Flow Injection-hydride Generation Atomic Absorption 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.

Status of groundwater arsenic contamination in all 17 blocks of Nadia district in the state of West Bengal, India: A 23-year study report

A comprehensive study was conducted in Nadia, one of the nine arsenic (As) affected districts in West Bengal, India to determine the extent and severity of groundwater As contamination and its health effects in particular, dermatological effects and neurological complications. We collected 28,947 hand tube-well water samples from all 17 blocks of Nadia district and analyzed for As by the flow injection-hydride generation atomic absorption spectrometer (FI-HG-AAS). We found 51.4% and 17.3% of the tube-wells had As above 10 and 50 μg/L, respectively and observed that groundwater of all 17 blocks contained As above 50 μg/L with maximum observed level of 3200 μg/L. We estimated that about 2.1 million and 0.6 million people could be drinking As contaminated water above 10 and 50 μg/L, respectively, while 0.048 million could be at risk of drinking As-contaminated water above 300 μg/L, the concentration predicted to cause overt arsenical skin lesions. We screened 15,153 villagers from 50 villages and registered 1077 with arsenical skin lesions resulting in a prevalence rate of 7.1%. Analyzing 2671 biological samples (hair, nail and urine), from people with and without arsenical skin symptoms we found 95% of the samples had As above the normal level, indicating many people in Nadia district are sub-clinically affected. Arsenical neuropathy was observed in 33% of 255 arsenicosis patients with 28.2% prevalence for predominant sensory neuropathy and 4.7% for sensorimotor. As groundwater is still the main source of drinking water, targeting low-As aquifers and switching tube-well from unsafe to nearby safe sources are two visible options to obtain safe drinking water.

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.

Chronic Arsenic Exposure and Adverse Pregnancy Outcomes in Bangladesh

Chronic exposure to arsenic through drinking water has the potential to cause adverse pregnancy outcomes, although the association has not been demonstrated conclusively. This cross-sectional study assessed the association between arsenic in drinking water and spontaneous abortion, stillbirth, and neonatal death. In this cross-sectional study, 533 women were interviewed. Information on sociodemographic characteristics, drinking water use, and adverse pregnancy outcomes was obtained through a structured pretested interviewer-administered questionnaire. The respondents reported use of a total of 223 tube wells; for 208 wells, water samples were measured using an ultraviolet/visible spectrophotometry method, whereas 15 were measured by flow-injection hydride generation atomic absorption spectrometry (FIHG-AAS). Excess risks for spontaneous abortion and stillbirth were observed among the participants chronically exposed to higher concentrations of arsenic in drinking water after adjusting for participant's height, history of hypertension and diabetes, and (for neonatal death only) age at first pregnancy. Comparing exposure to arsenic concentration of greater than 50 microg/L with 50 microg/L or less, the odds ratios were 2.5 (95% confidence interval=1.5-4.3) for spontaneous abortion, 2.5 (1.3-4.9) for stillbirth, and 1.8 (0.9-3.6) for neonatal death. These study findings suggest that chronic arsenic exposure may increase the risk of fetal and infant death.

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.

CHRONIC ARSENIC EXPOSURE AND ADVERSE PREGNANCY OUTCOMES IN BANGLADESH

Introduction Chronic arsenic exposure through drinking water has the potential to cause adverse pregnancy outcomes, though the association is not conclusive. This cross sectional study was carried out in twothree arsenic affected districts of Bangladesh to determine the association between chronic arsenic exposure through drinking water and spontaneous abortion, stillbirth and neonatal death. Methods In this cross-sectional study, 533 married, non-smoking females of reproductive age (range 15 to 49 years) with a history of at least one pregnancy, who had been living in the study area since their marriage and drank water from the respective tube well prior to and during the pregnancy were interviewed. Information on sociodemographics, drinking water use, occupation and adverse pregnancy outcomes were obtained through a structured pretested interviewer-administered questionnaire. Out of 2138 tube wells, 203198 water samples were measured using UV/Visible spectrophotometry method while 15 were measured by flow-injection hydride generation atomic absorption spectrometry (FIHG-AAS). Results A total of 533 female participated in this study. Their mean age was 31.22 years (standard deviation [SD] = 6.44) and the average duration of arsenic exposure of the participants was 8.11 years (SD = 7.32), median duration of exposure was 7 years. Out of the study subjects, 257 (48%) of the study participants did not receive any formal education. The majority of them (51%) got married before the age of 16-years. The mean number of pregnancies was 3.72 (SD = 1.79) and mean number of live births was 3.48 (SD = 1.65). Melanosis was observed among 51 (10%) and keratosis was observed among 43 (8%) participants. The mean and median arsenic concentration of the tube well drinking water of the study participants was 279(SD = 355) μg/L and 116 ppbμg/L respectively, ranging from non-detectable level to 1710 ppbμg/L. 356 (67%) participants were exposed to arsenic at more than 50 ppbμg/L, the recommended level of arsenic in drinking water for Bangladesh. Overall incidence of spontaneous abortion, stillbirth and neonatal death in this study were found as 59.61/1000 live birth, 35.55 /1000 live birth and 49.31 /1000 live birth respectively. Excess risks for spontaneous abortion, stillbirth and neonatal death were observed among the participants exposed to increasing concentrations of arsenic in drinking water, after adjusting for participant's education, age at marriage, antenatal care and parity. The odds ratio (OR) for spontaneous abortion, stillbirth and neonatal death was 1.93 (95% Confidence Interval [CI]: 1.11, 3.37), 1.82 (95% CI: 0.94, 3.51) and 1.89 (95% CI: 1.02, 3.53) respectively for females drinking water with >50ppbμg/L compared to £50ppbμg/L arsenic concentration. These risks are both clinically and statistically significant except stillbirth. There was, however, a statistically significant dose-response association between increasing arsenic concentration and stillbirth (p = 0.02), neonatal death (p = 0.01).

Determination of bismuth, selenium and tellurium in nickel-based alloys and pure copper by flow-injection hydride generation atomic absorption spectrometry—with ascorbic acid prereduction and cupferron chelation–extraction

Diverse matrix effects on the determination of bismuth, selenium and tellurium (μg g −1) in nickel-based alloys and pure copper by flow-injection hydride generation atomic absorption spectrometry (FIAS-HGAAS) were investigated. Sodium tetrahydroborate was used as the reductant. The separation of analytes from copper matrix was mandatory while the analytes were successfully determined without being separated from the alloy matrix. Hydrochloric acid was effective in the prereduction of bismuth and selenium, however, it did not give any satisfactory result for tellurium in nickel-based alloys. In this work, 5% (w/v) ascorbic acid was proved effective for the prereduction of tellurium. Successful determination of tellurium in copper was achieved when N-nitroso- N-phenylhydroxylamine (cupferron) chelation–extraction was employed for the separation of tellurium from copper matrix. Cupferron chelation–extraction was performed in phosphate buffer (a mixture of 0.2 mol l −1 sodium phosphate and 0.1 mol l −1 citric acid). Lanthanum hydroxide coprecipitation at pH 10.0±0.5 was effective for bismuth and selenium. Standard reference materials of nickel-based alloys and pure copper were analyzed using the proposed methods. The linear range for the calibration curves were 0.30–15 and 0.20–10 ng ml −1 for BiH 3 and H 2Se, respectively, with a correlation coefficient of 0.9995. For H 2Te, the linear range for the calibration curves was 0.50–12 ng ml −1 with the correlation coefficient of 0.9994. Good agreement was obtained between experimental values and certified values. Satisfactory recovery ranged from 91±1 to 106±2% was obtained from five replicate determinations.

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).

Determination of selenoethionine by flow injection-hydride generation-atomic absorption spectrometry/high-performance liquid chromatography-hydride generation-high power nitrogen microwave-induced plasma mass spectrometry

A simple direct flow injection hydride generation atomic absorption spectrometric method was developed using sodium tetrahydroborate and hydrochloric acid for the determination of selenoethonine (Seet) that excluded any chemical pretreatment prior to hydride generation. The detection limit (3 σ of blank) of the method was 0.25 ng ml −1 selenium (standard solutions in Milli-Q water). The reproducibility (R.S.D. of three analyses performed on three different days) and the repeatability (R.S.D. of seven successive analyses) of the method were 9.2% for 5.05 ng ml −1 and 2.8–9.5% for 20.0–1.00 ng ml −1 of standard selenium (Milli-Q water), respectively. The calibration graph was linear up to 20.0 ng ml −1. This HG method is very promising and was successfully applied for the on-line estimation of Seet (spiked) in human urine with using high-performance liquid chromatography-hydride generation-high power nitrogen microwave-induced plasma mass spectrometry (HPLC-HG-N 2-MIP-MS). The separation was performed on a GS-220 gel-permeating column with a 25 mM tetramethylammonium hydroxide+25 mM malonic acid buffer (pH 7.5), which showed 26–30% signal suppression due to less volatile hydride formation from Seet among the mobile phases examined. The recovery of Seet that was prepared in the above mobile phase is about 74% as that of the Seet prepared in Milli-Q water. In the PRP-X100 anion-exchange column with the 15 mM phosphate (pH 7.0) mobile phase, Seet eluted out after 600 s keeping a broad peak with enlarging the baseline signal. The concentration of selenite found in the human urine was 3.6±0.2 μg l −1 and that agreed well with the high-performance liquid chromatography inductively coupled plasma mass spectrometry (HPLC-ICP-MS) value (3.8±0.2 μg l −1).

Digestion procedures for the determination of antimony and arsenic in small amounts of peat samples by hydride generation–atomic absorption spectrometry

Closed-pressurised and open vessel digestion procedures for the mineralisation of small amounts (∼100 mg) of peat samples have been developed and evaluated. The two trace elements As and Sb were quantified in the diluted digests by flow injection–hydride generation–atomic absorption spectrometry (FI–HG–AAS). Optimisation of the analytical procedures was carried out with two bulk peat materials one of which was prepared as internal reference material. Both peat specimens were additionally characterised by instrumental neutron activation analysis with respect to their concentrations of As and Sb. Good agreement between instrumental neutron activation analysis (INAA) results and concentrations determined by HG–AAS were obtained. The use of adequate reference materials during the course of all experiments guaranteed precise and accurate results. Various acid mixtures with and without hydrofluoric acid were tested, because preliminary experiments revealed that HF in the digestion mixture leads to the formation of the gaseous AsF 5 resulting in diminished recoveries of As when open vessel digestion procedures are employed. Avoiding HF for mineralisation of peat led to low recoveries for Sb because distinct amounts of Sb are associated with silicates. Closed-pressurised vessel digestion proved to be less effective compared to open vessel mineralisation. For successful quantification of both elements, two digestion procedures are needed, one without HF for As and another one with HF to liberate Sb from the silicates. The optimised open vessel digestion procedure was applied to the determination of ancient peat samples dating back to 9300 calendar years before present. Concentrations of both elements showed a broad spread with values ranging from 18 to 1500 and 300 to 5700 ng g −1 for Sb and As, respectively.

Flow-injection hydride generation atomic absorption spectrometric study of the automated on-line pre-reduction of arsenate, methylarsonate and dimethylarsinate and high-performance liquid chromatographic separation of their l-cysteine complexes

An automated on-line pre-reduction of arsenate, monomethylarsonate (MMA) and dimethylarsinate (DMA) using flow injection hydride generation atomic absorption spectrometry (FI-HGAAS) is feasible. The kinetics of pre-reduction and complexation depend strongly on the concentration of l-cysteine and on the temperature in the following increasing order: inorganic As(V)<DMA<MMA. Arsenate is pre-reduced/complexed within less than 50 s at 70–100°C compared to 1 h at room temperature, while MMA and DMA require 1.5–2 min at 70–100°C and up to 1–2 h at room temperature. The characteristic masses and concentrations for 100 μl injections are 0.01 ng and 0.1 μg l −1 in integrated absorbance and 0.2 ng and 2 μg l −1 in peak height measurements, and the limits of detection are ca. 0.5 ng and 5 μg l −1, respectively. In a high-performance liquid chromatography (HPLC)–HGAAS system, the l-cysteine complexes of inorganic As(III), MMA and DMA are best separated within 7 min by HPLC on a strongly acidic cation exchange column such as Spherisorb S SCX 120×4 mm (5 μm) with a mobile phase containing 12 mmol l −1 phosphate buffer (KH 2PO 4/H 3PO 4)–2.5 mmol l −1 l-cysteine, pH 3.3–3.5. Upon dilution to l-cysteine levels below 10 mmol l −1, which are compatible with HPLC separations, the DMA–cysteine complex is unstable on storage. No baseline separations are possible with anion exchange and reverse phase C 18 HPLC columns. The limits of detection with 50 μl injections in peak area mode are ca. 0.5 ng and 10 μg l −1, respectively.

Flow injection-hydride generation atomic absorption spectrometric determination of Se(VI) and Se(IV): utility of a conventionally heated water bath for the on-line reduction of Se(VI)

A simple flow injection manifold coupled to a hydride generation atomic absorption spectrometer has been designed for Se(VI) and Se(IV) determination. On-line reduction of Se(VI) is performed by passing the sample, in 6.8 M hydrochloric acid, through a conventionally heated water bath. Complete conversion into Se(IV) is achieved in about 1 min. Conventional on-line heating has proved to be a good alternative for the fast conversion of Se(VI) into Se(IV). Its performance, in comparison to microwave heating, is discussed. Reaction kinetic parameters have been obtained via on-line experiments for the first time. A comparison with those values already reported is also presented. A limit of detection of 0.05 ng ml −1 ( n=10, 3 s) is obtained for both forms, with a precision (relative standard deviation, n=10, 3 s) better than 3%. The sample throughput is 60 samples/h, better than other flow injection systems reported up to date.

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.

Determination of Trace Elements in Power Plant Emissions by Inductively Coupled Plasma Mass Spectrometry: Comparison with Other Spectrometric Techniques

Particulate matter in stack effluents of coal-fired plants was collected with an isokinetic probe nozzle suitable for (a) total particulate samplings on membrane filters and (b) sampling with a low volume 10-stage single orifice cascade impactor plus a backup filter. A microwave digestion method using an acid mixture of HNO3–HCl–HF in a closed vessel was developed for the determination of major, minor, and trace elements in very small amounts of sample. Analyses were carried out by inductively coupled plasma mass spectrometry (ICP-MS). A recovery study was conducted using multielemental standard solutions, NIST1633a Trace Elements in Coal Fly Ash and NIST 1648 Urban Particulate Matter, to examine the capabilities of the method. The results for real samples dissolved by this procedure were compared with results obtained by instrumental neutron activation analysis, graphite furnace atomic absorption spectrometry, and flow-injection hydride generation atomic absorption spectrometry. The analytical capabilities of ICP-MS make it one of the techniques of choice for the determination of trace elements in emission particulate matter collected in different granulometric particle sizes.

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.