Inorganic arsenic speciation analysis of water samples by trapping arsine on tungsten coil for atomic fluorescence spectrometric determination

Arsine trapping on resistively heated tungsten coil was investigated and an analytical method for ultratrace arsenic determination in environmental samples was established. Several chemical modifiers, including Re, Pt, Mo, Ta and Rh, were explored as permanent chemical modifiers for tungsten coil on-line trapping and Rh gave the best performance. Arsine was on-line trapped on Rh-coated tungsten coil at 640 °C, then released at 1930 °C and subsequently delivered to an atomic fluorescence spectrometer (AFS) by a mixture of Ar and H₂ for measurement. In the medium of 2% (v/v) HCl and 3% (m/v) KBH₄, arsine can be selectively generated from As(III). Total inorganic arsenic was determined after pre-reduction of As(V) to As(III) in 0.5% (m/v) thiourea-0.5% (m/v) ascorbic acid solution. The concentration of As(V) was calculated by difference between the total inorganic arsenic and As(III), and inorganic arsenic speciation was thus achieved. With 8 min on-line trapping, the limit of detection was 10 ng L⁻¹ for As(III) and 9 ng L⁻¹ for total As; and the precision was found to be <5% R.S.D. (n = 7) for 0.2 ng mL⁻¹ As. The proposed method was successfully applied in total arsenic determination of several standard reference materials and inorganic arsenic speciation analysis of nature water samples.     

Determination of arsenic(III) and total inorganic arsenic in water samples using an on-line sequential insertion system and hydride generation atomic absorption spectrometry

A simple and robust on-line sequential insertion system coupled with hydride generation atomic absorption spectrometry (HG-AAS) was developed, for selective As(III) and total inorganic arsenic determination without pre-reduction step. The proposed manifold, which is employing an integrated reaction chamber/gas-liquid separator (RC-GLS), is characterized by the ability of the successful managing of variable sample volumes (up to 25 ml), in order to achieve high sensitivity. Arsine is able to be selectively generated either from inorganic As(III) or from total arsenic, using different concentrations of HCl and NaBH₄ solutions. For 8 ml sample volume consumption, the sampling frequency is 40 h⁻¹. The detection limit is c_L = 0.1 and 0.06 μg l⁻¹ for As(III) and total arsenic, respectively. The precision (relative standard deviation) at 2.0 μg l⁻¹ (n = 10) level is s_r = 2.9 and 3.1% for As(III) and total arsenic, respectively. The performance of the proposed method was evaluated by analyzing the certified reference material NIST CRM 1643d and spiked water samples with various concentration ratios of As(III) to As(V). The method was applied for arsenic speciation in natural waters samples.     

Characterization of As (V), As (III) by selective reduction/adsorption on palladium nanoparticles in environmental water samples

Hydrazine (HZ) and sodium borohydride (BH) are commonly used reagents for the production of palladium nanoparticles (PdNP) in aqueous solution and also for the reduction of arsenic from higher oxidation state to lower oxidation state. A methodology based on the quantitative adsorption of reduced arsenic species on PdNP generated in situ by BH and HZ is described to characterize As (V) and As (III) in environmental water samples. It was observed that PdNP obtained by BH gave quantitative recovery of As (V) and (III) and the PdNP obtained by HZ could account for As (III). The reduced palladium particles are collected and dissolved in minimum amount of nitric acid. The quantification of arsenic was carried out using GFAAS. Optimization of the experimental conditions and instrumental parameters were investigated in detail. The proposed procedure was validated by applying it for the determination of the content of total As in Certified Reference Material BND 301-02 (NPL, India). The detection limit of arsenic in environmental water samples was 0.029 μg L⁻¹ with an enrichment factor of 50. The relative standard deviation (R.S.D.) for 10 replicate measurements of 5 μg mL⁻¹ was 4.2%. The proposed method was successfully applied for the determination of sub ppm to ppm levels of arsenic (V), (III) in environmental water samples.     

原子荧光光谱法测定固体废弃物——氧化皮中的砷

建立了固体废弃物——氧化皮中砷的测定方法。氧化皮粉末样品经盐酸溶解,在溶液中添加硫脲和抗坏血酸预还原砷,以盐酸(2+98)为载流,硼氢化钠(10g/L)和氢氧化钾(5g/L)混合溶液为还原剂,砷与硼氢化钠、盐酸反应生成砷化氢,砷化氢利用氩气导入石英炉原子化器中原子化,以空心阴极灯为激发光源,测量砷产生的荧光强度。测试氧化皮中砷含量的相对标准偏差为不大于4.8%,检出限为0.12μg/L,回收率为97%～103%,结果准确度较好。方法具有试剂消耗少、快速、检出限低的优点。     

进口铜精矿中砷和汞的快速测定

试料经盐酸、硝酸溶解,添加硫脲和抗坏血酸预还原砷,以2%盐酸为载流,1%硼氢化钠和0.5%氢氧化钾溶液为还原剂,在氢化物发生器中,砷与硼氢化钠、盐酸反应生成砷化氢,汞则成为汞蒸气,用氩气导入石英炉原子化器中原子化,以空心阴极灯为激发光源,于原子荧光光谱仪上测量砷和汞的荧光强度。砷的标准偏差为0.0096%;汞的标准偏差为0.00015%,结果准确度较好。方法前处理快速,试剂消耗少,过程简单。     

Determination of arsenic in some water bodies, untreated ore and tailing samples at Konongo in the Ashanti region of Ghana and its surrounding towns and villages by instrumental neutron activation analysis

Instrumental neutron activation analysis (INAA) has been employed forthe determination of arsenic in samples of water bodies at Konongo an oldmining town in the Ashanti region of Ghana and its surrounding towns and villages.In some of the water samples, significant levels of arsenic were recordedbut others gave no indication of the metal. The precision and accuracy ofthe method was evaluated using real ore samples and standard reference materials.The accuracy of the method was found to be within ±6%. The averagearsenic levels found in the water samples ranged between 0.04 and 12.2 mg/l.Untreated ore and tailing samples were also analysed for arsenic. The surfaceore gave an arsenic concentration of 4,628±97 ppm while that of thebottom ore was 2,978±69 ppm. For the tailing samples, the range ofarsenic level was 1,776 to 1,787 ppm. It was observed that the upper sink(i.e., the surface portion of the ore) showed higher levels of arsenic thanthe lower one (i.e., bottom portion of the ore).     

The determination of arsenic in rocks,sediments and minerals by arsine generation and atomic absorption spectrometry

An arsine generation-atomic absorption method for the rapid and precise determination of 0.04–4000 p.p.m. arsenic in geological materials is described. The siliceous sample is decomposed with perchloric, nitric and hydrofluoric acids and potassium permanganate solution, and the residue is dissolved in dilute hydrochloric acid. Arsine is generated with potassium iodide, tin(II) chloride and zinc powder, and introduced to an argon—hydrogen flame. The method is applied to various standard rocks, NBS mineral standards, and geochemical exploration samples. The relative standard deviation is 4–14 %.     

Colorimetric analysis of water and sand samples performed on a mobile phone

Analysis of water and sand samples was done by reflectance measurements using a mobile phone. The phone's screen served as light source and front view camera as detector. Reflected intensities for white, red, green and blue colors were used to do principal component analysis for classification of several compounds and their concentrations in water. Analyses of colored solutions and colorimetric reactions based on widely available chemicals were performed. Classification of iron(III), chromium(VI) and sodium salt of humic acid was observed using reflected intensities from blue and green light for concentrations 2-10 mg/l. Addition of complex forming sodium salt of ethylenediaminetetraacidic acid enabled the discrimination of Cu(II) ions in the 2-10 mg/l concentration range based on reflection of red light. An alternate method using test strips for copper solutions with the phone as reader also demonstrated a detection limit of 2 mg/l. Analysis of As(III) from 25 to 400 μg/l based on reflection of red light was performed utilizing the bleaching reaction of tincture of iodine containing starch. Enhanced sensitivity to low concentrations of arsenic was obtained by including reflected intensities from white light in the analysis. Model colored sand samples representing discoloration caused by the presence of arsenic in groundwater were analyzed as a complementary method for arsenic detection.     

Arsenic contamination in groundwater: some analytical considerations

For countries such as Bangladesh with a significant groundwater arsenic problem, there is an urgent need for the arsenic-contaminated wells to be identified as soon as possible and for appropriate action to be taken. This will involve the testing of a large number of wells, potentially up to 11 million in Bangladesh alone. Field-test kits offer the only practical way forward in the timescale required. The classic field method for detecting arsenic (the 'Gutzeit' method) is based on the reaction of arsine gas with mercuric bromide and remains the best practical approach. It can in principle achieve a detection limit of about 10 mug l(-1) by visual comparison of the coloured stain against a colour calibration chart. A more objective result can be achieved when the colour is measured by an electronic instrument. Attention has to be paid to interferences mainly from hydrogen sulfide. Due to analytical errors, both from the field-test kits and from laboratory analysis, some misclassification of wells is inevitable, even under ideal conditions. The extent of misclassification depends on the magnitude of the errors of analysis and the frequency distribution of arsenic observed, but is in principle predictable before an extensive survey is undertaken. For a country with an arsenic distribution similar to that of Bangladesh, providing care is taken to avoid sources of bias during testing, modern field-test kits should be able to reduce this misclassification to under 5% overall.     

Determination of arsenic by hydride generation with a long absorption cell for atomic absorption spectrometry

A method is described for the determination of arsenic involving hydride generation and atomic absorption spectrometry with an improved long graphite-tube furnace capable of considerably higher temperatures than the conventional quartz-tube heaters. Arsine is generated with sodium tetrahydroborate, held in a nitrogen-cooled trap and then swept with helium into an alumina tube (19 cm long) placed within the graphite furnace. The optimum conditions for determination of arsenic are given. The detection limit is 0.2 ng ml^?1 with RSD of 2–3%. Results for various NBS Standard Reference Materials agreed well with expected values and were as follows: orchard leaves, 10 ± 1 μg g^?1; tomato leaves, 0.28 ± 0.03 μg g^?1; bovine liver, 0.046 ± 0.005 μg g^?1.     

Atomic absorption spectroscopic determination of arsenic in antimony compounds using solvent extraction and arsine generation

Summary An arsine generation-atomic absorption spectroscopic method for the determination of 0.04–4000 p. p. m. of arsenic in antimony compounds is described. The interference from antimony and other elements is eliminated by solvent extraction with benzene. The sample is dissolved in concentrated hydrochloric acid and reduced with titanium(III) chloride. Arsenic(III) is extracted into benzene from 10–12N hydrochloric acid at which concentration no antimony (III) is extracted; arsenic(III) is then back-extracted into water. Arsine is generated with potassium iodide, tin(II) chloride and zinc powder from 2.4N hydrochloric acid solution, and introduced to a nitrogen-hydrogen flame. The method has been tested with various antimony samples.

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Zusammenfassung Für die Bestimmung von 0,04–4000 ppm Arsen in Antimonverbindungen wurde ein Verfahren zur Arsinbildung und Atomarabsorption entwickelt. Die Störung durch Antimon und andere Elemente wurde durch Extraktion mit Benzol beseitigt. Die Probe wird in konz. Salzsäure gelöst und mit Titan(III)chlorid reduziert. Arsen(III) wird aus 10–12N Salzsäure mit Benzol extrahiert, ohne daß Antimon(III) mitextrahiert wird; As(III) wird dann in Wasser rückextrahiert. Mit Kaliumjodid, Zinn(II)chlorid und Zinkpulver wird aus 2,4N salzsaurer Lösung Arsin entwickelt und in eine Stickstoff-Wasserstoff-Flamme geleitet. Das Verfahren wurde mit verschiedenen Antimonproben getestet.

     

A Sensitive Colorimetric Method for the Determination of Arsenic in Environmental and Biological Samples

Results of a thorough study and application of leucocrystal violet for the determination of arsenic in parts per million (ppm) levels in environmental and biological samples is described here. The proposed method is based on the reaction of arsenic with potassium iodate to liberate iodine. The liberated iodine selectively oxidises leucocrystal violet to form crystal violet dye in the presence of sodium hydroxide. The dye formed shows maximum absorbance at 592 nm. The detection limit of arsenic is 0.002 μgmL^?1 and the method obeys Beer's law over the concentration range of 0.1 μg - 1.0 μg of per 25 mL of final solution (0.004–0.04 ppm). The molar absorptivity was found to be 1.49 × 10⁶ L mol^?1 cm^?1. The proposed method was successfully applied for the determination of arsenic in various environmental and biological samples. The results are in good agreement with the standard reported method.     

Determination of arsenic by inductively-coupled plasma atomic emission spectrometry enhanced by hydride generation from organized media

A method is described for the determination of arsenic, which combines a continuous flow hydride generation technique with an inductively coupled plasma atomic emission detection system. Some atomic absorption preliminary studies are described as well. Arsine is generated with NaBH(4) from a didodecyldimethylammonium bromide (DDBA) vesicular medium. The analytical performance of this vesicles-enhanced method is superior to the generation of the hydride from aqueous media: the detection limit (0.6 ppb) is improved by a factor of 2 and greater tolerance to interferences is observed for arsine generation from DDBA vesicles. Precision of As determinations is also improved. The proposed method has been validated for low As levels determinations in two Certified Reference Materials (CRM) sediments with satisfactory results. The potential of organized media to improve hydride generation is addressed.     

Bestimmung von geringen Mengen Arsen in Kupfer und Kupfersalzen

Zusammenfassung Es wird ein für routinemäßige Analysen geeignetes Verfahren zur Bestimmung kleiner Arsenmengen in Kupfer, Kupfer(I)- und Kupfer(II)-verbindungen beschrieben, mit dessen Hilfe Arsengehalte bis hinab zu 0,4 ppm, unter geeigneten Bedingungen bis zu 0,1 ppm bestimmt werden können. Die Methode beruht auf der Anreicherung des Arsens durch Mitfällung als Arsenat mit Magnesiumammoniumphosphat und anschließender Destillation als Arsenwasserstoff. Die Bestimmung erfolgt spektralphotometrisch mit Silberdiäthyldithiocarbamidat.

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Summary A method for the determination of small amounts of arsenic in copper, cupric and cuprous salts is described. Normaly values down to 0.4 ppm arsenic are detectable by this procedure, or even 0.1 ppm under special conditions. The method is especially well suitable for routine tests. The procedure is based on concentrating the arsenic by co-precipitation as arsenate with magnesium ammonium phosphate followed by a distillation of the arsenic via hydrogen arsenide and on the photometrical determination with silver diethyldithiocarbamate.

     

Spectrophotometric determination of molybdenum(VI)

Molybdenum(IV) gives a red colour with ammonium thiocyanate in 5-8M hydrochloric acid medium, the Sandell sensitivity index being 0.018 ppm Mo(VI)/cm(2). Molybdenum(VI) in 4-7M hydrochloric acid medium forms a red complex with ethyl xanthate and ammonium thiocyanate and this can be extracted into acetophenone. Beer's law is obeyed over the range of 1.2-13.8 ppm, and the Sandell indices at 370 and 470 nm are 0.0016 and 0.0068 ppm/cm(2) respectively. The colour is stable for 40 hr. Most cations do not interfere.     

Sensitive and ultra-fast determination of arsenic(III) by gas-diffusion flow injection analysis with chemiluminescence detection

A novel chemiluminescence gas-diffusion flow injection system for the determination of arsenic(III) in aqueous samples is described. The analytical procedure involves injection of arsenic(III) samples and standards into a 0.3 mol L⁻¹ hydrochloric acid carrier stream which is merged with a reagent stream containing 0.2% (w/v) sodium borohydride and 0.015 mol L⁻¹ sodium hydroxide. Arsine, generated in the combined carrier/reagent donor stream, diffuses across the hydrophobic Teflon membrane of the gas-diffusion cell into an argon acceptor stream and then reacts with ozone in the flow-through chemiluminescence measuring cell of the flow system. Under optimal conditions, the method is characterized by a wide linear calibration range from 0.6 μg L⁻¹ to 25 mg L⁻¹, a detection limit of 0.6 μg L⁻¹ and a sample throughput of 300 samples per hour at 25 mg L⁻¹ and 450 samples per hour at 25 μg L⁻¹.     

稀土—4—（2—吡啶偶氮）间苯二酚螯合物的高效液相色谱分离和测定

本文讨论了反相离子对液相色谱法分离和检测稀土-4-(2-吡啶偶氮)间苯二酚螯合物的各种条件,在12 min内完成了9种稀土螫合物的分离,校正曲线的线性范围是(ppm):La(0.01～3.20),Ce(0.03～2.8),Pr(0.06～3.5),Nd(0.05～3.8),Sm(0.01～3.0),Eu(0.05～3.4),Tb(0.02～3.0),Ho(0.01～3.4),Er(0.06～4.0).变异系数小于1.2％.     

Tandem on-line continuous separation and determination of arsenic by inductively coupled plasma atomic emission spectrometry

The principle of tandem on-line continuous separation techniques as an alternative means of introducing samples into plasmas was applied to the development of a sensitive, selective and convenient method for the determination of arsenic by inductively coupled plasma atomic emission spectrometry (ICP-AES). Arsenic is continuously extracted as AsI₃ into xylene from the sample dissolved in 0.1 M potassium iodide solution in 7.2 M hydrochloric acid. The xylene phase (containing the analyte) is continuously mixed on-line with NaBH₄ in dimethylformamide and acetic acid solutions. Arsine is thus continuously generated directly from the organic phase and is separated in a gas—liquid separation device which prevents most of the xylene phase vapour from reaching the ICP. The system was optimized for the continuous extraction of AsI₃, the direct generation of arsine from xylene and the final ICP determination of arsenic. Finally, the tandem on-line continuous separation ICP detection system was applied to the determination of arsenic in real samples (white metal, cast iron, cupro-nickel and orchard leaves standard materials). Very good agreement between the experimental results and the certified values was obtained.     

4－（2－氨基噻唑）－间苯二酚为柱前衍化剂液相色谱／电化学检测Fe、Co、Ni

４－（２－氨基噻唑）－间苯二酚为柱前衍化剂液相色谱／电化学检测Ｆｅ、Ｃｏ、Ｎｉ格日勒，李惠梅，李南强，汪尔康（中国科学院长春应用化学研究所电分析化学开放实验室，北京大学化学系，长春，１３００２２）关键词液相色谱，Ｆｅ，Ｃｏ，Ｎｉ，４－（２－氨基噻唑）...     

Determination of arsenic in geological materials by x-ray fluorescence spectrometry after solvent extraction and deposition on a filter

Rock, soil, or sediment samples are decomposed with a mixture of nitric and sulphuric adds. After reduction from arsenic(V) with ammonium thiosulphate, arsenic(III) is extracted as the chlorocomplex into benzene from a sulphuric-hydrochloric acid medium. The benzene solution is transferred onto a filter-paper disc impregnated with a solution of sodium bicarbonate and potassium sodium tartrate, and the benzene allowed to evaporate. The arsenic present is determined by X-ray fluorescence. In a 0.5-g sample, 1–1000 ppm of arsenic can be determined. The close proximity of the lead L peak (2θ 48.73°), to the arsenic K peak (2θ 48.83°) does not cause any interference, because lead is not extracted under the experimental conditions. Arsenic values obtained are in agreement with those reported for various reference samples.