Kikuo Terada

Preconcentration of silver(I), gold(III) and palladium(II) in sea water with p-dimethylaminobenzylidenerhodanine supported on silica gel

Abstract A water-insoluble chelating material, p-dimethylaminobenzylidenerhodanine on silica gel (DMABR—SG) is described for preconcentration of trace amounts of silver(I), gold(III) and palladium(II) from water samples. Radioactive tracers (110mAg and 195Au) were used to study the behavior of silver and gold; palladium was monitored spectrophotometrically as its 1-(2-pyridylazo)naphthol complex in chloroform. In batch experiments, silver was quantitatively retained on the DMABR—SG at acidities ranging from 1.7 M to pH 5, and gold from 3 M to pH 5; equilibrium was achieved within 1 min for both elements. From sea water, silver ion was completely retained at pH 1.0–6.5 and gold ion at pH 1.0–3.5. In the case of palladium, shaking for about 20 min was required for quantitative retention at pH 1.0–5.0 for aqueous solution and at pH 1.0–7.0 for sea water. The chelating capacity of the DMABR—SG was 23 μmol Ag, 11 μmol Au and 11 μmol Pd per g. Quantitative recovery of silver and gold on DMABR—SG columns from sea water was achieved at higher flow rates (1–2 l h-1 and 2–3 l h-1, respectively) than with other chelating resins, e.g., Chelex 100, palladium required slower flow rate (150 ml h-1). Silver retained on the DMABR—SG column was completely eluted with 20 ml of 2.5% sodium thiosulfate solution but palladium remained on the column. Silver, gold and palladium were quantitatively eluted with 20 ml of 0.1% thiourea in 0.1 M hydrochloric acid.

Silica gel as a support for inorganic ion- exchangers for the determination of caesium-137 in natural waters.

The preparation and characteristics of ammonium molybdophosphate and potassium or ammonium hexacyanocobalt ferrate supported in silica gel, and their application to the determination of (137)Cs in natural waters are described. Use of columns of these materials gives better recovery of (137)Cs from natural waters (in comparison with co-precipitation with ammonium molybdophosphate), requires less exchanger, so raising the gamma-counting efficiency of (137)Cs, and permits elimination of other radionuclides by washing with hydrofluoric acid.

Preconcentration of palladium(II) from water with thionalide loaded on silica gel

2-Mercapto-N-2-naphthylacetamide (thionalide) on silica gel is used for rapid preconcentration of μg l−1 levels of palladium(II) from aqueous solution, followed by atomic absorption spectrometric measurement. In batch experiments, palladium was quantitatively retained on the gel from solutions 5 M in acid to pH 8; equilibrium was achieved within 10 s. The chelating capacity of the gel was 7.5 μmol Pd g−1 at pH < 4. The effect of flow rate on retention was studied. Palladium retained on the column was completely eluted with 20 ml of 0.2 M thiourea in 0.1 M hydrochloric acid. The palladium concentration in sea water is shown to be < 0.3 μg l−1.

Sorption of copper(II) by some complexing agents loaded on various supports

Abstract 2-Mercaptobenzothiazole, 2-mercaptobenzimidazole and 2,5-dimercapto-1,3,4-thiadiazole loaded on silica gel, activated carbon and polytrifluorochloroethylene powder are compared for sorption and desorption of copper(II) ions. The separations are compared with those based on precipitation or extraction with these reagents. Columns of 2-mercaptobenzothiazole and 2-mercaptobenzimidazole on silica gel are particularly efficient for quantitative sorption of copper(II) from aqueous solutions at very high flow rates. 2-Mercaptobenzothiazole on silica gel is considered to be the most useful, as it reacts at pH 4.0, instead of pH 6.0 for 2-mercaptobenzimidazole. 2,5-Dimercapto-1,3,4-thiadiazole on silica gel removed copper from highly acidic solutions, but silica gel adsorbed this ligand only poorly, so that column capacity was severely restricted.

Separation and determination of selenium in rocks, marine sediments and plankton by direct evolution with the bromide-condensed phosphoric acid reagent.

A new method is presented for the quantitative separation and determination of selenium by direct evolution with the bromide-condensed phosphoric acid reagent (Br(-)-CPA) from rocks, marine sediments and plankton. In the reaction with the Br(-1)-CPA, selenium(IV) and (VI) in the solid samples are evolved as selenium tetrabromide, and can be collected in an absorbing solution of 0.3M hydrochloric acid and 06M perchloric add (1:1), and then determined spectrophotometrically with 4-substituted o-phenylenediamines followed by the extraction of the resulting 5-substituted piazselenol into toluene. Elemental selenium and selenide do not react with the Br(-)-CPA, but can be determined after oxidation to selenite with potassium iodate. Therefore, successive distillations, the first with Br(-)-CPA and the second with IO(3)(-)-Br(-)-CPA, give a satisfactory means of diflerential determination of selenium(IV) and (VI), and elemental selenium and selenide. This method can be successfully applied for the separation of selenium in the neutron-activation analysis of standard rock samples, marine sediments and plankton, giving good and reliable results.

Preconcentration of cobalt(II) in natural waters with 1-nitroso-2-naphthol supported on silica gel

A solid chelating material, 1-nitroso-2-naphthol supported on silica gel, provides a rapid and highly selective mean of preconcentrating cobalt(II) fro.

Differential preconcentration of arsenic(III) and arsenic(V) with thionalide loaded on silica gel

Abstract 2-Mercapto- N -2-naphtylacetamide (thionalide) on silica gel is used for differential preconcentration of μg l −1 levels of arsenic(III) and arsenic(V) from aqueous solution. In batch experiments, arsenic(III) was quantitatively retained on the gel from solutions of pH 6.5–8.5, but arsenic(V) and organic arsenic compounds were not retained. The chelating capacity of the gel was 5.6 μmol g −1 As(III) at pH 7.0. Arsenic retained on teh column was completely eluted with 25 ml of 0.01 M sodium borate in 0.01 M sodium hydroxide containing 10 mg l −1 iodine (pH 10). The arsenic was determined by silver diethyldithiocarbamate spectrophotometry. Arsenic(V) was subsequently determined after reduction to arsenic(III) with sulphite and iodide. Arsenic(III) and arsenic(V) in sea water are shown to be −1 , respectively.

Separation and determination of ruthenium by evolution with chromium(VI)-condensed phosphoric acid reagent

Ruthenium in various chemical forms can be evolved as the tetroxide from insoluble matrix materials by heating the sample with chromium(VI)-condensed phosphoric acid reagent (abbreviated as Cr(VI)-CPA). Because of its excellent decomposing power for various solid samples, condensed phosphoric acid is very useful in the chemical analysis of various insoluble materials, and when an oxidizing agent such as potassium dichromate is added in the CPA medium, drastic oxidation proceeds on heating. This method is now extended to the separation of ruthenium from marine sediments. During the reaction with Cr(VI)-CPA ruthenium tetroxide is evolved and collected in an absorbent solution of 6M hydrochloric acid and ethanol (1:1), and the ruthenium is then determined spectrophotometrically with thiourea or radiometrically by counting the beta or gamma-activity. Osmium, which can be evolved as the tetroxide by the same treatment, can be eliminated beforehand by heating the sample with Ce(IV)-CPA, which removes osmium but not ruthenium. The successive distillations by means of Ce(IV)-CPA and Cr(VI)-CPA give satisfactory results for the separation between osmium and ruthenium. This method might be useful for the separation of ruthenium in geochemical or neutron-activation analysis.

Preconcentration of antimony(III) from water with thionalide loaded on glass beads with the aid of collodion

2-Mercapto-N-2-naphthylacetamide (thionalide) loaded on glass beads with the aid of collodion is used for preconcentration of microgram levels of antimony(III) from aqueous solution. Antimony is quantitatively retained on the loaded beads from 0.4–0.8 mol l−1 hydrochloric acid solutions; equilibration is achieved within 1 min. The retention capacity of the beads is 0.2 μml Sb g−1 at 0.6 mol l−1 hydrochloric acid. The maximum flow rate for quantitative retention is 1.27 ml min−1 cm−2. Antimony retained on the column is completely eluted with 10 ml of 6.0 mol l−1 hydrochloric acid at flow rates<1.9 ml min−1 cm−2.

Spectrophotometric determination of iron(II) in sea water after preconcentration by sorption of its 3-(2-pyridyl)-5,6-bis(4-phenylsulphonic acid)-1,2,4-triazine complex with poly(chlorotrifluoroethylene) resin

Abstract A simple and selective method was established for the spectrophotometric determination of iron(II) in sea water after preconcentration by sorption of its 3-(2-pyridyl)-5,6-bis(4-phenylsulphonic acid)-1,2,4-triazine (ferrozine) complex with poly(chlorotrifluoroethylene) resin (PCTFE). The iron(II)-ferrozine complex was quantitatively retained as an ion-associate complex with tetrabutylammonium cation on PCTFE resin in the pH range 4.8–7.0. The retention capacity of the resin was 29 μg Fe(II) g−1 at a maximum flow-rate of 25 cm3 min−1. Iron(II) retained on the resin column was completely eluted with 5 cm3 of methanol and the eluate was directly submitted to spectrophotometric measurement at 562 nm. The recovery and detection limit of iron(II) from sea water were 97 ±2% and 88 ng dm−3 (1.6 nmol dm−3), respectively.