Water Certified Reference Materials Research Articles

Quantification capabilities of N2 MICAP-MS with solution nebulization and aerosol desolvation.

The analytical capabilities of a nitrogen-sustained high-power microwave inductively coupled atmospheric-pressure plasma mass spectrometer (N2 MICAP-MS) were investigated using solution nebulization with and without aerosol desolvation. The reduced solvent load for the desolvated aerosol and the increased aerosol transfer resulted in a signal enhancement of ten times for most elements in samples without a significant amount of dissolved solids. An exception was boron, whose signal decreased by a factor of seven when a desolvator was used. To compare the accuracy, reproducibility, and matrix susceptibility of the N2 MICAP-MS, the mass fractions of 30 elements were determined in two certified water reference materials using external calibration and standard addition. The results were generally found to agree within 10% of the certified reference values with a maximum deviation of 17% in the case of 64Zn. Comparing external calibration and standard addition provided comparable results regardless of the sample introduction method. To assess the extent of matrix effects, multi-element standard solutions were doped with amounts of up to 100 mg kg-1 calcium. This resulted in a signal suppression of up to 30% and 70% for conventional nebulization and aerosol desolvation, respectively. This substantially reduced the improvement in sensitivity observed for the desolvated aerosol. To further investigate the fundamental characteristics of the N2 MICAP-MS, the plasma gas temperature was estimated using three methods. The determined temperatures for the two most reliable methods were in the range of ∼5000-6000 K and were found to be independent of the sample introduction method and similar to those of an Ar ICP.

Micro-solid phase extraction of cobalt at trace levels as 1-nitroso-2-naphthol chelates on magnetic date palm fiber-WSe2 (mDPF@WSe2) nanocomposite from food, tobacco, and water samples

Magnetic date palm fiber-WSe2 (mDPF@WSe2) nanocomposite were synthesized by using hydrothermal synthesis and characterized by XRD, FTIR, and SEM for microsolid phase extraction (µ-SPE) of cobalt at trace levels. The analytical parameters such as pH, sample and eluent volumes, amount of 1-nitroso-2-naphthol as ligand and sorbent amounts, and eluent type were optimized. The influences of the matrix components were also examined. The limit of detection (LOD), the limit of quantification (LOQ), and relative standard deviation (%RSD) were calculated as 1.73 μg L−1, 5.78 μg L−1 and 3.2 respectively. The developed method was applied to NCS ZC73032 celery, NCS ZC73033 scallion and TMDA 64.3 fortified water-certified reference materials for method validation. The application of the µ-SPE method was performed for the determination of cobalt levels of food, tobacco, and water samples from Kayseri-Turkey.

An Electrochemical Sensor for the Determination of Trace Concentrations of Cadmium, Based on Spherical Glassy Carbon and Nanotubes.

The practical application of a novel, eco-friendly electrochemical sensor based on low-dimensional structures, spherical glassy carbon microparticles, and multiwall carbon nanotubes is described. This sensor, modified with a bismuth film, was used for the determination of Cd(II) by the anodic stripping voltammetric method. The instrumental and chemical factors influencing the sensitivity of the procedure were thoroughly investigated and their most favorable values were selected (acetate buffer solution pH = 3 ± 0.1; 0.15 mmol L-1 Bi(III); activation potential/time: -2 V/3 s; accumulation potential/time: -0.9 V/50 s). Under the selected conditions, the method exhibited linearity in the range of 2 × 10-9 to 2 × 10-7 mol L-1 Cd(II) with a detection limit of 6.2 × 10-10 mol L-1 Cd(II). The results obtained also showed that the application of the sensor for Cd(II) detection did not experience any significant interference in the presence of a number of foreign ions. The applicability of this procedure was evaluated using TM-25.5 Environmental Matrix Reference Material and SPS-WW1 Waste Water Certified Reference Material as well as river water samples through addition and recovery tests.

Development of an analytical method for accurate and precise determination of rare earth element concentrations in geological materials using an MC-ICP-MS and group separation.

The concentration of rare earth elements (REEs) in geological materials including SLRS-6 (natural water certified reference material) and JB1b, JA1, and JG2 (Standard Rock Materials of Geological Survey of Japan) can be used as a tracer to characterize various geochemical processes in earth systems. Particularly, accurate and precise determination of rare earth element concentration in natural waters is difficult due to their extremely low concentration and the interference of polyatomic oxides. In this study, we developed a method for accurate and precise determination of the REE (particularly heavy rare earth elements) concentrations in geological materials including natural waters using a multi-collector inductively coupled plasma mass spectrometer (MC-ICP-MS) and group separation by 2-hydroxyisobutyric acid (HIBA). The REEs were separated into light rare earth elements (LREEs, La-Ce-Pr-Nd), middle rare earth elements (MREEs, Sm-Eu-Gd-Tb), and heavy rare earth elements (HREEs, Dy-Ho-Er-Tm-Yb-Lu) by a cation-exchange column (AG50W-X8 200-400 mesh) using HIBA. The recovery rates of each REE in the natural water sample exceeded 98%, whereas the recovery rates of each REE in rock materials exceeded 95% except for HREEs. The method developed in this study can accurately measure the REE concentrations (particularly HREE) in geological materials without polyatomic oxide interference during the REE analysis by using the MC-ICP-MS and, thus, can correctly interpret the geochemical implications of REEs in geological systems. The determination of the Sr concentrations and Sr isotopic ratios of SLRS-6 CRM and JB1b, JA1, and JG2 SRMs is also reported, and they are shown to be in good agreement with the recommended values.

キレート樹脂固相抽出法を併用したICP質量分析法による下水処理施設周辺環境水の超高感度多元素分析

Analytical method for the determination of major-to-ultratrace elements in environmental water samples around sewage treatment plant by ICP-MS was examined in detail. In the present work, solid phase extraction using chelating-resin was adopted as the preconcentration method for the determination of ultratrace elements. Prior to solid phase extraction, environmental water samples were heated with nitric acid and hydrogen peroxide at 200 °C for 4h to decompose chelating agents contained in sewage effluent such as EDTA, which cause low recovery values for several elements. As a result, 53 elements in the concentration range from sub-ng/L to several 10 mg/L could be determined with good reproducibility. The reliability of the whole analytical procedure was confirmed by analyzing river water certified reference materials (JSAC 0301-4a and JSAC 0302-4a). From the analytical results for environmental water (river water) samples around sewage treatment plant (upstream, just below outlet, downstream 1 and downstream 2), it was found that various elements such as Fe, Co, Ni, Cu, Zn, Cd, and Pb were emitted from sewage effluent into environmental water (river water) as dissolved forms, while the element existed mainly in particulate matters (Al, Ti, and rare earth elements) showed low concentrations in sewage effluent. Distribution patterns of rare earth element for sewage effluent and downstream samples showed characteristic large Gd anomalies and increase from light REE to heavy REE, which were the same as other environmental water samples affected by the influx of sewage effluent.

Determination of Vanadium(IV) and Vanadium(V) in Beverages by Two-Step Direct Immersion Single-Drop Microextraction with Graphite Furnace Atomic Absorption Spectrometry (GFAAS)

A novel two-step direct immersion single-drop microextraction (TS-DI-SDME) was reported for the sequential separation and enrichment of V(V) and V(IV) followed by graphite furnace atomic absorption spectrometry detection. Theonyltrifluoroacetone (HTTA) and chloroform were used as the chelating reagent and extraction solvent for TS-DI-SDME. In the first step, V(V)-HTTA complexes were separated and enriched in one organic solvent drop at pH 2.5, while V(IV) remained in the solution. Next, another organic solvent drop containing HTTA was immersed in the original solution after the extraction of V(V) for the enrichment of V(IV) at pH 4.5. This procedure avoids tedious and complicated pre-oxidation/pre-reduction operations, which may cause contamination and error. Under the optimized conditions, the limits of detection were equal to 3.1 and 2.6 ng L−1 for V(IV) and V(V) with relative standard deviation values of 4.9 and 5.8%, respectively. An enrichment factor of 300-fold was achieved for V(IV) and V(V). This method was successfully utilized for the determination of V(IV) and V(V) in beverages. To validate this approach, a water-certified reference material was analyzed with satisfactory results.

Determination of Rare Earth Elements by Inductively Coupled Plasma-Tandem Quadrupole Mass Spectrometry With Nitrous Oxide as the Reaction Gas.

Nitrous oxide (N2O) was investigated as the reaction gas for the determination of rare earth elements (REEs) by inductively coupled plasma–tandem quadrupole mass spectrometry (ICP-QMS/QMS). The use of N2O as the reaction gas apparently improved the yields of m M16O+ for Eu and Yb in the reaction cell. As a result, the sensitivities for measurement of Eu and Yb were apparently improved in comparison to those obtained with O2 as the reaction gas. A high sensitivity measurement of the whole set of REEs was achieved, providing a typical sensitivity of 300,000 CPS mL/ng for REEs measured with an isotope having isotopic abundance close to 100%. The use of N2O as the reaction gas helped suppress Ba-related spectral interferences with the measurement of Eu, permitting the measurement of Eu in a natural sample without mathematic correction of spectral interferences. The detection limits (unit, pg/mL) for 14 REEs (except for Pm) from La to Lu were 0.028, 0.018, 0.006, 0.026, 0.006, 0.010, 0.017, 0.006, 0.016, 0.010, 0.016, 0.004, 0.023, and 0.012, respectively. The validity of the present method was confirmed by determining REEs in river water-certified reference materials, namely, SLRS-3 and SLRS-4.

Novel determination of copper(II) in natural waters by solid-phase extraction (SPE) flow-injection (FI) flame atomic absorption spectrometry (FAAS)

A novel functionalized silica gel with the Schiff base of N-{[3-[(3-aminopropyl)amino]propyl}-2-hydroxy-benzaldimine was fabricated and utilized for flow-injection (FI) solid-phase extraction (SPE) of Cu(II) ions with flame atomic absorption spectrometric determination in environmental water samples. The practical factors on the FI-SPE of Cu(II) ions, including flow rates and volumes of sample and eluent solutions, eluent type and concentration, sample pH, and matrix ions, were studied. The maximum absorbance of Cu(II) ions was obtained using sample solutions at pH 7.0 at 5.0 mL min−1 with elution by 500 µL of 1.0 M HCl. Batch adsorption capacity of the functionalized silica gel for Cu(II) ions was 24.7 ± 0.3 mg g−1. The developed FI-SPE method was successfully validated by the determination of Cu(II) in water certified reference materials, including water-trace elements (NWTM-15.2) and Ontario Lake water (NWTMDA-54.4). Cu(II) levels in environmental samples such as tap, river, and sea water were successfully determined using the reported FI-SPE method.

From sea salt to seawater: a novel approach for the production of water CRMs

Natural water certified reference materials (CRMs) are mostly available in a liquid form, and they are produced starting from suitable environmental samples. Many precautions are usually needed to avoid biological or physical degradation, including filtration, acidification, and sterilization. In this study, the drawbacks associated with liquid-based seawater CRMs were tackled by developing a salt-based seawater proxy for nutrients that could be reconstituted in water solution just before use. Phosphate, silicate, and nitrate were chosen as target analytes. Sea salt mimicking the composition of seawater was spiked with an aqueous solution of the analytes and homogenized using a high-energy planetary ball mill (uhom < 1.2%). The salt powder CRM SALT-1 (https://doi.org/10.4224/crm.2022.salt-1) demonstrated good short- and long-term stability for nutrients. When the SALT-1 was reconstituted in water at the 4.0% w/w level, the resulting solution had similar properties with respect to typical seawater in terms of major constituents (± 20%), trace metals, density (1.023 g/mL), pH (8.8–9.0), and optical properties relevant to the photometric characterization. Phosphate and silicate were quantified by photometry (molybdenum blue method, batch mode), whereas nitrate was quantified by isotope dilution GC−MS (uchar < 1.2%). In the SALT-1 reconstituted seawater solution at the 4.0% w/w salt level, the nutrient amount concentration was w(phosphate, PO43−) = 1.615 ± 0.030 μmol/L, w(silicate as SiO2) = 8.89 ± 0.31 μmol/L, and w(nitrate, NO3−) = 18.98 ± 0.45 μmol/L at the 95% confidence (k = 2). Overall, the SALT-1 CRM exhibits similar nutrient profile and general analytical characteristics as the MOOS-3 CRM. However, the SALT-1 has much reduced preparation, storage, and distribution cost, likely much better long-term stability, and it could enable the production of lower cost and more accessible seawater reference materials.Graphical abstract

Analysis of Seventeen Certified Water Reference Materials for Trace and Technology‐Critical Elements

Concentrations of elements in the aquatic environment are a key parameter for various scientific fields such as biogeochemistry, biology and environmental science. Within this context, the scientific community asks for new analytical protocols to be able to quantify more and more elements of the periodic table. Therefore, the requirements for aqueous reference materials have increased drastically. Even though a wide variety of CRMs of different water matrices are available, certified values of many elements (e.g., rare earth elements (REE), technology‐critical elements, such as Ga and In, and generally those elements which are not part of current monitoring regulations) do not yet exist. Therefore, the scientific community relies on published elemental concentrations of many CRMs provided by other researchers. Some elements of interest, such as the REE, are well studied and plenty of literature values exist. However, less studied elements, such as Ga and In, are rarely studied. In this study, an ‘externally’ calibrated quantification method based on an optimised online preconcentration method coupled with ICP‐MS/MS was used for the quantification of thirty‐four elements. The method was applied to seventeen water CRMs covering freshwater, brackish water and seawater. The measured data are combined with a comprehensive literature review on non‐certified values in selected water CRMs, and new consensus values are suggested for various non‐certified elements.

The Use of a Solid Bismuth Microelectrode for Vanadium Quantification by Adsorptive Stripping Voltammetry in Environmental Water Samples.

This paper presents for the first time the use of an environmentally friendly solid bismuth microelectrode for the voltammetric quantification of V(V) in natural water samples. These studies were designed to replace the film bismuth electrode that had been introduced to eliminate the conventional sensors based on highly toxic mercury. In the proposed procedure, V(V) is preconcentrated at the solid bismuth microelectrode surface via the formation of electroactive complexes with cupferron from a solution of 0.1-mol L−1 acetate buffer, pH = 4.6 at a potential of −0.4 V. The linearity of the calibration graph is in the V(V) concentration range from 8 × 10−10 to 1 × 10−7 mol L−1 with a preconcentration time of 1 min. The limit of detection (calculated as 3 σ) is 2.5 × 10−10 mol L−1 for a preconcentration time of 1 min. It was also demonstrated that significant improvement in analytical parameters was achieved as a result of the activation of the solid electrode surface at a potential of −2.5 V for 2 s. The developed procedure is highly selective for the presence of foreign ions and organic compounds in tested samples. The accuracy of the recommended procedure was checked using SPS-WW1 waste water-certified reference materials of a complex composition, in which the concentration of V(V) determined by the proposed method was 95.1 ± 1.6 ng mL−1. Moreover, in keeping with the outlined procedure, river, tap and rain water samples were analyzed without any pretreatment, and recovery values from 96% to 106% were obtained.

Collaborative determination of trace element mass fractions and isotope ratios in AQUA-1 drinking water certified reference material.

The Isotrace CNRS workgroup in collaboration with National Research Council of Canada has characterized a number of trace element mass fractions and isotope ratios currently not certified in AQUA-1 natural drinking water reference material (NRC Canada). This survey further expands the use of this material as a tool for environmental quality control, method validation, and method development tool for the international community. Simultaneously, the SLRS-6 river water was analyzed as quality control and also in order to compare both water characteristics, which were sampled in the same area but having undergone different treatment. Mass fractions for B, Cs, Li, Ga, Ge, Hf, Nb, P, Rb, Rh, Re, S, Sc, Se, Si, Sn, Th, Ti, Tl, W, Y, Zr, REEs, and six isotopic ratios are proposed for Sr and Pb. Measurements were mostly performed using ICP-MS with various calibration approaches. The results are reported as consensus or indicative values depending on the number of available datasets, with their associated uncertainties.

A journey towards whole water certified reference materials for organic substances: measuring polycyclic aromatic hydrocarbons as required by the European Union Water Framework Directive

In 2000, the Water Framework Directive (WFD) came into force in the European Union with the aim of protecting and improving water quality. The priority substances established to be monitored are predominantly organic compounds, for which the WFD sets the requirement of ‘whole water sample’ analysis. This legislative requirement poses analytical challenges for the monitoring laboratories as well as technical challenges for reference materials producers. In the past, there were attempts to produce reference materials as quality assurance/quality control tools for measuring organic priority substances in whole water. A critical reflection on the approaches and solutions applied to prepare such kind of matrix reference materials is presented along with a discussion on the difficulties encountered by the analytical laboratories in analysing such complex matrices. The Certified Reference Material (CRM) ERM-CA100 can be considered as a pioneer for a ‘whole water’ CRM (containing humic acids) and has been designed for the analysis of polycyclic aromatic hydrocarbons (PAHs). Further developments seem to be necessary to upgrade the design towards a CRM which will also include suspended particulate matter, another basic constituent of natural surface water samples.Graphical abstract

High Sensitivity Determination of Antimony with Application for the Characterization of Its Migration in Bottled Water by a Dielectric Barrier Discharge (DBD) Coupled with Hydride Generation – Atomic Fluorescence Spectrometry (HG-AFS)

An in situ dielectric barrier discharge (DBD) employed as a preconcentration device was coupled with hydride generation atomic fluorescence spectrometry (HG-AFS) for the determination of antimony (Sb) that migrated from plastic to bottle water. In the presence of oxygen under a 7.5 kV discharge, Sb was completely trapped on the surface of dielectric barrier discharge quartz tube. After 50 s of Ar carrier sweeping, water vapor interference was effectively eliminated and Sb was rapidly released by a discharge containing hydrogen using 6.8 kV. In addition, the investigation of Sb migration from bottle materials to water was carried out considering temperature and bottle materials. Under the optimized conditions, the detection of limit (LOD) was 9 pg or 5 pg/mL. The linearity of the calibration relationship R2 exceeded 0.996 for concentrations from of 0.05 to 50 μg/L. In addition, the determined Sb levels of water certified reference materials (CRMs) were in good agreement with the certified values. The spiked recoveries for bottled water samples were from 95% to 104% with 3% to 8% relative standard deviation values. In comparison, the HG-in situ DBD-AFS method is capable to increase the analytical sensitivity using the peak height by 7-fold compared to standard HG-AFS. DBD offers gas phase enrichment at room temperature with instrumental miniaturization for elemental analysis with low energy consumption, small size and low cost.

Towards the abatement of nitrate interference on selenium determination by photochemical vapor generation

A flow injection photochemical vapor generation atomic absorption spectrometry (FI-PVG-AAS) system was developed for selenium determination. The variables of influence of the photochemical generation process were evaluated and optimized. Sample already reduced to the Se(IV) state and mixed with the photochemical reagent (1.5% w/w HCOOH) was irradiated for 3 s. Selenium derivatives were transferred to an externally heated atomization cell by an argon-hydrogen mixture and selenium determined at 196.0 nm. Nitrogen was used as the carrier of the flow injection system. Nitrate is one of the most relevant interferents for the photochemical generation process; it is a very frequent concomitant as nitric acid is added for sample digestion or preservation. Hence, its removal before the vapor generation stage was studied. It was found that up to 3.0% w/w HNO3, it can be eliminated in the reduction stage of Se(VI) to Se(IV) with hydrochloric acid. For higher concentrations (up to 21% w/w HNO3), prior to the reduction step, the addition of 40% w/w H2CO and evaporation almost to dryness was successful for the abatement of the interference. The performance of the method was studied and its applicability evaluated with a Trace Element in Water Certified Reference Material (24.3 μg L−1 – Se, 2.8% w/w HNO3) and a spiked rice-flour microwave-assisted digest (103.1 μg L−1 – Se, 18.5% w/w HNO3).

Ultra-trace Element Characterization of the Central Ottawa River Basin using a Rapid, Flexible, and Low-volume ICP-MS Method

Ultra-trace (< 1 ng g−1) rare earth elements and yttrium (REE + Y) and high field strength element (HFSE) geochemistry of freshwater can constrain element sources, aqueous processes in hydrologic catchments, and the signature of dissolved terrestrial fluxes to the oceans. This study details an adapted method capable of quantifying ≥ 38 elements (including all REE + Y, Nb, Ta, Zr, Hf, Mo, W, Th, U) with minimal sample preparation in natural water aliquots as low as ≤ 2 mL. The method precision and accuracy are demonstrated using measurement of the National Research Council – Conseil national de recherches Canada (NRC-CNRC) river water certified reference material (CRM) SLRS-6 sampled from the Ottawa River (OR). Data from SLRS CRM are compared to those of new, filtered (< 0.45 µm) stream water samples from the central Ottawa River basin (ORB), and discussed in terms of processes and geochemical signatures inherited from the highly evolved igneous/metamorphic Archean and Proterozoic bedrock in the catchment. The ORB waters have significantly LREE > HREE-enriched REE + Y patterns, small natural positive Y and Gd anomalies, and negative Eu and Ce anomalies. These REE + Y features are coherent downstream in the OR apart from amplification of Eu and Ce anomalies during REE removal/dilution. The OR samples capture a downstream decrease in sparingly soluble HFSE (Th, Nb, Ta, Zr, Hf), presumably related to their colloid-particulate removal from the dissolved load, accompanied by crustal Zr/Hf (32.5 ± 5.1) and supercrustal Nb/Ta (25.1 ± 7.7) ratios. Subcrustal Th/U (0.17–0.96) and supercrustal Mo/W (12.0–74.5) ratios in all ORB waters indicate preferential release and aqueous solubility of U > Th and Mo > W, with the latter attributed primarily to preferential W adsorption on soil or upstream aquatic (oxy)(hydr)oxide surfaces.

Sensitive Anodic Stripping Voltammetric Copper Ions Determination Performed in Double Deposition and Double Stripping Steps System for Real Water Samples Analysis

AbstractThe article reports on utilization of double deposition and stripping steps for increasing sensitivity of Cu(II) determination by anodic stripping voltammetry (ASV) at two lead film working electrodes. A significant preconcentration of copper was achieved thanks to utilization of a simple design of four electrodes system that gives possibility to perform one measurement cycle consisting of two deposition and two stripping steps. Due to the fact that deposition step is doubled, the concentration of Pb(II) needed to lead film electrodes formation was significantly reduced as compared to traditional procedures using three electrodes system. The analytical procedure of Cu(II) determination was optimized. The experimental factors: supporting electrolyte's pH and its concentration, lead ions concentration, potential and time of deposition at both working electrodes were studied. The Cu(II) peak current was linearly dependent on its concentration from 5×10−10 to 2×10−8 mol L−1 (deposition time of 270 and 160 s at the first and the second working electrode, respectively). The obtained detection limit for copper ions determination was 2.1×10−10 mol L−1. The described procedure was validated by analysis of two water certified reference materials. The described procedure was also utilized for real water sample analysis.

A new dispersive micro-solid phase extraction based on rejection property method combined with FAAS for the simultaneous determination of cobalt and copper after optimisation by Box-Behnken design

ABSTRACT A new, fast and simple technique of dispersive micro-solid phase extraction based on rejection property (DMSPE-RP) combined with flame atomic absorption spectrometry (FAAS) for the simultaneous preconcentration and determination of trace amounts of cobalt and copper ions has been introduced. In this technique, 1-(2-pyridylazo)-2-naphthol (PAN) was used as a chelating agent and adsorbent. The experimental factors affecting the analytical performance of the method such as pH of the sample solution, the concentration of PAN and salting-out effect were evaluated and optimised using Box–Behnken design. Under the optimum conditions, the method exhibited linear dynamic ranges of 5.0–350.0 µg L−1 for cobalt and 5.0–500.0 µg L−1 for copper with the coefficients of determination higher than 0.997. The detection limits were 1.2 and 1.5 µg L−1 and the enrichment factors were 184.0 and 154.0 for cobalt and copper, respectively. The accuracy of the method was evaluated by the analysis of water-certified reference material (TMDA 53.3 water). The results indicated that the presented method is a good technique for the determination of target metal ions in natural water samples.

Design and optimization of a single-use optical sensor based on a polymer inclusion membrane for zinc determination in drinks, food supplement and foot health care products.

A single-use optical sensor was designed for Zn(II) determination based on the immobilisation of the colorimetric reagent 2-acetylpyridine benzoylhydrazone (2-APBH) in a polymer inclusion membrane (PIM) adhered on the surface of an inert rectangular strip of polyester (Mylar). Different components for the membrane preparation were tested and those resulting in membrane with good appearance, proper physical and optical properties and ease of preparation were selected. Factorial design 23 with three replicates of the central point was applied for the optimisation of the membrane composition. The optimal composition consisted of 2.5g of poly(vinyl chloride) (PVC), 4mL of tributyl phosphate (TBP) and 0.04g of 2-APBH. The optode showed a linear dynamic range from 0.03 (detection limit) to 1mgL-1 of Zn(II) ions with a response time of 30min in aqueous solution at pH6 and a relative standard deviation of 3.90% for 0.4mgL-1 of Zn(II). The sensor exhibited good selectivity to Zn(II) over other commonly ions. It was successfully applied to the determination of Zn(II) in a water certified reference material, spiked tap water, vitamin-mineral drink, food supplement and foot health care products, as contribution to the concern about this heavy metal due to its significant role in many biological and physiological processes although toxicant at high doses.

Anodic Stripping Voltammetry of Tl(I) Determination with the Use of a Solid Bismuth Microelectrode

For the first time a solid bismuth microelectrode was utilized for anodic stripping voltammetry in the course of Tl(I) ions determination. The proposed solid bismuth microelectrode (ϕ 25 μm) is more environmentally friendly sensor in comparison to bismuth film electrodes as bismuth ions are not added to the supporting electrolyte for bismuth film formation. Furthermore, an amount of metallic bismuth needed for fabrication of proposed sensor is significantly minimized as compared to solid bismuth electrode with a large surface area. Furthermore, the measurements may be carried out from unstirred solutions that gives possibility of performing fields analysis. The optimization of the analytical parameters of Tl(I) determination procedure was presented. A calibration graph for Tl(I) determination was linear in the range from 2 × 10−9 to 2 × 10−7 mol l−1 (deposition time of 120 s). The detection limit for thallium ions determination was 8.3 × 10−10 mol l−1 for deposition time of 120 s. Repeatability of the proposed procedure calculated as RSD% for Tl(I) at concentration of 2 × 10−8 mol l−1 was 5.2% (n = 5). The accuracy of the proposed procedure was successfully checked by analysis of a lake water certified reference material TM 25.5.