Katsushi Nishizawa

Measurement of temperature dependence for the vapor pressures of twenty‐six polychlorinated biphenyl congeners in commercial Kanechlor mixtures by the Knudsen effusion method

The vapor pressures of the major congeners in commercial polychlorinated biphenyl (PCB) mixtures (Kanechlors; Kanebuchi Chemical Industry, Tokyo, Japan) have been experimentally determined by Knudsen mass loss effusion. We obtained vapor pressures for the individual PCBs in the crystalline solid, liquid, and subcooled liquid forms as a function of temperature. We derived the thermodynamic parameters, such as the enthalpies of sublimation and vaporization, from the temperature dependence of the vapor pressure by the Clausius-Clapeyron equation. To decide whether the commercial PCB mixtures were ideal solutions, we obtained the activity coefficients by comparing our experimental vapor pressures for pure PCB congeners with those calculated from Kanechlor molar compositional data and vapor pressure values. In many cases, we found that, at 298 K, the values of the activity coefficients of major PCBs in Kanechlor 300 and 500 ranged from 1 to 2. Thus, we suggested that the commercial PCB mixtures show slight positive deviations from ideal solution (Raoults Law) behavior at ambient temperatures.

Vapor pressure of ten polychlorinated biphenyl congeners and two commercial fluids as a function of temperature

The Knudsen mass-loss effusion technique was used to measure the vapor pressures of commercial Kanechlor fluids (Kanechlor 300 and Kanechlor 500) and 10 major individual polychlorinated biphenyls (PCBs) in Kanechlors as a function of temperature and ortho-chlorine substitution. From the temperature dependence of vapor pressure, the thermodynamic parameters, such as enthalpies and entropies of sublimation and vaporization, were derived using the Clausius-Clapeyron equation. The results were compared with both experimental and calculated literature values. The ortho-chlorine substitution effects on the vapor pressure of major PCB congeners in Kanechlor mixtures were studied on the same homologous series. Within this series, the greater the number of chlorine substitutions in the ortho-positions, the higher the vapor pressure, because of the ortho-effect.

Analysis of trace metal elements in water using laser-induced fluorescence of laser-breakdown plasma

Laser induced breakdown and laser-excited atomic fluorescence spectroscopy were used to analyze trace metal atoms in water. Laser breakdown plasma was generated by a Q-switched Nd:YAG laser and an optical parametric oscillator (OPO) laser was used to excite target atoms in water. The wavelength of second laser was tuned to the absorption line of the target atom, and its time delay from the first one was optimized in order to maximize the fluorescence signal under low background light. Furthermore, the optimum transition lines were selected in terms of oscillator strength, branching ratio, and level population of target atom. In the case of Fe doped solution, the Fe concentration of less than a hundred ppb was detected. With this method, a lower detection limit of Fe was achieved than that in the case of the method using only laser-induced breakdown spectroscopy. The developed system is applicable for quick and supersensitive detection of trace metal atoms in water.