Kazuo Hiiro

Phosphate ion-sensitive coated-wire/field-effect transistor electrode based on cobalt phthalocyanine with poly(vinyl chloride) as the membrane matrix

Abstract An ion-selective coated-wire/field-effect transistor electrode responding to dihydrogenphosphate is described. The device consists of a coated-platinum wire electrode connected to the gate of a conventional field-effect transistor. Cobalt phthalocyanine is used as ion-exchange electroactive substance and poly(vinyl chloride) as the membrane matrix. The characteristics of the device are investigated and its response is studied by two methods, the linear dependence of the square root of the drain current in the saturated region on the logarithm of ion activity for sodium dihydrogenphosphate, and the dependence of the gate-source potential on the logarithm of ion activity of the same ion. A linear response is obtained in the range of ion activity 10−5-10−1 mol dm−3 and the response slope is 45 mV per decade change of H2PO4− ion activity; the selectivity coefficients are discussed.

Perchlorate-selective electrodes with urushi as the membrane matrix

Abstract Perchlorate-selective electrodes prepared from a new matrix, Urushi, and tri-n-octylmethylammonium perchlorate or the Corning perchlorate liquid ion-exchanger are described. The electrodes have linear response ranges and selectivity similar to those of commercial perchlorate-selective electrodes. The membranes are hard, lustrous and smooth; their useful lifetimes exceed 1000 h.

Urushi matrix sodium, potassium, calcium and chloride-selective field-effect transistors

Abstract Sodium, potassium, calcium and chloride ion-selective field-effect transistors (ISFETs) with Urushi (natural oriental lacquer) matrix membrane were fabricated. The Urushi matrix ISFETs have good stability and durability for over a month because of the strong adhesion of the Urushi matrix membrane to the Si3N4 gate. The sensitivity, linear response range and selectivity of the Urushi matrix ISFETs are coincident with those of the corresponding polyvinylchloride (PVC) matrix ion-selective electrodes. The hardening mechanism and the matrix mechanism of the Urushi matrix membrane are discussed.

Use of crown ethers in the isotachophoretic determination of metal ions

Abstract The effects of crown ethers on the effective mobilities of various metal ions in capillary isotachophoresis were studied. The effective mobilities of thallium, lead and silver ions decreased when the concentration of crown ethers in an ordinary leading electrolyte was increased up to 50 mM. Thus, by use of 18-crown-6, ammonium and thallium ions and thallium and lead ions were completely separated and could be determined. Similarly, by use of 15-crown-5, potassium and thallium ions and ammonium and silver ions were completely separated and could be determined.

Simultaneous determination of low concentrations of ammonium and potassium ions by capillary type isotachophoresis

Low concentrations of ammonium and potassium ions (<2.0 mg/l.) were determined simultaneously by capillary type isotachophoresis based on the interaction between potassium and 18-crown-6 in the aqueous leading electrolyte. The PU value of potassium ion increased with increasing concentration of 18-crown-6 up to 3mM, whereas that of the ammonium ion remained almost constant. Thus complete separation of ammonium and potassium ions could be obtained by using 1-3mM 18-crown-6. The error in the analysis of mixtures containing ammonium and potassium ions (250-mul sample injection) was less than +/- 20% with a leading electrolyte containing 3mM 18-crown-6. The analysis time was 18 min.

A novel urushi matrix sodium ion-selective field-effect transistor

Abstract A durable sodium ion-selective field-effect transistor (ISFET) is proposed with Urushi as the membrane matrix. The sodium ion-sensing membrane is composed of sodium ionophore (ETH 227), di-2-ethylhexylphthalate, potassium tetrakis(p-chlorophenyl)borate and Urushi. The prepared Urushi matrix ISFET showed a linear response in the sodium ion activity range from 100 M to 10−3.5 M and about 53 mV per decade change of sodium ion activity. The selectivity of the Urushi matrix ISFET was almost the same as that of the corresponding PVC matrix ion-selective electrode. The Urushi ISFET showed excellent stability with drift below 0.15 mV per hour and durability for over a month, because of strong adhesion of the membrane to the Si3N4 gate.

A novel Urushi matrix chloride ion-selective field effect transistor

A durable chloride ion-selective field effect transistor (ISFET) is proposed with Urushi as the membrane matrix. The chloride ion-sensing material is a quaternary ammonium chloride: trioctylmethylammonium chloride (TOMA-Cl) or tridodecylmethylammonium chloride (TDMA-Cl). The optimum composition of the Urushi membrane was found by use of Urushi ion-selective electrodes. The mixture with the most favourable composition was coated on the gate region of the FET device. The Urushi ISFET with TDMA-Cl proved to be superior to that with TOMA-Cl, in sensitivity, linearity and selectivity. The Urushi ISFET with TDMA-Cl showed a linear response of about -51 mV per decade change of chloride ion activity in the range 10(-4)-1M. The Urushi ISFET showed excellent stability and durability for over two months, because of strong adhesion of the membrane to the Si(3)N(4) gate.

Determination of sulphide in sea-water by capillary isotachophoresis

Abstract A new analytical procedure for sulphide in sea-water was developed using capillary isotachophoresis and a tubular microporous polytetrafluoroethylene membrane for preliminary enrichment. Hydrogen sulphide generated by adding sulphuric acid to the sea-water samples was allowed to permeate through the membrane and dissolved in sodium hydroxide solution. Barium cation-exchange resin was then added to the sodium hydroxide solution to remove the carbon dioxide dissolved. A linear calibration graph was obtained for artificial sea-water samples containing up to 2.0 mg/1 of sulphide. The method was applied to the determination of sulphide in surface and bottom sea-water samples.

Determination of total carbon dioxide in seawater by capillary type isotachophoresis

SummaryA new analytical procedure for total carbon dioxide in seawater was developed: a capillary-type isotachophoresis which applied a tubular microporous PTFE membrane as a preliminary enrichment was used. Carbon dioxide was generated by adding sulfuric acid to seawater samples, permeated through a tubular microporous PTFE membrane and dissolved in sodium hydroxide solution for the separation from large amounts of coexisting anions, such as chloride and sulfate ions. A linear working curve was obtained for artificial seawater samples containing up to 40 mg/l of total carbon dioxide. The proposed method was applied to the determination of total carbon dioxide in surface and bottom seawater samples. Concentrations of the total of free carbon dioxide and carbonic acid, hydrogencarbonate and carbonate ions in these samples were calculated from the concentration of total carbon dioxide, temperature, pH and salinity of samples measured in situ.

Methods for the preparation and characterisation of a selenocyanate ion-sensitive field effect transistor with Urushi as the membrane matrix

A selenocyanate ion-sensitive field effect transistor (ISFET) was fabricated from a silicon wafer with Urushi (natural lacquer) as the membrane matrix. The proposed ion sensor has excellent durability for over 2 months. The ISFET can be characterised by the relationship between the square root of the drain current and the logarithm of the ion activity in the saturation region of the ISFET. It was found that the linear response range of the Urushi ISFET was from 10–5 to 10–1M selenocyanate ion activity and the selectivity coefficients were almost the same as those of the Urushi ion-selective electrode.