Arabinda K. Das

Metal speciation in solid matrices

The literature on metal ion speciation in solid matrices is reviewed, taking into account its applications in the analysis of soil, sediment, biological materials, foodstuff and other solid samples. The pretreatment methods of various solid materials required for carrying out speciation studies have been highlighted. The basis of the methods of separation of different species from matrices, such as sequential extraction, selective extraction, etc. is discussed. The instrumental techniques used for the characterization of different chemical species in solid matrices have been mentioned. The literature survey reveals the analytical details of the developed methodologies, and these have been examined in terms of the limit of detection, precision and accuracy.

Literature survey of on-line elemental speciation in aqueous solutions

The literature about the on-line speciation in water has been comprehensively studied. Critical examination of this subject reveals that a great deal of work has been performed in this area for inorganic metal species and some organic compounds. The topic studied mainly includes the speciation of chromium, selenium, copper, arsenic, lead, cadmium, mercury, iron, aluminium, nickel, tin, antimony, phosphorus, nitrogen and others. The present literature survey includes also comments about the possibilities and problems of speciation as a function of analytical steps, general strategies involved and methods proposed in the literature for each element or a series of elements.

Synthesis and characterization of a new resin functionalized with 2-naphthol-3,6-disulfonic acid and its application for the speciation of chromium in natural water

A polystyrene divinyl benzene (8%) copolymer has been functionalized by coupling it through NN group with 2-naphthol-3,6-disulfonic acid (NDSA). The resulting resin has been characterized by elemental analysis, thermogravimetric analysis and infrared spectra. The hydrogen ion, water regain and metal ion capacities of the resin have been determined. Two forms of chromium show different exchange capacities at different pH values, viz. Cr(III) selectively retained at pH 6.5 whereas Cr(VI) retained at pH 1.5. Hence complete separation of the two forms of chromium is possible. The kinetic studies show that the exchange of Cr(III) and Cr(VI) follows second-order kinetics. The metal ion concentration was measured by flame atomic absorption spectrometry. The method has been successfully applied for the speciation of chromium in natural water samples.

A review on molybdenum determination in solid geological samples

This review highlights the necessity for the development of proper sampling and storage, fast pretreatment methodology followed by highly sensitive detection for the determination of molybdenum in geological samples. Distribution of concentration and chemical speciation of molybdenum analysis in solid geological matrices have also been discussed.

Metal speciation in biological fluids — a review

The literature on the speciation of metal ions in biological fluids is comprehensively reviewed. Critical examination on this subject reveals that major work has been done in blood and urine. Speciation in materials like milk has not yet been widely studied. On the other hand, only few references could be found on sweat, saliva, cell lysate, cerebrospinal, seminal, tear and bronchoalveolar fluids. The topics studied for these fluids were mainly the speciation of arsenic, mercury, aluminium and selenium. Work on the speciation of other elements like zinc, chromium, cadmium, lead, copper, iron etc. have also been carried out in such matrices. The present literature survey includes also a critical comment about the sampling and storage of the fluids, general methodologies and analytical details of the developed methods for studying such metal ion speciation.

ICP-MS multielement determination in fly ash after microwave-assisted digestion of samples

A microwave assisted digestion procedure has been developed for dissolution of fly ash samples prior to the inductively coupled plasma-mass spectrometric determination of their elemental composition. The developed methodology was validated by carrying out the analysis of two high-silicate containing reference materials (CRM 134R sewage amended soil and NIES JR 1 rock) and by means of the comparison between results found by microwave-assisted digestion and ICP-MS of fly ash samples with those found by neutron activation analysis (NAA) for Sb, Cs, Cr, Co, Fe, U and Zn determination. The method developed can be recommended for routine multielement analysis of fly ash.

Inorganic arsenic species in groundwater: A case study from Purbasthali (Burdwan), India

A regional groundwater quality survey from 20 tube wells in the Purbasthali area of the Burdwan district of West Bengal province (India) identified arsenic pollution in this area. Arsenic was detected in 19 cases at a concentration level 0.5 to 135.9 micrograms/L. Speciation studies indicate that As(III) is present in only one sample and organo-arsenic compounds have not been detected. Iron, antimony and pH of such water samples were also studied to see if there is any correlation of the presence of arsenic and these parameters. A high concentration of iron (0.3 to 10.7 mg/L) has been detected. Antimony is present in all these water samples (0.03 to 0.9 microgram/L). The pH value of the groundwater in this area shows that it is more or less neutral.

Determination of chromium by electrothermal atomic absorption spectrometry after rapid microwave-assisted digestion of sediment and botanical samples

Determination of chromium by electrothermal atomization atomic absorption spectrometry with normal electrographite tube has been investigated after microwave-assisted digestion of sediment and botanical samples. Microwave oven-assisted procedures involve digestion with aqua regia, HF (for sediments) and H2O2 in a poly (tetrafluoroethylene)(PTFE) reactor followed by treatment with saturated H3BO3(where HF is used in the earlier step). Comparative studies on the determination of chromium using three previously reported chemical modifiers, Mg(NO3)2, Pd(NO3)2 and Triton X-100, and a new modifier NaVO3, have been made. Sodium vanadate was identified as an effective chemical modifier for chromium in botanical samples such as tomato leaves and citrus leaves. Whereas, for river sediment and sewage sludge, chromium has been determined accurately without the need of any chemical modifier. The advantages of the present method are its simplicity, low cost, high speed of sample attack and rapid calibration.

Removal of arsenic from drinking water using modified fly-ash bed

The removal of arsenic from drinking water by filtration through modified fly-ash bed is discussed. The preparation and characteristics of the bed material and the effects of different parameters like pH and the presence of other constituents are described. Various arsenic compounds in synthetic mixtures as well as drinking water samples containing arsenic have been investigated. The effectiveness of the modified fly-ash bed for the control of arsenic has been demonstrated by taking different quantities of arsenic(III) and arsenic(V) salts. The results of filtering through fly-ash bed were found to be satisfactory which makes it a low cost treatment method for the removal of arsenic, improving the quality of drinking water. The utilisation of the bed material after use is also discussed.

Indirect determination of free cyanide in industrial waste effluent by atomic absorption spectrometry

An indirect method is described for the determination of free cyanide in industrial waste effluent samples by atomic absorption spectrometry (AAS). In an alkaline medium, cyanide forms a stable complex species [Cu(BPTC)(CN)] (BPTC = 2-benzoylpyridine thiosemicarbazone), which can be extracted into a mixture of isobutyl methyl ketone-isopentyl alcohol (7 + 1) with an efficiency of greater than 98.5%. The extract can be analysed directly for copper (and hence indirectly for cyanide) by flame AAS. The calibration graph is linear up to 5.7 micrograms of cyanide per millilitre of solvent mixture and the limit of detection is 4.8 ng ml-1. A large number of foreign ions were found not to interfere with the proposed method.