Speciation and determination of thallium by on-line microcolumn separation/preconcentration by flow injection-flame atomic absorption spectrometry using immobilized oxine as sorbent.

A flow injection analysis (FIA) system incorporation a microcolumn of immobilized oxine on surfactant-coated alumina had been devised for performing rapid thallium enrichment/matrix removal in flame atomic absorption spectrometry (FAA). The preconcentration is based on the deposition of thallium(I) on microcolumn and subsequent elution with 500 microl of sodium thiosulfate (1 moll(-1)). In the presence of EDTA, only Tl(I) was retained on the microcolumn. Total thallium was determined after reduction of Tl(III) to Tl(I) by hydroxyl amine hydrochloride. A sample volume of 25 ml resulted in a preconcentration factor of 77. Precision at 30 microgl(-1) was 2.6% RSD (n=10). With 25 ml sampling volume a detection limit of 2.5 microgl(-1) was determined. The effect of potential interfering ions on the determination was studied. The method was applied for the determination of thallium in water, waste water, hair, nail, coal, and standard reference alloys. The accuracy was assessed through recovery experiment, independent analysis by Furnace-AAS, and analysis of certified reference alloys.

Trace enrichment and determination of silver by immobilized DDTC microcolumn and flow injection atomic absorption spectrometry.

Flow injection (FI) system incorporating a microcolumn of immobilized diethyldithiocarbamate (DDTC) on surfactant-coated alumina was combined with atomic absorption spectrometry for on-line trace enrichment and determination of silver in different matrices. Silver was deposited on the microcolumn by processing a standard or solution of analyte at pH 3-4 on the column. Injection of 250mul of ethanol then served to elute the retained species to atomic absorption spectrometry (AAS). A sample volume of 20ml resulted in a pre-concentration factor of 125, and precision at the 20mugl(-1) was 4% (R.S.D.). The procedure was applied to tap water, well water, rain water, sea water, radiology film, and lead concentrate samples. The accuracy was assessed through recovery experiments, independent analysis by furnace-AAS, and analysis of certified reference material.

On-line preconcentration and determination of cobalt by chelating microcolumns and flow injection atomic spectrometry.

A simple and sensitive flow injection analysis-atomic absorption spectrometric procedure is described for the determination of cobalt. The method is based upon on-line preconcentration of cobalt on a microcolumn of 2-nitroso-1-naphthol immobilized on surfactant coated alumina. The trapped cobalt is then eluted with ethanol (250 microl) and determined by flame atomic absorption spectrometry. The analytical figures of merit for the determination of cobalt are as follows: detection limit (3 S), 0.02 ng ml(-1); precision (RSD), 2.8% for 20 ng ml(-1) and 1.7% for 70 ng ml(-1) of cobalt; enrichment factor, 125 (using 25 ml of sample). The method has been applied to the determination of cobalt in water samples, vitamin B(12) and B-complex ampoules and accuracy was assessed through recovery experiment and independent analysis by furnace AAS.

Spectrophotometric determination of some catecholamine drugs using sodium bismuthate.

A novel spectrophotometric method is described for the determination of epinephrine (EP) and norepinephrine (NE). The method is based on the development of a red colour with sodium bismuthate, as a sensitive chromogenic reagent, in aqueous medium at pH 3. Oxidation of these catecholamines produces aminochrome derivatives which can be measured spectrophotometrically at 486.0 nm. Calibration graphs are linear in the range 4.8-800 (micromol l(-1)) for epinephrine bitartarate and 4.8-600 (micromol l(-1)) for norepinephrine bitartarate with detection limits of 0.26 (micromol l(-1)) and 2.46 (micromol l(-1)) for epinephrine and norepinephrine bitartarate salts, respectively. The method has successfully been applied to determination of these catecholamines in pharmaceutical preparations.

Spectrophotometric determination of some vic-diol containing drugs using ion-exchange resins.

Periodic acid and its salts have been widely used for the quantitative oxidation of vic-diol containing compounds including carbohydrates and catecholamine drugs. The advantage of using a polymeric resin (periodate form) over free periodate ions is that the resin quantitatively retains both unconsumed periodate ions and the iodate ions produced in the oxidation and, hence, enables one to undertake further studies on the structural, synthetic or preparative work. The resin (periodate form) was found to be a clean and sensitive chromogenic reagent for the spectrophotometric determination of some catecholamine drugs. The calibration graphs of absorption versus concentration in the range studied (5-50 ppm) were linear.

Spectrophotometric determination of nitrite based on its catalytic effect on the oxidation of carminic acid by bromate.

A highly sensitive and selective method is described for the determination of trace amounts of nitrite based on its effect on the oxidation of carminic acid with bromate. The reaction was monitored spectrophotometrically by measuring the decrease in absorbance of carminic acid at 490 nm after 3 min of mixing the reagents. The optimum reaction conditions were 1.8x10(-1) mol l(-1) H(2)SO(4), 3.8x10(-3) mol l(-1) KBrO(3), and 1.2x10(-4) mol l(-1) carminic acid at 30 degrees C. By using the recommended procedure, the calibration graph was linear from 0.2 to 14 ng ml(-1) of nitrite; the detection limit was 0.04 ng ml(-1); the R.S.D. for six replicate determinations of 6 ng ml(-1) was 1.7%. The method is mostly free from interference, especially from large amounts of nitrate and ammonium ions. The proposed method was applied to the determination of nitrite in rain and river water.