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.

Impact of nanotechnology on progress of flow methods in chemical analysis: A review

In evolution of instrumentation for analytical chemistry as crucial technological breakthroughs should be considered a common introduction of electronics with all its progress in integration, and then microprocessors which was followed by a widespread computerization. It is seems that a similar role can be attributed to the introduction of various elements of modern nanotechnology, observed with a fast progress since beginning of this century. It concerns all areas of the applications of analytical chemistry, including also progress in flow analysis, which are being developed since the middle of 20th century. Obviously, it should not be omitted the developed earlier and analytically applied planar structures like lipid membranes or self-assembled monolayers They had essential impact prior to discoveries of numerous extraordinary nanoparticles such as fullerenes, carbon nanotubes and graphene, or nanocrystalline semiconductors (quantum dots). Mostly, due to catalytic effects, significantly developed surface and the possibility of easy functionalization, their application in various stages of flow analytical procedures can significantly improve them. The application of new nanomaterials may be used for the development of new detection methods for flow analytical systems in macro-flow setups as well as in microfluidics and lateral flow immunoassay tests. It is also advantageous that quick flow conditions of measurements may be helpful in preventing unfavorable agglomeration of nanoparticles. A vast literature published already on this subject (e.g. almost 1000 papers about carbon nanotubes and flow-injection analytical systems) implies that for this reviews it was necessary to make an arbitrary selection of reported examples of this trend, focused mainly on achievements reported in the recent decade.

Development of Micro-Column Preconcentration Method Using a Restricted-Access Poly(protoporphyrin-co-vinyl pyridine) Adsorbent for Copper Determination in Water and Milk Samples by FIA-FAAS

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.

A Chelating Resin of EDTA-Type Modified Cross-Linking Polystyrene to Preconcentrate Trace Metals for Seawater Detection

The determination of trace metals in seawater is an important project of marine environmental monitoring. However, the presence of many alkali metal ions with high concentration, such as sodium ion, seriously interferes with the detection limit and accuracy of atomic absorption spectrometry (AAS, flame/graphite furnace integrated). The conventional chemical methods for the enrichment of trace metals are complex, and low boiling point organic solvents are used. In this paper, a kind of commercial cross-linked polystyrene resin microspheres was chloromethylated and aminated to introduce EDTA-type amino polycarboxylic groups and then loaded in a column as the absorption filler. A set of seawater pretreatment and enrichment devices was designed and assembled. The enriching process and conditions of trace Cu, Zn, Pb, and Cd in standard seawater were studied. 10 g of the modified resin could enrich the equivalent seawater and remove successfully the light metal ions. pH = 5∼9 and 0.2 mL/min of the flow rate were the suitable conditions for preconcentration. The enriched metal ions in the eluent were analyzed on the AAS. Compared with the conventional solvent method, the novel material and enrichment device have high preconcentration efficiency, strong anti-interference ability, and low cost and could be directly applied for routine seawater detection.

Combination of supramolecular solvent-based microextraction and ultrasound-assisted extraction for cadmium determination in flaxseed flour by thermospray flame furnace atomic absorption spectrometry

This study describes the development of a new analytical method for cadmium determination in flaxseed flour based on ultrasound-assisted extraction combined with supramolecular preconcentration followed by thermospray flame furnace atomic absorption spectrometry. Cadmium from flaxseed flour was extracted by ultrasound-assisted radiation in acid medium (1.5 mol L-1HNO3) followed by liquid-liquid microextraction of the acid extractwith dodecanoic acid/THF supramolecular solvent using diethyl dithiophosphate as a chelating agent. The limit of detection and the analytical curve range were found to be 0.10 μg L-1 and 0.35 to 20.0 μg L-1, respectively. The cadmium concentration in the flaxseed flours was ranged from 0.11 ± 0.04 to 0.79 ± 0.03 µg g-1. The proposed methodis considered simpler, faster, low-cost, and environmentally friendly compared to procedures currently used for the determination of cadmium based on acid digestion and using graphite furnace atomic absorption spectrometry and inductively coupled plasma mass spectrometry.

Development of selective preconcentration/clean-up method for imidazolinone herbicides determination in natural water and rice samples by HPLC-PAD using an imazethapyr imprinted poly(vinylimidazole-TRIM)

The development of a novel molecularly imprinted solid-phase extraction (MISPE) method for simultaneous preconcentration of imazapyr (IMP), imazapic (IMZ) and imazethapyr (IMT) with determination by HPLC-PAD (High performance liquid chromatography - photodiode-array detector) is proposed. The polymer synthesis was performed using imazethapyr as template molecule and 1-vinylimidazole as functional monomer. The method is based on preconcentration of 100.0 mL of sample through 200.0 mg of molecularly imprinted poly(vinylimidazole-TRIM) (MIP-1VN) at pH 4.0, followed by elution with 2.0 mL of MeOH:CH₂Cl₂:HAc (34:62:4, v/v). The range of analytical curve (0.29-200.0, 0.21-200.0 and 0.15-200.0 µg L^-1), limits of detection (0.09, 0.06 and 0.04 µg L^-1) and preconcentration factors (92, 96 and 98) determined for the herbicides, IMP, IMZ and IMT, respectively, were greatly superior when compared with those ones obtained with commercial adsorbents. The analytical method was successfully applied to spiked surface water and rice samples with good results of recovery values (86-107%).