Flow Injection Hydride Generation Research Articles

A robust method for the determination of lead in water samples using flow injection hydride generation atomic absorption spectrometry

Flow injection hydride generation atomic absorption spectrometry (FI-HGAAS) is a sensitive technique for the quantification of trace amounts of lead. However, plumbane generation is not straightforward and usually HG methods for lead are not robust enough for routine analysis. The optimum pH range for Pb HG is very narrow, so strict control of the acidity of the reaction medium is required for reliable results and in some cases even acid concentrations used for sample preservation can interfere. Moreover, some elements, like Cu, can interfere in the HG reaction suppressing the Pb signal. In this paper we report the development and validation of a method for the determination of Pb in water samples that is robust towards acidity and Cu levels usually found in water samples.All hydride generation parameters were optimized, but special emphasis was put on robustness. The use of borate as a buffer significantly improved the robustness of the method towards acidity, compared to the typical non-buffered HG. Furthermore, the interference of Cu, Sb and Sn in the HG reaction was overcome using thiocyanate as a masking agent. Other elements do not interfere at levels typically found in water samples. The limit of quantification achieved (0.9 μg L−1) is below the current guideline value for Pb in drinking water (10 μg L−1). The linearity of the method was verified between the LOQ and up to 15 μg L−1. An analytical frequency of 25 samples per hour with 3 measurement replicates each was achieved. The method was applied to the analysis of 50 water samples. The concentrations found ranged from <LOD (0.3 μg L−1) and up to 88.8 μg L−1.The proposed method is robust, cost-effective, easily automated and does not require unconventional or expensive equipment. It can be applied for routine analysis of different types of water samples.

Non-chromatographic Speciation Analysis of Tellurium by HG-ICP-MS/MS at Sub ng L-1 Concentration in Natural Waters Using TiIII as a Pre-Reducing Agent.

An automated and high-throughput (36 h-1) method for extremely sensitive determination of the two main tellurium species in the environment, namely, tellurite (TeIV) and tellurate (TeVI), was developed. Flow injection hydride generation was interfaced for the first time with inductively coupled plasma triple quadrupole mass spectrometry (ICP-MS/MS) detection to assure interference-free tellurium analysis. ICP-MS/MS conditions were studied in detail. Using a mixture of He + O2 gases in the reaction cell, the background signals significantly dropped and Xe isobaric interference was eliminated, allowing measurement with the most abundant Te isotopes, that is, 128Te and 130Te, and offering a huge increase in sensitivity. Volatile H2Te was selectively generated by a HCl/NaBH4 reaction from TeIV or from both TeIV and TeVI (TeIV+VI) after pre-reduction of TeVI by a TiCl3 solution. The optimum conditions for TiCl3 as a pre-reductant and the pre-reduction kinetics were also investigated. Different reduction rates were found depending on the sample stabilization media (HCl, HNO3, or EDTA). The same sensitivity was found for TeIV and TeVI, measured after pre-reduction, and no significant matrix effect was observed in both fresh and seawaters. Therefore, external calibration was used for quantification in real samples. Under optimal conditions, this method reached an unprecedented limit of detection of 0.07 ng L-1 for both TeIV and TeIV+VI and an intra-day repeatability of 5.2% at the 5 ng L-1 level. The methodology was successfully applied to the speciation analyses in commercially available certified reference materials of river water and seawater, and in bottled water and lake water samples.

Selenium speciation in soils using flow injection hydride generation atomic absorption spectrometry with on-line removal of organic matter interferences

A method based on flow injection hydride generation atomic absorption spectrometry (FI-HGAAS) with an on-line pre-reduction of Se(VI) to Se(IV) was developed and optimized to determine phosphate-extractable Se (0.1 M phosphate buffer KH2PO4/K2HPO4 at pH 7). The extracted fraction involves water-soluble Se (i.e. the most mobile Se fraction) and exchangeable Se (i.e. sorbed onto soil component surface). Kinetic discrimination mechanisms allowed the complete removal of interferences caused by organic matter due to the formation of humic substances (HS)–Se(IV) complexes observed when batch pre-reduction processes were used. Se(IV) and Se(VI) recoveries ranged 95–105% at a fortification level of 150 μg kg−1. The pre-reduction was efficiently carried out in 20 s in a 6 M HCl medium at 100 °C. Results from phosphate-extractable fractions were comparable to those obtained by ICP-MS. Se bound to organic matter was released digesting the remaining material from the phosphate buffer extraction with 0.1 M K2S2O8. Detection and quantification limits were 15 μg kg−1 Se and 50 μg kg−1 Se, respectively, in each fraction. The methodology was applied to 10 agricultural soils from Argentina with total Se concentration levels between 130 μg kg−1 and 419 μg kg−1.

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.

Ultra-trace tellurium preconcentration and speciation analysis in environmental samples with a novel magnetic polymeric ionic liquid nanocomposite and magnetic dispersive micro-solid phase extraction with flow-injection hydride generation atomic fluorescence spectrometry detection

A highly efficient magnetic dispersive micro-solid phase extraction (M-D-μSPE) method was developed for Te preconcentration and speciation analysis in different environmental samples. A novel magnetic polymeric ionic liquid nanocomposite synthesized based on the Radziszewski reaction was applied for the selective retention of Te(IV) species, followed by elution with 5 mol L−1 HCl and determination by flow-injection hydride generation atomic fluorescence spectrometry. Te(VI) was selectively determined by difference between total Te and Te(IV) after a pre-reduction step. Studies on the sorption capacity of the nanocomposite were performed, while several parameters concerning the retention, separation and elution were optimized. A 100% retention efficiency and a sensitivity enhancement factor of 67 were achieved. Limits of detection of 1.9 ng L−1 and 3.7 ng L−1, and standard deviations of 4.3% and 5.1% were obtained for Te(IV) and Te(VI). A gas-liquid separator with a low dead volume was used for reduced dispersion of the flow injection signals and additional sensitivity enhancement. Finally, the feasibility of the proposed M-D-μSPE method for Te speciation was demonstrated by the analysis of several environmental samples, such as tap, rain, river and underground waters, soils and sediments, with excellent recovery results in spiked samples.

Arbuscular mycorrhizal fungi reduce arsenic uptake and improve plant growth in Lens culinaris.

Arsenic (As) is a carcinogenic and hazardous substance that poses a serious risk to human health due to its transport into the food chain. The present research is focused on the As transport in different lentil genotypes and the role of Arbuscular Mycorrhizal Fungi (AMF) in mitigation of As phyto-toxicity. Arsenic transport from soil to root, shoot and grains in different lentil genotypes was analyzed by flow injection hydride generation atomic absorption spectrophotometry. AMF were applied for the reduction of As uptake as well as the improvement of plant growth in lentil genotypes. Arsenic phyto-toxicity was dose-dependent as evidenced by relatively higher shoot length, fresh and dry weight of root and shoot in 5 and 15 mgkg-1 As-treated lentil plants than that in 100 mgkg-1 As-treated lentil. Arsenic accumulation occurred in roots and shoots of all BARI-released lentil genotypes. Arsenic accumulation in grains was found higher in BARI Mashur 1 than other lentil genotypes. AMF treatment significantly increased growth and biomass accumulation in lentil compared to that in non-AMF plants. Furthermore, AMF effectively reduced the As concentrations in roots and shoots of lentil plants grown at 8 and 45 mgkg-1 As-contaminated soils. This study revealed remarkable divergence in As accumulation among different BARI-released lentil genotypes; however, AMF could reduce As uptake and mitigate As-induced phyto-toxicity in lentil. Taken together, our results suggest a great potential of AMF in mitigating As transfer in root and shoot mass and reallocation to grains, which would expand lentil cultivation in As-affected areas throughout the world.

Is There Any Role of Arsenic Toxicity in HPV Related Oral Squamous Cell Carcinoma?

Arsenic is a potent human carcinogen affecting the rate of cancer deaths worldwide. In India, West Bengal is the worst affected state by arsenic. To our best knowledge, this is the first study relating arsenic toxicity with oral carcinoma, along with HPV infection, the latter being well established in western countries. To find out a possible correlation between arsenic toxicity and oral carcinoma in the population of West Bengal, in or without any association with human papilloma virus infection. Ethical clearance of this study was obtained from the institutional committee. One hundred and four malignant and 103 premalignant cases were selected for this study along with 200 healthy age and sex-matched individuals selected as control (100 each for malignant and premalignant) (2013-2017). On proper consent, their buccal swab and hair samples were assessed for the presence of HPV DNA by DNA extraction, followed by PCR and arsenic estimation by flow injection hydride generation atomic absorption spectrometry respectively. A very highly significant correlation has been observed between arsenic toxicity, HPV infection and the occurrence of oral carcinoma (p value=2.18e-06; p value=0.00100 respectively). A correlation has also been observed between these two factors simultaneously, contributing to this malignancy (phi coefficient = 0.2194839). A statistically significant correlation observed between this metal toxicity and viral infection in the occurrence of oral carcinoma in this population indicates a possible symbiotic role between these two factors in this malignancy.

Inter-laboratory validation of an inexpensive streamlined method to measure inorganic arsenic in rice grain.

With the establishment by CODEX of a 200ng/g limit of inorganic arsenic (iAs) in polished rice grain, more analyses of iAs will be necessary to ensure compliance in regulatory and trade applications, to assess quality control in commercial rice production, and to conduct research involving iAs in rice crops. Although analytical methods using high-performance liquid chromatography-inductively coupled plasma-mass spectrometry (HPLC-ICP-MS) have been demonstrated for full speciation of As, this expensive and time-consuming approach is excessive when regulations are based only on iAs. We report a streamlined sample preparation and analysis of iAs in powdered rice based on heated extraction with 0.28M HNO3 followed by hydride generation (HG) under control of acidity and other simple conditions. Analysis of iAs is then conducted using flow-injection HG and inexpensive ICP-atomic emission spectroscopy (AES) or other detection means. A key innovation compared with previous methods was to increase the acidity of the reagent solution with 4M HCl (prior to reduction of As5+ to As3+), which minimized interferences from dimethylarsinic acid. An inter-laboratory method validation was conducted among 12 laboratories worldwide in the analysis of six shared blind duplicates and a NIST Standard Reference Material involving different types of rice and iAs levels. Also, four laboratories used the standard HPLC-ICP-MS method to analyze the samples. The results between the methods were not significantly different, and the Horwitz ratio averaged 0.52 for the new method, which meets official method validation criteria. Thus, the simpler, more versatile, and less expensive method may be used by laboratories for several purposes to accurately determine iAs in rice grain. Graphical abstract Comparison of iAs results from new and FDA methods.

Implications of extrapolative factors and their role in the development of breast cancer in females susceptible to Autoimmune Thyroid Disorders (AITDs)

Background: Apart from different cancer types in females, breast cancer falls among frequent cancers all over the world. The data from the current studies shows that females with advanced stages of breast cancer also prone to Autoimmune Thyroid Disorders (AITDs). Methodology: Hundred breast cancer patients (Stage-III) with palpable thyroid nodule in the age group of 30-75 y were eligible for inclusion in the study. Hundred age and sex-matched clinically apparently healthy individuals were included as controls. FT3, FT4, TSH, TPOAb, TgAb, TSHr Ab, prolactin and estradiol were estimated by using ELISA kit method. Serum Protein-Bound Iodine (PBI) and selenium were estimated by using a flow injection hydride generation Atomic Absorption Spectrometric (AAS) method. Results: The mean age and weight for diseased group were 58.36 ± 11.78 y and 74.96 ± 12.66 kg. The decreased levels (3.73 ± 0.189 pmol/L) of T3 were observed in newly diagnosed breast cancer patients as compared to controls (4.72 ± 0.24 pmol/L). Higher levels of T4 (17.86 ± 4.98 pmol/L) were recorded in patients as compared to controls (10.11 ± 1.64 pmol/L). The serum TSH levels in the breast cancer patients were raised (3.54 ± 0.26 mIU/L) in contrary to control group (1.9 ± 0.134 mIU/L). Significantly higher levels of Thyroglobulin Antibodies (TgAb), Thyro-Peroxidase Antibodies (TPOAb) and Thyrotropin Stimulating Hormone receptor Antibodies (TSHrAb) were recorded in breast cancer patients (62.07 ± 6.94 pmol/L, 24.1 ± 6.81 and 3.1 ± 0.43 IU/L pmol/L) as compared to controls respectively. The levels of iodine and selenium in patients were reduced (32.03 ± 4.76 ng/ml and 51.03 ± 2.13 mlU/L) as compared to the controls. Highly significant higher serum levels of prolactin (35.09 ± 4.76) were observed in diseases group as compared to controls (7.14 ± 1.57 pg/ml). Serum estrogen levels in patients were 10.47 ± 1.67 pg/ml, while in healthy individuals they were 6.55 ± 0.88 pg/ml, which shows statistically highly significant profile between the two groups. Conclusion: The present study show an association in between breast cancer and thyroid disorders, as thyroid hormone profile regulates breast cancer initiation. Therefore, these biomarkers can be used in prognosis i.e., in management and progression of breast cancer.

Quantitative Determination of Antimony, Bismuth, and Tellurium in Geological Samples by Inductively Coupled Plasma Mass Spectrometry and Flow Injection Hydride Generation Atomic Absorption Technique

Quantitative Determination of Antimony, Bismuth, and Tellurium in Geological Samples by Inductively Coupled Plasma Mass Spectrometry and Flow Injection Hydride Generation Atomic Absorption Technique

Approved Method of Recovery Arsenic by Using Reference Materials by FI-HG-AAS

A flow injection hydride generation atomic (FI-HG-AAS) method was developed for determination of arsenic in certified reference materials after open wet digestion of samples. Steps of the method were optimized and analytical as well as statistical parameters of the method were determined (Detection limit 1 μg/kg-1, Quantification limit 3 μg/kg-1). Accuracy of the method was evaluated using GBW10043 (Rice), GBW100052 (Green tea), T0770 (soya flour), NCS-ZC 73013 (Spinach), NCS-ZC 73015 (Milk powder) reference materials.

Determination of mercury in urine by flow injection hydride generation cold atomic absorption spectrometry

Determination of mercury in urine by flow injection hydride generation cold atomic absorption spectrometry

Groundwater arsenic contamination from parts of the Ghaghara Basin, India: influence of fluvial geomorphology and Quaternary morphostratigraphy

A groundwater arsenic (As) distribution in Faizabad, Gonda, and Basti districts of Uttar Pradesh is shown in the entrenched channels and floodplains of the Ghaghara River. Tubewell water samples were analysed for As through flow injection hydride generation atomic absorption spectrometry (FI-HG-AAS) system. About 38, 61, and 42 % of tubewells in Faizabad, Gonda, and Basti districts, respectively, have As >10 µg/l (WHO guideline). Moreover, 15, 45, and 26 % of tubewells in Faizabad, Gonda, and Basti districts, respectively, have As above 50 µg/l. About 86, 69, and 35 % of tubewells in Faizabad, Gonda, and Basti districts, respectively, are from shallow depth (21–45 m), and it is worth noticing that 47 % As-contaminated (As >10 µg/l) tubewells in these three districts are located within the depth of 10–35 m in Holocene Newer Alluvium aquifers. The high content of As (7.11 mg/kg) is measured in suspended river sediments of the Ghaghara River. Most of the As-contaminated villages in the Ghaghara Basin are located close to abandoned or present meander channels and floodplains of the Ghaghara River. In contrast, tubewells in Faizabad, Ayodhya, and Nawabganj towns are As-safe because of their positions on the Pleistocene Older Alluvium upland surfaces. Quaternary geomorphology plays an important role in groundwater arsenic contamination in the Ghaghara Basin. The sources of groundwater arsenic are geogenic and perennial mountainous rivers in the Ghaghara Basin supplied high sediment loads. The arsenic in groundwater of Ghaghara Basin is getting released from associated sediments which were likely deposited from the Himalayas. The process of release of groundwater arsenic is reductive dissolution of iron hydroxides.

Accuracy of a method based on atomic absorption spectrometry to determine inorganic arsenic in food: Outcome of the collaborative trial IMEP-41

A collaborative trial was conducted to determine the performance characteristics of an analytical method for the quantification of inorganic arsenic (iAs) in food.The method is based on (i) solubilisation of the protein matrix with concentrated hydrochloric acid to denature proteins and allow the release of all arsenic species into solution, and (ii) subsequent extraction of the inorganic arsenic present in the acid medium using chloroform followed by back-extraction to acidic medium. The final detection and quantification is done by flow injection hydride generation atomic absorption spectrometry (FI-HG-AAS).The seven test items used in this exercise were reference materials covering a broad range of matrices: mussels, cabbage, seaweed (hijiki), fish protein, rice, wheat, mushrooms, with concentrations ranging from 0.074 to 7.55mgkg−1.The relative standard deviation for repeatability (RSDr) ranged from 4.1 to 10.3%, while the relative standard deviation for reproducibility (RSDR) ranged from 6.1 to 22.8%.

A comparative study of two nanosubstrates for the on-line solid phase extraction of antimony by FI-HG-AAS

Nanoporous carbon (NPC) prepared from metal organic frameworks (MOFs) was studied to serve as a sorbent for preconcentrating Sb(III) at trace levels. The performance of NPC regarding sensitivity, enrichment factor, analytical throughput and recovery was compared with that of multiwalled carbon nanotubes functionalised with l-proline (pro-MWCNTs). In this study, Sb(III) was preconcentrated using both substrates using an on-line flow injection hydride generation atomic absorption spectrometry (FI-HG-AAS) system. A low molecular weight polyethylene was added to the sorbent material to fill the preconcentration columns to avoid nanoparticle aggregation. A comprehensive study of the type and concentration of the reaction media and the eluent was carried out to select the best substrate not only in terms of adsorption capacity but also considering potential interferent control. The study evidenced that for Sb(III) retention, phtalate buffers (1.0mM at pH=6) resulted the best alternative. Under optimal conditions, both substrates exhibited high adsorption capacities: 343mgSbg−1 NPC and 559mgSbg−1 pro-MWCNTs. The preconcentration factors reached were: 258 and 420 for NPC and pro-MWCNTs, respectively. The high adsorption capacity of both substrate allowed reaching detection limits (3σ) of 1.47 and 0.52ngL−1 for NPC and pro-MWCNTs, respectively when using a sorbent column containing only 1.0mg of sorbent. Precision, expressed as relative standard deviation (RSD) turned to be ~2% at the 0.1μgL−1 level (n=10) for both substrates. Trueness test for the entire analytical procedure was performed by means of the Standard Reference Material (SRM) NIST 1643e (Trace elements in water) and results were in good agreement with the certified values. The system was evaluated for quantitative determination of Sb(III) in different kind of waters. The method is simple and relatively cheap in comparison with other methodologies.

Total arsenic in selected food samples from Argentina: Estimation of their contribution to inorganic arsenic dietary intake

An optimized flow injection hydride generation atomic absorption spectroscopy (FI-HGAAS) method was used to determine total arsenic in selected food samples (beef, chicken, fish, milk, cheese, egg, rice, rice-based products, wheat flour, corn flour, oats, breakfast cereals, legumes and potatoes) and to estimate their contributions to inorganic arsenic dietary intake. The limit of detection (LOD) and limit of quantification (LOQ) values obtained were 6μgkg−1 and 18μgkg−1, respectively. The mean recovery range obtained for all food at a fortification level of 200μgkg−1 was 85–110%. Accuracy was evaluated using dogfish liver certified reference material (DOLT-3 NRC) for trace metals. The highest total arsenic concentrations (in μgkg−1) were found in fish (152–439), rice (87–316) and rice-based products (52–201). The contribution to inorganic arsenic (i-As) intake was calculated from the mean i-As content of each food (calculated by applying conversion factors to total arsenic data) and the mean consumption per day. The primary contributors to inorganic arsenic intake were wheat flour, including its proportion in wheat flour-based products (breads, pasta and cookies), followed by rice; both foods account for close to 53% and 17% of the intake, respectively. The i-As dietary intake, estimated as 10.7μgday−1, was significantly lower than that from drinking water in vast regions of Argentina.

Arsenic groundwater contamination and its health effects in Patna district (capital of Bihar) in the middle Ganga plain, India

We investigated the extent and severity of groundwater arsenic (As) contamination in five blocks in Patna district, Bihar, India along with As in biological samples and its health effects such as dermatological, neurological and obstetric outcome in some villages. We collected 1365 hand tube-well water samples and analyzed for As by the flow injection hydride generation atomic absorption spectrometer (FI-HG-AAS). We found 61% and 44% of the tube-wells had As above 10 and 50 μg/l, respectively, with maximum concentration of 1466 μg/l. Our medical team examined 712 villagers and registered 69 (9.7%) with arsenical skin lesions. Arsenical skin lesions were also observed in 9 children of 312 screened. We analyzed 176 biological samples (hair, nail and urine). Out of these, 69 people had arsenical skin lesions and rest without skin lesions. We found 100% of the biological samples had As above the normal levels (concentrations of As in hair, nail and urine of unexposed individuals usually ranges from 20 to 200 μg/kg, 20–500 μg/kg and <100 μg/l, respectively), indicating many people are sub-clinically affected. Arsenical neuropathy was observed in 40.5% of 37 arsenicosis patients with 73.3% prevalence for predominant sensory neuropathy and 26.7% for sensor-motor. Among patients, different clinical and electrophysiological neurological features and abnormal quantitative sensory perception thresholds were also noted. The study also found that As exposed women with severe skin lesions had adversely affected their pregnancies. People including children in the affected areas are in danger. To combat As situation in affected areas, villagers urgently need (a) provision of As-safe water for drinking and cooking, (b) awareness about the danger of As toxicity, and (c) nutritious food.

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

On-line solid phase extraction of bismuth by FI–HG–AAS using l-proline immobilised on carbon nanotubes combined with factorial design

This study explores further the analytical capabilities of functionalised multiwalled carbon nanotubes with l-proline (pro-MWCNTs) for the reliable preconcentration and determination of Bi(III) in waters using an on-line flow injection hydride generation atomic absorption spectrometry (FI–HG–AAS) system. To avoid carbon nanoparticles aggregation, the preconcentration was carried out on a microcolumn filled with functionalised pro-MWCNTs and a low molecular weight polyethylene. The optimisation was performed by employing a full factorial design. The factors related to the optimisation process were the concentration of eluent and pH of the sample. The best performance was achieved packing the substrate in a microcolumn of 2.3mm (i.d)×25mm (pro-MWCNTs net length: 10mm), the pH was 7.0 and the concentration of the eluent (HCl) was 10% (v/v). Under optimal conditions, the adsorption capacity of the substrate was found to be 0.1mgg−1 reaching a preconcentration factor (PF) of 160. A detection limit (3σ) of 0.7ngL−1 was achieved, when using only 3.0mg of substrate. Interferences affecting Bi(III) signal were carefully studied. Precision, expressed as relative standard deviation (RSD) turned to be 1.5% at the 0.1μgL−1 level (n=10). Accuracy test for the entire analytical procedure was performed by means of the Standard Reference Material (SRM) NIST 1643e (trace elements in water) and results were in good agreement with the certified values. The system was evaluated for quantitative determination of Bi(III) in different categories of waters.

Groundwater arsenic contamination in Bangladesh—21 Years of research

Department of Public Health Engineering (DPHE), Bangladesh first identified their groundwater arsenic contamination in 1993. But before the international arsenic conference in Dhaka in February 1998, the problem was not widely accepted. Even in the international arsenic conference in West-Bengal, India in February, 1995, representatives of international agencies in Bangladesh and Bangladesh government attended the conference but they denied the groundwater arsenic contamination in Bangladesh. School of Environmental Studies (SOES), Jadavpur University, Kolkata, India first identified arsenic patient in Bangladesh in 1992 and informed WHO, UNICEF of Bangladesh and Govt. of Bangladesh from April 1994 to August 1995. British Geological Survey (BGS) dug hand tube-wells in Bangladesh in 1980s and early 1990s but they did not test the water for arsenic. Again BGS came back to Bangladesh in 1992 to assess the quality of the water of the tube-wells they installed but they still did not test for arsenic when groundwater arsenic contamination and its health effects in West Bengal in Bengal delta was already published in WHO Bulletin in 1988. From December 1996, SOES in collaboration with Dhaka Community Hospital (DCH), Bangladesh started analyzing hand tube-wells for arsenic from all 64 districts in four geomorphologic regions of Bangladesh. So far over 54,000 tube-well water samples had been analyzed by flow injection hydride generation atomic absorption spectrometry (FI-HG-AAS). From SOES water analysis data at present we could assess status of arsenic groundwater contamination in four geo-morphological regions of Bangladesh and location of possible arsenic safe groundwater. SOES and DCH also made some preliminary work with their medical team to identify patients suffering from arsenic related diseases. SOES further analyzed few thousands biological samples (hair, nail, urine and skin scales) and foodstuffs for arsenic to know arsenic body burden and people sub-clinically affected. SOES and DCH made a few follow-up studies in some districts to know their overall situations after 9 to 18 years of their first exposure. The overall conclusion from these follow-up studies is (a) villagers are now more aware about the danger of drinking arsenic contaminated water (b) villagers are currently drinking less arsenic contaminated water (c) many villagers in affected village died of cancer (d) arsenic contaminated water is in use for agricultural irrigation and arsenic exposure from food chain could be future danger. Since at present more information is coming about health effects from low arsenic exposure, Bangladesh Government should immediately focus on their huge surface water management and reduce their permissible limit of arsenic in drinking water.