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The chromatographic behavior of eight pesticides has been examined on cationic-micelles impregnated silica layers using mixed organic solvent (different combinations of hexane-acetone, v/v) systems. The chromatographic system constituting 0.01% CTAB (N-cetyl-N,N,N-trimethyl ammonium bromide) impregnated silica gel as stationary phase, and hexane-acetone in 1:1 ratio (v/v) as mobile phase was most favorable for on-plate identification of pesticides with preliminary separation. Surface modification of silica gel on impregnation, as indicated by SEM and FTIR studies was responsible for improved chromatographic performance. The results obtained on 0.01% CTAB impregnated silica layers were compared with those achieved on 0.01% CTAB impregnated kieselguhr, cellulose, or alumina layers. With selected chromatographic system, fivecomponent mixtures of pesticides (glyphosate, acephate, chlorpyrifos, malathion/methyl parathion, and isoproturon) were successfully resolved. The interference of metal cations as impurities on separation of pesticides from their mixtures was also examined. The developed method was successfully applied to the identification of pesticides in cereals, vegetables, and fruit grains. The applicability of the proposed method for the identification of five-component mixture of pesticides present in maize grains was also tested after separation on TLC plates. The limit of detection of glyphosate, acephate, chlorpyrifos, malathion, methyl parathion, and isoproturon was ≈20 μg per zone. For validation and reproducibility of the developed method, standard deviation (SD), ΔR F, and separation factor (α) were calculated.

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Abstract  

A flow injection on-line determination of uranium(VI) after preconcentration in a minicolumn having amberlite XAD-4 resin impregnated with dibenzoylmethane (DBM) is described. Uranium(VI) is selectively adsorbed from aqueous solution of pH 5.5 in the minicolumn (5.5 cm long with 5.0 mm i.d.) at a flow rate of 13.6 mL min−1. The uranium(VI) complex was desorbed from the resin by 0.1 mol dm−3 HCl at a flow rate of 4.2 mL min−1 and mixed with arsenazo-III solution (0.05% solution in 0.1 mol dm−3 HCl, 4.2 mL min−1), and taken to the flow through cell of spectrophotometer where its absorbance was measured at 651 nm. Various parameters affecting the complex formation and its elution were optimized. Peak height (absorbance) was used for data analyses. The preconcentration factors of 36 and 143, detection limits of 0.9 and 0.232 μg L−1, sample throughputs of 40 and 10 were obtained for preconcentration time of 60 and 300 s, respectively. The tolerance limits of many interfering cations like Th(IV) and rare-earth elements were improved. The proposed method was applied on different water (spiked tap, well and sea water) and biological samples and good recovery was obtained. The method was also validated on mocked uranium ore sample and the results were in good agreement with the reported value.

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Abstract  

A very sensitive and selective flow injection on-line determination method of thorium (IV) after preconcentration in a minicolumn having XAD-4 resin impregnated with N-benzoylphenylhydroxylamine is described. Thorium (IV) was selectively adsorbed from aqueous solution of pH 4.5 in a minicolumn at a flow rate of 13.6 mL min−1, eluted with 3.6 mol dm−3 HCl (5.6 mL min−1), mixed with arsenazo-III (0.05% in 3.6 mol dm−3 HCl stabilized with 1% Triton X-100, 5.6 mL min−1) at confluence point and taken to the flow through cell of spectrophotometer where its absorbance was measured at 660 nm. Peak height was used for data analyses. The preconcentration factors obtained were 32 and 162, detection limits of 0.76 and 0.150 μg L−1, sample throughputs of 40 and 11 h−1 for preconcentration times of 60 and 300 s, respectively. The tolerance levels for Zr(IV) and U(VI) metal ions is increased to 50-folds higher concentration to Th(IV). The proposed method was applied on different spiked tap water, sea water and biological sample and good recovery was obtained. The method was also applied on certified reference material IAEA-SL1 (Lake Sediment) for the determination of thorium and the results were in good agreement with the reported value.

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Introduction Agricultural residues represent an important but mostly unused source for composite preparation. The goal of this study was to learn if some agricultural residues could find application as a source for impregnation

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Journal of Thermal Analysis and Calorimetry
Authors: Sanjiv Arora, Mahesh Kumar, and Mahender Kumar

, and boron. Blasi et al. [ 5 ] worked on the thermal and catalytic decomposition of impregnated wood with sulfur and phosphorus compounds containing ammonium salts. Further, Luneva and Petrovskaya [ 6 ] have clarified the thermal decomposition and

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the oxidation of alcohols. However, whatever impregnation method was adopted in the literatures mentioned above, the structures of the supports would decompose because most of the zinc-containing structures are very sensitive to water [ 15 ] even in

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Abstract  

Adsorption behaviour of the individual tracer ions:134Cs(I),85,89Sr(II),131,133Ba (II),90Y(III),141Ce(III),152,154Eu(III),95Zr(IV),175,181Hf(IV),95Nb(V),60Co(II),115Cd(II),99mTc(VII), and131I(-I) on charcoal impregnated with stannic chloride from Hcl solutions, was investigated. Batch equilibrium distribution coefficients of the respective ions indicated strong anion exchange properties towards impregnated charcoal. The column breakthrough sorption capacity was of the order of 0.62–0.66 meq·g–1 of dry adsorbent. Small chromatographic columns of impregnated charcoal could achieve rapid and quantitative separation procedures in HCl medium. Strongly adsorbed anions such as TcO 4 and I ions could be eluted with NH4SCN and NH4NO2 eluents, respectively.

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Abstract  

Ion-exchange papers were prepared by impregnating chromatographic Whatman No. 3 paper with pyridinium tungstoarsenate exchanger. The composition of the material loaded on the paper shows that the compound has the formula (C5H5NH)3 W1 2AsO4 0·Rf values of 30 metal ions were determined on these ion-exchange papers by developing with ascending technique in solvents containing mixtures of n-propanol and hydrochloric or nitric acid. Several binary, ternary and some quaternary separations were also achieved on these papers. Studies were also made on plain papers for comparison.

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Abstract  

A new ion exchange material prepared by impregnating Aliquat-336 on silica-gel has been investigated for the recovery of plutonium from nitric-oxalic acid solutions. The distribution ratio of Pu(IV) was studied at various concentrations of nitric and oxalic acids. The presence of Al(III) and Fe(III) in the solution, enhances the uptake of Pu(IV). Pu(IV) breakthrough capacities (btc) have been determined using 2.5 ml bed of the ion exchange material column in the absence and the presence of Al(III) and Fe(III) nitrate. The elution behavior of Pu(IV) was also studied using nitric acid solutions containing reducing agents. More than 90% of plutonium could be recovered from nitric-oxalic acid solutions.

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Abstract  

Sorption of uranium(VI) has been inbestigated using an open-cell plyurethane foam impregnated with 5,8-diethyl-7-hydroxy-6-dodecanone oxime (LIX 63). Above pH 4.5 more than 99% of uranium is sorbed onto the LIX 63 impregnated foam, and uranium can be desorbed with a dilute acid from the foam. The sorption capacity for uranium increases linearly with increasing concentration of impregnated LIX 63. Quantitative removal of uranium from salt solutions was accomplished.

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