Vanadium In Water Research Articles

Task specific microextraction column based on monolith for magnetic field-assisted in-tube solid phase microextraction of vanadium species in complex samples prior to online chromatographic analysis

The dominant species of vanadium (V) are V(IV) and V(V) which exhibit different toxicity and biological effects. Thus, speciation of V(IV) and V(V) is highly essential. Efficient sample preparation is the core step in the quantification of V(IV) and V(V). In the present study, a new task specific microextraction column based on monolith mingled with Fe3O4 nanoparticles (MBMC) was in situ synthesized in capillary and utilized as the extraction phase of magnetic field-assisted in-tube solid phase microextraction (MA-IT-SPME) of V(IV) and V(V) species which were coordinated with ethylene diamine tetraacetic acid (EDTA). The prepared MBMC presented porous and superparamagnetic properties, and possessed abundant functional groups. Results revealed that the exertion of magnetic field during adsorption and eluting steps boosted the extraction efficiency of V(IV)-EDTA and V(V)-EDTA chelates from 65.1 % to 55.7 %–90.0 % and 80.1 %, respectively. Under the beneficial extraction parameters, the established MA-IT-SPME was online hyphenated with HPLC/DAD to perform speciation of trace vanadium in water and vegetable samples, the achieved limits of detection were 0.054–0.060 μg/L and 1.4–1.5 μg/kg in water and vegetable samples, respectively, and the spiked recoveries varied from 82.5 to 118 %. In addition, relevant extraction mechanism under magnetic field was explored. In comparison with existing methods, the developed MA-IT-SPME technique displays some attractive merits such as automation, good anti-interference ability, high extraction efficiency, low cost and less use of organic solvent, in the capture of V species. The established online MBMC@MA-IT-SPME-HPLC/DAD system can become a competitive approach for sensitive speciation of V(IV) and V(V) at trace levels in complex samples.

Constraining the major pathways of vanadium incorporation into sediments underlying natural sulfidic waters

Vanadium (V) is a redox-sensitive trace metal. Interconversion between different vanadium species (e.g., VIII, VIV, VV) occurs rapidly in association with changes in redox conditions in natural environments. Different vanadium species exhibit variable geochemical behavior that impacts if and how they are sequestered into sediments, which makes vanadium a useful proxy for ancient ocean redox conditions. However, we still lack constraints on how different dissolved vanadium sink pathways impact distributions of vanadium in water column, pore waters, and sediments, especially in natural sulfidic settings. In the present study, we combined field and experimental data to constrain the major scavenging processes that influence the partitioning of vanadium between aqueous and solid phases to provide an improved picture of vanadium geochemical cycling under anoxic-sulfidic conditions. We find that in the sulfidic bottom waters and sediment pore waters of the Chesapeake Bay, vanadium concentrations are correlated with manganese (Mn) concentrations in both aqueous and solid phases. Our experimental results support our interpretation that elevated concentrations of vanadium in anoxic-sulfidic waters result from the release of vanadium due to desorption from and/or dissolution of Mn oxides in anoxic/sulfidic waters. While sorption of vanadium results in strongly adsorbed complexes on both Mn oxides and pyrite surfaces, vanadium preferentially sorbs to Mn oxides rather than to pyrite. Thus, the impact of Mn oxides on vanadium geochemistry is greater than that imposed by scavenging via sorption on pyrite, although both processes should be considered. Mn oxides also have a greater impact on vanadium geochemistry than reductive formation of solid V(OH)3 by H2S. Sorption of vanadium is sensitive to pH conditions (especially in anoxic waters), moderately sensitive to ionic strength, and weakly sensitive to phosphate concentrations. In addition, our results show that as waters become more sulfidic, dissolved V/Mn molar ratios increase, whereas solid phase V/Mn molar ratios decrease, indicating that the V/Mn molar ratio can be used to trace redox changes. Finally, we investigate the V/Mn record of black shales that span the Proterozoic and Phanerozoic to show a framework of utilizing this proxy with applicability to identify changes in redox conditions associated with both oxygenation and anoxic events in ancient oceans.

Cloud point extraction coupled with back-extraction for speciation of inorganic vanadium in water and determination of total vanadium in food samples by ICP-OES

A preconcentration procedure based on cloud point extraction and back-extraction (CPE-BE) was proposed for speciation of inorganic vanadium (V4+ and V5+) followed by determination by inductively coupled plasma-optical emission spectrometry (ICP-OES). Two consecutive steps are used in this technique. The traditional CPE technique was applied as a first step, V5+ reacts with bis(3,4-dihydroxybenzylidene)isophthalohydrazide (DHBIP) forming a hydrophobic complex at pH 7.0. The formed complex is then entrapped in a surfactant-rich phase of Triton X-114, while V4+ kept in the aqueous phase. Following this stage, a back-extraction step was performed to minimize the deteriorating effect of the organic matrix on the plasma performance. For this purpose, the surfactant-rich phase containing the analyte was incubated at 45 °C with 1.0 mL of 1.0 mol L−1 of HNO3 solution for 15 min. Finally, the analyte in the aqueous phase was determined by ICP-OES. The total vanadium was determined as V5+ after oxidation of V4+ by using hydrogen peroxide. The calibration graph is linear from 0.4–750.0 μg L-1 for V5+ at the optimum conditions (pH 7.0, 10-4 mol L-1 DHBIP, 0.1 % (v/v) Triton X-114 and 45 °C). The detection and quantification limits of V5+ were 0.12 μg L-1and 0.40 μg L-1, respectively, with an enrichment factor of 49.5, and the relative standard deviation was less than 2.5 % (n = 7, c = 10 μg L-1). The method has been used for speciation of inorganic V in water samples and determination of total V in cabbage, carrots, mint, and tomato samples with satisfactory results.

Leaching of Metals from Steel Slag and Their Ecological Effects on a Marine Ecosystem: Validating Field Data with Mesocosm Observations.

Steel slag is being used worldwide for a variety of applications, among which is underwater dyke reinforcement. In the present study the leaching and bioaccumulation of 18 inorganic compounds from basic oxygen furnace (BOF) steel slag were monitored in marine experimental ecosystems (mesocosms) for 12 wk. Triplicate mesocosms were installed at 2 refreshment rates, one reflecting the situation in the Oosterschelde estuary where BOF steel slag was applied and the other at a 35 times lower rate. Vanadium in both water and biota turned out to be the best tracer for the presence of BOF steel slag in the mesocosms. The mesocosm data helped to interpret the results of a 4‐yr field sampling program in the Oosterschelde estuary where no elevated levels of vanadium in water or biota were found near locations where steel slag was applied. Also, no ecological impact could be established in the field, which was in line with the observations in the mesocosms. The present study shows the added value of a tailor‐made mesocosm study for realistic risk assessment and provides support for applying this tool as a basis for designing efficient field monitoring programs. Environ Toxicol Chem 2021;40:2499–2509. © 2021 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

A novel direct-immersion single-drop microextraction combined with digital colorimetry applied to the determination of vanadium in water

In this study, a method based on direct-immersion single-drop microextraction was developed for the determination of vanadium in water. The detection system uses digital images obtained directly from the solvent drop after the sorption of V(V). The extraction solvent used was the ionic liquid 1-hexyl-3-methylimidazolium hexafluorophosphate ([C6MIM][PF6]). The images were obtained directly from the solvent drop, with the aid of a camera. The digital images were stored, and the RGB (red, green, and blue) data were obtained. The data collected by the red channel were used to construct the analytical curve since it showed higher sensitivity compared with green and blue channels. Under optimized conditions, the method presented an enrichment factor of 50 and a limit of detection of 0.6 μg L−1 for 3.5 mL sample volume. The limit of quantification and the relative standard deviation (50.0 μg L−1) obtained were 1.8 μg L−1 and 4.8%, respectively. Certified reference material (Plankton) was used to assess the accuracy of the method. The simple, fast, efficient, and low-cost procedure was successfully applied to the determination of V(V) in water samples. The proposed method is also following the principles of green chemistry since it uses minimal volumes of samples, reagents, and solvents and yields a small amount of waste.

A global systematic review, meta-analysis, and risk assessment of the concentration of vanadium in drinking water resources

The presence of toxic metals such as vanadium in water resources has attracted considerable attention as a new concern in international health. Systematic review and meta-analysis were performed to assess the concentration of vanadium in water resources along with the relevant ecological risk assessment. Databases of Scopus, PubMed, and Embase were investigated to retrieve the related articles from January 01, 1974 to December 25, 2019. Twenty-eight articles containing 152 samples from 24 countries were included. Furthermore, the meta-analysis was conducted by the approach of z-score to estimate differences in the effect size. In addition, the mean of concentrations of vanadium was applied to calculate the risk assessment only to the water surface and choose the maximum environmental concentration (MEC) for demonstrate a worst-case scenario. Here, the risk assessment approach was used to show that the MEC of vanadium confirm the risk it for aquatic ecosystems, being fish (e.g., Danio rerio) our model organism due to their sensibility. According to findings, the MEC of vanadium in surface water varied from 0.010 μg L−1 (USA) and 68 μg L−1 (China), with an overall mean of 6.21 ± 13.3 μg L−1 (mean ± standard deviation). The ecological risk assessment demonstrated that people living in some countries such as China and Japan were at an adverse ecological risk of vanadium in the water resources. Hence, essential control plans besides adequate removal techniques must be implemented for significant deracination of heavy metals like vanadium.

Green and innovative technique develop for the determination of vanadium in different types of water and food samples by eutectic solvent extraction method

A green and innovative eutectic solvent based extraction method was proposed for the determination of trace level vanadium in water and food samples by graphite furnace atomic absorption spectrometry. In this extraction technique magnetic stirrer was used for preparation of eutectic solvent by mixing of zinc chloride and acetamide at different molar ratios. Extraction capability of eutectic solvent was increased by adding a non ionic surfactant (Triton X-114) to enhanced phase transfer ratio, to significantly increase the recovery of hydrophobic complex of vanadium with ammonium pyrrolidine dithiocarbamate. A multivariate technique was applied to evaluate the important extraction parameters, which plays important role for optimum recovery of the targeted analyte by proposed extraction method. Multivariate techniques such as (factorial design and central composite design) were applied to screening out the most significant extraction parameters and optimized them. Under optimized extraction conditions, limit of detection and enhancement factor were found to be 0.01 µg L−1 and 64.6, respectively. The relative standard deviation for the determination of trace level vanadium at 0.32 µg L−1 concentration, was achieved to be <3.0% (n = 10). Validity and accuracy of the proposed extraction method was checked by analysis of certified reference materials of Canadian lake water and tomato leaves with % age recovery >98%. The eutectic solvent extraction method was successfully applied for the determination of the trace level vanadium in real water samples of different sources and acid digested food samples, collected from different locations of Tokat city, Turkey.

Constructed wetlands for steel slag leachate management: Partitioning of arsenic, chromium, and vanadium in waters, sediments, and plants

Constructed wetlands can treat highly alkaline leachate resulting from the weathering of steel slag before reuse (e.g. as aggregate) or during disposal in repositories and legacy sites. This study aimed to assess how metal(loid)s soluble at high pH, such as arsenic (As), chromium (Cr), and vanadium (V) are removed in constructed wetlands and how they accumulate in the sediments and the plants (Phragmites australis, common reed). The results show that reedbeds were very effective at removing calcium (98%), aluminium (81%), barium (98%), chromium (90%), gallium (80%), nickel (98%), and zinc (98%), and lowering pH and alkalinity. No statistical difference was found for As and V between leachate influent and wetland samples, showing that these metal(loid)s were not efficiently removed. As, Cr, and V were significantly higher in the reedbed sediments than in a reference site. However, sediment concentrations are not at levels that would pose a concern regarding reuse for agricultural purposes (average values of 39 ± 26 mg kg−1 for As, 108 ± 15 mg kg−1 for Cr, and 231 ± 34 mg kg−1 for V). Also, there is no significant uptake of metals by the aboveground portions of the reeds compared to reference conditions. Results show statistically significant enrichment in metal(loid)s in rhizomes and also a seasonal effect on the Cr concentrations. The data suggest minimal risk of oxyanion-forming element uptake and cycling in wetlands receiving alkaline steel slag.

A new portable micropipette tip-syringe based solid phase microextraction for the determination of vanadium species in water and food samples

Simple, rapid and miniaturized portable micropipette tip-syringe solid phase microextraction method was developed for speciation of vanadium in water and food samples. Tetra ethylene pentamine functionalized multiwalled carbon nanotubes were synthesized and packed in micropipette tip-syringe system. The surface morphology of adsorbent was characterized, and the effective factors that influence the efficiency of developed method such as pH, amount of adsorbent, concentration of acid solution for desorption cycles were studied. The V(V) could be adsorbed on the modified adsorbent surface with tetra ethylene pentamine, while V(IV) could not be retained. The assay of V(IV) was based on subtracting values of V(V), from total vanadium. The extracted total vanadium and V(V) were injected directly into the electrothermal atomic absorption spectrometry for analysis. Enhancement factor and detection limit were found 50 and 0.008μgL−1, respectively. Accuracy of the method was checked by analysis of certified reference materials. The developed method was applied to water and food samples.

The use of δ18O as an indicator of vanadium movement in a dormant stratovolcano region

ABSTRACTThe oxygen isotope (δ18O) stable water tracer can be a promising new tool for identifying trace metals in volcanoes and their sources. In the present study, the origin of vanadium in water from a spring at the base of Mt. Fuji is examined using δ18O, a dormant stratovolcano consisting of lava and basalt rock located on the North Pacific Coast of Japan. A comparison of water from the main springs at the foot of the Mt. Fuji volcano indicates that only V, Cr, Mn and Co enrichment could be related to volcanic events, whereas Ni, Cu, Cd and Pb originate from the dissolution of particles of anthropogenic origin from the industrial areas of Fuji and Fujinomiya. The average V concentrations at the mountain sites ranged from 50 to 110 µg L−1 and from 18 to 47 µg L−1 in the coastal areas. The δ18O became depleted at higher elevations and increased in coastal areas as well as in some NO3−-contaminated water. Therefore, variations in the dissolved V/δ18O ratio in springs of the study area occur due to the elevations of their catchments and the increased concentrations of δ18O from NO3− as a contaminant.

The distribution of heavy metals content in the bottom deposits of the trans-border Uzh river system

The dynamics and peculiarities of the heavy metals (Cu, Pb, Zn, As, V, Cr, Ni) migration were established in the system of the river Uzh bottom deposits. An excess in maximum permissible concentration among such elements as Zn, V, As, and Cu was detected in surface waters. We may connect the elevated level of Cu and Zn with natural (metals appearing in ground water run-off, ablation from iron ore, the reaction of interstitial water), anthropogenic (sewage disposals from communal households and manufacturing plants, agricultural run-offs), and hydrochemical (pH of water medium, methylation of non-organic metal compounds, metals release from the organic compounds composition, ingress from bottom deposits) factors. The high concentrations of vanadium in water as well as in bottom deposits are most probably induced by the leaching of elements from the regional volcanic rocks. The plumbum content did not exceed the higher-than-normal rates; however, significant element accumulation was detected in bottom deposits outside the city of Uzhgorod which may be the result of ecotoxicant ingress along with land runoff from the riverside highways laid parallel to the water course. In comparison with background measures, the highest chromium and nickel concentrations were detected near the streamlet Domoradzh and, therefore, it is assumed that the industrial wastewaters serve here as a source of heavy metals. The reservoir in the lowland is above all enriched by arsenic. Areas under agricultural use are significantly concentrated in lowlands. Runoffs from these areas are the main source of the ore supply. However, the impact of municipal domestic waste water which contains arsenic-containing detergents should not be excluded. Moreover, we found a relationship between the relief heterogeneity of the study area and distribution of heavy metals in the hydro-ecosystem. The accomplished comparative analysis of the territories under study indicates the significant pollution level of the surface waters in technologically transformed areas, whereas the largest accumulation of pollutants is concentrated in bottom deposits of the river, which indicates a constant supply of pollutants to the streamflow.

Magnetic stirrer induced dispersive ionic-liquid microextraction for the determination of vanadium in water and food samples prior to graphite furnace atomic absorption spectrometry

A new dispersive liquid–liquid microextraction, magnetic stirrer induced dispersive ionic-liquid microextraction (MS-IL-DLLME) was developed to quantify the trace level of vanadium in real water and food samples by graphite furnace atomic absorption spectrometry (GFAAS). In this extraction method magnetic stirrer was applied to obtained a dispersive medium of 1-butyl-3-methylimidazolium hexafluorophosphate [C4MIM][PF6] in aqueous solution of (real water samples and digested food samples) to increase phase transfer ratio, which significantly enhance the recovery of vanadium – 4-(2-pyridylazo) resorcinol (PAR) chelate. Variables having vital role on desired microextraction methods were optimised to obtain the maximum recovery of study analyte. Under the optimised experimental variables, enhancement factor (EF) and limit of detection (LOD) were achieved to be 125 and 18ngL−1, respectively. Validity and accuracy of the desired method was checked by analysis of certified reference materials (SLRS-4 Riverine water and NIST SRM 1515 Apple leaves). The relative standard deviation (RSD) for 10 replicate determinations at 0.5μgL−1 of vanadium level was found to be <5.0%. This method was successfully applied to real water and acid digested food samples.

Ionic Liquid-based Ultrasound-Assisted In Situ Solvent Formation Microextraction Combined with Electrothermal Atomic Absorption Spectrometry as a Practical Method for Preconcentration and Trace Determination of Vanadium in Water and Food Samples

A new and practical sample enrichment method termed ionic liquid-based ultrasound-assisted in situ solvent formation microextraction (IL-UA-ISFME) was combined with electrothermal atomic absorption spectrometry (ETAAS) for preconcentration and trace determination of vanadium in real samples. In this sample enrichment methodology, a hydrophilic ionic liquid (IL) ([Hmim][BF4]) was added to the aqueous media containing an ion-exchange reagent (NaPF6), in order to obtain a hydrophobic IL ([Hmim][PF6]) as the microextraction solvent. The hydrophobic extraction solvent formed under these conditions was completely dispersed into the sample solution using ultrasonic radiation. Vanadium was complexed with N-benzoyl-N-phenylhydroxylamine (BPHA), and extracted into the IL phase during the dispersion of the hydrophobic IL. Main variables affecting the recommended method was studied in details and optimized. Under the optimum conditions, the combined methodology provided a linear dynamic range of 15–2,500 ng l−1, a limit of detection (LOD) of 4.7 ng l−1 and a relative standard deviation (RSD) of 4.0 %. The accuracy and validity of the method was checked by analyzing a certified standard reference material of water (SRM-1643e). Finally, the developed method was utilized for quantitation of vanadium in real water and milk samples.

Evaluation of Total Hydrocarbons Levels and Traces Metals in Water and Sediment from Main Outfall Drain in Al-Nassiriya City/Southern Iraq

This study was conducted during Dec2011-Nov2012 on three stations located in the south sector of Main Outfall Drain (MOD) River. Station 1 was near Al-Holandee Bridge which was the general carriage way in the center of Al-Nassiriya city, station 2 was 20 km far from the first station, while station 3 was in the beginning of the new branch. This study reveals the Seasonal Variation of Total petroleum hydrocarbons (TPHs) in both surface waters, sediment and it is related with trace metals nickel and vanadium in water (dissolved, particulate) and sediment (residual and exchangeable) phases. Also, the study shows the relationships between the concentration of Ni and V with Total Organic Carbon (TOC%) in the sediment.

Graphite furnace atomic absorption spectrometric detection of vanadium in water and food samples after solid phase extraction on multiwalled carbon nanotubes

Vanadium(V) ions as 8-hydroxyquinoline chelates were loaded on multiwalled carbon nanotubes (MWNTs) in a mini chromatographic column. Vanadium was determined by graphite furnace atomic absorption spectrometry (GFAAS). Various analytical parameters including pH of the working solutions, amounts of 8-hydroxyquinoline, eluent type, sample volume, and flow rates were investigated. The effects of matrix ions and some transition metals were also studied. The column can be reused 250 times without any loss in its sorption properties. The preconcentration factor was found as 100. Detection limit (3s) and limit of quantification (10s) for the vanadium in the optimal conditions were observed to be 0.012µgL−1 and 0.040μgL−1, respectively. The capacity of adsorption was 9.6mgg−1. Relative standard deviation (RSD) was found to be 5%. The validation of the method was confirmed by using NIST SRM 1515 Apple leaves, NIST SRM 1570a Spinach leaves and GBW 07605 Tea certified reference materials. The procedure was applied to the determination of vanadium in tap water and bottled drinking water samples. The procedure was also successfully applied to microwave digested food samples including black tea, coffee, tomato, cabbage, zucchini, apple and chicken samples.

A simple flow-injection chemiluminescence method for the determination of trace pentavalent vanadium in water samples

A simple method for rapid determination of trace pentavalent vanadium in natural water was presented by flow-injection chemiluminescence (CL). Through water injection, luminol and potassium permanganate were eluted from the anion exchange column to generate the CL, which was enhanced in the presence of V(V). Under the optimum conditions, the increased CL intensity was linear with V(V) concentration in the range from 0.1 to 100 ng mL−1. The limit of detection was 50 pg mL−1 (3σ) and the relative standard deviation (RSD) was 2.24% (n = 5) for a 1.0 ng mL−1 V(V). At a flow rate of 2.0 mL min−1, one cycle of analysis could be performed in 0.5 min with a RSD of less than 3.0%. The proposed method was successfully applied to the determination of vanadium in natural water.

Solidified floating organic drop microextraction and spectrophotometric determination of vanadium in water samples

Solidified floating organic drop microextraction (SFODME) was used as a sample preparation method prior to spectrophotometric determination of trace amounts of vanadium in water samples. 8-Hydroxyquinoline (oxine) was used as the chelating agent. The main parameters affecting the performance of SFODME, such as pH, concentration of oxine, extraction time, sample and organic phase volume, extraction temperature, and the nature of the organic solvent, were optimized. Under the optimized conditions, an enhancement factor of 38, detection limit of 0.97 \mu g L^{-1}, and good relative standard deviation of \pm 3.9% at 10 \mu g L^{-1} were obtained. The method was successfully applied to the determination of vanadium in tap water, well water, river water, and sea water. The accuracy of the method was assessed through a recovery experiment and independent analysis by graphite furnace atomic absorption spectrometry.

Separation/preconcentration and determination of vanadium with dispersive liquid–liquid microextraction based on solidification of floating organic drop (DLLME-SFO) and electrothermal atomic absorption spectrometry

A novel dispersive liquid–liquid microextraction based on solidification of floating organic drop (DLLME-SFO) for separation/preconcentration of ultra trace amount of vanadium and its determination with the electrothermal atomic absorption spectrometry (ETAAS) was developed. The DLLME-SFO behavior of vanadium (V) using N-benzoyl-N-phenylhydroxylamine (BPHA) as complexing agent was systematically investigated. The factors influencing the complex formation and extraction by DLLME-SFO method were optimized. Under the optimized conditions: 100 μL, 200 μL and 25 mL of extraction solvent (1-undecanol), disperser solvent (acetone) and sample volume, respectively, an enrichment factor of 184, a detection limit (based on 3S b/m) of 7 ng L −1 and a relative standard deviation of 4.6% (at 500 ng L −1) were obtained. The calibration graph using the preconcentration system for vanadium was linear from 20 to 1000 ng L −1 with a correlation coefficient of 0.9996. The method was successfully applied for the determination of vanadium in water and parsley.

A sensitive method for determining total vanadium in water samples using colorimetric-solid-phase extraction-fiber optic reflectance spectroscopy

A selective colorimetric-solid-phase extraction (C-SPE) method for the determination of total vanadium in water samples was developed. This method introduced a new variation of C-SPE. The colour reaction is based on the reaction of vanadium(V) ternary complex formed with 1-(2-Pyridylazo)-2-naphtol (PAN) in the presence hydrogen peroxide (H 2O 2). In this technique, the target analytes in samples are extracted onto solid matrix loaded with a colorimetric reagent and then quantified directly on the adsorbent surface by using a miniature fiber optic reflectance spectrometer. The measurements were carried out at a wavelength of 589.4 nm since it yielded the largest divergence different in reflectance spectra before and after reaction with the vanadium. The overall time required for the C-SPE procedure was ∼20 min. The amount of concentrated V is then determined in a few seconds by using miniature reflectance spectrometer. At the optimal conditions, a calibration curve was constructed, revealing a linear range of 0.05–0.52 mg L −1 and a detection limit as low as 0.01 mg L −1 while the RSD lower than 2.8%. In order to verify the accuracy of the method, a certified reference water samples (TMDA) were analysed and the results obtained were in good agreement with the certified values. The proposed method was applied to the determination of vanadium in tap water, seawater samples with a recovery for the spiked samples in the range of 98–102%.

Speciation of vanadium(iv) and (v) in mineral water by anion exchange liquid chromatography-inductively coupled plasma mass spectrometry after EDTA complexation

HPLC with on-line ICP-MS was used for the determination of V(IV) and V(V) in natural mineral water. Cationic and anionic tetravalent and pentavalent vanadium species were converted into V–EDTA complexes, i.e.[VO(EDTA)]2− and [VO2(EDTA)]3−, which could be effectively separated on a short anion exchange column in <6 min. Pre-column EDTA complexation also prevented species interconversion as a result of loss of CO2 from samples and their exposure to atmospheric oxygen. A low-salt mobile phase (4 mM carbonate buffer and 5 mM EDTA–Na2) compatible with ICP-MS detection was used in chromatographic separations. The method was tested on real samples spanning one order of magnitude of V concentrations and encompassing a wide range of potential interfering ions and total dissolved solids, providing accurate and reproducible results. Mass balance budgets gave a mean value of 100% (range 96–107%). Recoveries from spiking experiments were in the range 98–103%. Precision as average intra-day repeatability was 1.2% and 0.9% for V(IV) and V(V), respectively. Average inter-day repeatability was 5.5% and 1.4% for V(IV) and V(V), respectively. Limits of detections were 0.16 μg L−1 for V(IV) and 0.025 μg L−1 for V(V). The interference arising by 35Cl16O was resolved chromatographically. V(V) was found to largely predominate in PET-bottled mineral water samples. Species distribution was consistent with theoretical predictions based on thermodynamic equilibria of vanadium in water. Overall, a rapid, sensitive, on-line method is provided which can be readily employed for monitoring purposes.