Suwaru Hoshi

Preparation of Amberlite XAD resins coated with dithiosemicarbazone compounds and preconcentration of some metal ions

The Amberlite XAD resins coated with dithiosemicarbazones were prepared and their collection behavior of metal ions from aqueous solution was investigated. Among the resins used, the reagent-loaded Amberlite XAD-7 was found to be superior for the collection of metal ions to other reagent-loaded resins used. The quantitative collection of mercury(II), palladium(II) and copper(II) was obtained from acidic medium, while cadmium(II) and lead(II) was obtained from neutral medium by the Amberlite XAD-7 resin coated with dimethylglyoxal bis(4-phenyl-3-thiosemicarbazone) (DMBS). These metal ions collected on the resin were easily eluted with a small volume of N,N-dimethylformamide as their DMBS chelates. This collection-elution method was applied to the determination of their metal ions by reversed-phase high performance liquid chromatography with a spectrophotometric detection.

The spectrophotometric determination of trace molybdenum (VI) after collection and elution as molybdate ion on protonated chitin

Collection and elution method for inorganic anion on protonated chitin has been applied to the spectrophotometric determination of molybdenum (VI). The molybdenum (VI) is collected as molybdate ion on a column of chitin in weak acidic medium which is easily eluted with a small volume of 0.1 M ammonia buffer solution (pH 10). The molybdenum (VI) in the eluent is determined by bromopyrogallol red-Zephiramine method spectrophotometrically. Beers law is obeyed over the concentration range of 0.1-0.8 mug of molybdenum (VI) in 1 ml of eluent at 634 nm. The apparent molar absorptivity is 6x10(4) dm(3) mol(-1) cm(-1). The tolerance limits for WO(4)(2-), VO(3)(-), CrO(4)(2-) and Fe (III) is low, that is, 1-100 times that of molybdenum (VI), but some metal ions and common inorganic anions do not interfere in concentration range of 1000-5000 times that of molybdenum (VI). The present method can be applied to the determination of molybdenum (VI) in natural water samples.

The simple and rapid spectrophotometric determination of trace chromium(VI) after preconcentration as its colored complex on chitin

Preconcentration method with collection of metal complexes on a chitin has been applied to the spectrophotometric determination of chromium(VI) in water. The chromium(VI) is collected as its 1,5-diphenylcarbazide(DPC) complex on a column of chitin in the presence of dodecyl sulfate as counter-ion. The Cr-DPC complex retained on the chitin is eluted with a methanol-1 M acetic acid mixture (7:3, v/v), and the absorbance of the eluent is measured at 541 nm. Beers law is obeyed over the concentration range of 0.05-0.6 mug of chromium(VI) in 1 ml of the eluent. The apparent molar absorptivity is 3.5x10(4) dm(3) mol(-1) cm(-1). The tolerance limits for Fe(III) is low, i.e. ten times that of chromium(VI), but some metal ions and common inorganic anions do not interfere in concentration range of 100-10 000 times that of chromium(VI). The present method can be applied to the determination of chromium(VI) in natural water samples.

Simultaneous determination of platinum(II) and palladium(II) by reversed phase high-performance liquid chromatography with spectrophotometric detection after collection on and elution from resin coated with dimethylglyoxal bis(4-phenyl-3-thisomicarbazone).

Amberlite XAD-7 resin coated with dimethylglyoxal bis(4-phenyl-3-thiosemicarbazone) (DMBS) was prepared and applied to the preconcentration of platinum(II) and palladium(II) from aqueous solution. Platinum(II) and palladium(II) were collected quantitatively on resin coated with the reagent (DMBS-XAD-7) from acidic solution in the presence of iodide ion by a bach method. The metal ions were then easily eluted from DMBS-XAD-7 as their DMBS chelates with a small volume of N,N-dimethylformamide. This collection and elution method was applied to the simultaneous determination of platinum(II) and palladium(II) by reversed-phase high-performance liquid chromatography with spectrophotometric detection using an ODS column and acetone-water as the mobile phase. The proposed method was applied to the determination of the metals in commercially available samples.

Voltammetric detection of silver(I) using a carbon paste electrode modified with keratin

The voltammetric detection of silver(I) was carried out at a carbon paste electrode (CPE) modified with keratin. Silver(I) was selectively accumulated on the electrode on the basis of its interaction with the thiol and disulfide groups of keratin in 0.1 mol dm–3 acetate buffer (pH 6.7) + 0.1 mol dm–3 NaClO4. After reduction of silver(I) had been carried out, the reoxidation wave of silver(0) appeared at 0.14 V (versus Ag/AgCl) on scanning the potential in the positive direction in 0.1 mol dm–3 acetate buffer (pH 6.7). The detection limit of silver(I) was 2 × 10–8 mol dm–3 when the accumulation time was 10 min. Interference from co-existing substances was slight in the voltammetric measurement because of the interaction with sulfur atoms and the exchange of the medium. The proposed method was applied to the determination of silver(I) in a photographic developer.

Accumulation voltammetry of avidin and biotin using a biotin labeled with Nile Blue A

Abstract Avidin and biotin were detected in accordance with an electrochemical procedure using labeling. Biotin labeled with Nile Blue A, an electroactive dye, was prepared and used in avidin-biotin assay. The binding of the biotin part with avidin makes labeled biotin (LB-N) electroinactive. This is because the part of Nile Blue A is also taken in biotin sites of avidin. Therefore, the concentration of avidin could be estimated by measuring the peak current of LB-N. When biotin and LB-N competed for the site of avidin, biotin was also determined by the changing of the electrode response. Levels of detection for avidin and biotin were 10 −9 M. This method has merit that does not require a separation procedure of the free LB-N from the bound one. On the contrary, an effect for length of spacer between Nile Blue A and the biotin part was investigated. It was shown that adsorption of reagent to the electrode increased with increasing the length of the spacer.

Determination of trace elements in sea-water by inductively coupled plasma mass spectrometry after preconcentration by formation of water-soluble complexes and their adsorption onC18-bonded silica gel

A simple and reliable preconcentration method was developed for the determination of seven trace metals (Mn, Fe, Ni, Cu, Zn, Cd and Pb) in sea-water by ICP-MS. The method is based on the formation of water-soluble complexes in an aqueous sample followed by adsorption of the complexes onto a C18-bonded silica gel column. The chelating reagent used was 2-(5-bromo-2-pyridylazo)-5-(N-propyl-N-sulfopropylamino)phenol (5-Br-PAPS). By passage of 100 ml of sea-water sample, after addition of 5-Br-PAPS and adjustment of the pH to 8.3, quantitative adsorption of the metal complexes onto the column took place while the major matrix ions in sea-water passed through the column. A similar but separate sample work-up at pH 4.5 provided acceptably low blank values for Fe. The metals were subsequently eluted with 4.0 ml of 1.0 M HNO3. All seven elements were determined with an all-argon plasma, whereas ultratrace levels of Fe were determined with a nitrogen–argon mixed-gas plasma to reduce the isobaric interference by 40Ar16O on 56Fe. The detection limits of the method, based on a 25-fold preconcentration, range from 0.08 ng l–1 for Cd to 16 ng l–1 for Fe. The precision and accuracy of the method were demonstrated by analyzing coastal and open-ocean sea-water certified reference materials.

Reversed-phase partition high-pressure liquid chromatography of trace amounts of inorganic and organic mercury with silver diethyldithiocarbamate

Inorganic and organic mercury diethyldithiocarbamates have been separated by reversedphase partition high-pressure liquid chromatography. The mercury chelates were formed by an exchange reaction with silver diethyldithiocarbamate in chloroform, in the presence of acetate buffer (pH 5.0). The inorganic and organic mercury chelates in the extract were separated within 30 min on a 3.9 x 300 mm mu-Bondapak C(18) column. EDTA (10(-4)M) in methanol-water mixture (78:22 v v ) was used as eluent at a flow-rate of 0.5 ml min .

Simple and rapid spectrophotometric determination of iron after preconcentration as its 1,10-phenanthroline complex on the natural polymer “chitin”

Preconcentration by collection of metal complexes on chitin has been applied to the spectrophotometric determination of iron in water. The iron is collected as its 1,10-phenanthroline (phen) complex on a column of chitin in the presence of tetraphenylborate as counter-ion. The iron(II)-phen complex retained on the chitin is eluted with an acetone-1M acetic acid mixture (8:2 v/v), and the absorbance of the eluate is measured at 512 nm. Beers law is obeyed over the concentration range 1.1-11.2 mug of iron in 10 ml of eluate. In the presence of EDTA as masking agent, Ca, Mg, Al, Mn, Zn, Cd and Pb do not interfere in concentrations up to 100 times that of iron(II) and Co, Ni and Cu do not interfere in concentrations up to 20 times that of iron(II). Common inorganic anions do not interfere in concentrations up to 10,000 times that of iron(II). The proposed method has been applied to determination of iron in tap water.

Electrochemical behavior of cysteine at a Nafion® |cobalt(II) modified electrode

Abstract An interaction between cysteine and cobalt(0) was investigated at a Nafion® |cobalt(II) modified electrode. In the presence of cysteine, cobalt(II) was reduced at lower overvoltage compared with that in the absence of cysteine. An oxidation peak of cobalt(0) was observed at −0.25 V (Ag|AgCl). As the shift of the overvoltage depends on the concentration of cysteine, cysteine could be determined by the oxidation peak on the basis of the shift. The calibration curve of cysteine was linear from 4 × 10 −8 to 1 × 10 −6 M. The relative standard deviation at 5 × 10 −8 M cysteine was 5.8% ( n = 5). In addition, the amount of cobalt participating in the electrode reaction was estimated. As a result, it was found that 1/30 of the cobalt in the electrode took part in the electrode reaction.