Isoshi Nukatsuka

Enrichment of trace amounts of copper as chelate compounds using a finely divided ion-exchange resin

The enrichment of trace amounts of copper as complexes with various chelating agents was examined with the use of finely divided anion- and cation-exchange resins of the macroreticular type. Of the 16 chelating agents studied, bathocuproinedisulphonate (BCS) combined with the use of a finely divided anion-exchange resin was the most effective for the rapid enrichment of copper from large sample volumes. The resin particles holding the copper(I)-BCS complex were collected on a membrane filter and subsequently suspended in a small volume of 0.1 M hydrochloric acid. The resin suspension was then subjected to electrothermal atomisation atomic absorption spectrometry. The method was applied to the determination of copper in sea and river water samples and the results were compared with those obtained by densitometric measurement of the solid-state absorbance of the copper(I)-BCS complex in the resin phase.

Solid-phase extraction of trace amounts of beryllium(II) from natural water samples on a glass-fibre filter followed by solid-phase spectrophotometric determination using Chromazurol B

A selective and sensitive method for the determination of beryllium(II) is described, based on the combined use of solid-phase extraction on a glass-fibre filter (GFF) and solid-phase spectrophotometry using Chromazurol B (CAB). In solid-phase spectrophotometry, beryllium(II) is fixed and determined directly on a membrane filter as the BeII–CAB complex formed in the presence of hexadecyltrimethylammonium bromide. The detection limit is 0.4 ng for 30 cm3 of sample solution. Trace amounts of beryllium(II) in aqueous sample solutions are first extracted on a GFF from a solution containing ethylenediaminetetraacetic acid as a masking agent of co-existing ions at pH 9.5, then determined after desorption from the GFF with 30 cm3 of 0.1 mol dm–3 hydrochloric acid. A recovery of 96.3% is achieved. The proposed method was applied to river water and hot spring water samples with pH values in the range 1.6–3.6 using 3.0–50.0 cm3 of sample solution. The concentrations of beryllium(II) found were in the range 0.12–3.52 ppb.

Determination of molybdenum in sea water by solid-phase spectrophotometry

Abstract A simple and sensitive spectrophotometric method for the determination of molybdenum(VI) in sea water samples was developed. It is based on the extraction of the Mo(VI)-phenylfluorone complex on a membrane filter by simple filtration and direct measurement of the absorbance on the filter. The extraction was done in the presence of zephiramine and only 2–10 ml of sample solution was required. No preliminary treatment of the sea water sample was required to isolate molybdenum(VI) from the matrix. The absorbance was measured by the zero and first derivative modes. The tolerance limit for foreign ions was improved by measuring the first derivative absorbance.

Solid-phase spectrophotometric determination of germanium on a membrane filter after collection using phenylfluorone and Zephiramine

A highly sensitive and simple method for the determination of germanium(IV) has been developed. Germanium(IV) was extracted on a membrane filter as the phenylfluorone complex from a dilute hydrochloric acid (1 + 7) medium containing Zephiramine and the complex on the membrane filter was then determined by solid-phase spectrophotometry. A 1000-fold molar excess of Zephiramine over germanium(IV) at the nmol level was required for the formation of the germanium(IV)-phenylfluorone complex. The detection limit of germanium(IV) was found to be 1.9 ng for 40 ml of the sample solution. The method was applied to the determination of germanium(IV) in hot spring water and groundwater. The concentrations of germanium(IV) found were in the range 4.36–37.7 p.p.b. for hot spring water and 0–1.97 p.p.b. for groundwater.

A glycomic approach to proteoglycan with a two-dimensional polysaccharide chain map.

Glycosaminoglycan chains were liberated from proteoglycans (bovine lung, tracheal cartilage, and cerebrum) by successive digestion with actinase and with cellulase from Aspergillus niger, which has endo-beta-xylosidase activity. The glycosaminoglycan chains were fluorescence-labeled with 2-aminopyridine after digestion with Streptomyces hyaluronidase. The resulting pyridylamino-glycosaminoglycans, including heparan sulfate, chondroitin sulfate/dermatan sulfate, and heparin, were separated by high-performance liquid chromatography. Each separated fraction was analyzed by two types of high-performance liquid chromatography: gel-filtration chromatography and anion-exchange chromatography. The correlation between molecular weight and degree of sulfation could be shown on the two-dimensional polysaccharide chain map. Use of a commonly available cellulase with endo-beta-xylosidase activity together with the two-dimensional polysaccharide chain map allows easy analysis of various glycosaminoglycan chains and comprehensive comparison among the structures. These techniques will become useful tools in the further development of glycotechnology and glycome analysis.

Studies on the adsorption of trace amounts of beryllium(II) on the surface of silica fibres from an aqueous phase for the development of a novel enrichment technique for electrothermal atomic absorption spectrometry

Trace amounts of beryllium(II) were adsorbed on the surface of silica fibres from a weak alkaline solution. The distribution ratio depended on the pH of the solution; however, a constant value (log D= 5.1) was obtained at pH 9.5 in the concentration range 6.4–220 µmol kg–1 in the silica phase. From the pH versus D curve, it was deduced that the beryllium(II) species adsorbed was (—SiO)Be(OH)2– or (–SiO)2Be(OH)22–. Based on these phenomena a simple enrichment technique was developed for the determination of trace amounts of beryllium(II) by electrothermal atomic absorption spectrometry. A 50–500 ml portion of the sample solution (pH 9.5) containing up to 6 ng of beryllium(II) was passed through a stack of three sheets of silica-fibre filter to collect the beryllium(II), which was then desorbed using three 0.5 ml portions of 0.5 mol l–1 HCl containing 15 mg l–1 of silicon for electrothermal atomic absorption spectrometry. A concentration factor of over 300 was easily attained. The detection limit, based on three times the standard deviation of the blank, was 0.15 ng of beryllium(II) for 500 ml of solution. The method was applied to the determination of beryllium(II) in natural water samples. A quantitative recovery was obtained when 3.0 or 6.0 ng of beryllium(II) were added to 500 ml of sea-water.

Determination of trace amounts of aluminium in tap water by spectrophotometry after collection on a membrane filter using Chrome Azurol S and Zephiramine

A sensitive and selective spectrophotometric method for the determination of aluminium(III) using Chrome Azurol S and Zephiramine is described. The ion-pair precipitate formed between Zephiramine and perchlorate ions is effective for the enrichment of aluminium(III) on a membrane filter as its ternary complex with Chrome Azurol S and Zephiramine. The solid-state absorbance of the complex on the membrane filter is measured at 640 and 700 nm against a blank thin layer and the difference is calculated. Although the calibration graph does not obey Beers law good reproducibility is observed, the relative standard deviation for 0.10 µg of aluminium(III) in a 20-ml sample volume being 3.1%(n= 5). A ligand buffer solution, composed of trans-cyclohexane-1,2-diaminetetraacetic acid and an excess of zinc(II), is effective for masking interferences from foreign ions, particularly iron(III). The method has been applied to the determination of aluminium in tap water.

Effects of divalent cations on bovine testicular hyaluronidase catalyzed transglycosylation of chondroitin sulfates

Glycosaminoglycans were prepared as salts of different divalent cations and tested as donors in bovine testicular hyaluronidase catalyzed transglycosylation reactions. All of the metal cations examined had similar binding efficiency of divalent cations to hyaluronan. However, cations bound with different efficiencies to chondroitin sulfate species and the differences were marked in the case of chondroitin 6-sulfate; the numbers of cations bound per disaccharide unit were estimated to be 0.075 for Mn, 1.231 for Ba, 0.144 for Zn, and 0.395 for Cu. While barium salt of chondroitin sulfates enhanced transglycosylation, the zinc salt of chondroitin sulfates inhibited transglycosylation. Therefore, by selecting the proper divalent cation salt of chondroitin sulfates as a donor in the transglycosylation reaction it is possible to improve the yields of the products.

Collection of niobium-phenylfluorone complex on a membrane filter for the determination of traces of niobium by solid-phase spectrophotometry

Abstract A simple and sensitive spectrophotometric method for the determination of traces of niobium(V) is based on the colour reaction between niobium(V) and phenylfluorone (Pfn) in the presence of Zephiramine micelles in dilute hydrochloric acid and extraction of the complex on a membrane filter. The absorbance of the Nb(V)-Pfn complex is measured directly on the filter. The detection limit is 4 ng for 30 ml of sample solution.

Simple and Rapid Immobilization of Coating Polymers on Poly(dimethyl siloxane)-glass Hybrid Microchips by a Vacuum-drying Method

A simple and rapid vacuum-drying modification method was applied to several neutral and charged polymers to obtain coating layers for controlling electroosmotic flow (EOF) and suppressing sample adsorption on poly(dimethyl siloxane) (PDMS)-glass hybrid microchips. In the vacuum-dried poly(vinylpyrrolidone) coating, the electroosmotic mobility (μeo) was suppressed from +2.1 to +0.88 × 10(-4) cm(2)/V·s, and the relative standard deviation (RSD) of μeo was improved from 10.2 to 2.5% relative to the bare microchannel. Among several neutral polymers, poly(vinylalcohol) (PVA) and poly(dimethylacrylamide) coatings gave more suppressed and repeatable EOF with RSDs of less than 2.3%. The vacuum-drying method was also applicable to polyanions and polycations to provide accelerated and inversed EOF, respectively, with acceptable RSDs of less than 4.9%. In the microchip electrophoresis (MCE) analysis of bovine serum albumin (BSA) in the vacuum-dried and thermally-treated PVA coating channel, an almost symmetric peak of BSA was obtained, while in the native microchannel a significantly skewed peak was observed. The results demonstrated that the vacuum-dried polymer coatings were effective to control the EOF, and reduced the surface adsorption of proteins in MCE.