Study of cross-linked poly(methacrylic acid) and polyvinylimidazole as selective adsorbents for on-line preconcentration and redox speciation of chromium with flame atomic absorption spectrometry determination

A magnetic poly (methacrylic acid-co-ethylene glycol dimethacrylate) copolymer for extraction of anticonvulsants from saliva followed by high performance liquid chromatography analysis

Neurological diseases like epilepsy are commonly treated with anticonvulsants, and the dosage control of these medications has been carried out with therapeutic biomonitoring, mainly in blood. Saliva is a less invasive sample, and its drug concentration is proportional to the blood fraction concentration not bound to the proteins, making it an important alternative to blood. Therefore, this study describes the synthesis of a magnetic poly (methacrylic acid-co-ethylene glycol dimethacrylate) copolymer (M-CP) and its use in magnetic dispersive solid phase extraction of primidone (PMR), phenobarbital (PB), phenytoin (PHT), and carbamazepine (CB) from saliva, followed by their determination by high performance liquid-chromatography. M-CP was synthesized in 4 steps and the material was characterized by infrared spectroscopy, scanning electron microscopy, zeta potential, and thermal analysis. The sample preparation protocol was optimized by central composite rotatable design and the optimal conditions were obtained for pH 5.78, 12.8 mg of M-CP, and 2.18 mL of diluted saliva. In the adsorption studies, the Avrami and Jovanovic models demonstrated the best fit for describing the adsorption kinetics and isotherm, respectively. The equilibrium time was reached in 60 min, and 10.96 mg g-1 was the maximum adsorption capacity. The developed method was linear (R2 > 0.99) in the range of 2 to 30 mg L-1 for PMR and PB, 1 to 20 mg L-1 for PHT, and 1 to 30 mg L-1 for CBZ. Precisions were obtained in the range of 1.35 to 19.44 %, and accuracy from -14.92 % to 18.83 %. The limits of detection ranged from 0.48 to 1.30 mg L-1, while the limits of quantification were lower than the therapeutic levels of each drug, being suitable for the method application. The developed method is simple, fast, and requires few amounts of saliva, sorbent, and solvents, being a good alternative for the therapeutic biomonitoring of anticonvulsants in saliva samples.

Synthesis of ionically imprinted Poly(Alylthiourea) in the presence of 1-(2-Pyridylazo)-2-Napthol (PAN) for preconcentration in magnetic dispersive solid phase of nickel ions in water and food samples

In the present study, a magnetic ion-imprinted polymer based on n-allylthiourea in the presence of 1-(2-pyridylazo)-2-naphthol (MIIP-PAN) was synthesized, characterized, and applied in the preconcentration of nickel ions by dispersive magnetic solid phase extraction (DMSPE) with FAAS detection. For comparison, non-imprinted polymer (MNIP-PAN) and imprinted polymer without PAN were synthesized. The characterization of the polymers was performed by FT-IR, DRX, TEM, TGA, VSM, and BET. Selectivity studies were performed comparing the competitive adsorption of Ni2+ with other cations on MIIP-PAN and MNIP-PAN, achieving higher relative selectivity coefficients for MIIP-PAN than for MNIP-PAN and NIP. Under optimized conditions, the method provided a preconcentration factor of 76.70, detection limit of 0.25 µg/L and intra-day (2.06 - 2.33 %) and inter-day (1.82 - 4.90 %) precision. The developed method was applied to samples of water, teas, and chocolate powder, and its precision was evaluated through tests of recovery and analysis of certified materials.

New magnetic chelating sorbent for chromium speciation by magnetic solid phase extraction on-line with inductively coupled plasma optical emission spectrometry

A novel sorbent material employing magnetic nanoparticles (MNPs) coupled to graphene oxide (GO) functionalized with 4-aminobenzenesulfonic acid (M@GO-ABS) has been synthesized and applied to develop an inexpensive and automatic method for Cr(III) and Cr(VI) speciation in environmental samples; the developed method combines inductively coupled plasma optical emission spectrometry (ICP-OES) with on-line magnetic solid phase extraction (MSPE). Two magnetic-knotted reactors containing M@GO-ABS were installed in the eight-port injection valve of a flow injection (FI) manifold. Two different eluents were used, one for Cr(VI) (the most toxic chromium species) and one for total Cr concentration. Cr(III) concentration was calculated by the difference between Cr(VI) concentration and total Cr concentration. The optimized method presented detection limits (LOD, peak height) of 0.1 μg L^-1 for chromium (VI) and 0.08 μg L^-1 for total chromium, and enrichment factors of 15 and 23, respectively. Certified reference materials (TMDA 54.5 fortified lake water and SPS-SW2 surface water) and spiked aqueous samples were used to validate the developed method. The developed method was fruitfully applied to chromium speciation in environmental water samples such as seawater, well water and tap water collected in Málaga (Spain). The obtained values were in good agreement with the certified values, and the recoveries were found in the range of 91-108% for the spiked samples.

Polystyrene-divinyl benzene microspheres with amino methyl phosphonic acid functional hairy brushes for the sorption and speciation of chromium prior to inductively coupled plasma mass spectrometric determination

This article describes the synthesis and application of a novel sorbent for Cr(III) and Cr(VI) speciation prior to their quantitation by inductively coupled plasma mass spectrometry. The sorbent consists of polystyrene-divinyl benzene microbeads that were graft-coated with poly(oligo (ethylene glycol) methacrylate)-block-poly(glycidyl methacrylate). The particles were finally modified with phosphomethylated triethylene tetramine. The resulting microbeads are shown to be a viable sorbent for Cr(VI). The total concentration of chromium was determined after oxidation of Cr(III) to Cr(VI) with KMnO₄ using the novel sorbent. The Cr(III) amount was then calculated by subtracting the concentration of Cr(VI) from that of total chromium. The optimum conditions for batch type sorption were established. Under optimal conditions, the limit of detection and quantification are 0.015 μg L^-1 and 0.050 μg L^-1, respectively. The kinetics and isotherms of the sorption of Cr(VI) were investigated. Following desorption with 0.1 M hydroxylamine hydrochloride, the method was successfully applied to spiked real water samples and a certified reference material. Graphical abstract Schematic presentation of a method for the sorption and speciation of chromium using amino methyl phosphonic acid functional brushes on polystyrene-divinyl benzene microspheres.

Speciation analysis of chromium by carboxylic group functionalized mesoporous silica with inductively coupled plasma mass spectrometry

Carboxyl-group functionalized mesoporous silica (CFMS) prepared by one-pot co-condensation method was employed for the solid phase extraction (SPE) of chromium species for the first time. A new approach of SPE coupled to inductively coupled plasma mass spectrometry (ICP-MS) was thus established for the speciation of chromium in environmental water samples. The influences of pH, volume of sample, extraction time, amount of adsorbent, elution conditions, co-existing ions and adsorption capacity were investigated on adsorption or elution of chromium species. Cr(VI) was not retained on the CFMS material in the pH range of 1.0-9.0, while Cr(III) was quantitatively adsorbed at pH 5.0-9.0. The captured Cr(III) was enriched by using 1.5 mol L^-1 HNO₃ as elution solvent and detected by ICP-MS. Under the optimized SPE conditions, the maximum adsorption capacity of the CFMS for Cr(III) was 57.67 mg g^-1 and the enrichment factor was 25, with the detection limit (LOD) of 0.02 μg L^-1. The proposed protocol has been successfully applied to chromium speciation in rain, lake and river water samples, which exhibited a prospect in field separation and enrichment of chromium species in environmental waters.

Polyaniline-deposited cellulose fiber composite prepared via in situ polymerization: enhancing adsorption properties for removal of meloxicam from aqueous media

Polyaniline (PAni), cellulose fiber (CF) and a PAni–CF composite, which were characterized by infrared spectroscopy, scanning electron microscopy and thermogravimetry, were investigated in adsorption studies of meloxicam (MLX) from aqueous media.

Iminodiacetic acid functionalized magnetic nanoparticles for speciation of Cr(iii) and Cr(vi) followed by graphite furnace atomic absorption spectrometry detection

In this work, iminodiacetic acid (IDA) functionalized magnetic nanoparticles (Fe₃O₄@SiO₂@IDA) were prepared and the adsorption behavior of Cr(iii)/(vi) on them was investigated.

Investigation on the Performance of Chemically Modified Aquatic Macrophytes-Salvinia molesta for the Micro-Solid Phase Preconcentration of Cd(II) On-Line Coupled to FAAS

In this study, a new method for the preconcentration of cadmium ions using modified aquatic macrophytes - Salvinia molesta as biosorbent in an on-line preconcentration system coupled to flame atomic absorption spectrometry (FAAS) was developed. The method is based on preconcentration of 20.0 mL sample at pH 3.75 through 35.0 mg of biosorbent at 10.0 mL min^-1 and subsequent elution with 0.5 mol L^-1 HNO₃. A preconcentration factor of 31-fold, linear dynamic range from 5.0 to 70.0 µg L^-1 (r = 0.9996) and detection and quantification limits of 0.15 and 0.51 µg L^-1 were obtained. The characterization of the biosorbent chemically modified with NaOH and citric acid, was performed through FTIR and SEM measurements. The method precision was found to be 3.97 % and 1.48 % for 5.0 and 60.0 µg L^-1 Cd(II) solutions, respectively. The applicability of method was checked by analysis of different kind of water samples and certified reference material.