Downscaling conventional methods for the spectrophotometric study of metal ions complexation

One of the major challenges in a chemistry laboratory is the continuous search for a more sustainable practice, following Green Chemistry guidelines. The present work was devoted to the development of a high throughput and miniaturized strategy for chemistry conventional protocols for the study of complex formation of metallic compounds. In this scenario, the spectrophotometric calibration curve method and the Job’s method of continuous variation were adapted to the microplate format. This work involved several metal ions (Co(II), Cu (II), Cd(II), Fe(III), Mn(II), Ni(II), Pb(II) and Zn(II)) and two different complexing agents, 2-Carboxy-2′-hydroxy- 5′-sulfoformazyl-benzene (Zincon) and 4-(2-Pyridylazo)resorcinol (PAR). Microplate assays demonstrated to be useful tools for the investigation of the equilibrium process of metal ion complexes. Additionally, these methods involved lower volume of reagents and the analysis throughput was augmented when compared with conventional strategiesinfo:eu-repo/semantics/publishedVersio

Single flow-based system for the automatic multiparametric nutrients (NPK & Fe) assessment in soil leachates

A multiparametric sequential injection system for the determination of phosphate, nitrite, nitrate, potassium, and iron(III) in a single manifold was developed. The main goal of the proposed method was to develop an efficient tool to assess a number of essential chemical compounds in soils, providing the corresponding information on soil fertility and, additionally, information on possible groundwater contamination. The method was applied for the quantification of the aforementioned parameters in simulated leachates produced in laboratory-scale core columns. The relative standard deviations of ten replicate analyses of a standard were: 6% for phosphate; 2% for nitrite; 2% for nitrate; 5% for potassium; and 6% for iron(III). The limits of detection and quantification were: 2.15 and 7.18 μmol/L for phosphate determination; 0.22 and 0.73 μmol/L for nitrite determination; 3.42 and 8.00 μmol/L for nitrate determination; 39 μmol/L (limit of detection) for potassium determination; and 0.46 and 1.85 μmol/L for iron(III) determination. The sequential injection system was successfully applied for the quantification of multiple soil chemical components (PO43−, NO2−, NO3−, K+, and Fe3+) in soil leachates. The analysis of a sample, involving all the analytes, has a duration of 28 min.info:eu-repo/semantics/publishedVersio

Interferences minimization using solid phase extraction in a multiparametric sequential injection system

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Biparametric sequential injection system with on-line solid phase extraction for the determination of copper and zinc in waters

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Use of a polymer inclusion membrane and a chelating resin for the flow-based sequential determination of copper(II) and zinc(II) in natural waters and soil leachates

A bi-parametric sequential injection method for the determination of copper(II) and zinc(II) when present together in aqueous samples was developed. This was achieved by using a non-specific colorimetric reagent (4-(2-pyridylazo)resorcinol, PAR) together with two ion-exchange polymeric materials to discriminate between the two metal ions. A polymer inclusion membrane (PIM) and a chelating resin (Chelex 100) were the chosen materials to retain zinc(II) and copper(II), respectively. The influence of the flow system parameters, such as composition of the reagent solutions, flow rates and standard/sample volume, on the method sensitivity were studied. The interference of several common metal ions was assessed, and no significant interferences were observed (<10% signal deviation). The limits of detection were 3.1 and 5.6 µg L−1 for copper(II) and zinc(II), respectively; the dynamic working range was from 10 to 40 µg L−1 for both analytes. The newly developed sequential injection analysis (SIA) system was applied to natural waters and soil leachates, and the results were in agreement with those obtained with the reference procedure.info:eu-repo/semantics/publishedVersio

Polymer inclusion membranes (PIMs) as an alternative for on-line solid phase extraction (SPE) in flow analysis

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A robust flow-based system for the spectrophotometric determination of Cr(VI) in recreational waters

A flow-based method for the spectrophotometric determination of chromium (VI) in recreational waters with different salinities was developed. Chromium can occur in the environment in different oxidation states with different related physiological properties. With regard to chromium, the speciation is particularly important, as the hexavalent chromium is considered to be carcinogenic. To achieve that purpose, the use of the diphenylcarbazide (DPC) selective colored reaction with the hexavalent chromium was the chosen strategy. The main objective was to develop a direct and simple spectrophotometric method that could cope with the analysis of different types of environmental waters, within different salinity ranges (fresh to marine waters). The potential interference of metal ions, that can usually be present in environmental waters, was assessed and no significant interferences were observed (<10%). For a complete Cr(VI) determination (three replicas) cycle, the corresponding reagents consumption was 75 µg of DPC, 9 mg of ethanol and 54 mg of sulfuric acid. Each cycle takes about 5 min, including the system clean-up. The limit of detection was 6.9 and 12.2 µg L−1 for waters with low and high salt content, respectively. The method was applied for the quantification of chromium (VI) in both fresh and marine water, and the results were in agreement with the reference procedure.info:eu-repo/semantics/publishedVersio

A solid phase extraction flow injection spectrophotometric method for the zinc determination in plants

A solid phase extraction flow injection system for the spectrophotometric determination of total zinc in plant digests was developed. Solid phase extraction was chosen as a strategy for zinc preconcentration and removal of some interferences. The determination of zinc was based on the colorimetric reaction with Zincon. As detection system, a multi-reflection flow cell coupled with a light emitting diode was used. The analytical characteristics of the methodology such as pH of standard/sample solution, nitric acid concentration, the placement of SPE column within the manifold and preconcentration flow rate were studied. The interference of some metals present in plants was also assessed. The limits of detection and quantification achieved were 0.04 mg L−1 and 0.12 mg L−1, respectively. The corresponding Zincon consumption was 0.17 mg for each determination. The developed system was applied to plant digests and the results obtained were in agreement with those obtained with reference procedure.info:eu-repo/semantics/publishedVersio

Microplate and flow injection strategies for the spectrophotometric detection of zinc (II) with two complexng agents: PAR and Zincon

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