Determination of copper(II) based on its catalytic effect on thiosemicarbazide-H(2)O(2)-CTMAB chemiluminescence reaction.

A novel chemiluminescence (CL) reaction, thiosemicarbazide (TSC)-H(2)O(2), for the determination of copper at nanogram per milliliter level in batch type is described. The method is based on the catalytic effect of copper(II) on the oxidation of TSC with hydrogen peroxide to produce light emission. The emitted light was observed by using a conventional fluorescence detector. In the optimum conditions, calibration graph was linear in the range of 0.1-1.3ppm. The limit of detection was 10ppb. The relative standard deviation for five determinations of 0.5ppm copper(II) was 1.93%. The proposed method permitted the selective and sensitive determination of Cu(II) in human hair and wheat flour with sufficient precision. The possible mechanism for the new chemiluminescence reaction was also discussed.

Spectrophotometric determination of osmium based on its catalytic effect on the oxidation of carminic acid by hydrogen peroxide.

A highly sensitive spectrophotometric method is described for the determination of trace amounts of osmium(VIII), based on its catalytic effect on the oxidation of carminic acid by hydrogen peroxide. The reaction was monitored spectrophotometrically by measuring the decrease in absorbance of carminic acid at 540 nm after 3 min of mixing the reagents. The optimum reaction conditions were 1x10(-4) mol l(-1) carminic acid, 0.013 mol l(-1) hydrogen peroxide and pH 10 at 25 degrees C. By using the recommended procedure, the calibration graph was linear from 0.1 to 1.5 ng ml(-1) of osmium; the detection limit was 0.02 ng ml(-1); the RSD for five replicate determinations of 0.2-1.4 ng ml(-1) was in the range of 1.8-4.7%. The influence of several foreign ions on osmium determination were studied and the effect of interfering ions were removed by extracting osmium into isobuthyl methyl ketone and back extracting into sodium hydroxide solution.

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.

Chromium speciation by a surfactant-coated alumina microcolumn using electrothermal atomic absorption spectrometry.

A simple and convenient method has been developed for the speciation of chromium(III) and chromium(VI) in aqueous solutions using a sodium dodecyl sulphate coated alumina micro-column (1.5 cm x 5 mm i.d.) and graphite furnace-atomic absorption spectrometry (GF-AAS). Under the optimized conditions (pH 0.6, adjusted with hydrochloric acid; flow rate, 1 ml min(-1)) chromium(VI) is retained on the column and chromium(III) is collected and determined by GF-AAS. Total chromium is directly determined by GF-AAS and chromium(VI) is calculated by difference. The relative standard deviations (10 replicate analyses) at the 20 mug l(-1) level for chromium(III) and chromium(VI) and at the 40 mug l(-1) level for total chromium were 1.4%, 3.6% and 1.8%, and the corresponding limits of detection (based on 3sigma) were 0.57 mug ml(-1), 0.61 mug ml(-1) and 0.35 mug l(-1) respectively. No large interference effects have been observed from other investigated species and the method has been successfully applied to a range of water samples.

Indirect inductively coupled plasma atomic emission determination of fluoride in water samples by flow injection solvent extraction.

An indirect determination of fluoride in water by inductively coupled plasma atomic emission spectrometry combined with flow injection coupled with solvent extraction is reported in this paper. A manifold for rapid determination of fluoride has been designed that uses a single coil for complex formation and extraction. The method involves the formation of lanthanum/alizarin complexone/fluoride complex and its extraction into hexanol containing N,N-diethylaniline. The concentration of fluoride is determined indirectly by introduction of the organic layer into the plasma and measurement of the emission intensity of the La II 333.75-nm line. The optimum experimental conditions for the determination are described. A coiled groove phase separator fitted with a grid and PTFE porous membrane was used in this work. The sampling rate was 36 samples per hour and the calibration graphs were linear from 0.03 to 1.3 micrograms/mL. The relative standard deviation found was 2.16% for 200 microL of 1 microgram/mL of fluoride. The method is selective and has been applied satisfactorily to the determination of fluoride in water samples.

Inductively-coupled plasma-optical emission spectrometry Application to the determination of molybdenum, cobalt and boron in soil extracts.

An inductively-coupled radiofrequency plasma method applicable to the determination of Mo, Co and B in soil extracts has been developed. The interferences caused by some common metals and acids have been investigated. The detection limits observed at the chosen wavelengths were 0.01, 0.05 and 0.05 ppm for Mo, Co and B respectively. The mean relative standard deviation determined over an extended period of time was 0.9%.