J. Mary Gladis

Preconcentration techniques for uranium(VI) and thorium(IV) prior to analytical determination- : an overview

The need for the preconcentration of trace and ultratrace amounts of uranium(VI) and thorium(IV) in conjunction with various detection techniques was clearly brought out in the introductory part. Subsequently, various off-line and on-line procedures developed for uranium(VI) and thorium(IV) prior to their analytical determination since 1990 were critically reviewed in terms of enrichment factor, retention/sorption capacity, validation using certified reference materials and application to complex real samples. The relative merits and demerits of various preconcentration and/or separation of uranium(VI) and thorium(IV) prior to quantitation by a plethora of analytical techniques are discussed in concluding part of the review article.

Amberlite XAD-4 functionalized with succinic acid for the solid phase extractive preconcentration and separation of uranium(VI)

Amberlite XAD-4 resin has been functionalized with succinic acid by coupling it with dibromosuccinic acid after acetylation. The resulting resin has been characterized by FT-IR, elemental analysis and TGA and has been used for preconcentrative separation of uranium(VI) from host of other inorganic species prior to its determination by spectrophotometry. The optimum pH value for quantitative sorption of uranium(VI) in both batch and column modes is 4.5-8.0 and desorption can be achieved by using 5.0ml of 1.0moll(-1) HCl. The sorption capacity of functionalized resin is 12.3mgg(-1). Calibration graphs were rectilinear over the uranium(VI) concentrations in the range 5-200mugl(-1). Five replicate determinations of 50mug of uranium(VI) present in 1000ml of solution gave a mean absorbance of 0.10 with a relative standard deviation of 2.56%. The detection limit corresponding to three times the standard deviation of the blank was found to be 2mugl(-1). Various cationic and anionic species at 200-fold amounts do not interfere during the preconcentration of 5.0mug of uranium(VI) present in 1000ml (batch) or 100ml (column) of sample solution. Further, adsorption kinetic and isotherm studies were also carried out by a batch method to understand the nature of sorption of uranium(VI) with the succinic acid functionalized resin. The accuracy of the developed solid phase extractive preconcentration method in conjunction with Arsenazo III procedure was tested by analyzing marine sediment (MESS-3) and soil (IAEA soil-7) reference material. Further, the above procedure has been successfully employed for the analysis of soil and sediment samples.

Preconcentrative separation of chromium(VI) species from chromium(III) by coprecipitation of its ethyl xanthate complex onto naphthalene

A rapid, sensitive and selective method is described for the determination of chromium(VI) in presence of 100-fold amounts of chromium(III) by flame atomic absorption spectrometry (FAAS) in conjunction with coprecipitative preconcentration of its ethyl xanthate complex onto naphthalene. The solid mixture consisting of the chromium(VI) complex together with naphthalene is dissolved in 8.0ml of dimethyl formamide (DMF) and chromium(VI) content was established by FAAS. Calibration graphs were rectilinear over the chromium(VI) concentration in the range 0-200mugl(-1). Five replicate determinations of 20mug of chromium(VI) present in 1.0l of sample solution gave a relative standard deviation of 3.1%. The detection limit corresponding to three times the standard deviation of the blank was found to be 0.5mugl(-1). The developed procedure has been successfully utilized for the estimation of chromium(VI), chromium(total) (after oxidation with bromate) and chromium(III) (by subtracting chromium(VI) content from chromium(total) value contents of several tannery industries.

Effect of γ-irradiation of ion imprinted polymer (IIP) particles for the preconcentrative separation of dysprosium from other selected lanthanides

The selectivity of zinc with respect to copper ions was improved by gamma-irradiation of surface imprinted polymer particles. We have reported the preparation of dysprosium ion imprinted polymer (IIP) particles by covalent approach during molecular imprinting. This paper reports the results obtained after gamma-irradiation of dysprosium IIP particles and their use in the preconcentration/separation of dysprosium from dilute aqueous solutions containing other selected lanthanides. Further, the characterisation of blank and dysprosium IIP particles was carried out either with and without irradiation by IR, thermogravimetric analysis (TGA), differential thermal analysis (DTA), XRD and surface area and pore size analysis techniques. The significant features observed in these experiments in the non-selectivity of blank polymer particles for dysprosium over other lanthanide ions and 35-180-fold enhancement in selectivity coefficients of irradiated dysprosium IIPs formed by covalent approach. In addition, the selectivity coefficients obtainable by gamma-irradiated were compared with unirradiated dysprosium IIP particles and separation factors obtained by liquid-liquid extraction separation using di(2-ethyl hexyl) phosphoric acid as extractant.

Overview of analytical methodologies for sea water analysis: Part I - Metals

A comprehensive, critical and up-to-date review of analytical methods developed during the last decade for metals present in sea water is presented. Separate sections are devoted to singular and multimetal determinations. Furthermore, a critical comparison of relative merits or demerits of a particular procedure is made in terms of sensitivity, selectivity and precision. Various aspects of analysis of sea water samples for metals are summarized, and the future trends are discussed.

Catechol functionalized aminopropyl silica gel : Synthesis, characterization and preconcentrative separation of uranium(VI) from thorium(IV)

Summary A novel solid phase extractant is prepared by chemically immobilizing catechol with diazotized aminopropyl silica gel. The resulting catechol functionalized silica gel (CASG) was characterized by FTIR, and microanalysis and was used for selective enrichment of uranium(VI) from other inorganic ions. The optimum pH range for maximum sorption of uranium(VI) and thorium(IV) was found to be in the range 3.5–6.0. The above actinides were eluted with 10 cm3 of 1.0 mol dm−3 HCl and determined by using an Arsenazo III spectrophotometric procedure. The calibration graph was rectilinear over the uranium(VI) concentration in the range 2–100 μg dm−3 with a relative standard deviation of 2.15% (for 25 μg of uranium(VI) present in 1.0 dm3 of sample). The validation of the developed preconcentration procedure was carried out by analyzing marine sediment (MESS-3, NRC, Canada) and soil (IAEA soil-7, Austria) reference materials. The developed preconcentration method enables a simple instruments like a spectrophotometer gave comparable values of uranium(VI) to that of standard inductively coupled plasma-mass spectrometric values during the analysis of real soil and sediment samples.

Solid phase extractive preconcentration of thorium onto 5,7-dichloroquinoline-8-ol modified benzophenone.

The preparation of solid reagent 5,7-dichloroquinoline-8-ol modified benzophenone for preconcentration of thorium is described. The thorium-5,7-dichloroquinoline-8-ol complex is quantitatively retained on benzophenone in the pH range 6.0-6.5. The solid mixture consisting of the metal complex together with benzophenone is dissolved in 5 ml of acetone and thorium content was established spectrophotometrically by using Arsenazo III procedure. Calibration graphs are rectilinear over the thorium concentration range 0.001-0.2 mug ml(-1). Five replicate determinations of 20 mug of thorium present in 1 l of sample solution gave a mean absorbance of 0.320 with a relative standard deviation of 2.9%. The detection limit corresponding to three times the standard deviation of the blank was found to be 0.0005 mug ml(-1). The developed procedure has been successfully utilized for the estimation of thorium content of pure Rare earth chloride solution collected from Indian Rare Earths (IRE) Limited, Alwaye.

Biomimetic Sensors for Toxic Pesticides and Inorganics based on Optoelectronic/Electrochemical Transducers—An Overview

Toxic pesticides and heavy metals constitute an important class of pollutants that degrade the environment due to their persistent nature and their unavoidable use in increasing the agricultural output and industrial importance respectively. The design and development of portable devices such as sensors rather than laboratory based instruments in monitoring the above species at trace levels in real samples is prime challenge to analytical chemists at this juncture. Because of the poor physical and chemical stability of biosensors despite their specificity and sensitivity preclude their use in environmental analysis. On the other hand, in conventional chemical sensors are beset with problems of selectivity. Molecularly imprinted polymers (MIPs) are being increasingly used as recognition elements in mimicking molecular/ionic recognition by natural receptors. A brief survey of synthetic strategies and characterization of MIPs, transducers that convert binding event into a detectable signal, integration strategies of recognition element with a suitable transducer and finally the reported sensors for toxic pesticides and inorganics is discussed. Future outlook of such biomimetic sensors in environmental analysis has been highlighted.

Synthesis of malonic acid-functionalized Amberlite XAD-4 and its use in solid phase extraction/preconcentrative separation of thorium(IV)

Summary A new chelating polymer has been developed wherein Amberlite XAD-4 has been functionalized by coupling it with diethylmalonate after acetylation. The resulting resin has been characterized by IR spectral and microanalysis studies and has been used for preconcentrative separation of thorium(IV) in the presence of alkali, alkaline earth, transition elements and lanthanides. Various physico-chemical parameters influencing the sorption of thorium(IV) onto the polymeric matrix was investigated and optimized by both batch and column methods. Quantitative extraction of thorium(IV) was obtained in the pH range 6.0–8.0. The sorption capacity of the malonic acid functionalized resin is 19.28 mg per g of polymer with an enrichment factor of 500. Moreover, the system showed faster exchange kinetics for extraction of thorium(IV) thus resulting in quantitative enrichment at flow rates as high as 16.0 cm3/min using 0.2 g of resin packed column (7 mm dia). Five replicate determinations of 10 μg of thorium(IV) present in 2.5 dm3 of sample solution gave a mean absorbance of 0.160 with a relative standard deviation of 2.54%. The detection limit corresponding to 3 times the standard deviation of the blank was found to be 0.2 μg dm3. The developed procedure has been successfully utilized for the estimation of thorium(IV) content of pure rare earth chloride solution collected from Indian Rare Earths Limited, Alwaye, India.

Quinoline-8-ol modified cellulose as solid phase extractant (SPE) for preconcentrative separation and determination of thorium(IV)

Abstract Cellulose has been functionalized by coupling with 5-chloro-quinoline-8-ol in the presence of alkali. The resulting polymer material has been characterized by IR spectra and has been used for preconcentrating thorium prior to its determination by spectrophotometry. The optimum pH value for quantitative extraction is 5.0–7.0 and can be eluted with 5cm3 of 1mol dm-3 of HCl. The retention capacity of the quinoline-8-ol modified cellulose is 20.0mg g-1. The effect of various cations, anions and neutral electrolytes on the preconcentration of thorium in conjunction with the determination procedure has been studied and we have found that none of interferents including uranium (up to 10 fold amounts) interfere. The enrichment factor for preconcentration of thorium was found to be 200. Ten replicate determinations of 10μg of thorium (IV) present in 1dm3 of sample gave a mean absorbance of 0.084 with a relative standard deviation 1.52. The detection limit (corresponding to three times the standard deviation of the blank) was found to be 2μg dm-3. The thorium content of mixed rare earth chloride solution obtained from Indian Rare Earths Limited (IRE), India was estimated by using quinoline-8-ol immobilized cellulose for preconcentration and subsequent determination by spectrophotometry.