Tokuo Shimizu

Determination of bismuth in sea-water by electrothermal atomic absorption spectrometry after liquid–liquid extraction and micro-volume back-extraction

A method for the determination of bismuth at ng l–1 levels in sea-water is described. Bismuth is extracted into xylene as the dithiocarbamate complex and subsequently back-extracted into 100 µl of nitric acid for determination by electrothermal atomic absorption spectrometry (ETAAS). The high efficiency of extraction and back-extraction allows bismuth to be concentrated about 25000-fild with a combined single extraction and back-extraction. The back-extracted solution is suitable for the determination of bismuth by ETAAS. Detection limit for Bi is 0.27 mg l–1 based on a 3300-fold preconcentration. The concentration of bismuth in coastal sea-water was found to be 1.6 ng l–1 by the proposed method. The accuracy of the results was assessed by comparison with those obtained by other analytical techniques.

High-performance liquid chromatographic separation of iron, bismuth, indium and thallium by pre-column chelation with 2-(5-bromo-2-pyridylazo)-5-(N-propyl-N-sulphopropylamino)phenol

The reversed-phase high-performance liquid chromatographic separation of several metal chelates with 2-(5-bromo-2-pyridylazo)-5-(N-propyl-N-sulphopropylamino)phenol (5-Br-PAPS) on a C18-bonded stationary phase using methanol-water mixtures as the mobile phase is reported. The FeIII-BiIII-, InIII-and TlIII-5-Br-PAPS chelates were separated in about 20 min using a LiChrosorb RP-18 column (125 × 4 mm i.d.) with methanol-water (65 + 35) as the mobile phase containing 1 × 10–4M 5-Br-PAPS, 0.06 M butylamine and 0.05 M chloracetate buffer (pH 3). Visible detection limits at 580 nm are established in the range 0.1–1.2 ng of metal, except for TlIII, which cannot be determined owing to degradation of the chelate on the column.

Spectrophotometric and analogue derivative spectrophotometric determination of rhodium(III) with 2-(5-bromo-2-pyridylazo)-5-(N-propyl-N-sulphopropylamino)phenol

A sensitive spectrophotometric method for the determination of rhodium(III) has been established by reacting rhodium(III) with 2-(5-bromo-2-pyridylazo)-5-(N-propyl-N-sulphopropylamino)phenol (5-Br-PAPS). 5-Br-PAPS reacts with rhodium(III) to form a water-soluble 1 : 2 (metal : ligand) complex on heating at 95 °C. The rhodium(III)-5-Br-PAPS complex has two absorption maxima at 557 and 600 nm in the pH range 4.0–9.2. The molar absorptivity is 1.09 × 105 l mol–1 cm–1 at 600 nm. The favourable selectivity of the method is obtained by the addition of EDTA as a masking agent after formation of the rhodium(III)-5-Br-PAPS complex. The sensitivity of the method can be increased about ten times by employing analogue derivative spectrophotometry.

Thermal-induced growth of gold nanoparticles conjugated with thermoresponsive polymer without chemical reduction

The growth of gold nanoparticles without chemical reduction of gold (III) ions was achieved by the disruption of thermoresponsive polymers conjugated with the gold nanoparticles through the phase transition of the polymers. When a solution of gold nanoparticles coated with thermoresponsive polymers was heated, chains of the thermoresponsive polymers were disrupted because of dehydration, resulting in the fusion of gold nanoparticles to form larger nanoparticles. The evolution of the extinction band around 550 nm evidenced the formation of these large (post-fusion) gold nanoparticles, which were characterized by transmission electron microscope (TEM) and dynamic light scattering (DLS). TEM images verified the formation of the large gold nanoparticles having particle sizes of 80-100 nm, whereas DLS indicated the existence of large nanoparticles with hydrodynamic diameters exceeding 200 nm. The deposition did not require the addition of reductants or trivalent gold ions for the formation of the large gold nanoparticles. Both the heating and the solution conditions were studied to elucidate the mechanism of the formation of large gold nanoparticles.