Manas Kanti Deb

Direct and rapid determination of sulphate in environmental samples with diffuse reflectance Fourier transform infrared spectroscopy using KBr substrate

The feasibility of employing diffuse reflectance Fourier transform infrared spectroscopy (DRS-FTIR) as a sensitive tool in the submicrogram level determination of sulphate (SO(4)(2-)) was checked in this work. This paper presents the development of a new, rapid and precise analytical method for ppb levels of sulphate (SO(4)(2-)) in environmental samples like coarse and fine aerosol particles, dry deposits and soil. The determination of submicrogram levels of sulphate is based on the selection of a quantitative analytical peak at 617cm(-1) among the three observed vibrational peaks and preparing calibration curve using different known concentrations of sulphate by diffuse reflectance-Fourier transform infra red spectrometric (DRS-FTIR) technique. Pre-weighed and ground IR grade KBr was used as substrate over which remarkably wide range of known concentration of sulphate was sprayed and dried. The dried sample was analysed by DRS-FTIR. Three calibration curves for three different concentration ranges of sulphate were prepared for samples containing low and relatively higher sulphate contents. The relative standard deviation (n=8) for the sulphate concentration ranges, 2.5-35.5, 25.5-165, 55-1000mug/0.5g KBr, as used to prepare calibration curves, were 2.4%, 2.1% and 1.5%, respectively. The relative standard deviation for the sulphate concentration in real samples were found to be in the range, 3.11-5.76% (n=16), 4.05-7.75% (n=16) and 1.48-3.52% (n=10) for aerosol, dry deposits and soil, respectively. The LOD of the method is 0.20mug/g SO(4)(2-). The F- and t-tests were performed to check the analytical quality assurance test. The noteworthy feature of the reported method is the non-interference of any of the associated anions and cations. The results were compared with that of ion-chromatographic method with high degree of acceptability. The method can be applied in wide concentration ranges. A method for sulphate determination was introduced that did not require pretreatment of samples. This method employed the direct determination of the sulphate. The method is reagent less, nondestructive, very fast, repeatable, and accurate and has high sample throughput value.

Single-drop micro-extraction and diffuse reflectance Fourier transform infrared spectroscopic determination of chromium in biological fluids

The present paper deals with a new micro-extraction procedure for selective separation of Cr(VI) in the form of a metaloxy anionic species namely dichromate (Cr(2)O(7)(2-)) with N(1)-hydroxy-N(1),N(2)-diphenylbenzamidine (HOA) in to dichloromethane and its subsequent and rapid diffuse reflectance Fourier transform infrared spectroscopic (DRS-FTIR) determination employing potassium bromide matrix. The diffuse reflectance Fourier transform infrared spectroscopy gives both qualitative and quantitative information about the dichromate. The determination of chromium is based on the analytical peak selection, among the various vibrational peaks, at 902 cm(-1). The micro-extraction was based on the liquid-liquid solvent extraction (LLSE) principle. The dichromate binds with the nitrogen and oxygen atoms of N(1)-hydroxy-N(1),N(2)-diphenylbenzamidine (HOA) and forms 1:2, Cr(VI):HOA complex in 0.1 mol L(-1) HCl medium. The formation of above complex, in the acidic medium, is confirmed by the appearance of chocolate-brown color in the micro-extract. The speciation studies of Cr(III) and Cr(VI) is done by conversion of Cr(III) into Cr(VI) utilizing H(2)O(2) as an oxidizing agent. The chemistry of pure dichromate and that of its HOA complex is discussed. The limit of detection (LoD) and the limit of quantification (LoQ) of the method are found to be 0.01 microg g(-1) Cr(2)O(7)(2-) and 0.05 microg g(-1) Cr(2)O(7)(2-), respectively. The standard deviation value and the relative standard value at a level of 10 microg Cr(2)O(7)(2-)/0.1g KBr for n=10 is found to be 0.26 microg Cr(2)O(7)(2-) and 2.6%, respectively. The relative standard deviation (n=8 and 6) for the determination of dichromate (Cr(2)O(7)(2-)) in real human biological fluid samples is observed to be in the range 3.1-7.8%.

Microwave-assisted synthesis of platinum nanoparticles and their catalytic degradation of methyl violet in aqueous solution

A green synthesis of polyvinylpyrrolidone stabilized platinum nanoparticles (PtNPs) has been done by microwave irradiation in the presence of glucose. The formation process of the PtNPs is pursued by UV–visible spectroscopy. The morphology of the PtNPs was characterized by transmission electron microscopy and X-ray diffraction techniques. Catalytic activity of the above PtNPs has been substantiated through photodecolorization of aqueous methyl violet solution.

Assessment of Atmospheric Arsenic Level in Airborne Dust Particulates of an Urban City of Central India

An assessment of arsenic contamination in Raipur city (21°14′N, 18°38′E) of Chhattisgarh in the central part of India is reported here, for a monitoring period between November 1996 to June 1997, in airborne dust particulates. The concentration level of As were higher in the industrial site, followed by heavy traffic as compared to other sites. The monthly atmospheric arsenic deposition, in μg As per g of dust fall, of 6 sites are in the range of 0.100(μ0.020)–4.00(μ0.020); site no. 1 industrial area, 0.100(μ0.020)–0.320(μ0.020); site no. 2 residential area, 0.044(μ0.070)–0.337(μ0.030); site no. 3 commercial area, 0.093(μ0.068)–1.870(μ0.020); site no. 4 residential area, 0.111(μ0.020)–1.912(μ0.010); site no. 5 residential area and 0.068(μ0.040)–3.037(μ0.060); site no. 6 heavy traffic area. The total annual flux of As in the fall-out at different zones is in the range 0.033–1.12 kg km-2 yr-1. The month wise collection and analysis of dust fall out rate between 3.0(μ0.10)–91.3(μ1.4) mt (metric tonnes) km-2 month-1 were observed at all 6 sampling sites. Anthropogenic and environmental factors play important roles in the contribution of arsenic in airborne particulate matters.

Cloud point extraction and diffuse reflectance-Fourier transform infrared spectroscopic determination of chromium(VI): A probe to adulteration in food stuffs

A new cloud point extraction (CPE) method for the determination of hexavalent chromium i.e. Cr(VI) in food samples is established with subsequent diffuse reflectance-Fourier transform infrared (DRS-FTIR) analysis. The method demonstrates enrichment of Cr(VI) after its complexation with 1,5-diphenylcarbazide. The reddish-violet complex formed showed λmax at 540nm. Micellar phase separation at cloud point temperature of non-ionic surfactant, Triton X-100 occurred and complex was entrapped in surfactant and analyzed using DRS-FTIR. Under optimized conditions, the limit of detection (LOD) and quantification (LOQ) were 1.22 and 4.02μgmL-1, respectively. Excellent linearity with correlation coefficient value of 0.94 was found for the concentration range of 1-100μgmL-1. At 10μgmL-1 the standard deviation for 7 replicate measurements was found to be 0.11μgmL-1. The method was successfully applied to commercially marketed food stuffs, and good recoveries (81-112%) were obtained by spiking the real samples.

Dicarboxylic acids, ω-oxocarboxylic acids, α-dicarbonyls, WSOC, OC, EC, and inorganic ions in wintertime size-segregated aerosols from central India: Sources and formation processes

The size distributions of aerosols can provide evidences for their sources and formation processes in the atmosphere. Size-segregated aerosols (9-sizes) were collected in urban site (Raipur: 21.2°N and 82.3°E) in central India during winter of 2012-2013. The samples were analyzed for dicarboxylic acids (C2-C12), ω-oxocarboxylic acids (ωC2-ωC9), pyruvic acid and α-dicarbonyls (C2-C3) as well as elemental carbon (EC), organic carbon (OC), water-soluble OC (WSOC) and inorganic ions. Diacids showed a predominance of oxalic acid (C2) followed by succinic and azelaic acid whereas ω-oxoacids exhibited a predominance of glyoxylic acid and glyoxal was more abundant than methylglyoxal in all the sizes. Diacids, ω-oxoacids and α-dicarbonyls showed bimodal size distribution with peaks in fine and coarse modes. High correlations of fine mode diacids and related compounds with potassium and levoglucosan suggest that they were presumably due to a substantial contribution of primary emission from biomass burning and secondary production from biomass burning derived precursors. High correlations of C2 with higher carbon number diacids (C3-C9) suggest that they have similar sources and C2 may be produced via the decay of its higher homologous diacids in fine mode. Considerable portions of diacids and related compounds in coarse mode suggest that they were associated with mineral dust particles by their adsorption and photooxidation of anthropogenic and biogenic precursors via heterogeneous reaction on dust surface. This study demonstrates that biomass burning and dust particles are two major factors to control the size distribution of diacids and related compounds in the urban aerosols from central India.

Microwave green synthesis of PVP-stabilised gold nanoparticles and their adsorption behaviour for methyl orange

In this work, gold nanoparticles (AuNPs) were prepared by the microwave irradiation method and comparative studies on the removal of dye by adsorption on activated carbon (AC) and polyvinylpyrrolidone (PVP)-supported AuNPs-coated AC were made. The uniform and stable AuNPs were prepared by the reduction of gold chloride (HAuCl4) using glucose as reducing agent and PVP as a stabilising and capping agent. The resulting AuNPs were characterised by transmission electron microscopy (TEM) and UV-Vis spectroscopy. The TEM technique showed the presence of AuNPs with an average size of 20 nm. The effect of various process parameters has been investigated by following the column adsorption technique at room temperature. Percentage removal of dye increased with the decrease in initial concentration and increased with the increase in contact time. Adsorption data were modelled with the Freundlich isotherms. The Freundlich isotherm model has been applied to the equilibrium adsorption data. Desorption studies were made to elucidate recovery of the adsorbate and adsorbent for the economic competitiveness of the removal system. The adsorption capacity of the water-desorbed adsorbate reduced from 97% to 60% for n = 6 cycles.

Efficient Sorption of Basic Organic Dyes from Aqueous Solution Using Green Synthesized Silver Nanoparticles Beads

In this article, the potential of alginate stabilized silver nanoparticles beads for efficient sorption of methylene blue, malachite green, and rhodamine B from aqueous solutions was investigated. The adsorption data have been correlated with both Freundlich and Langmuir adsorption models. The kinetic studies for dyes adsorption showed rapid sorption dynamics by second-order kinetic model. The common problem of classical adsorbents towards efficient recyclability was overcome when alginate stabilized silver nanoparticles beads was used. The alginate stabilized silver nanoparticles beads were successfully recycled for 25 successive adsorption-desorption cycles indicating its high reusability.

Sources and formation processes of water‐soluble dicarboxylic acids, ω‐oxocarboxylic acids, α‐dicarbonyls, and major ions in summer aerosols from eastern central India

The sources and formation processes of dicarboxylic acids are still under investigation. Size-segregated aerosol (9-sizes) samples collected in the urban site (Raipur: 21.2°N and 82.3°E) in eastern central India during summer of 2013 were measured for water-soluble diacids (C2-C12), ω-oxoacids (ωC2-ωC9), α-dicarbonyls (C2-C3), and inorganic ions to better understand their sources and formation processes. Diacids showed the predominance of oxalic acid (C2), whereas ω-oxoacids showed the predominance of glyoxylic acid (ωC2), and glyoxal (Gly) was a major α-dicarbonyl in all the sizes. Diacids, ω-oxoacids, and α-dicarbonyls as well as SO42-, NO3-, and NH4+ were enriched in coarse mode, where Ca2+ peaked, suggesting that they are preferentially produced in coarse mode via adsorption as well as heterogeneous and aqueous-phase oxidation reaction of precursors on the surface of water-soluble mineral dust particles having more alkaline species. Strong correlations of diacids and related compounds with NO3- (r = 0.66-0.91) and aerosol water content (AWC) (r = 0.63-0.93) further suggest an importance of heterogeneous and aqueous-phase production in coarse mode. We found strong correlations of C2/(C2-C12), C2/ωC2, and C2/Gly ratios with AWC in coarse mode (r = 0.83, 0.86, and 0.85, respectively), indicating that enhanced AWC is favorable for the production of C2 diacid through aqueous-phase oxidation of its higher homologous diacids, ωC2, and Gly. These results demonstrates unique reactivity of water-soluble mineral dust particles for the enhanced production of diacids and related compounds in aqueous-phase, having implications on the aerosol-cloud interaction, solubility, and hygroscopicity of a dominant fraction of water-soluble organic aerosol mass. [250]

Synthesis of silver nanoparticles using N 1, N 2-diphenylbenzamidine by microwave irradiation method

Silver nanoparticles have been prepared under microwave irradiation from a solution of silver nitrate in the presence of N 1,N 2-diphenylbenzamidine (DPBA) or simply amidine without any stabilizing agent. Different morphologies of silver colloids with charming colors could be obtained using N 1,N 2-diphenylbenzamidine (DPBA). The structures of silver colloids were determined by TEM. UV-Vis spectroscopy was used to follow the reaction process and to characterize the optical properties of the resultant silver colloids. The influence of unconventional reducing agent on the morphology of silver was investigated.