BUNSEKI KAGAKU Abstracts

With an increase in the consumption of fossil fuels, large amounts of pollutants released into the atmosphere cause serious health problems. Polycyclic aromatic hydrocarbons (PAHs) and nitropolycyclic aromatic hydrocarbons (NPAHs) are among the atmospheric hazardous pollutants. The mutagenicities of several NPAHs are much stronger than those of PAHs, but the concentrations of NPAHs are much lower than those of PAHs in the environment. However, the progress of studies on the environmental behaviors and health effects of NPAHs has been much slower than that of PAHs, because of the lack of a sensitive analytical method available for trace NPAHs. This review deals with the development of sensitive determination methods for NPAHs starting the in late 1980s and recent studies on the contributors and atmospheric behaviors of NPAHs and human exposure to them.

The relative standard deviation of concentration estimates in a hapten immobilized competitive immunoassay can be estimated from the major error sources of the analytical procedures (mainly, pipetting errors) without any repetition of real samples. This RSD, called precision profile, exactly corresponds to the RSD estimated from the repetition of real samples over a wide range of concentration. The detection limit and quantitation limit are obtained from a continuous plot of the precision profile as 30％ and 10％ RSD, respectively. The results of this paper lead to a new proposition of the uncertainty estimation in ELISA.

A flow injection system is presented for the simple, rapid and sensitive determination of trace Cr(VI), incorporating in-line an activated alumina column utilized as an integrated medium for the separation, preconcentration and detection reaction of Cr(VI) in a flow-injection system. After Cr(VI) in the injected sample solution was adsorbed onto an alumina column, a diphenylcarbazide (DPC) solution in 0.1 M sulfuric acid and 6％ acetone was introduced directly into the column by switching its flowing stream. The complex formation of Cr(VI) with DPC occurred and proceeded rapidly while the DPC solution flowed through the column and thus the absorbance change due to the Cr(VI)-DPC complex in the effluent from the column was monitored spectrophotometrically at 540 nm. The variables related to such reactions and the manifold were studied in detail, and the optimal conditions and manifold configurations were established. A linear calibration with a 10 m sample loop (ca. 2 mL sample size) was obtained for Cr(VI) in the range of 0〜0.03 mg/mL. The coefficient of variation for 0.02 μg/mL Cr(VI) was 1.6％ (n＝4), and the estimated limit of detection (3 σ) was 0.7 ng/mL. Only 7 min was required for an analytical measurement after sample injection. An analysis rate of ca. 9/h was estimated. Most of the examined ions did not show significant interference with the determination when present 100 times or more in excess. River-water samples were analysed by the proposed FI system and satisfactory recoveries of 96〜101％ were found for spiked Cr(VI). The proposed FI system has the advantages that an additional stream line for a chromogenic reagent just like as in the case of post-column detection, is avoided, which makes the analytical system simpler and inexpensive, and also minimizes any unnecessary lowering of the sensitivity due to dilution.

The effect of the matrix on internal standardization in inductively coupled plasma-optical emission spectrometry has been studied. Solutions containing cobalt, iron and nickel as analytical elements; rhodium and yttrium as internal-standard elements; and sodium, potassium and sulfuric acid as co-existing elements were prepared. The atomic emission intensities of cobalt, iron, nickel, rhodium and yttrium were observed in both the axial and the radial observation modes. When sodium was co-existing, the intensities of the atomic lines of analytical and internal elements were decreased with increasing sodium concentration in the axial observation mode. On the other hand, in the radial observation mode, the intensities of the atomic lines of analytical and internal elements were increased with increasing sodium concentration. When potassium was co-existing, the intensities of the atomic lines of the analytical and internal elements were decreased with increasing sodium concentration in both the axial and radial observation modes. As a result, rhodium was very useful as an internal standard element, while yttrium was not. This effect could be caused by the differential of the ionization potential of the analytical elements and the internal-standard elements. The ionization potential of rhodium is similar to that of these analytical elements, while the ionization potential of yttrium is less than that of the analytical elements.

A rapid and reproducible method for determining fluoride ion (F⁻) in cements using a pyrolytic separation technique and an alizarine complexone photometric FIA method has been established. A 0.5 g portion of cement with tungsten oxide (1.25 g) was pyrolysed for 10 min under a stream of moist air (0.7 L min⁻¹) in a furnace (1050 °C). The volatilized fluorine was absorbed in a 1 mmol L⁻¹ sodium acetate solution (100 mL). The solution (200 μL) was injected into the FIA system. A good relation was obtained between F⁻ found in cements by the proposed method and the Cement Association of Japan Standard (CAJS) method. The time taken to analyze the cement was only 20 min. (15 min for weighing and pyrolysis plus 5 min for FIA measurement). The sample throughput for this method was 12-times higher compared to that for the CAJS method.

A trace amount of zinc was determined by an electrically heated quartz tube atomization (QTA) atomic absorption spectrometry (AAS) with a continuous-flow gas-phase sample introduction technique by using both nitric acid and hydroxylamine hydrochloride solutions as reaction media, and sodium tetrahydroborate (III) as a reductant. Under the optimized experimental conditions, the best attainable detection limit for zinc at 213.86 nm was 0.2 ng m. The instrumental precision, expressed as the relative standard deviation (RSD) from ten replicate measurements of 50 ng m for zinc by QTA-AAS, was 5.0％. After the effects of diverse elements on the determination of zinc were examined, this method was applied to the determination of low concentrations of zinc in water and leaves. The results obtained by the present method were in good agreement with the certified values.

The surface of a gold (Au) disk electrode was modified with layer-by-layer (LBL) films consisting of phenylboronic acid polymer and carboxymethylcellose to fabricate a voltammetric sugar sensor. The modified Au electrode exhibited a voltammetric response to D-glucose and D-frucose in the presence of Fe(CN)₆³⁻ ion in the sample solution at neutral pH. The peak current of the cyclic voltammograms decreased, depending on the concentration of sugars. The dynamic range in the calibration graph is 0.1〜300 mM for D-glucose and D-fructose.

In the dye-binding method based on a protein error of a pH indicator, the upper-limit pH (pH_UL) at which an absorbance increase occurs exists. In the present work, the relationship between pH_UL and the buffer concentration in color reagent was investigated by a calculation and an experiment using four sulfonephthalein pH indicators. pH_UL was observed in reactions of all the dyes and human serum albumin; it was not affected by the buffer concentration. In addition, the equilibrium constant did not affect pH_UL, suggesting that it does not change due to the kind of buffer. The pH_UL value was peculiar to each dye, and correlated moderately with the dissociation constants of each dye. The pH_UL changed only according to the ratio (ε_PD/ε_D) of the molar absorptivities between the dye-protein complex (ε_PD) and the dissociated dye anion (ε_D), and shifted to a higher pH due to an increase in its ratio. pH_UL was found to exist only when the ratio of the molar absorptivities was ε_PD/ε_D＜1.

The facilitated ion transport from one aqueous phase (W1) to another (W2) across a bilayer lipid membrane (BLM) in the presence of nonactin (Non) as an ion carrier in a BLM was elucidated. A cation-Non complex is distributed into the BLM with an anion as a counter ion to hold the electroneutrality within the BLM phase. It was found that the anion transferred between W1 and W2 across the BLM in the opposite direction from that of the objective cation upon applying the membrane potential. These phenomena can be interpreted based on the relation between the distribution coefficient and the hydration energy and on the dependence of the ion transport facilitated by Non through a BLM on the concentration of Non in the BLM, the stability constant of Non with cations and the hydrophobicity of both cations and anions.