J. Arunachalam

Preconcentration and speciation of inorganic and methyl mercury in waters using polyaniline and gold trap-CVAAS.

Applicability of polyaniline (PANI) has been investigated for the preconcentration and speciation of inorganic mercury (Hg(2+)) and methyl mercury (CH(3)Hg(+)) in various waters (ground, lake and sea waters). Preliminary experiments (batch) with powdered PANI for the quantitative removal of both Hg(2+) and CH(3)Hg(+) showed that the retention of Hg(2+) was almost independent of pH while a pH dependent trend from pH 1 to 12 was seen for CH(3)Hg(+) with maximum retention at pH>5. Time dependence batch studies showed that a contact time of 10min was sufficient to reach equilibrium. The K(d) values were found to be approximately 8x10(4) and approximately 7x10(3) for Hg(2+) and CH(3)Hg(+), respectively. Subsequently column experiments were carried out with PANI and the separation of the species was carried out by selective and sequential elution with 0.3% HCl for CH(3)Hg(+) and 0.3% HCl-0.02% thiourea for Hg(2+). This was then followed by further pre-concentration of mercury on a gold trap and its determination by CVAAS. The uptake efficiency studies showed that the PANI column was able to accumulate up to 100mgHg(2+)/g and 2.5mgCH(3)Hg(+)/g. This method allows both preconcentration and speciation of mercury with preconcentration factors around 120 and 60 for Hg(2+) and CH(3)Hg(+), respectively. The interfering effects of various foreign substances on the retention of mercury were investigated.

A rapid ultrasound-assisted thiourea extraction method for the determination of inorganic and methyl mercury in biological and environmental samples by CVAAS.

A rapid ultrasound-assisted extraction procedure for the determination of total mercury, inorganic and methyl mercury (MM) in various environmental matrices (animal tissues, samples of plant origin and coal fly ash) has been developed. The mercury contents were estimated by cold vapour atomic absorption spectrometry (CVAAS). Inorganic mercury (IM) was determined using SnCl(2) as reducing agent whereas total mercury was determined after oxidation of methyl mercury through UV irradiation. Operational parameters such as extractant composition (HNO(3) and thiourea), sonication time and sonication amplitude found to be different for different matrices and were optimized using IAEA-350 (Fish homogenate), IM and MM loaded moss and NIST-1633b (Coal fly ash) to get quantitative extraction of total mercury. The method was further validated through the analysis of additional certified reference materials (RM): NRCC-DORM2 (Dogfish muscle), NRCC-DOLT1 (Dogfish liver) and IAEA-336 (Lichen). Quantitative recovery of total Hg was achieved using mixtures of 5% HNO(3) and 0.02% thiourea, 10% HNO(3) and 0.02% thiourea, 20% HNO(3) and 0.2% thiourea for fish tissues, plant matrices and coal fly ash samples, respectively. The results obtained were in close agreement with certified values with an overall precision in the range of 5-15%. The proposed ultrasound-assisted extraction procedure significantly reduces the time required for sample treatment for the extraction of Hg species. The extracted mercury species are very stable even after 24h of sonication. Closed microwave digestion was also used for comparison purposes. The proposed method was applied for the determination of Hg in field samples of lichens, mosses, coal fly ash and coal samples.

A combined treatment approach using Fenton’s reagent and zero valent iron for the removal of arsenic from drinking water

Studies on the development of an arsenic remediation approach using Fentons reagent (H2O2 and Fe(II)) followed by passage through zero valent iron is reported. The efficiency of the process was investigated under various operating conditions. Potable municipal water and ground water samples spiked with arsenic(III) and (V) were used in the investigations. The arsenic content was determined by ICP-QMS. A HPLC-ICPMS procedure was used for the speciation and determination of both As(III) and (V) in the processed samples, to study the effectiveness of the oxidation step and the subsequent removal of the arsenic. The optimisation studies indicate that addition of 100 microl of H2O2 and 100 mg of Fe(II) (as ferrous ammonium sulphate) per litre of water for initial treatment followed by passing through zero valent iron, after a reaction time of 10 min, is capable of removing arsenic to lower than the US Environmental Protection Agency (EPA) guideline value of 10 microg/l, from a starting concentration of 2 mg/l of As(III). Using these suggested amounts, several experiments were carried out at different concentrations of As(III). Residual hydrogen peroxide in the processed samples can be eliminated by subsequent chlorination, making the water, thus, processed, suitable for drinking purposes. This approach is simple and cost effective for use at community levels.

Determination of elemental constituents in different matrix materials and flow injection studies by the electrolyte cathode glow discharge technique with a new design

An open-to-air type electrolyte cathode discharge (ELCAD) has been developed with a new design. The present configuration leads to a stable plasma even at low flow rates (0.96 mL/min). Plasma fluctuations arising from the variations in the gap between solid anode and liquid cathode were eliminated by providing a V-groove to the liquid glass-capillary. Cathode (ground) connection is given to the solution at the V-groove itself. Interfaced to atomic emission spectrometry (AES), its analytical performance is evaluated. The optimized molarity of the solution is 0.2 M. The analytical response curves for Ca, Cu, Cd, Pb, Hg, Fe, and Zn demonstrated good linearity. The limit of detections of Ca, Cu, Cd, Pb, Hg, Fe, and Zn are determined to be 17, 11, 5, 45, 15, 28, and 3 ng mL(-1). At an integration time of 0.3 s, the relative standard deviation (RSD) values of the acid blank solutions are found to be less than 10% for the elements Ca, Cu, Cd, Hg, Fe, and Zn and 18% for Pb. The method is applied for the determination of the elemental constituents in different matrix materials such as tuna fish (IAEA-350), oyster tissue (NIST SRM 1566a), and coal fly ash (CFA SRM 1633b). The obtained results are in good agreement with the certified values. The accuracy is found to be between 7% and 0.6% for major to trace levels of constituent elements and the precision between 11% and 0.6%. For the injection of 100 microL of 200 ng mL(-1) mercury solution at the flow rate of 0.8 mL/min, the flow injection studies resulted in the relative standard deviation (RSD) of 8%, concentration detection limit of 10 ng/mL, and mass detection limit of 1 ng for mercury.

Study of mercury pollution near a thermometer factory using lichens and mosses

Mercury has a widespread environmental distribution, originating both from anthropogenic and natural processes. Once in the air, mercury can be widely dispersed and transported to longer distances. In the environment mercury can exist in a number of physical and chemical forms with toxicity is well known to be highly dependent on chemical form (Clarkson, 1997). As a consequence, considerable effort and progress has been made in the development of techniques for the separation and identification of individual mercury species in environmental samples (Sanchez Uria and SanzMedel, 1998). Biomonitoring using lichens and mosses is an effective method for assessing the levels of atmospheric trace element pollution including mercury (Merian, 1991; Conti and Cecchetti, 2001; Horvat et al., 2000) as lichens and mosses pick up nutrients directly from ambient air and deposition retaining many trace elements (Ruhling and Tyler, 1968). In this work, mercury contamination due to a mercury thermometer-making factory situated in the hill station Kodaikkanal (about 2120 m above mean sea level), in a southern state of India, was investigated using lichen (Parmelia sulcata) and moss (Funaria hygrometrica) samples. The content of mercury in these samples collected from different sites was determined using CV-AAS mercury analyzer and ICP–QMS in order to obtain information on the extent of mercury contamination. As mercury undergoes extensive transformation into various forms as it cycles among the atmosphere, land and water (Ebadian et al., 2001), we have carried out investigations to establish the chemical form of mercury—elemental (Hg), inorganic (Hg) or organic—in these chosen biomonitors.

Feature extraction from spectral and other data by the principal components and discriminant function techniques

Abstract Principal component analysis is applied to the interpretation of 13 C-n.m.r. spectra and to the resolution of mass spectral data. A procedure is given for determining the relative amounts of pure components, with and without the use of pure mass lines, in mass spectra of mixtures. The use of the Fisher discriminant method in combination with the principal components technique is demonstrated in the treatment of trace element data on hair for environmental purposes. The importance of feature generation and selection is emphasized.

Determination of inorganic selenium species [Se(IV) and Se(VI)] in tube well water samples in Punjab, India.

Abstract Tube-well water samples in several parts of the Northeastern region of Indian Punjab, where extensive cases of selenosis were reported earlier, have been analyzed for Se(IV) and Se(VI). The total selenium in tube well water samples range from 12 to 93 μgL−1. No speciation information has been reported so far in these water samples. Bioavailability of selenium from water is affected by its various chemical forms. As selenate and selenite are the dominant forms of Se in water, an ion-chromatography–inductively coupled plasma mass spectrometry (IC–ICPMS) method was developed for the on-line separation of selenite [Se(IV)] and selenate [Se(VI)] and their determination in the tube well water samples. The selenium species were separated using an anion exchange column. A good baseline separation of both the species was obtained within 11 minutes. The detection limits for the Se species are Se(IV) = 0.3μgL−1 and Se(VI) = 0.8μgL−1. An eluent suppressor was used after the analytical column to reduce the salt content of the eluent: NaOH and the water sample. The dominant selenium species identified in these tube well water samples was found to be Se(VI). The concentration of total inorganic selenium in many of the water samples analyzed in this study exceeded the WHO limit (10μgL−1).

Trace element analysis of high purity arsenic through vapour phase dissolution and ICP-QMS.

Vapour phase dissolution (VPD) has been used for the dissolution of high purity arsenic through acid vapours generated by aquaregia mixture, prior to trace element characterization. Trace impurities in As were determined by employing ion-exchange and volatilization methodologies for quantitative separation of the As matrix. After dissolving the As matrix through VPD procedure, sample solution in 0.1 M HF medium was loaded on Dowex-50WX8. The sorbed elements were then eluted first with a 20 ml aliquot of 4 M HNO(3) followed by another 10 ml of 6 M HNO(3) for the elution of REE (La, Ce, Gd and Lu). In the volatilization procedure, arsenic was removed from H(2)SO(4) medium as volatile bromide by three successive additions of HBr at a temperature of about 220 degrees C. The trace element determinations were carried out by ICP-QMS. In both the matrix separation procedures namely on Dowex-50WX8 in 0.1 M HF medium and volatilization from H(2)SO(4)+HBr medium showed that the removal of arsenic matrix was nearly quantitative (>99.99%). The recoveries of trace elements were found to be >95%. Good agreement was obtained for many elements in both the procedures. The VPD approach provides considerable reduction of the process blank levels for all the elements when compared with conventional open dissolution approach. The subsequent ion-exchange or volatilization steps, contribute more to the overall process blanks.