BUNSEKI KAGAKU Abstracts

Excellent fluorescence reagents used for a sensitive fluorescent analysis of boron are 1,8-dihydroxynaphthalene-3,6-disulfonic acid (chromotropic acid) and 1,8-dihydroxynaphthalene (1,8-DHN). When these two reagents are compared, chromotropic acid is more sensitive because it has two sulfo groups. Hence, similar effectivenese can be suggested between 2,3-dihydroxynaphthalene (2,3-DHN) and 2,3-dihydroxynaphthalene-6-sulfonic acid (2,3-DHNS). Therefore, 2,3-DHNS has been studied as a new fluorescent reagent for the determination of boron in this work. 2,3-DHNS generates a complex with boron at a ratio of 1 : 2 (boron : 2,3-DHNS). The complex and the reagent were detected at λ_ex = 295 nm, λ_em = 360 nm. The effects of the pH, reagent concentration and time were mainly studied. Under the resulting optimum conditions, a calibration curve was drawn, which was linear over the range of 0 to 1 ppm. The detection limit was 9 ppb and the determination limit was 27 ppb. A triangular quartz cuvette was applied to the above method. By using a triangular cuvette instead of the standard quartz cuvette, the reabsorbtion of an excitation beam by the reagent, itself, the inner filter effect can be reduced. The optimum conditions, such as the reaction pH, reagent concentration and the directions of the triangular cuvette, were studied using the triangular cuvette. Under the resulting optimum conditions, a calibration curve was drawn, which was linear over the range of 0 to 1 ppm. The detection limit was 3 ppb and the determination limit was 9 ppb. This proposed method was applied to standard river water, and showed good agreements with certified values.

The authors have developed an analytical method for 13 residual organochlorine pesticides (Aldrin, Dieldrin, Endrin, Heptachlor, Heptachlor epoxide, α-BHC, β-BHC, γ-BHC, δ-BHC, o,p'-DDT, p,p'-DDD, p,p'-DDE and p,p'-DDT) in soil by CO₂ supercritical fluid extraction (SFE). 1-Hexanesulfonic acid sodium salt was used as a modifier on SFE in this experiment. The recovery from 81 to 103% under condition where 2 mL of water was added to 2 g of spiked air-dried soil. The extraction efficiency was equivalent to that obtained by Soxhlet extraction. Furthermore, the soil contaminated with Dieldrin and p,p'-DDT was extracted by SFE and Soxhlet extractions so as to validate our SFE method. The result revealed that the recovery rates obtained by SFE were from 100 to 105% of those obtained by Soxhlet. This method has such advantages as simple operation, shorter extraction time (approximately 30 min) and less organic solvent required for extraction. These results suggest that our SFE method is effective to analyze residual organochlorine pesticides in soil.

A simple method has been developed for the determination of bismuth in iron and steel by using flame atomic absorption spectrometry (FAAS) coupled with ion-pair solid-phase extraction. A weighted sample (ca. 0.5 g) was decomposed with hydrochloric and nitric acids and hydrogen peroxide, and prepared as a 40-mL solution of 0.1 M potassium iodide−0.1 M nitric acid−4% ascorbic acid−3.1×10⁻⁴ M tetrabutylammonium (TBA) bromide. A sample solution thus prepared was loaded on a column (15 mm i.d.×10 mm) packed with 0.5 g of polystyrene-divinylbenzene polymer, and a bismuth-iodo-TBA complex was adsorbed on the column, being separated from iron that passed through the column. Bismuth retained on the column was eluted with 70% methanol−0.1 M nitric acid. The effluent was evaporated to dryness and prepared as a 10-mL solution of 0.1 M nitric acid to be subjected to FAAS. The proposed method has been applied to the determination of bismuth at several tens of μg g⁻¹ in steel reference materials provided by Japan Iron and Steel Federation, yielding reasonable results with regard to the accuracy and repeatability. The detection and quantification limits of the present method were found to be 1.4 μg g⁻¹ and 4.6 μg g⁻¹ in iron and steel, respectively.

A flow-injection amperometric analysis system for the determination of glucose in human urine was analyzed. The glucose sample was mixed with glucose oxidase, and was introduced into the flow-injection system. Hydrogen peroxide produced by an enzymatic reaction was amperometrically detected by a platinum electrode modified with Nafion, and an electrochemically polymerized saccharide substituted polypyrrole. The influence of electroactive compounds such as ascorbic acid, uric acid, and acetaminophen to the glucose response observed in this system was negligible. A good linear relationship between the glucose concentration and the response current was obtained within a concentration of up to 22.4 mmol dm⁻³. The relative standard deviation for ten replicate analyses of 5.6 mmol dm⁻³ glucose in human urine was 7.4%.

A simultaneous determination method of anions and cations in sewage water by an ion chromatographic method using a dual flow path system has been investigated. This analytical method provides a high linearity of the calibration curve as well as repeatability and reproducibility. The correlation coefficients of the calibration curve were estimated to be from 0.9980 to 0.9999 for anions and cations in the low concentration range from 0.1 mg L⁻¹ to 2.0 mg L⁻¹. The detection limits by an EC detector calculated on 3σ were 0.01 mg L⁻¹ for F⁻, 0.01 mg L⁻¹ for Cl⁻, 0.02 mg L⁻¹ for NO₂⁻, 0.02 mg L⁻¹ for Br⁻, 0.02 mg L⁻¹ for NO₃⁻, 0.02 mg L⁻¹ for PO₄³⁻, 0.01 mg L⁻¹ for SO₄²⁻, 0.01 mg L⁻¹ for Li⁺, 0.01 mg L⁻¹ for Na⁺, 0.01 mg L⁻¹ for NH₄⁺, 0.03 mg L⁻¹ for K⁺, 0.01 mg L⁻¹ for Mg²⁺, and 0.01 mg L⁻¹ for Ca²⁺. In addition, the detection limits by UV detector calculated on 3σ were 0.02 mg L⁻¹ for NO₂⁻, 0.02 mg L⁻¹ for Br⁻, and 0.01 mg L⁻¹ for NO₃⁻. These analytical methods could be successfully applied to the determination of anions and cations in inlet water of sewage water.

In Mar. ’06 to May ’08, the Japan Society for Chemical Analysis has operated stability tests on seven reference materials being stored by JSAC : JSAC 0302-river water for the analysis of inorganic components, JSAC 0311-wastewater for the analysis of dioxins, and so on. Interlaboratory comparison tests were performed with the participation of 6 laboratories for each reference material. In the tests, reference materials in storing were analyzed for the same components as in their certification or assignation. En numbers defined in ISO Guide 43-1 and En' numbers that derived from En were calculated from the test results and certified/assigned values in order to quantify the deviation of test results from the certified/assigned values. The stability of a reference material can be evaluated through the absolute value of its En' number. As a result, almost all results of stability tests of every reference material showed good relations with their certified/assigned values. Therefore, it was concluded that the reference materials tested here were stable.

The Japan Society for Analytical Chemistry has carried out proficiency testing on food analysis four times from 2004 to 2008 following the procedure specified in ISO/IEC GUIDE 43-1. The test sample was different in each test : powdered milk for 1st, fish sausage for 2nd, pudding for 3rd and baby food for 4th. The constituents to be analyzed were common for each test ; they were protein, lipid, ash, water, calcium, iron, sodium and phosphorus. The number of laboratories that participated was 65 at the most (3rd), and 53 at least (4th). The analytical methods applied in the testing were the Japanese official method concerning food analyses. In the test, samples were distributed to laboratories after being tested concerning homogeneity, and analytical reports from laboratories were evaluated using z scores of the robust method. The ratios of laboratories evaluated as being satisfactory, or | z |≦2, were 79〜91% in 1st PT, 76〜96% in 2nd PT, 74〜90% in 3rd PT and 83〜86% in 4th PT, depending on the constituents.

The rapid identification of bacteria has become of importance in various fields, such as food industries, biomedical assays, and environmental analyses. In this study, a simple, rapid, and highly reliable method for the identification and classification of bacteria by matrix-assisted laser desorption/ionization-mass spectrometry (MALDI-MS) was developed. In this method, ca. 50 different kinds of ribosomal proteins were used as biomarkers for bacteria characterization. To verify the actual state of sequence information of ribosomal proteins registered in the protein databases, a simple intact protein analysis using only cell lysate without the purification of ribosomal proteins was developed. Through the characterization of ribosomal proteins of genome-sequenced lactic acid bacteria (LAB), a guideline for selecting reliable biomarkers used for the rapid identification of LAB by MALDI-MS was proposed. Although the amino acid sequences of ribosomal proteins is highly conserved, slight sequence variations of some ribosomal proteins can occur at the strain level, reflecting different phylogenetic evolution rates. Such sequence variations could be detected as mass differences in the MALDI mass spectra. The profile of the mass differences of ribosomal proteins was processed by cluster analysis, and generating a phylogenetic tree. Using this method, the phylogenetic classification of a total of 16 strains of Pseudomonas putida was demonstrated. The classification result of P. putida strains was highly comparable to those based on a conventional DNA sequence analysis.