Michio Zenki

Repetitive determination of chloride using the circulation of the reagent solution in closed flow-through system.

The precipitation reaction of silver chloride (AgCl) is carried out in a large amount of ammonia (NH(3)). This makes possible to adopt a closed-loop flow injection (FI) system and to determine chloride repetitively. A solution of 30 mmol l(-1) silver nitrate and 80 mmol l(-1) NH(3) in a single reservoir (250 ml) is continuously circulated through the flow cell at a flow rate of 2.0 ml ml(-1). The chloride containing sample (100 mul) was introduced into this reagent solution by means of six-way valve. AgCl precipitates formed in the sample zone are monitored spectrophotometrically (at 500 nm) in the flow system. After passing through the flow cell, the excess NH(3) in the circulating reagent solution dissolves AgCl precipitates and the stream then returns to the reservoir. Various variables of the FI system were optimized and a study of interfering ions was also carried out. A linear calibration graph was obtained from 3.0 to 30 mg l(-1) chloride. Two hundred repetitive injections of 5.0 mg l(-1) chloride into the circulating reagent solution have shown unchanged base-line and good reproducibility. The method was successfully applied to the determination of chloride in tap, natural and the reference waters.

Triazamacrocycle having pyridine-pendant arms as a new Na+ ion-selective ionophore

Abstract A new type of azamacrocycles having pyridine-pendant arms mediated highly selective and efficient transport of Na + ion via three-dimensional complexation, which was not attained by common azamacrocycle, crown, and hemispherand compounds.

Determination of residual chlorine in tap water by flow-injection spectrophotometry

Abstract The method is based on the redox reaction between 4,4′-tetramethyldiaminothiobenzophenone (thio-Michlers ketone) and chlorine at pH 3.5; 2-methoxyethanol and Triton X-100 are used to keep the reagent in solution. The absorbance of the blue quinoidal product is measured at 640 nm. Linear calibration is obtained for 0.2−1.0 mg l−1 chlorine. The method is suitable for tap waters.

Spectrophotometric determination of nitrite in natural waters by flow injection analysis

Abstract The method described is suitable for the determination of low μg l−1 levels of nitrite in waters. Nitrite diazotises p-aminoacetophenone and the product is coupled with m-phenylenediamine at 30°C. The limit of detection is 0.2 μg l−1 for sample injections of 650 μl. The sampling rate is about 30 h−1 and the relative standard deviation is ≦ 1.3%.

Clean analytical methodology for the determination of lead with Arsenazo III by cyclic flow-injection analysis.

A clean analytical methodology, where the sample determined and the reagent used are both toxic, has been proposed. A cation exchange mini-column was incorporated after the flow-through cell for on-line regeneration of the main reagent and the accumulation of heavy metal ions. The method involves the spectrophotometric determination of lead with Arsenazo III, the accumulation of lead onto the cationic exchanger, and subsequent regeneration of the chromogenic reagent, which makes the system reversible and the reagents reusable. The developed method provides a satisfactory way to cut down on the toxic reagent consumption and the produced volume of waste, an important step towards the zero emissions research initiative concept. The excellent repeatability and reproducibility, and the simplicity of this method are well suited for continuous measurements. The method was successively applied to the assay of lead in high-octane gasoline.

Repetitive determination of ascorbic acid using iron(III)-1.10-phenanthroline-peroxodisulfate system in a circulatory flow injection method.

Ascorbic acid (AA) could be determined in large quantities of a co-existing oxidant. The incorporation of an on-line reagent regeneration step based on redox reaction eliminates the baseline drift in the procedure. This makes it possible to adopt a circulatory flow injection method (cyclic FIA) and to determine AA repetitively. The method is based on the reduction of iron(III) to iron(II) by the analyte, the reaction of the produced iron(II) with 1,10-phenanthroline (phen) in a weak acidic medium to form a colored complex, and the subsequent oxidation reaction of iron(II) to iron(III) by the co-existing peroxodisulfate. A solution (50ml) of 3.0x10(-4)moll(-1) ferric chloride, 9.0x10(-4)moll(-1) phen and 5.0x10(-2)moll(-1) ammonium peroxodisulfate in acetate buffer (0.2moll(-1), pH 4.5) is continuously circulated at a constant flow rate of 1.0mlmin(-1). Into this stream, an aliquot (20mul) of the sample solution containing AA is quickly injected by means of a six-way valve. The complex formed is monitored spectrophotometrically (at 510nm) in the flow system. The stream then returns to the reservoir after passing through a time-delay coil (50m). The iron(II)-(phen)(3) complex is oxidized to iron(III)-(phen)(3) complex by peroxodisulfate which exists excessively in the circulating reagent solution. The proposed method allows as many as 300 repetitive determinations of 15mgl(-1) AA with only 50ml reservoir solution. The contents of AA in commercial pharmaceutical products were analyzed to demonstrate the capability of the developed system.

Determination of sulphate in natural water by flow-injection analysis

ZusammenfassungAls Reagens dient Dimethylsulfonazo-III. Die Störung durch Calcium bei dieser Bestimmung wird durch eine Kationenaustauschersäule eliminiert, die direkt nach dem Probeinjektions-Ventil angeordnet ist. Zur Erhöhung der Empfindlichkeit und Reproduzierbarkeit ist es notwendig, die Trägerlösung mit Bariumsulfat zu sättigen sowie bei Nichtbenutzung des Systems den Reaktionsteil mit Ethanol-Wasser (1∶1) zu füllen. Mit dem so modifizierten Verfahren ergaben sich Standardabweichungen von 0,94–1,2% für 6–10 mg/l Sulfat, die Nachweisgrenze liegt bei 0,2 mg/l. Die Eichkurve ist bis 14 mg/l linear. Mg2+, NH4+, Na+, K+, Cl−, NO3−, PO43−, HCO3−und SiO32−stören in den normalerweise vorkommenden Konzentrationen nicht.SummarySulphate was determined in natural water samples by flow-injection analysis using dimethylsulphonazo-III as reagent. The interference by Ca was eliminated by a cation-exchanger column inserted directly after the sample injection valve. In order to ensure high sensitivity and reproducibility it was necessary to saturate the carrier solution with barium sulphate and to fill the reaction coil with ethanol-water (1∶1) when not in use. Standard deviations were 0.94–1.2% for 6–10mg/l sulphate. The limit of detection was about 0.2mg/l. The calibration graph was linear up to 14mg/l Mg2+, NH4+, Na+, K+, Cl−, NO3−, PO43−, HCO3−and SiO32−did not interfere in the normally occurring concentrations.

Flow injection spectrophotometric determination of boron with D-sorbitol using Methyl Orange as an indicator

A spectrophotometric method for the determination of boron by flow injection, based on the complexation reaction between D-sorbitol and boric acid followed by the acid–base reaction of Methyl Orange, is described. Under the optimum conditions, the calibration graph was essentially linear up to 1.2 mg l–1 of boron (120 µl injections) and the detection limit was 0.02 mg l–1(signal to noise ratio = 3). Twenty samples can be analysed per hour with a relative standard deviation of 0.28–0.54%. The method was applied to the determination of boron in commercial eye lotions. By using a 0.6% m/v sodium chloride solution as the carrier stream, boron in sea-water samples was also determined.

Determination of nitrate in natural waters by flow-injection analysis

ZusammenfassungNitrat wird bei dieser Methode mit Hilfe einer Cu/Cd-Reduktionssäule zu Nitrit reduziert, das mit p-Aminoacetophenon und m-Phenylendiamin zur Reaktion gebracht wird. Die gebildete Verbindung wird spektral-photometrisch gemessen. Die Nachweisgrenze beträgt etwa 1,5 μg/l bei injizierten Probevolumina von 650 μl. Der Probendurchsatz beträgt 40/h. Die relative Standardabweichung liegt über 1% bei 0,1–0,3 mg/l Nitrat-Stickstoff. Vorhandenes Nitrit wird gesondert bestimmt und abgezogen.SummaryNitrate was determined in natural water samples by flow-injection spectrophotometry. It was reduced to nitrite with copperized cadmium and the nitrite thus produced reacted with p-aminoacetophenone and m-phenylenediamine. The limit of detection was about 1.5 μg l−1 for sample injections of 650 μl. The sampling rate was about 40 samples h−1 and the relative standard deviation was above 1% for 0.1–0.3 mg l−1 nitratenitrogen. Nitrite present in the sample was determined separately and subtracted.

The color reactions of sulfonazo-III isomers with lanthanum and alkaline earth metal ions

Abstract Six sulfonazo-III isomers were synthesized, and their color reactions with alkaline earth metals and lanthanum investigated. All six reagents had good sensitivities for lanthanum (ϵ = 1.9–5.0·10 4 ), but the sensitivities for alkaline earth metals were fairly low except for the barium chelate of sulfonazo-III (ϵ = 2.8 · 10 4 ). The position of the sulfo group on the phenyl ring and the symmetry of the reagent are important for the barium reactions, but of little significance for the lanthanum reactions. The effects of water-miscible solvents are also described.