface heterogeneity and involvement of both chemisorption and physisorption process. Thermodynamic results documented the endothermic and spontaneous nature of adsorption. The sorbent manifest the economic feasibility maintaining its sorption efficiency after the regeneration by 1 M HNO₃ and reusability up to 6 adsorption/desorption cycles. The developed method exhibited the preconcentration factor of 30 and a high degree of tolerance for matrix ions. Limit of detection (LOD) and quantification (LOQ) were calculated as 3.054 and 10.182 μg L^-1 respectively. The developed method was validated by the standard reference material and spiking addition method in real samples, and obtained results showed good agreement in accordance with spiking values. The ease of magnetic separation, high selectivity, good adsorption capacity and faster kinetics made this material a promising candidate for Cd(II) determination in various food and aqueous samples.

Preparation of a new magnetic ion-imprinted polymer and optimization using Box-Behnken design for selective removal and determination of Cu(II) in food and wastewater samples

A new magnetic Cu(II) IIP (Fe₃O₄@IIP-IDC) is synthesized by polymerization of Imidazole-4,5-dicarboxylic acid functionalized Allyl chloride, and significant improvement of its performance has been compared. SPE parameters were optimized using Box-Behnken design to achieve the twin objectives of quantitative determination and removal of Cu(II). FLPSO kinetic model and BS isotherm model fits well with the capacity of 175 mg g^-1. Analytical figures of merit includes a linearity range of 10-5,000 µg L^-1 (R² = 0.9986), preconcentration factor of 50 after eluting with 5 mL of 1 M HNO₃, LOD of 1.03 µg L^-1 and LOQ of 4.5 µg L^-1. Accuracy was assessed by analysis of SRM (Standard Reference Material) and recovery experiments after spiking in food samples (Tea, coffee, chocolate, spinach, infant milk substitute) and battery wastewater. Ease of use, reusability (15 cycles), rapid adsorption and high selectivity makes it a promising candidate for efficient and selective removal and trace determination.

Efficacy of engineered GO Amberlite XAD-16 picolylamine sorbent for the trace determination of Pb (II) and Cu (II) in fishes by solid phase extraction column coupled with inductively coupled plasma optical emission spectrometry

Graphene oxide (GO) was immobilized innovatively through azo spacer arm onto the surface of polymeric Amberlite XAD-16 resin in order to expose all oxygen functionalities freely available for metal ions coordination and further modification with picolylamine which governs selectivity. The GO Amberlite XAD-16 picolylamine enables the development of SPE column coupled with ICP-OES for preconcentration and determination of Pb (II) and Cu (II) in water and fish samples. Elution was performed by mild acid (2M HCl) no other carcinogenic organic solvent was used, prevents ligand leaching. Under optimized conditions, the preconcentration factors of 150 and detection limits 1.434 and 0.048 µg L⁻¹ for Pb (II) and Cu (II)  were obtained respectively.

Fabrication of porous covalent organic frameworks as selective and advanced adsorbents for the on-line preconcentration of trace elements against the complex sample matrix

Herein, for the first time, the typical porous Covalent Organic Frameworks (COFs) CTpBD with superior chemical stability and large surface area were applied as sorbents for solid phase extraction of trace ions via flow injection followed by inductively coupled plasma mass spectrometry (ICP-MS) detection. The well-prepared and fully-characterized CTpBD COFs were filled in solid phase extraction cartridge as novel and robust adsorbents for element analysis. Separation and enrichment of Cr (III), Mn (II), Co (II), Ni (II), Cd (II), V (V), Cu (II), As (III), Se (IV), and Mo (VI) was then carried out, and the contents were measured by ICP-MS. Owing to the large surface area and instinctive porous structure of CTpBD, preconcentration of the target trace elements via COF-filled on-line SPE column has achieved low detection limits of 2.1-21.6ngL^-1 along with a wide linearity range at 0.05-25μgL^-1 for all target ions. The relative standard deviations (RSD) of 1.2%-4.3% obtained via 11 parallel determinations at the sample concentration of 100ngL^-1 revealed excellent repeatability of the developed methods Our proposed methods have been successfully utilized for trace element analysis in environmental and food samples.

Spherical covalent organic frameworks as advanced adsorbents for preconcentration and separation of phenolic endocrine disruptors, followed by high performance liquid chromatography

As a promising generation of porous micro-materials, covalent organic frameworks (COFs) have great potentials for applications in separation and adsorption. In the present study, an advanced food-safety inspection method involving COFs as the adsorbents of solid phase extraction (SPE) is proposed for sensitive and accurate determination of target hazardous substances. Typical spherical TpBD COFs with large surface area and superior chemical stability were utilized as adsorbents for the preconcentration of phenolic endocrine disruptors (PEDs), followed by high performance liquid chromatography (HPLC) analysis. The well-prepared TpBD COFs were encapsulated in SPE cartridges and applied in food research, namely, for the separation and enrichment of four target endocrine disruptors in food samples. The possible factors influencing the SPE performance including the composition of the sample solvent, sample solution pH, sample flow rate, composition of the eluent, and the volume of the eluent were investigated and optimized. Due to the porous architecture and superior surface area of spherical TpBD, the enrichment of analytes via a COF-filled SPE column gave extremely low detection limits of 0.056–0.123 μg L⁻¹ along with a wide linear range of 0.5–100 μg L⁻¹ for all the analytes. Nine parallel determinations of the mixed standard with a concentration of 10 μg L⁻¹ produced the relative standard deviations of 2.23–3.08%, indicating the excellent repeatability of the COF-SPE assay. This study can open up a new route for the employment of COFs as efficient SPE adsorbents for the enrichment and quantification of trace/ultra-trace hazardous materials in complex food samples.

Spherical COFs as efficient adsorbents for preconcentration and separation of phenolic endocrine disruptors, followed by high performance liquid chromatography.