Separation and preconcentration of lead from aquatic environment using Microcystis--based biosorbent.

The naturally abundant Microcystis surrounded by a slime layer has been immobilized as biofilm on a polymer-modified silica gel to obtain a lead-selective robust column packing material which is recyclable for 70 times without any distinct deterioration. The biosorbent has shown quantitative sorption with a preconcentration factor of 83 for trace level lead ion (initial concentration 0.48 microg ml(-1)) in multielemental/natural water samples at pH 5.0 and flow rate 1.0 ml min(-1).

Determination of cefaclor by selective sample enrichment/clean-up on silica gel bonded polyelectrolyte in ion-exchange column chromatography.

A silica gel-bound cationic polyelectrolyte, poly[N-chloranil N,N,N',N'- tetramethylethylene diammonium dichloride], modified as ion-exchanger capable of molecular recognition of beta-lactam antibiotic, was used in solid phase extraction through column chromatography for a sample clean-up and enrichment of analyte from a dilute solution. The optimum and selective sorption conditions for a model antibiotic, cefaclor, were established. The high selectivity of polymer at pH 9.5 and flow rate as high as 5 ml/min were observed for the quantitative sorption of cefaclor. The desorption by 0.1 N HCl at flow rate of 0.1 ml/min and subsequent heating at 80 degrees C for 2 h allowed the antibiotic to be detected as corresponding oxazolone form in UV-spectrophotometric and differential pulse adsorptive stripping voltammetric measurements. The potential of the suggested approach was illustrated by estimating cefaclor in urine and blood plasma samples.

Evaluation of metal fractions in river sediments and waters: application of chelation chromatography-differential pulse anodic stripping voltammetry.

The ability of chelation chromatography in combination with differential pulse anodic stripping voltammetry (DPASV) to provide a simple, fast and reliable way of dealing with interionic interferences, competitive complexations, re-adsorption of released metal ions and sorption of spiking metal ions by organic/inorganic materials in the complex matrixes of real natural samples has been critically examined. The technique is based on the selective complexation of target metal fractions on some novel sorbents which are polymeric chelating resins doped on stationary supports (Whatman No. 1 paper and silica gel). The usual complications of leaching of the resin and/or the chelating ligand and colloid retention on the sorption bed at any stage of separation were largely obviated with these sorbents under the operational conditions of metal sorption. A detailed study on the application of such sorbents to the differentiation of ionic (free), labile (ionic plus weakly complexed) and bound (strongly complexed) metal fractions present in local river-sediment and water samples was carried out. Chelating resin-impregnated paper (CRIP) and chelating resin-immobilized silica gel column (CRISC) methods of chromatographic separation of analyte trace metals in combination with the follow-up 'standard addition' procedure of the DPASV technique were employed. A modest attempt has been made to formulate a speciation (fractionation) scheme for metal contents present in river-sediments and waters on the basis of selective retention of ionic and labile fractions on complexing resins.

Chelating resin-impregnated paper chromatography, applications to trace element collection of ferrous and ferric ions, and determination by differential pulse anodic stripping voltammetry.

An ion-exchange approach to the preparation of chelating resin is demonstrated whereby a typical sulfonated chelating agent, 7-iodo-8-hydroxy quinoline-5-sulfonic acid, is immobilized as counterions on a piperazinium polyelectrolyte matrix. The resulting chelate forming resin has been used to effect the selective separation of ferrous as well as ferric ion from a known mixture containing other trace elements without any complication of the leaching of either chelating ligand or resin from the stationary support. The chelating resin-impregnated paper chromatographic technique followed with differential pulse anodic stripping analysis is described for the preconcentration, separation, and recovery of divalent and trivalent ions of iron from the various heavy metals in aqueous phases. The combination of chelation and paper chromatography involves a differential migration procedure which provides a technique for the separation of analyte ions quantitatively without any interference from the complex matrices.