Injection-hydride Generation-atomic Absorption Spectrometry Research Articles

Selective determination of As(III) and total inorganic arsenic in rice sample using in-situ μ-sorbent formation solid phase extraction and FI-HG AAS

A noteworthy solid phase extraction procedure was developed for speciation of inorganic arsenic in rice samples using flow injection-hydride generation atomic absorption spectrometry (FI-HG AAS). The procedure is based on the in-situ formation of quaternary ammonium salt as μ-sorbent. A small amount of tetra-n-butylammonium bromide (TBAB) was used as phase-transfer agent and injected into the sample solution. After shaking, a small volume of perchlorate was added as ion-pairing agent. Due the interaction between these agents, fine particle solids are formed. As(III) was selectively extracted after complexation with ammonium pyrrolidinedithiocarbamate (APDC). The suspension was centrifuged and the sedimented phase can be leached with HCl and introduced into the FI-HG AAS to recover the adsorbed analyte. The advantages of this procedure include short extraction time, good dispersion, good recovery and low residue formation. The variables were optimized by fractional factorial design and response surface methodology. The LOD and LOQ were, respectively, 0.01 and 0.04 μg g−1. The procedure shows potential for determination of low concentrations of As(III), with pre-concentration factor 17 and RSD of 5.5 %. The method was applied on IRMM-804 Rice Flour and no significant difference (p>0.05) was observed, it can be successfully applied to the monitoring of arsenic in real samples.

FI-HG-AAS를 이용한 전처리 과정에서 사용되는 예비환원제의 종류에 따른 요중 비소 분석결과 비교

*Institute for Occupational & Environmental Health, Korea University, Seoul, Republic of korea**Graduate School of Public Health, Yonsei University, Seoul, Republic of KoreaABSTRACTObjectives: The method of analyzing urinary arsenic by flow injection hydride generation atomicabsorption spectrometry (FI-HG-AAS) is generally used because it shows relatively greater sensitivity, lowdetection limits, low blocking action, and is simple to operate. In this study, the results of analysisaccording to three pre-reductants commonly used in the FI-HG-AAS method were compared with eachother. Methods: To analyze urinary arsenic, nineteen urine samples were collected from adults aged 43-79 years oldwithout occupational arsenic exposure. Analysis equipment was FI-HG-AAS (AAnalyst 800/FIAS 400, Perkin-Elmer Inc., USA). The three pre-reductants were potassium iodide (KI/AA), C3H7NO2S (L-cysteine), and amixture of KI/AA and L-cysteine (KI/AAL 74.96µg/L for L-cysteine; 69.23µg/L for KI/AA and L-cysteine; 13.06µg/L for KI/AA) and were significantlycorrelated (R2=0.882). In addition, they showed the lowest coefficient of variation in the results between twolaboratories that applied the same method.Conclusion: The efficiency of hydride generation is considered highly important to the analysis of urinaryarsenic via FI-HG-AAS. This study suggests that using L-cysteine as a pre-reductant may be suitable and themost rational among the FI-Hg-AAS methods using pre-reductants. Keywords: Hydride Generation atomic absorption spectrometry, KI/ascorbic acid, L-cysteine, Pre-reductant,Urinary arsenic

Speciation and determination of inorganic arsenic species in water and biological samples by ultrasound assisted-dispersive-micro-solid phase extraction on carboxylated nanoporous graphene coupled with flow injection-hydride generation atomic absorption spectrometry

In this paper, carboxylated nanoporous graphene as a nanoadsorbent was evaluated in two types of ultrasound assisted-dispersive micro-solid phase extraction for speciation of trace As(v) and As(iii) ions in natural water and human biological samples.

Determination of arsenic in chilli and tomato grown in North East Thailand

Heavy metals in edible fruits constitute a health hazard. We present an analytical procedure for determining inorganic arsenic (As) species in hot chilli pepper and tomato fruits at the red-ripe stage using microwave assisted digestion (MAD) followed by flow injection-hydride generation atomic absorption spectrometry (FI-HGAAS). The optimum conditions for the acid digestion method and arsenic hydride (AsH3) determination were studied in detail. The plant sample (0.5 g) was digested with 5 ml of concentrated nitric acid by MAD programmed at 900 W for 35 min. Arsenite, As(III), in the acid digests could only be analysed by FI-HGAAS using 1% (v/v) HCl as a carrier solution and 0.5% (w/v) NaBH4 in 0.04% (w/v) NaOH as a reducing agent, while total As content was determined after pre-reduction of arsenate, As(V), to As(III) with 2% (w/v) thiourea prior to measurement. The concentration of As(V) was then calculated as the difference between total As and As(III). Detection limits for As(III) and As(V) were 0.004 and 0.006 µg/l, respectively. The relative standard deviation of the data was less than 5% (n = 10). The recovery of the samples spiked with 10 µg/l As was 98-103%. The proposed method was applied to determine traces of As in six varieties of hot chilli pepper (0.55-0.88 µg/g As(III) and 0.22-0.93 µg/g As(V)) and seven varieties of tomato (0.36-0.64 µg/g As(III) and 0.22-0.60 µg/g As(V)) samples.

Ultra-trace Arsenic Determination in Urine and Whole Blood Samples by Flow Injection-Hydride Generation Atomic Absorption Spectrometry after Preconcentration and Speciation Based on Dispersive Liquid-Liquid Microextraction

A noble method for pre-concentration and speciation of ultra trace As (III) and As (V) in urine and whole blood samples based on dispersive liquid-liquid microextraction (DLLME) has been developed. In this method, As (III) was complexed with ammonium pyrrolidine dithiocarbamate at pH = 4 and Then, As (III) was extracted into the ionic liquid (IL). Finally, As (III) was back-extracted from the IL with hydrochloric acid (HCl) and its concentration was determined by flow injection coupled with hydride generation atomic absorption spectrometry (FI-HGAAS). Total amount of arsenic was determined by reducing As (V) to As (III) with potassium iodide (KI) and ascorbic acid in HCl solution and then, As (V) was calculated by the subtracting the total arsenic and As (III) content. Under the optimum conditions, for 5-15 mL of blood and urine samples, the detection limit (3σ) and linear range were achieved 5 ng L �1 and 0.02-10 μg L �1 , respectively. The method was applied successfully to the speciation and determination of As (III) and As (V) in biological samples of multiple sclerosis patients with suitable precision results (RSD < 5%). Validation of the methodology was performed by the standard reference material (CRM).

Antimony as a traffic-related element in size-fractionated road dust samples collected in Buenos Aires

The growing interest of public opinion in environmental problems conducted us to investigate the levels of a toxic traffic-related element such antimony in 19 size-fractionated street dust samples. Samples were collected in the megacity of Buenos Aires during two months at 19 sites with different urban characteristics and traffic profile. Samples were sieved in four fractions (F1 < 37 µm, F2: 37–55 µm, F3: 55–75 µm and F4: 55–100 µm) before elemental analysis. A mixture of aqua regia and hydrofluoric acid was used to digest all samples. Antimony concentrations were quantified by inductively coupled plasma optical emission spectrometry (ICP OES) or flow injection hydride generation-atomic absorption spectrometry (FI-HG-AAS). Twenty four out of 73 sub-samples analyzed showed Sb levels < 0.05 µg g − 1 ; in the rest of the samples mean Sb concentrations varied from 1.4 to 20.4 µg g − 1 . Maximum and minimum concentrations (in µg g − 1 ) found in individual samples in the four fractions were: Fraction 1, < 0.05–20.4; Fraction 2, < 0.05–18.4; Fraction 3, < 0.05–6.3; Fraction 4, < 0.05–7.7. Antimony was found to be enriched in the smallest size fraction of road dust, with mean enrichment factors varying between 27 (F3) and 272 (F1). Concentrations of Sb were correlated with those of other traffic-related elements such as Cu and Pb and higher levels were found in areas with medium and high traffic densities.

Speciation and preconcentration of inorganic antimony in waters by Duolite GT-73 microcolumn and determination by segmented flow injection-hydride generation atomic absorption spectrometry (SFI-HGAAS)

A selective matrix removal/separation/enrichment method, utilizing a microcolumn of a chelating resin with SH functional groups (Duolite GT-73), was proposed for the determination of Sb(III) in waters by segmented flow injection-hydride generation atomic absorption spectrometry (SFI-HGAAS). The resin was selective to Sb(III) at almost all pH and acidity values employed, whereas Sb(V) was not retained at all and could be determined after a pre-reduction step with l-cysteine. Spike recoveries were tested at various concentration levels in different water types and were found to vary between 85 and 118%. Accuracy of the proposed methodology was checked by analyzing a standard reference material and a good correlation was found between the determined (13.3 ± 1.1 μg l −1) and the certified value (13.79 ± 0.42 μg l −1). The method was applied to several bottled drinking water samples for antimony determination with and without preconcentration and none of the samples were found to contain antimony above the permissible level (5 μg l −1). The characteristic concentration (the concentration of the analyte corresponding to an absorbance of 0.0044) was 0.55 μg l −1 and the 3 s limit of detection (LOD) based on five times preconcentration was 0.06 μg l −1. The applicability of the microcolumn separation/preconcentration/matrix removal method for flow injection systems was also demonstrated.

Determination of tellurium in lead and lead alloy using flow injection-hydride generation atomic absorption spectrometry

A method based on flow injection-hydride generation atomic absorption spectrometry (FI-HG AAS) for the determination of trace amount of Te in lead and lead alloy is described. A flow injection system (FI) and related analytical parameters as well as Te determination and interference caused by Pb, Bi and Ag on Te were investigated. The Pb interference could be overcome by using a small sample volume, while the Bi interference could be overcome by thiourea. However, it was not possible to minimise the interference caused by Ag on Te. The optimised conditions for Te determination in the analysed samples were: 6 mol l −1 HCl as sample carrier solution, 0.75% (m/v) sodium tetrahydroborate as Te reductant, 40 μl of sample solution, and 200 ml min −1 Ar flow rate as carrier gas. The limit of quantification (LOQ) was 1.0 μg g −1 Te (using 250 mg of sample in 50 ml final solution), the limit of detection (LOD) was 2.5 μg l −1 and the relative standard deviation (RSD) was 6% for five consecutive measurements of sample solution. The standard addition calibration method was used. Relatively high sample throughput (ca. 45 sample runs can be performed in a working hour), reduced sample manipulation since matrix separation is not necessary, and minor waste generation are the main advantages of the proposed method for Te determination by FI-HG AAS.

Ultrasonic extraction followed by sonolysis-ozonolysis as a sample pretreatment method for determination of reactive arsenic toward sodium tetrahydroborate by flow injection-hydride generation AAS.

A new sample pretreatment method based on ultrasonic extraction in HCI medium and subsequent oxidation of the extracts by sonozone (i.e., sonolysis-ozonolysis) has been developed for determination of reactive arsenic toward sodium tetrahydroborate [mainly As(III) + As(V)] by flow injection-hydride generation atomic absorption spectrometry. This method avoids the use of intensive treatments with concentrated and corrosive acids, high pressures, and temperatures that are inherent with traditional wet or dry ashing procedures and entails reduced waste production and reagent consumption. A sonozone process at room temperature was optimized to break the bond of As to proteins and macromolecular constituents which was an essential requirement for effective reduction by L-cysteine prior to arsine generation. Spiking experiments showed that As(III), As(V), MMA, and DMA were fully recovered from several matrixes on applying the above treatment. On the other hand, a nonreducible As species such as arsenobetaine that is predominant in some biological samples remained unchanged. Application of the method to sediment, soil, fly ash, and plant CRMs demonstrated that, in general, a good agreement existed between certified and found As contents, thereby indicating the absence of nonreducible As forms. Low As recoveries were observed for fish CRMs, as a result of the nondegradability of arsenobetaine by sonozone. The detection limit of As in the samples investigated was in the range 0.19-2.8 microg g(-1).

A practical exercise for the determination of As(III) by flow injection hydride generation-atomic absorption spectrometry

A practical exercise is presented for determination of very low amounts (ng/l) of As(III) by flow injection (FI) and hydride generation and atomic absorption spectrometry detection. The exercise is directed towards students at the advanced undergraduate level, and it is intended to be an introduction to procedures of FI, which by relatively uncomplicated equipment provide analysis with excellent performance. With the method presented, it can be shown that assays of As(III) in natural waters can be performed only if an on-line preconcentration step is incorporated into the FI manifold. The method offers a unique illustration of the versatility of the FI approach in sample manipulation to reach low detection limits as well as a demonstration of cleverly exploiting kinetic discrimination schemes for promoting the main reaction and eliminating potential side reactions and interferences.

Fast automated determination of toxicologically relevant arsenic in urine by flow injection-hydride generation atomic absorption spectrometry

Lower results for arsenic in urine are encountered when potassium iodide-ascorbic acid is used as a pre-reductant in flow injection-hydride generation atomic absorption spectrometry (FI-HGAAS). For the determination of toxicologically relevant arsenic in urine, i.e. the sum of inorganic As(III) and As(V) and its organic metabolites (monomethylarsonate and dimethylarsinate) has been elaborated a simple analytical procedure: ten-fold diluted urine is treated with l-cysteine (1%, m/v) in 0.03 mol 1 −1 hydrochloric acid medium for 1 h, and then a 500 μl aliquot is directly injected into an automated, commercially available FI-HGAAS system. The effects of most critical instrumental and chemical parameters have been studied and optimum conditions are recommended, comprising of relatively low sample and carrier acidities, 0.03 and 0.01 mol 1 −1 HCl, respectively, higher sodium tetrahydroborate levels (0.5%, m/v), lower flow rates of reagents than that typically recommended for this system to ensure longer reduction and residence times in the gas-liquid separator, and integrated absorbance measurements for eliminating the residual kinetic effects in hydride generation and transport of individual arsenic species. The recoveries of spiked As(III), As(V), MMA and DMA in urine are 100%, 100%, 96% and 95%, respectively. This procedure has been validated by analysis of several certified reference materials and collaborative study samples, the results being in good agreement with the certified values. The limit of detection (3σ) is 0.1 μg 1 −1 in 1 : 10 diluted urine, corresponding to 1 μg 1 −1 of As in undiluted urine. The relative standard deviation is 2% and 7% (within-run and between-run in three successive days, respectively) at 3 μg 1 −1 (1.5 ng) As level. The sampling frequency is up to 50–55 measurements per hour.

Evaluation of the Gas–Liquid Separation Efficiency of a Tubular Membrane and Determination of Arsenic Species in Groundwater by Liquid Chromatography Coupled With Hydride Generation Atomic Absorption Spectrometry

An experimental approach for evaluating the hydride separation efficiency of a tubular microporous poly(tetrafluoroethylene) (PTFE) membrane by flow injection hydride generation atomic absorption spectrometry (HGAAS) is described. A method is also proposed for determining arsenic species in groundwater by coupling ion-pair chromatography (IPC) with HGAAS. The evaluation was undertaken with a combined gas–liquid separator (GLS), consisting of a tubular PTFE membrane and a conventional U-shaped glass device. Two important controlling variables, viz ., the length of the microporous PTFE tubing and the ratio of the tubing id to the wall thickness, were investigated. The results showed that the absolute separation efficiency of the PTFE membrane can be effectively evaluated with the combined GLS. In addition, arsenic speciation in groundwater was also investigated by IPC–HGAAS. The chromatographic separation of arsenic species with this analytical system was examined in terms of the effects of pH and concentration of eluent. The absolute detection limits achieved with a 100 µl injection can be as low as 0.07, 0.11, 0.12 and 0.30 ng for arsenite (As III ), dimethylarsinic acid, monomethylarsonic acid and arsenate (As V ), respectively. A commercially available standard (NIST SRM 1643b Trace Elements in Water) and the spike additions method were used to confirm the analytical reliability of the method. The proposed method has already been routinely applied to the speciation of arsenic in groundwater samples.

Preconcentration and separation of inorganic selenium on Dowex 1X8 prior to hydride generation—atomic absorption spectrometry

Exchange reactions between inorganic selenium species and chloride were studied on Dowex 1X8. The concentration exchange constants were determined with the batch technique at room temperature and used to predict the chromatographic enrichment and separation of tetra- and hexavalent selenium. A procedure for the determination of total selenium after digestion with permanganate and anion exchange preconcentration was also developed. The enrichment techniques were applied to the determination of Se(IV) and total dissolved selenium in drinking water and fresh water using flow injection hydride generation—atomic absorption spectrometry (HG—AAS). Results agreed with those obtained in a HG—AAS system where selenium was preconcentrated as hydrogen selenide in a trap at liquid nitrogen temperature.

Flow-injection and continuous-flow systems for the determination of Se(IV) and Se(VI) by hydride generation atomic absorption spectrometry with on-line prereduction of Se(VI) to Se(IV)

The on-line reduction of Se(VI) to Se(IV) and subsequent determination of Se(IV) by flow injection-hydride generation atomic absorption spectrometry are proposed. To reduce Se(VI) quantitatively to Se(IV), the sample is acidified with concentrated HCl and the sample coil is heated to 140°C. Hydride generation is performed in an ice-bath to prevent decomposition of the NaBH 4. The sensitivity of the proposed method is about twice that of the traditional method without heating, the relative standard deviation is below 5%, the recovery is 95–105% and the selectivity is significantly increased. No Se losses occur because the reduction system is closed until the selenium hydride reaches the phase separator. The method has been successfuly applied to the determination of Se(IV) and Se(VI) in sea water.

Investigations for the determination of tin by flow injection hydride generation atomic-absorption spectrometry

It could be shown that the pre- or double peaks which are frequently observed in the determination of tin by hydride generation atomic-absorption spectrometry are not due to reagent contamination or memory effects. Rather they originate from the silica material used to make the quartz tube atomizer. At elevated temperatures the tin diffuses to the surface and it can be volatilized and atomized only in the presence of hydrogen. The height of the pre-peak depends, among other things, on the time for which the quartz tube atomizer has been at a high temperature without hydrogen. The pre-peaks disappear when argon with 10% (v/v) hydrogen is used as the purge gas. In flow injection the pre-peaks can be separated in time from the analytical signal by using a program in which hydrogen is generated by reaction of sodium tetrahydroborate reluctant solution with the acid carrier prior to the injection of the sample. Also investigated was the influence of the acid and sodium tetrahydroborate concentration on sensitivity and freedom from interferences. Best results were obtained when a saturated boric acid solution containing 0.1 M hydrochloric acid was used for standards, samples and carrier solution, and a 0.4% (m/v) sodium tetrahydroborate solution with 0.05% (m/v) sodium hydroxide as the reluctant. Under these conditions tin could be determined accurately in the range 0.008-0.1% in low alloy steel standard reference materials, with matrix-free standard solutions for calibration.