Tomihito Kambara

A liquid membrane type perchlorate ion-selective electrode

A liquid membrane type ion-selective electrode sensible to perchlorate ion was prepared on the basis of the ion-pair extraction system. Methylene blue cation forms an ion-pair with perchlorate ion in aqueous phase, which is easily extractable into nitrobenzene. The extract functions as the perchlorate ion-selective membrane. The calibration curve showed an ideal Nernstian slope of 58 mV per activity decade at the perchlorate ion activity range from 10−6 to 1 M. Potentials measured with 0.1 mM perchlorate test solutions were not affected by the change in pH value from 2 to 12.5 under the constant ionic strength of 0.1 M. Selectivity coefficients for various anions were evaluated; the coefficient decreases in the order IO4−>I−>SCN−>>SO42−, … NO3−, Cl−, Br−.

Revision of the van deemter theory for diffusion and pressure drop in the gas phase

Abstract Provided that the flow rate of carrier gas in a gas chromatographic column is maintained constant and the pressure and the linear velocity are distributed as shown, and also the diffusion coefficient in gas phase is inversely proportional to the pressure, one can formulate the problem. Assuming that the solution is shown by a Gaussian distribution as given the above problem is converted into the intergration of the ordinary differential concerning the peak variance. The calculation provides a revised equation for gas chromatographic peak that includes the familiar Van Deemter theory as a limiting law.

Catalytic determination of molybdenum(VI) by means of an iodide ion-selective electrode and a landolt-type hydrogen peroxide-iodide reaction.

A trace amount of molybdenum(VI) can be determined by using its catalytic effect on the oxidation of iodide to iodine by hydrogen peroxide in acidic medium. Addition of ascorbic acid added to the reaction mixture produces the Landolt effect, i.e., the iodine produced by the indicator reaction is reduced immediately by the ascorbic add. Hence the concentration of iodide begins to decrease once all the ascorbic acid has been consumed. The induction period is measured by monitoring the concentration of iodide ion with an iodide ion-selective electrode. The reciprocal of the induction period varies linearly with the concentration of molybdenum(VI). The most suitable pH and concentrations of hydrogen peroxide and potassium iodide are found to be 1.5, 5 and 10mM, respectively. An appropriate amount of ascorbic acid is added to the reaction mixture according to the concentration of molybdenum(VI) in the sample solution. A calibration graph with good proportionality is obtained for the molybdenum(VI) concentration range from 0.1 to 160 muM. Iron(III), vanadium(IV), zirconium(IV), tungsten(VI), copper(II) and chromium(VI) interfere, but iron(III) and copper(II) can be masked with EDTA.

Differential pulse polarographic determination of nitrate in environmental materials

Nitrate can be determined with reliable accuracy and sensitivity by differential pulse polarography utilizing the catalytic reaction between nitrate and uranyl ion in the presence of potassium sulphate. The differential pulse polarographic peak-height is proportional to nitrate concentration from 1 to 50 muM. The calculated detection limit for nitrate is 8 x 10(-7)M in pure aqueous solution. The method has been applied to determination of nitrate in fresh snow, and river waters and animal feeds.

Temperature dependence of the height equivalent to a theoretical plate

Abstract It was predicted theoretically that the plate number of a given column varies with temperature. From the VAN DEEMTER theory 2 it was shown that the logarithm of the plate number, or of HETP, plotted against the reciprocal of the absolute temperature gives two straight lines. This prediction was experimentally confirmed and it was found that each column shows the maximum plate number at a temperature near the boiling point of the sample.

Liquid-membrane dodecylbenzenesulphonate ion-selective electrode employing Victoria Blue as the counter-ion

The dodecylbenzenesulphonate anion forms an ion-pair with the Victoria Blue cation and this is easily extracted into nitrobenzene. It was found that the calibration curve of the dodecylbenzenesulphonate ion-selective electrode based on this system shows good linearity in the range 10(-3)-10(-7)M. Selectivity coefficients were evaluated for some anions. The results indicated a poor tolerance towards dodecyl sulphate, perchlorate and periodate. Dodecyl sulphate, dodecylbenzenesulphonate and several kinds of synthetic anionic detergents have been successfully titrated potentiometrically with a solution of Zephiramine (benzyldimethyltetradecylammonium chloride) by using the electrode as an indicator electrode.

Flow coulometry on a porous electrode under condition of limiting current

Summary A theoretical model is described for coulometry employing a flow electrolytic cell with a porous electrode working under condition of a limiting current. The model allows the “cell factor” of a flow electrolytic cell to be calculated. The possibility of eliminating secondary electrochemical reactions in the flow coulometric determination is discussed. A relation is derived for the upper limit of the chemical rate constant in an e.c.e. mechanism, so that the second electron transfer will not be observed in the flow coulometric determination.

Effect of the external resistance on the high-frequency polarographic wave height

Summary Two expressions as shown by eqns. (1) and (3) are postulated and verified experimentally for the dependencies of the HF polarographic wave height, i HF , on the depolarizer concentration C , the amplitude Δ E HF of the HF pulse, and the external resistance R ext . The statistical analysis of data has shown that eqn. (3) holds more accurately than eqn. (1) (see Table 3). The importance of lowering the circuit resistance in HF polarography is emphasized.

Voltammetric study of the speciation of cadmium(II) with L-aspartic acid in sea water

The complexation of Cd(II) with L-aspartic acid has been studied in model solutions of ionic strength 0.7 M, in artificial and genuine sea water by linear sweep anodic stripping voltammetry (LASV) at a low overall Cd(II) concentration of 9×10−8M. The side reactions of the Cd2=+ ion and of the organic ligand L in the sea water medium have been take into account and their effects on the conditional stability constant of the Cd(II)—L aspartic acid complexes have been clarified. Cd(II) forms two complexes of the type CdL and CdL2, which behave reversibly under polarographic conditions. Using the DeFord—Hume approach, we have evaluated the conditional stability constants from the dependence of the half-wave potential shift on the ligand concentration. A more precise equation for the half-wave potential shift in a multi-ligand system has been derived taking into account the mean coordination number n of the metal ion. The stability constants of Cd—L aspartic acid complexes are of the same order of magnitude as those obtained earlier for the Cd—glycine complexes. Taking into account the low dissolved organic matter (DOM) content of the open sea, it can be concluded that amino acids of this type cannot contribute significantly to the chelation of cadmium. Yet in estuarine waters and in interstitial waters of sediments, the often substantially higher DOM level may cause a certain degree of chelation of the dissolved trace metal Cd(II) by these amino acids.

Properties of a membrane electrode based on liquid ion exchanger incorporated in poly(vinyl chloride) and its application to potentiometric titration of bismuth(III)

Abstract The response of the membrane electrode based on poly(vinyl chloride) with incorporated quaternary ammonium chloride compound, capriquat, was studied in solutions containing various amounts of total iodide over the total bismuth(III) concentration range of 10−3–10−5 M. The electrode was highly sensitive to tetraiodobismuthate(III) ion which was more strongly bound by the membrane than chloride, iodide and other anions studied. In the solution containing 0.2 M total iodide, the potential change between 10−5 and 10−4 M total bismuth(III) was greater than 150 mV, as the result of anion exchange reaction between iodide and tetraiodobismuthate(III) ions at the membrane—solution interface. The electrode was successfully applied to the potentiometric titration of bismuth(III) in iodide solution with EDTA.