Preconcentration Of As Research Articles

Determination of trace metals in vegetables and water samples using dispersive ultrasound-assisted cloud point-dispersive µ-solid phase extraction coupled with inductively coupled plasma optical emission spectrometry

A simple method combining ultrasound assisted cloud point extraction (UA-CPE) and dispersive μ-solid phase extraction (D-μ-SPE) was developed for preconcentration of As, Cd, Cr, Co, Sb, Pb and Tl to inductively coupled plasma optical emission spectrometric (ICP-OES). At optimum conditions, the linearity, limits of detection and limits of quantification were 0.20–1000 µg L−1, 90–150 ng L−1 and 200–500 ng L−1, respectively. The intraday (n = 20) and intraday (n = 5) precisions reported as the relative standard deviation ranged from 1.5 to 3.5% and 1.9–4.5%. The trueness of the method was investigated using CRM BCR679, NIST SRM 1573a, and SRM 1640a, as well as spiked recovery experiments. Satisfactory recoveries and relative errors ranging from 97 to 99.3% and −4.0 to 2.4% were obtained. The proposed UA-CPE-D-µ-SPE/ICP-OES method was successfully applied for various real samples such as groundwater, bottled mineral water, river water and borehole water and food samples.

On-site Determination of Arsenic, Selenium, and Chromium(VI) in Drinking Water Using a Solid-phase Extraction Disk/Handheld X-ray Fluorescence Spectrometer.

A rapid, simple technique combining disk solid-phase extraction and handheld X-ray fluorescence (XRF) spectrometry was developed for the on-site determination of As, Se, and Cr(VI) in drinking water. For the preconcentration of As, Se, and Cr(VI), a 50-mL aqueous sample was adjusted to pH 4, followed by passage through a Ti-loaded anion-exchange disk (Ti-AED). Both sides of the Ti-AED were coated with an adhesive cellophane tape prior to drying using a cordless hair iron, followed by a handheld XRF measurement. The Ti-AED adsorbed As(III), As(V), Se(IV), Se(VI), and Cr(VI) in water without requiring oxidation and reduction. The detection limits of As, Se, and Cr(VI) were all 1.0 μg L-1. Good recoveries were obtained by measuring certified reference materials, and spiking natural mineral water with As, Se, and Cr(VI). As the proposed method does not require a power supply or toxic reagents in any analytical step, it is suitable for the on-site determination of toxic elements in drinking water.

Anodic stripping voltammetric analysis of trace arsenic(III) enhanced by mild hydrogen-evolution at a bimetallic Au–Pt nanoparticle modified glassy carbon electrode

Abstract A glassy carbon electrode (GCE) modified with electrodeposited bimetallic Au–Pt nanoparticles (Au–PtNPs) was applied to sensitively detect As(III) by linear sweep anodic stripping voltammetry (LSASV). In 0.5 M aqueous H2SO4, atomic hydrogen and molecular hydrogen were easily electrogenerated at the Pt sites on Au–PtNPs/GCE, which can chemically reduce As(III) to As(0) and enhance the cathodic preconcentration of As(0) at both the Pt sites and the neighboring Au sites. Since the As(0)–Au affinity is weaker than the As(0)–Pt affinity, the preconcentrated As(0) can be rapidly oxidized on/near the surface Au sites of Au–PtNPs/GCE, yielding sharper and higher LSASV current peaks. Under optimum conditions (700 s preconcentration at − 0.1 V, 5 V s− 1), the LSASV peak current for the As(0)–As(III) oxidation responded linearly to As(III) concentration from 0.005 to 3.0 μM with a limit of detection (LOD) of 3.7 nM (0.28 ppb) (S/N = 3), while that for the As(III)–As(V) oxidation was linear with As(III) concentration from 0.01 to 3.0 μM with a LOD of 6.0 nM (0.45 ppb) (S/N = 3). This method was applied for analysis of As(III) in real water samples.

Enhanced Cathodic Preconcentration of As(0) at Au and Pt Electrodes for Anodic Stripping Voltammetry Analysis of As(III) and As(V)

We report that the cathodic preconcentration of electron-insulating As(0) on Au and Pt electrodes can be enhanced by chemical reduction of As(III) and As(V) by electrogenerated H2, as studied by cyclic voltammetry. This finding is used for sensitive anodic stripping voltammetry (ASV) analysis of As(III) and/or As(V) at the Au electrode. About three As(0) monolayers were cathodically preconcentrated on the Pt electrode at −0.3 V (vs SCE) in 0.5 M aqueous H2SO4, as a result of both the chemical reduction of the solution-state As(III) near the electrode surface by the electrogenerated H2 and the direct electroreduction of As(III) on the highly catalytic surface Pt sites. Only one As(0) monolayer was electrodeposited at −0.2 V (vs SCE) on the Au electrode in 0.5 M aqueous H2SO4, but about two As(0) monolayers were deposited on the Au electrode at a more negative potential at which the mild evolution of H2 occurred. The electrogenerated H2 could also chemically reduce As(V), though the direct electroreduction ...

Preconcentration of toxic elements in artificial saliva extract of different smokeless tobacco products by dual-cloud point extraction

Smokeless tobacco (SLT) has been associated with oral cancer. In present study, the total and artificial saliva extracted toxic elements (TEs), arsenic (As), cadmium (Cd), nickel (Ni) and lead (Pb) were estimated in SLT products (gutkha, green and brown snuff). Dual-cloud point extraction has been used for the preconcentration of As, Cd, Ni and Pb in artificial saliva extract, using complexing reagent, ammonium pyrrolidinedithiocarbamate. The dual-cloud point extraction procedure was based on forming complexes of elemental ions with complexing reagent and subsequent entrapping of the complexes in nonionic surfactant. Then the surfactant rich phase containing the complexes was treated with nitric acid, and detected ions were back extracted again into aqueous phase at the second cloud point extraction stage, and finally determined by electrothermal atomic absorption spectrometry. The validity of methodology was tested by simultaneously analyzing certified reference material and spike recovery test. The experimental enhancement factors of As, Cd, Ni and Pb were found to be 52, 58, 48 and 44, respectively. The concentration of As, Cd, Ni and Pb in artificial saliva extracts corresponds to 18–24, 45–75, 30–55, and 20–30%, respectively, of the total contents of TE in different types of SLT products (gutkha, brown and green snuff). It was estimated that 10g intake of SLT products (gutkha, brown and green snuff) could contribute 2.2–13, 21–69, 3.4–48 and 10–75% of the provisional maximum tolerable daily intake of As, Cd, Ni and Pb, respectively for adults ~60kg.

Simultaneous determination of inorganic arsenic, antimony, selenium and tellurium by ICP-MS in environmental waters using SPE preconcentration on modified silica

This paper deals with a simplified multi-element profiling of inorganic arsenic, antimony, selenium and tellurium in the form of 75As, 82Se, 121Sb and 125Te by ICP-MS for amounts less than 10 µg L−1. Internal standards such as 72Ge and 209Bi were successfully used for the suppression of both influence of macro elements Na+, K+, Ca2+, Mg2+ or Al3+, and interference of limited concentrations of heavy metal ions. Modified silica sorbents Separon™ SGX C18, C8, CN, NH2, RPS and Phenyl were tested for the preconcentration of As, Sb, Se and Te (0.25–5 µg L−1) in the form of ion associates with cationic surfactants from 50–250 mL sample volume. 1-etoxycarbonyl-pentadecyltrimethylammonium bromide (Septonex®, 0.005 mol L−1) was suitable for this purpose in the presence of 4-(2-pyridylazo) resorcinol, 2-pyrrolidinecarbodithioate and 8-hydroxyquinoline-5-sulphonic acid. The quantitative retention occurred at pH 7 ± 0.2 and the mixture of acetone with ethanol in ratio 1 : 1 in the presence of 0.1 mol L−1 HCl was used for the quantitative elution. Organic solvents and the excess of acid were removed by evaporation prior to the determination by ICP-MS. The determination of the above trace metalloids in various kinds of water with enrichment factor till 50 times on silica Separon™ SGX C18 and the above reagents were compared with the standard addition method.

Stibine and bismuthine trapping in quartz tube atomizers for atomic absorption spectrometry. Part 2: a radiotracer study

A trap-and-atomizer device based on a multiatomizer has been described recently. This compact and universal device enables the preconcentration of As, Sb, Bi and Se hydrides on-line prior to their AAS detection. Up to date only optimization of the method and its analytical applications have been described. In this work, 125Sb and 205,206Bi radioactive indicators were used to quantify the efficiency of the individual steps of preconcentration procedure as well as to investigate the spatial distribution of the analytes. The investigation proved the complete trapping and volatilization of Sb and Bi. The trapping efficiency of Sb was better than 93% (RSD < 6%) between 200 and 800 °C. The trapping efficiency of Bi was above 96% (RSD < 5%) between 100 and 800 °C whereas it fell to 83% at 900 °C. The area of the trapping spot increased with increasing trapping temperature. The trap is capable of trapping up to 400 ng of Bi and 2 µg of Sb, respectively. Typically, 1–10 ng of analyte is preconcentrated in ultratrace analysis. No change in either trapping efficiency, or in the spatial distribution of analyte was observed with increasing trapped analyte mass. Also the volatilization step proved to be efficient – only (1.8 ± 1.6)% and (2.9 ± 0.9)% of original Bi and Sb activity, respectively, was found in the traps after the volatilization at 900 °C.

Resolution of an intense sweetener mixture by use of a flow injection sensor with on-line solid-phase extraction

An integrated solid-phase spectrophotometry-FIA method is proposed for simultaneous determination of the mixture of saccharin (1,2-benzisothiazol-3(2H)-one-1,1-dioxide; E-954) (SA) and aspartame (N-L-alpha-aspartyl-L-phenylalanine-1-methyl ester; E-951) (AS). The procedure is based on on-line preconcentration of AS on a C18 silica gel minicolumn and separation from SA, followed by measurement, at lambda = 210 nm, of the absorbance of SA which is transiently retained on the adsorbent Sephadex G-25 placed in the flow-through cell of a monochannel FIA setup using pH 3.0 orthophosphoric acid-dihydrogen phosphate buffer, 3.75x10(-3) mol L(-1), as carrier. Subsequent desorption of AS with methanol enables its determination at lambda = 205 nm. With a sampling frequency of 10 h(-1), the applicable concentration range, the detection limit, and the relative standard deviation were from 1.0 to 200.0 microg mL(-1), 0.30 microg mL(-1), and 1.0% (80 microg mL(-1), n = 10), respectively, for SA and from 10.0 to 200.0 microg mL(-1), 1.4 microg mL(-1), and 1.6% (100 microg mL(-1), n = 10) for AS. The method was used to determine the amounts of aspartame and saccharin in sweets and drinks. Recovery was always between 99 and 101%. The method enabled satisfactory determination of blends of SA and AS in low-calorie and dietary products and the results were compared with those from an HPLC reference method.

X-ray fluorescence determination of As, Bi, Co, Cu, Fe, Ni, Pb, Se, V and Zn in natural water and soil extracts after preconcentration of their pyrrolidinedithiocarbamates on cellulose filters

A simple method for the elements preconcentration on thin-layer paraffin-treated cellulose filters was proposed. It was found that pyrrolydinedithiocarbamates of As(III), Bi, Cd, Co, Cu, Fe(III), Ni, Pb, Se(IV), V(V) and Zn obtained after mixing of sample (3–5 ml min −1) and reagent (0.7–1.0 ml min −1) streams were quantitatively recovered from 100 ml sample. The sample acidity was adjusted to pH 4.8–5.2 for preconcentration of Cd, Co, Cu, Fe(III), Ni, Pb, V(V) and Zn, and to 2 M HCl for preconcentration of As, Bi and Se. The optimum reagent concentration was found to be 0.1%. The elements were determined on the filters by X-ray fluorescence spectrometry. The detection limits achieved were 0.1–4.0 μg of element on the filter. Relative standard deviation (R.S.D.) was not higher than 0.08 while determining 5–50 μg of elements on filter. Accuracy and precision of the technique proposed were evaluated by the analysis of spiked natural samples.