Minoru Hara

Simultaneous determination of several trace metals by asv after preconcentration by adsorption as padap complexes on C18-bonded glass beads

Traces of zinc, lead, copper and cadmium are determined simultaneously by anodic-stripping voltammetry (ASV) combined with a preconcentration technique utilizing C(18)-bonded glass beads. The metals are collected as their 2-(2-pyridylazo)-5-diethylaminophenol (PADAP) complexes on a column of the beads and the complexes are eluted with a small volume of ethanol-hydrochloric acidchloroform mixture. The eluate is evaporated to dryness in the presence of hydrogen peroxide and the residue dissolved in a small volume of acetic acid-sodium acetate buffer. The concentrations of the metals are measured by ASV, Quantitative recoveries are obtained for 0.01-ng ml levels of the metals. Many ions which interfere in the direct ASV procedure do not interfere in the present method.

Positive feedback compensation of iR-drop in modified normal pulse polarography of sodium ion in acid solution.

The well-defined polarographic wave for sodium, obtained by modified normal pulse polarography in which the polarographic current is sampled after the fall of each pulse, shifts to more negative potentials with decrease in the pH of the solution. The shift is attributed to the effect of the uncompensated resistance of the sample solution, and can be compensated by a positive feedback circuit.

Modified normal pulse polarography of alkali-metal ions in acid solution

Well-defined polarograms of five alkali-metal ions in 0.01M hydrochloric acid were obtained by means of modified normal pulse polarography. The method uses the procedure of anodic stripping chronoamperometry during the life-time of a drop from a dropping mercury electrode, namely preparation of electrode, accumulating step and anodic stripping step of a metal. The instantaneous polarographic currents were sampled only once per mercury drop after the fall of each pulse. The wave heights for alkali-metal ions by the present method are free from the interference caused by 0.01M hydrochloric acid. The present method is applicable to monitoring of alkali-metal ions in fluid acid streams.

Reversed-Phase Liquid Chromatography of Alkylphenols Depending on Their Dissociation Constants

Abstract The reversed-phase liquid chromatography of structural isomers of alkylphenols has been studied. Octyl-bonded silica gel was useful as stationary phase and addition of a trace of triethylamine to the eluent was effective for this purpose. The separation of nine structural isomers of alkylphenols, ethylphenols and xylenols, was accomplished by such liquid chromatographic system. Thus the good reproducibility of the capacity ratios was obtained. The increase of retention of the solute was not observed by addition of the ion-pair reagent to the eluent.

Ion-Pair Liquid Chromatography of Alkylanilines

Abstract The optimization of ion-pair liquid chromatography of structural isomers of carbon number two alkyl anilines has been studied. The shorter alkyl cha in bonded silica gel demonstrated the stereo selectivity. the alkyl chain length of ion-pair reagent ruled the equilibration of ion-pair formation. the longer chain of ion-pair reagent formed hydrophobic ion-pair and the shorter chain could not form ion-pair, and ionized solute formed ion-pair with polar ion which was a component of eluent. Three ethylanilines and six xylidines mixture was separated on an octadecyl-bonded silica gel column using an eluent containing methanol/water mixture with sodium 1-dodecanesul-fonate.

Modified reverse pulse polarographic behaviour of magnesium ion in aqueous solution

Modified reverse pulse polarography (MRPP) is proposed for measuring the quantity of a reduction product formed at the initial potential in reverse pulse polarography. A double potential-step method is employed for this purpose. MRPP has been applied to the study of the electrochemical behaviour of magnesium in aqueous solution. For magnesium the height of the MRPP anodic wave was proportional to concentration at low pH, but not in unbuffered neutral solution. This difference is attributed to formation of hydroxo-magnesium complexes because of depletion of hydrogen ions near the electrode in a neutral solution.

Application of modified normal pulse polarography and its differential mode to alkaline-earth metal ions in acid solutions

The simultaneous determination of alkaline-earth metal ions in acid solution was studied by modified normal pulse polarography. Well-defined waves were recorded for calcium, strontium and barium, but no limiting current was found for magnesium, because of its very negative reduction potential. The differential mode of this method gives peak-type polarograms and is useful for the simultaneous determination of species for which the half-wave potentials lie close together. The interference of dissolved oxygen was eliminated by the use of tetramethylammonium chloride as a supporting electrolyte.