BUNSEKI KAGAKU Abstracts

Polycyclic aromatic hydrocarbons (PAHs) and fatty acids in oil-mist emitted from thermal treatments of 8 foods were analyzed with GC/MS. As a result, the total PAHs and total fatty acids in oil-mist were detected in 0.06 – 976 ng g⁻¹-food and 0.000250 – 7.51 mg g⁻¹-food, respectively. Thermal treatment of fish (Mackerel Pike) resulted in that PAHs were generated over 100 times more when the fish was heated in the fire directly. Also, the amount of PAHs generated was positively correlated with the amount of fat in the food, whereas not with the amount of protein and carbohydrate in the food. This result showed that PAHs were generated mainly by incomplete combustion of fat in the food. Finally, the carcinogenic risk by exposure of oil-mist emitted from several cooking was evaluated, resulting in that the carcinogenic risk by exposing oil-mist generated from cooking of fish (grilled), fish (directly fired) and beef (grilled) was 1.1 × 10⁻⁷, 4.3 × 10⁻⁵, 2.0 × 10⁻⁷, respectively.

Natural colloidal particles including soils often form porous complexes due to aggregation and adsorption of polymeric substances, etc. Characterization of their behavior in soil and aquatic environments, such as coagulation, deposition, and transport, requires a comprehensive analysis of both hydrodynamic and electrokinetic properties of colloidal complexes, while chemical and physical heterogeneity of the suspension complicates the measurements. In fact, conventional measurement techniques, e.g. dynamic light scattering, are incapable of extracting neither hydrodynamic data on individual uneven complexes composing a poly-dispersed suspension nor structural conformation of polymers adsorbed on colloidal surfaces since the instruments output an averaged characteristic of the whole sample. We have approached this experimental issue through developing a new particle sizing technique that allows us to characterize hydrodynamic properties of a single, individual colloidal complex by analyzing its Brownian motion under a simple optical microscope. Using this single particle tracking technique, we clarified the influence of initial floc growth on the hydrodynamic diameter of a micrometer dimension. In comparison with corresponding electrophoretic mobilities, this technique has further revealed that electro-osmotic flow arises deeply inside a porous floc under the electric field. We also show kinetic transition of adsorbing polyelectrolytes on colloidal surfaces detected through the temporal analysis of the Brownian diffusion of single particles. All measurements above lead us to an implication that fluid flows inside colloidal complexes differ markedly with and without imposed electric field, hence permeability of porous media is an important parameter to be considered.

Isotope analysis of lead in fractions (1 – 5), fractionated by a sequential extraction procedure for contaminated soil found in the ground of Asahikawa and Iwamizawa stations of Hokkaido Railroad Company (JR Hokkaido), have been carried out. The amounts of lead in fractions 3 and 4 were relatively larger than that in the other fractions. The lead isotope ratio of the fraction 1 – 4 for each soil sample was different from that of each fraction 5. The lead isotope ratio of fractions 1 – 4 of Iwamizawa soil was not the same as those of Asahikawa. The isotope ratio of lead in white metal which was used as an axle bracket of freight car, was close to those of fractions 1 – 4 of Iwamizawa soil. The presence of tin was found in Iwamizawa soil, and the ratio of the amount of tin to lead in the soil was near the ratio of that in a kind of WM. Therefore, it is presumed that the source of contamination with lead in Iwamizawa soil is due to the WM used previously in JR Hokkaido. Tin was not detected in Asahikawa soil. Thus, the source may be different from that of Iwamizawa.

A sensitive and selective method for determination of Cr(VI) has been developed using chromium-catalyzed oxidation of o-phenylenediamine with hydrogen peroxide. Under an optimized condition, the absorbance at 430 nm and at a fixed reaction time of 10 min was proportional to the concentration of Cr(VI) up to 1 mg L⁻¹. A detection limit (DL) was 1 μg L⁻¹. On-site determinations were carried out using a laboratory-made palm-top size colorimeter with a red-green-blue light emitting diode. Measurement of the absorbance for blue light was used for the determination up to 1 mg L⁻¹ with a DL of 1 μg L⁻¹. A kinetic study derived an on-site reaction time of τ = τ_oexp[b(1/T – 1/T_o)], where the standard reaction time τ_o = 10 min, b = 7.65 × 10³, a standard reaction temperature T_o = 298 K. By this equation, τ giving an absorbance value at τ_o and T_o can be calculated for any on-site temperature (T) between 20 and 40°C. On-site analyses within an error of 6% were carried out without control of reaction temperature and with a laboratory-prepared calibration curve at τ_o and T_o. The proposed method was successfully applied to natural and standard river-water samples and an industrial waste-water sample.

An LC/MS method with high sensitivity and selectivity was developed for the chiral separation and quantification of α-lipoic acid in dietary supplements. Excellent mutual separation of the optical isomers of α-lipoic acid was achieved by using CHIRALPAK AD-RH as a chiral column. Solid-phase extraction after liquid-liquid extraction resulted in sufficient purification of the sample matrix, which in turn improved quantification. The LOD and LOQ of the proposed method were 5 ng/mL and 10 ng/mL, respectively. Enantiomeric analysis of α-lipoic acid in commercially available dietary supplements revealed the presence of some unknown enantiomers in the samples. The d-enantiomer may have been converted into the l-enantiomer during the manufacturing process. The developed method can be used to measure the optical isomers of α-lipoic acid in dietary supplements, and is expected to be useful for the quality evaluation of a product.

An alternative simultaneous injection-effective mixing analysis system controlled by a personal computer was proposed for the determination of residual chlorine. This system consists of a sequential injection mode (SI), a multi-commutation mode (MC) and a flow injection mode (FI). Chlorine reacts with 4,4'-bis-dimethylaminothiobenzophenon dissolved in Triton X-100, 2-methoxyethanol and formic acid/fomate buffer to form a blue compound (λ_max, 640 nm). The calibration graph was linear in the range of 0 – 1.68 mg L⁻¹ chlorine and the regression coefficient was 0.999. The RSD for 0.56 mg L⁻¹ chlorine (n = 5) was 0.37% and the repeatability was excellent. The sampling rate for one analysis was 41 s. This method is less reagent consuming and the sensitivity is excellent. This method is applicable to the determination of residual chlorine in tap water.

This paper reports the selectivity of dithizone dye nanofiber-coated test strip (Dith DNTS) for the detection of Hg^II at ppb level. The Dith DNTS having thin layer (less than 500 nm) composed of 100% dithizone ensures highly sensitive Hg^II detection in the range of 0.1 to 20 ppb with the 3 σ detection limit of 0.057 ppb within 17 min by filtration enrichment of 100 mL of sample solution and subsequent reflection absorption measurement. The detection method has been shown to possess high tolerance to various cations and anions based on solid-liquid separation between dithizone layer and aqueous solutions in the presence of suitable reagents. Consequently, the allowable limits for reliable detection of 10 ppb of Hg^II with their removal requirements were as follows : Na ⁺ (10000 ppm), K ⁺ (5000 ppm), Ca^II (5000 ppm), Al^III (500 ppm), Cr^III (200 ppm), Cr^VI (3 ppm), Mn^II (100 ppm), Fe^III (100 ppm), Ni^II (100 ppm), Cd^II (10 ppm) and Pb^II (100 ppm) under acidic conditions, Cu^II (6.4 ppm) and Zn^II (100 ppm) using EDTA as a masking reagent to form water-soluble chelates, Fe^II (70 ppm) with KBrO₃ to oxidize Fe^II to Fe^III, and Ag ⁺ (50 ppb) by filtration a sample solution containing NaI through a membrane filter to remove AgI precipitates. This highly sensitive and selective detection system is a promising method for simple and reliable on-site monitoring of Hg^II in real water samples.

An analytical method for the determination of Brilliant Blue FCF in water by liquid chromatography mass spectrometry (LC/MS) has been developed. A hundred milliliter of water sample portion of passed through an anion exchange solid phase extraction cartridge at a flow rate of 3 mL min⁻¹. The cartridge eluted with 5 mL of 5%-NH₄OH/methanol. The eluate was concentrated to ca. 0.5 mL, and Fast Green FCF was added as an internal standard and adjusted to 1 mL with purified water. This solution was determined by LC/MS (ESI negative ion mode). The averages of recoveries of Brilliant Blue FCF from purified water and pond water were 97.4% and 94.8%, respectively. For the 32 rivers in Ibaraki Prefecture investigated by this method, Brilliant Blue FCF was detected from 26 rivers. A detected mean concentration was 0.13 μg L⁻¹, and the maximum concentration was 1.2 μg L⁻¹. This result shows that Brilliant Blue FCF exists in the environment widely.