Water Certified Reference Materials Research Articles

Improvement of copper FAAS determination conditions via preconcentration procedure with the use of salicylaldoxime complex trapped in polymer matrix

The paper presents application of a new resin dedicated to copper(II) flow-injection on-line preconcentration prior its flame atomic absorption spectrometric (FAAS) determination. The new sorbent, obtained by suspension polymerization technique, was styrene-divinylbenzene copolymer modified with 5-dodecylsalicylaldoxime-copper(II) complex. In flow mode leaching of initially imprinted Cu(II) ions from polymer beads was effective with 1% (v/v) nitric acid, however for elution of ions retained on the sorbent during the loading process sufficient efficiency was obtained for 0.5% (v/v) nitric acid. The most effective copper(II) sorption was observed within sample pH ca. 6.3 at flow rate 7.5mLmin−1. Furthermore, preconcentration studies of Cu(II) ions realized in the presence of popular foreign ions like Cd(II), Pb(II), Zn(II), Ni(II), Mn(II), Co(II) did not reveal significant interference. The expected effect of Cu(II)-imprinting was confirmed by higher tolerance level for interferents ions concentration for the new sorbent than for the control polymer. It was found that alkaline metals ions and humic acid had the most relevant influence on copper(II) uptake. Accuracy of the evaluated method was assessed for analysis of water samples (tap and mineral water, river water, artesian water) and certified water reference materials compare them to results obtained by inductively plasma mass spectrometry. The satisfactory relative error values obtained with use of standard addition calibration method, confirms the feasibility of this method for Cu(II) determination in water samples. Application of 120s sorption time enabled to obtain 74-fold enrichment factor and limit of detection (3σ) equal to 0.4μgL−1.

Speciation of Cr(III) and Cr(VI) in environmental samples by using coprecipitation with praseodymium(III) hydroxide and determination by flame atomic absorption spectrometry

A speciation procedure has been established for the flame atomic absorption spectrometric determination of Cr(III) and Cr(VI) based on coprecipitation of Cr(III) by using praseodymium(III) hydroxide (Pr(OH)3) precipitate. In the presented system, Cr(III) was quantitatively (>95%) recovered at the pH range of 10.0–12.0 on Pr(III) hydroxide, while the recoveries of Cr(VI) were below 10%. The method was applied to the determination of the total chromium after reduction of Cr(VI) to Cr(III) by using hydroxylamine hydrochloride. The concentration of Cr(VI) is calculated by difference of total chromium and Cr(III) levels. The analytical parameters including pH of the aqueous medium, amount of Pr(III), centrifugation speed, sample volume were optimized. The influences of matrix ions were also investigated. The method was validated by the analysis of TMDA 70 fortified lake water certified reference material. The method was applied to the speciation of chromium in water samples.

Cloud point extraction for the determination of cadmium and lead employing sequential multi-element flame atomic absorption spectrometry

A cloud point extraction procedure for pre-concentration and determination of cadmium and lead in drinking water using sequential multi-element flame atomic absorption spectrometry is described. 4-(2-thiazolylazo)-orcinol (TAO) has been used as complexing agent and the micellar phase was obtained using the non-ionic surfactant octylphenoxypolyethoxyethanol (Triton X-114) and centrifugation. The conditions for reaction and extraction (surfactant concentration, reagent concentration, effect of incubation time, etc) were studied and the analytical characteristics of the method were determined. The method allows the determination of cadmium and lead with quantification limits of 0.30 µg L−1 and 2.6 µg L−1, respectively. A precision expressed as relative standard deviation (RSD, n = 10) of 2.3% and 2.6% has been obtained for cadmium concentrations of 10 µg L−1 and 30 µg L−1, respectively, and RSD of 1.3% and 1.7% for lead concentrations of 10 µg L−1 and 30 µg L−1, respectively. The accuracy was confirmed by analysis of a natural water certified reference material. The method has been applied for the determination of cadmium and lead in drinking water samples collected in the cities of Ilhéus and Itabuna, Brazil. Recovery tests have also been performed for some samples, and results varied from 96 to 105% for cadmium and 97 to 106% for lead. The cadmium and lead concentrations found in these samples were always lower than the permissible maximum levels stipulated by World Health Organization and the Brazilian Government.

Determination of mercury in ambient water samples by anodic stripping voltammetry on screen-printed gold electrodes

The applicability of commercial screen-printed gold electrodes (SPGEs) for the determination of Hg(II) in ambient water samples by square wave anodic stripping voltammetry has been demonstrated. Electrode conditioning procedures, chemical and instrumental variables have been optimized to develop a reliable method capable of measuring dissolved mercury in the low ng mL −1 range (detection limit 1.1 ng mL −1), useful for pollution monitoring or screening purposes. The proposed method was tested with the NIST 1641d Mercury in Water Standard Reference Material (recoveries 90.0–110%) and the NCS ZC 76303 Mercury in Water Certified Reference Material (recoveries 82.5–90.6%). Waste water samples from industrial origin and fortified rain water samples were assayed for mercury by the proposed method and by a reference ICP-MS method, with good agreement. Screen printing technology thus opens a useful way for the construction of reliable electrochemical sensors for decentralized or even field Hg(II) testing.

Solid-phase extraction of heavy metal ions on bucky tubes disc in natural water and herbal plant samples

A preconcentration-separation procedure has been established based on solid-phase extraction of Fe(III) and Pb(II) on bucky tubes (BTs) disc. Fe(III) and Pb(II) ions were quantitatively recovered at pH 6. The influences of the analytical parameters like sample volume, flow rates on the recoveries of analytes on BT disc were investigated. The effects of co-existing ions on the recoveries were also studied. The detection limits for iron and lead were found 1.6 and 4.9 μg L⁻¹, respectively. The validation of the presented method was checked by the analysis of TMDA-51.3 fortified water certified reference material. The presented procedure was successfully applied to the separation-preconcentration and determination of iron and lead content of some natural water and herbal plant samples from Kayseri, Turkey.

Catalytic Adsorptive Stripping Voltammetry of Cobalt in the Presence of Nitrite at an In Situ Plated Bismuth Film Electrode

AbstractFor the first time an in situ plated bismuth film electrode has been applied to catalytic adsorptive stripping voltammetry of cobalt in the presence of nitrite. At optimised conditions bismuth film was plated before each measurement for 30 s at −1.0 V from a sample solution with the added supporting electrolyte and Bi(III) in the form of its complex with tartrate. The calibration graph for Co(II) for an accumulation time of 120 s was linear from 5×10−10 to 1×10−8 mol L−1. The detection limit was 1.1×10−10 mol L−1. The proposed procedure was applied for Co(II) determination in certified water reference material.

Modern sampling and analytical methods for the determination of trace elements in marine particulate material using magnetic sector inductively coupled plasma–mass spectrometry

Trace elements often limit phytoplankton growth in the ocean, and the quantification of particulate forms is essential to fully understand their biogeochemical cycling. There is presently a lack of reliable measurements on the trace elemental content of marine particles, in part due to the inadequacies of the sampling and analytical methods employed. Here we report on the development of a series of state-of-the-art trace metal clean methods to collect and process oceanic particulate material in open-ocean and sea ice environments, including sampling, size-fractionated filtration, particle digestions and analysis by magnetic sector inductively coupled plasma–mass spectrometry (ICP–MS). Particular attention was paid to the analysis of certified reference materials (CRMs) and field blanks, which are typically the limiting factor for the accurate analysis of low concentrations of trace metals in marine particulate samples. Theoretical detection limits (3 s of the blank) were low for all 17 elements considered, and varied according to filter material and porosity (sub-μg L −1 for polycarbonate filters and 1–2 μg L −1 for quartz and polyester filters). Analytical accuracy was verified using fresh water CRMs, with excellent recoveries noted (93–103%). Digestion efficiencies for various acid combinations were assessed using sediment and plankton CRMs. Using nitric acid only, good recoveries (79–90%) were achieved for Mo, Cd, Ba, Pb, Mn, Fe, Co, Ni, Cu, Zn and Ga. The addition of HF was necessary for the quantitative recovery of the more refractory trace elements such as U, Al, V and Cr. Bioactive elements such as P can also be analysed and used as a biomass normaliser. Our developed sampling and analytical methods proved reliable when applied during two major field programs in both the open Southern Ocean and Antarctic sea ice environments during the International Polar Year in 2007. Trace elemental data are presented for particulate samples collected in both suspended and sinking marine material, and also within sea ice cores.

Adsorptive Stripping Voltammetry of Nickel at an In Situ Plated Bismuth Film Electrode

AbstractFor the first time an in situ plated bismuth film electrode is applied to adsorptive stripping voltammetry at mild alkaline conditions, to pH of 10. As an example of the application of such an electrode a procedure for trace Ni(II) determination by adsorptive stripping voltammetry is elaborated. For stabilization of Bi(III), tartrate as a strong complexing agent for Bi(III) was added to an ammonia buffer used as a supporting electrolyte. The appropriate concentration of Bi(III) was added to the electrolyte in the form of its complex with tartrate. The calibration graph for Ni(II) for an accumulation time of 120 s is linear from 5×10−9 to 5×10−8 mol L−1. The proposed procedure was applied for Ni(II) determination in certified water reference material.

Goldschmidt Abstracts 2010 – F

We report on two novel procedures for the determination of several trace elements in seawater, including elements characterized by very low abundance (sub-0.1 to 1 ng l-1) in the ocean, such as REEs, Hf, and Th. Our methods are based on the procedure developed recently by Bayon et al. [1], and applied successfully to a wide range of geological samples. It involves addition of a Tm spike and pre-concentration using co-precipitation, prior to analysis by inductively coupled plasma-sector field mass spectrometry (ICP-SFMS). The addition of a small amount of Tm to the sample produces a positive Tm anomaly in the resulting REE pattern, which allows calculation of precise trace element concentrations. Two different procedures were investigated during the course of this study: 1) coprecipitation onto iron hydroxides (after addition of a Fe-spike); and 2) magnesium co-precipitation (no spike required). The validity of the procedures was assessed through a series of co-precipitation experiments, using ultra-diluted solutions of a certified rock standard (BIR-1), and analyses of natural water certified reference materials (CRMs). Results obtained for NASS-5, CASS-4, and SLEW-3 are in agreement with published working values for REEs. A set of proposed values for these CRMs, with uncertainties typically better than 8% (RSD), is also proposed for Hf, Zr, and Th. The advantages and disavantages of using the iron vs magnesium co-precipitation procedure for determining trace element concentrations in seawater will be compared and discussed.

Preparation of monolithic chelating adsorbent inside a syringe filter tip for solid phase microextraction of trace elements in natural water prior to their determination by ICP-MS

A syringe-based sample pretreatment tool, named herein "tip-in chelating monolith", has been developed for simple and facile solid phase microextraction (SPME) of trace elements in natural waters. The tip-in chelating monolith was directly prepared within the confines of a commercially available syringe filter tip by a two-step process: (1) in situ polymerization of a monomer solution consisting of 22.5% glycidyl methacrylate (GMA), 7.5% ethylene glycol dimethacrylate (EDMA), 35% 1-propanol, 28% 1,4-butanediol, and 7% water and (2) its subsequent modification with 1molL(-1) of iminodiacetate solution (adjusted to pH 10) via ring-opening reaction of epoxide. The adsorption properties of the tip-in chelating monolith thus obtained were evaluated through an adsorption/desorption experiment, where the effects of sample solution pH and eluent on the SPME of trace metals and metalloids were systematically examined. Consequently, when sample solution pH was adjusted to 5.0 and 0.9mL of 2molL(-1) nitric acid was used as an eluent, good recoveries of more than 80% were obtained for 27 elements in a single-step extraction. The proposed SPME method was validated through the analysis of two river water certified reference materials (CRMs: JSAC 0301-1 and NMIJ 7201-a). After 50-fold preconcentration (from 50mL of the original river water sample to 1.0mL of final analysis solution), 22 trace elements including Ti, Fe, Co, Ni, Cu, Ga, Cd, Sn and REEs were quantitatively determined by inductively coupled plasma mass spectrometry (ICP-MS). The analytical detection limits were in the range from 0.000003microgL(-1) for Ho to 0.18microgL(-1) for Fe. Good agreement of the observed values with the certified or reference values indicates that the proposed SPME using the tip-in chelating monolith is practically applicable.

Ethanol/water solutions as certified reference materials for breath alcohol analyzer calibration

The Federal Institute for Materials Research and Testing (BAM), Germany, has issued a series of large volume ethanol in water certified reference materials (CRMs), primarily developed for the calibration of evidential breath alcohol analyzers in Germany. The certified parameter is the ethanol mass concentration at 20 °C. When used in a wet bath simulator, the solutions deliver gas samples that meet the requirements set by the Organization of Legal Metrology for calibration of breathalyzers. The materials were prepared gravimetrically by spiking of ethanol into water in single 5 L units. A complete uncertainty budget for the preparation process has been established. The purity of the commercial ethanol stock solution was identified to be the main source of uncertainty. For stability and homogeneity measurements and for the verification of the gravimetric mass concentration of the CRMs, a robust high-precision gas chromatography, with flame-ionization detection method for ethanol determination in aqueous samples was developed and validated. The good performance of this method has been demonstrated in several international comparisons organized by the Consultative Committee for Amount of Substance—Metrology in Chemistry at the International Bureau of Weights and Measures.

Preparation of a new Cd(II)-imprinted polymer and its application to determination of cadmium(II) via flow-injection-flame atomic absorption spectrometry

A new cadmium(II)-imprinted polymer based on cadmium(II) 2,2′-{ethane-1,2-diylbis[nitrilo( E)methylylidene]} diphenolate-4-vinylpyridine complex was obtained via suspension polymerization. The beads were used as a minicolumn packing for flow-injection-flame atomic absorption spectrometry (FI-FAAS) determination of cadmium(II) in water samples. Sorption effectiveness was optimal within pH range of 6.6–7.7. Nitric acid, 0.5% (v/v) was used as eluent. Fast cadmium(II) sorption by the proposed material enabled to apply sample flow rates up to 10 mL min −1 without loss in sorption effectiveness. Enrichment factor (EF), concentration efficiency (CE) and limit of detection (LOD, 3 σ) found for 120-s sorption time were 117, 39.1 min −1 and 0.11 μg L −1, respectively. Sorbent stability was proved for at least 100 preconcentration cycles (RSD = 2.9%). When compared to non-imprinted polymer the new Cd(II)-imprinted polymer exhibited improved selectivity towards cadmium(II) against other heavy metal ions, especially Cu(II) and Pb(II), as well as light metal ions. Accuracy of the method was tested for ground water and waste water certified reference materials and fortified water. The method was applied to Cd(II) determination in natural water samples.

Modification of carbon screen-printed electrodes by adsorption of chemically synthesized Bi nanoparticles for the voltammetric stripping detection of Zn(II), Cd(II) and Pb(II)

A simple procedure for the chemical synthesis of bismuth nanoparticles and subsequent adsorption on commercial screen-printed carbon electrodes offer reliable quantitation of trace zinc, cadmium and lead by anodic stripping square-wave voltammetry in nondeareated water samples. The influence of two hydrodynamic configurations (convective cell and flow cell) and the effect of various experimental variables upon the stripping signals at the bismuth-coated sensor are explored. The square-wave peak current signal is linear over the low ng mL −1 range (120 s deposition), with detections limits ranging from 0.9 to 4.9 ng mL −1 and good precision. Applicability to waste water certified reference material and drinking water samples is demonstrated. The attractive behaviour of the new disposable Bi nanoparticles modified carbon strip electrodes, coupled with the negligible toxicity of bismuth, hold great promise for decentralized heavy metal testing in environmental and industrial effluents waters.

Determination of cadmium by stripping voltammetry at a lead film electrode

A procedure for trace cadmium determination by stripping voltammetry at a lead film electrode is presented. Measurements consist of three steps: simultaneous in situ formation of lead film and a deposition of metallic cadmium at a lead film electrode, oxidation of cadmium for 1 s and in the last step registering the current corresponding to Cd(II) reduction. The calibration graph was linear from 2 × 10−9 to 1 × 10−6 mol L−1 for a deposition time of 300 s. A detection limit for cadmium following deposition time of 300 s was 6 × 10−10 mol L−1. The relative standard deviation at cadmium concentration 2 × 10−8 mol L−1 was 3.6%. The measurements were carried out from undeaerated solutions. The procedure proposed was validated by analysis of rain water certified reference material.

Determination and interference studies of bismuth by tungsten trap hydride generation atomic absorption spectrometry

The determination of bismuth requires sufficiently sensitive procedures for detection at the μg L −1 level or lower. W-coil was used for on-line trapping of volatile bismuth species using HGAAS (hydride generation atomic absorption spectrometry); atom trapping using a W-coil consists of three steps. Initially BiH 3 gas is formed by hydride generation procedure. The analyte species in vapor form are transported through the W-coil trap held at 289 °C where trapping takes place. Following the preconcentration step, the W-coil is heated to 1348 °C; analyte species are released and transported to flame-heated quartz atom cell where the atomic signal is formed. In our study, interferences have been investigated in detail during Bi determination by hydride generation, both with and without trap in the same HGAAS system. Interferent/analyte (mass/mass) ratio was kept at 1, 10 and 100. Experiments were designed for carrier solutions having 1.0 M HNO 3. Interferents such as Fe, Mn, Zn, Ni, Cu, As, Se, Cd, Pb, Au, Na, Mg, Ca, chloride, sulfate and phosphate were examined. The calibration plot for an 8.0 mL sampling volume was linear between 0.10 μg L −1 and 10.0 μg L −1 of Bi. The detection limit (3 s/m) was 25 ng L −1. The enhancement factor for the characteristic concentration ( C o) was found to be 21 when compared with the regular system without trap, by using peak height values. The validation of the procedure was performed by the analysis of the certified water reference material and the result was found to be in good agreement with the certified values at the 95% confidence level.

Evaluation of the use of multiple lines for determination of metals in water by inductively coupled plasma optical emission spectrometry with axial viewing

Inductively coupled plasma optical emission spectrometers (ICP OES) allow fast simultaneous measurements of several spectral lines for multiple elements. The combination of signal intensities of two or more emission lines for each element may bring such advantages as improvement of the precision, the minimization of systematic errors caused by spectral interferences and matrix effects. In this work, signal intensities for several spectral lines were combined for the determination of Al, Cd, Co, Cr, Mn, Pb, and Zn in water. Afterwards, parameters for evaluation of the calibration model were calculated to select the combination of emission lines leading to the best accuracy (lowest values of PRESS– Predicted error sum of squares and RMSEP– Root means square error of prediction). Limits of detection (LOD) obtained using multiple lines were 7.1, 0.5, 4.4, 0.042, 3.3, 28 and 6.7 µg L − 1 ( n = 10) for Al, Cd, Co, Cr, Mn, Pb and Zn, respectively, in the presence of concomitants. On the other hand, the LOD established for the most intense emission line were 16, 0.7, 8.4, 0.074, 23, 26 and 9.6 µg L − 1 ( n = 10) for these same elements in the presence of concomitants. The accuracy of the developed procedure was demonstrated using water certified reference material. The use of multiple lines improved the sensitivity making feasible the determination of these analytes according to the target values required for the current environmental legislation for water samples and it was also demonstrated that measurements in multiple lines can also be employed as a tool to verify the accuracy of an analytical procedure in ICP OES.

Quantification of major and trace elements in water samples by ICP-MS and collision cell to attenuate Ar and Cl-based polyatomic ions

Inductively coupled plasma mass spectrometry (ICP-MS) is the best fitted analytical technique for multi-element analysis of waters, because of its low detection limits. One limitation is the polyatomic interferences produced in the plasma and in the interface (e.g., 35Cl16O+ on 51V+, 40Ar16O+ on 56Fe+, 40Ar35Cl+ on 75As+ and 40Ar38Ar+ on 78Se+). These polyatomic ions can be significantly reduced by ion molecule interactions in a collision cell (CC). Several experiments done in a ICP-MS equipped with a CC pressurized by premixed H2 7% in He, under optimized gas flow rates, demonstrate the beneficial effect of KED to suppress Ar and Cl-based interferences. These results are opposed to reports where the role of KED was denied. Under such conditions the background equivalent concentration of 51V, 52Cr, 56Fe, 63Cu, 75As and 78Se were improved by two orders of magnitude, allowing the quantification of these elements at low ng L−1 level, without the need for mathematical corrections. Moreover, we present results obtained with a multi-mode method of analysis for twenty eight elements in two water certified reference materials (CRM). In this method isotopes free from polyatomic interferences are measured in standard mode and interfered ones using CC mode. The certified and reference values were used to evaluate the analytical trueness, which was better than 5%, with all z-scores within the recommended limit. Intermediate precision was mostly better than 6% and method detection limits are fit for hydrogeochemical studies and to monitor regulated toxic trace elements in waters.

Pre-concentration of trace metals on centrifugal microfluidic discs with direct determination by laser ablation inductively coupled plasma mass spectrometry

Solid Phase Extraction (SPE) is commonly used for pre-concentration and matrix removal in trace metal determinations. We present a novel centrifugal microfluidic device for field sampling and on-site pre-concentration of water samples. Metal-8-hydroxyquinoline complexes are adsorbed onto miniature C18-bonded silica gel columns on centrifugal microfluidic discs. Laser Ablation (LA) is used to directly vaporize the analytes from the column, instead of eluting the pre-concentrated analytes for introduction in an Inductively Coupled Plasma Mass Spectrometer (ICP-MS) by conventional solution nebulization. Absolute detection limits ranging between 0.1 and 12 ng were obtained for Ni, Cu, V, Pb and Co in drinking water Certified Reference Materials (CRMs). These centrifugal devices require only 1–600 µL samples and necessitate no more than a simple motor to actuate fluid flow. The discs can be used to perform multiple extractions simultaneously as well as allowing the easy storage of samples before transport to the laboratory for LA-ICP-MS analysis.

Double tungsten coil atomic emission spectrometry: signal enhancement and a new gas phase temperature probe

A new double atomizer arrangement for tungsten coil atomic emission spectrometry is described. Two small constant current power supplies, a Czerny–Turner spectrograph, and a charge coupled device (CCD) detector are used to determine refractory elements in water samples. The analytical figures of merit for Ba, Sr, Ti, and V are reported and compared with the single coil arrangement. The use of two atomizers provides more energy for the atomization and excitation of the analytes and consequently improves sensitivity. Addition of a second coil improves limits of detection for refractory elements by a factor of 40 (V) and 5 (Ti). Using 25 µl sample volumes, the limit of detection for V is 10 µg l−1 at the 437.9 nm emission line, and 400 µg l−1 for the 399.9 nm Ti emission line. Vanadium is determined in a polluted water certified reference material, and the results agree with the certified value (250 mg l−1) at the 95% confidence level. For Ba and Sr, which emit strongly with a single coil, the double coil detection limits are improved by less than a factor of two: 0.007 µg l−1Ba and 0.4 µg l−1Sr. Emission signals for Ag, Cu and Sn are observed for the fist time with a tungsten coil atomic emission spectrometry (WCAES) system. A new method to determine the gas phase temperature by atomic emission spectrometry is also presented. Emission intensities for Dy (418.7 and 421.1 nm) and Eu (462.7 and 466.2 nm) are used to calculate Boltzmann temperatures for both the single and double coil arrangements. Temperature values calculated by this method agree with the traditional optical two-line absorption method using Sn (284.0 and 286.3 nm).

Arsenic speciation in natural water samples by coprecipitation-hydride generation atomic absorption spectrometry combination

A speciation procedure for As(III) and As(V) ions in environmental samples has been presented. As(V) was quantitatively recovered on aluminum hydroxide precipitate. After oxidation of As(III) by using dilute KMnO 4, the developed coprecipitation was applied to determination of total arsenic. Arsenic(III) was calculated as the difference between the total arsenic content and As(V) content. The determination of arsenic levels was performed by hydride generation atomic absorption spectrometry (HG-AAS). The analytical conditions for the quantitative recoveries of As(V) including pH, amount of aluminum as carrier element and sample volume, etc. on the presented coprecipitation system were investigated. The effects of some alkaline, earth alkaline, metal ions and also some anions were also examined. Preconcentration factor was calculated as 25. The detection limits (LOD) based on three times sigma of the blank ( N: 21) for As(V) was 0.012 μg L −1. The satisfactory results for the analysis of arsenic in NIST SRM 2711 Montana soil and LGC 6010 Hard drinking water certified reference materials for the validation of the method was obtained. The presented procedure was successfully applied to real samples including natural waters for arsenic speciation.