Toshio Deguchi

Spectrofluorimetric determination of cyanide and thiocyanate based on a modified König reaction in a flow-injection system

Abstract Cyanide and thiocyanate were determined spectrofluorimetrically by the isonicotinic acid-barbituric acid (modified Konig) reaction method. The resulting solution was excited at 605 nm and the fluorescence was measured at 620 nm. The intermediate was also fluorescent; the excitation and emission wavelengths were 527 nm and 556 nm. The flow-injection procedure has a linear calibration range of 0−50 μM cyanide (or 40 μM thiocyanate), detection limits of 30 nM for both anions and a sample throughput of 30 h−1. The relative standard deviation is 0.95% for ten determinations of 1 μM cyanide.

Simultaneous determinationof cyanide and thiocyanate by the pyridine/barbituric acid method after diffusion through a microporous membrane

Abstract A flow-injection system for the simultaneous determinationof cyanide and thiocyanate is described. A microporous tubular PTFE membrane module with an outer casing was constructed and included inthe system. Cyanide and thiocyanate diffuse thourgh the membrane wall from the phosphoric acid donor stream to a phosphate or carbonate buffer acceptor stream. Percentage transference of cyanide and thiocyanate were 68% and 59%, respectively, at pH 6.0. At pH 8.1, the percentage transference of cyanide was only 19%. The transferred cyanide and thiocyanate are determined by a pyridine/barbituric acid method. Thiocyanate reacts slowly with chloramine-T at pH 8.1, so that cyanide can be determined without interference from thiocyanate. Total cyanide and thiocyanate are determined at pH 6.0. The detection limits ( S/N = 3) are 0.3 μM cyanide and 0.2 μM thiocyanate at pH 6.0, and 5 μM cyanide at pH 8.1. A mechanism for the transference thourgh the membrane is discussed. Bromine interferes with the determination of cyanide and thiocyanate at both pH 6.0 and 8.1. Hexacyanoferrate(II) and hexacyanoferrate(III) interfere at pH 8.1, but not at pH 6.0. Cyanate, oxaloacetate, oxalate, tartrate, albumin, globulin and lysozyme do not interfere.

Preconcentration of inorganic mercury with an anion-exchange resin and direct reduction—aeration measurements by cold-vapour atomic absorption spectrometry

Abstract Inorganic mercury ions (5–50 ng l-1) present in natural waters (500 ml) are concentrated on anion-exchange resin (0.2 g; chloride form) in a batchwise operation. The resin is filtered off and introduced into a bubbler containing tin(II) solution. The adsorbed mercury ions are reduced to the metal and vaporized with a stream of air in a closed system. Satisfactory recoveries are obtained for sea waters made 0.1 M in nitric acid, and for river and spring waters also made 0.1 M in nitric acid or 0.01 M in ammonium thiocyanate. The method preconcentrates traces of inorganic mercury ions by an order of magnitude, and is also effective in preventing mercury loss during sample storage.

The effect of ammonium thiocyanate and sodium chloride on loss and recovery of mercury from water during storage

Abstract The effect of inorganic complexing agents such as thiocyanate and chloride on the stability of distilled water and natural waters spiked with 1 μg Hg l -1 in polyethylene containers is reported. Distilled water solutions can be stored for several months without significant losses of mercury if they contain HNO 3 (0.05–0.1 M) + NH 4 SCN(0.001–0.01 M) or HNO 3 (0.1 M) + NaCl(higher than 0.01 M). For river and pond waters, addition of HNO 3 (0.1 M) + NH 4 SCN(0.01 M) not only has a pronounced effect on preventing mercury losses, but also gives quantitative recoveries from spiked sample solutions from which mercury has been “lost”. Thiocyanate ion-favors desorption of mercury from solid phases; chloride is less effective in this respect.

Dissociation of metal dithizonates during gel chromatography

Abstract Metal dithizonates in carbon tetrachloride were dissociated through gel chrometographic columns packed with Sephadex LH-20 or Merckogel OR-PVA 2000. The liberated metal ions were adsorbed on the surface of the gels, and the dithizone] in its neutral form was eluted from the column. Detailed investigation of this phenomenon was carried out by batch methods. The proposed mechanism is the geration of hydrogen chloride caused by the interfacial reaction of the gels with carbon tetrachloride.