BUNSEKI KAGAKU Abstracts

The analysis of volatile organic compounds (VOCs) in environmental samples has become a more important aspect in the field of analytical science. Typically, a kind of sample preparation process is needed to determine trace levels of VOCs before analysis in gas chromatography (GC).

Recently, two needle-type sample preparation devices, fiber-packed needle and particle-packed needle, have been successfully introduced to the determination of various VOCs in environmental samples. For a fiber-packed needle, a bundle of fine filaments coated with polymeric materials was longitudinally packed into the needle. Several polycyclic aromatic hydrocarbons (PAHs) in aqueous samples were rapidly extracted by the fiber-packed needle, and the needle was further applied for the simultaneous derivatization/extraction of gaseous VOCs, such as volatile aldehydes, ketones and ethylene oxide. A particle-packed needle, where porous polymer particles were packed, has also been developed for the extraction of VOCs commonly found in environmental gaseous samples. After optimization of the experimental parameters with the particle-packed extraction needle, the device was applied to the analysis of several real samples including human breath, environmental tobacco smoke and air related to third-hand smoking. A further application of the needle device to fire investigations was also suggested. In this article, an overview for the development of needle-type extraction devices was presented along with some applications to real sample analysis in GC.

We examined the alkali metal-recognition property and the structure of an amphiphilic crown ether azoprobes (15C5-Azo-Cn ; n = 4, 6, 8)/cyclodextrin (CyD) complex in water by UV-Vis absorption spectroscopy and circular dichroism (CD) spectroscopy. The 15C5-Azo-Cn formed a stable complex with γ-CyD by making H-aggregate, and its apparent affinity was intensified by about 10 times for K⁺, and not for Na⁺. It was suggested that a H-aggregate of 15C5-Azo-C4 and 15C5-Azo-C6 bound one γ-CyD molecule, and 15C5-Azo-C8 bound one or two γ-CyD molecules by the addition of K⁺. The induced CD analysis revealed that γ-CyD bound with both the phenylazo moiety and the alkyl chain unit of the azoprobe by the addition of K⁺, although γ-CyD bound with mainly the phenylazo moiety of azoprobe by the addition of Na⁺.

Color information of unbleached kraft tapes were scanned by a scanner as digital color images. The scanned digital color images were converted to three histograms of 256-bit depth for each color (red, green, blue) based on an RGB color model, using image-processing software. We thought that a RGB curve, obtained from summing three histograms at every depth, corresponded to an inherent spectrum. They were also used to discriminate the kraft tapes, which had a very similar color appearance. Each RGB curve was smoothed by a simple moving average of 5 points, and was analyzed by a cluster analysis and a statistical calculation. The cluster analysis was carried out on 410 data obtained from 41 samples. This yielded a dendrogram indicating that the RGB curves can be divided into three groups. Finally, 28 samples formed each isolated cluster, including their 10 RGB curves. However, 13 samples formed six mixed clusters. Thus, apparently similar colored kraft tapes can be discriminated from one another using this chemometric digital image method.

A simple separation method using hydrophilic interaction liquid chromatography (HILIC) with an ultraviolet detector (UV) on an aminopropyl (NH2) silica-gel column has been studied for the determination of anserine (ANS) and carnosine (CARN) in chicken meat. As a result of validation tests, our proposed method provides good linearity of the calibration curve as well as both repeatability and reproducibility. In addition to that, the correlation coefficient of the working curve of calibration were estimated to be from 0.9980 to 0.9984 for ANS and CARN in the concentration range from 10 pmol μL⁻¹ to 100 pmol μL⁻¹. The limits of detection (LOD) at 5 measurement times (N = 5), calculated on 3 σ at 10 pmol μL⁻¹, were 0.51 pmol μL⁻¹ for ANS, and 0.48 pmol μL⁻¹ CARN. The limits of quantification (LOQ) at N = 5, calculated on 10 σ at 10 pmol μL⁻¹, were 1.71 pmol μL⁻¹ for ANS, and 1.60 pmol μL⁻¹ for CARN. Comparing to ion-pair method and our proposals, they had a good correlation. Our proposed method could be successfully applied to the determination of ANS and CARN in chicken meat.

Simple and sensitive headspace gas-chromatographic (GC) analysis of urinary methanol using syringe equilibration method was developed. A glass syringe containing 30 μL of urine sample and 50 mg of glass wool was heated at 85℃ for 20 minutes and the HS vapor equilibrated under normal pressure in the syringe was injected directly into the GC-FID, and the analysis was carried out successfully without contamination. Relative standard deviations of less than 5% were observed for 20–80 μg/mL methanol spiked urine samples. The quantitative detection limit for urinary methanol was 0.3 μg/mL.

A quantitative method for the determination of urea in human urine was studied. An ion chromatograph (IC) with a conductivity detector was used in this method, where the chromatograph was modified by placing a cation exchanger-an immobilized urease column on the injection loop with a 6-way valve in IC. A cation exchanger was prepared by the treatment of cedar sawdust with fuming sulfuric acid (exchange capacity, 1.2 meq g-resin⁻¹). Immobilized urease was prepared by the adsorption of urease on cedar sawdust with triethylenetetramine (activity, 3500 U g⁻¹). The reactor with a cation exchanger-an immobilized urease column could convert urea in urine to ammonium ion (conversion efficiency, 100%) even if a sample solution was passing through column at a 9 mL min⁻¹ rate. Simultaneously, the above-mentioned reactor could also completely hold NH₄⁺, Na⁺ and K⁺ in urine. The calibration curves of urea were very linear over 4.0–20 mg L⁻¹. The urea concentration in urine could be determined within 7 min after developing the urine sample.

Rare-earth elements are essential materials for manufacturing high-performance products. Wasted home appliances are called "urban mines" ; there are many parts that contain rare metals, such as rare-earth elements. For effective recycling, it is necessary to measure the rare-earth elements in urban mines. The measurement conditions of the rare-earth elements with polarized Zeeman atomic absorption spectrometry were optimized. In the presence of ethanol and potassium nitrate, sensitivities of rare-earth elements were improved, and no interference of coexisting iron. Rare-earth magnets were chosen as an example of urban mines. In rare-earth magnets, Nd, Dy, Pr, Gd and Sm were measured by polarized Zeeman atomic absorption spectrometry. Spike recoveries were obtained from 90 to 110%. Rare-earth elements in rare-earth magnets could be measured satisfactorily.

In the development of organic reference materials, a purity evaluation by the freezing point depression method, which is regarded as one of primary methods of measurement, is used to ensure traceability to the International System of Units (SI). However, because this method is difficult to apply to some organic compounds, a subtraction method based on chromatographic techniques under ISO Guide 35 : 2006 was developed for purity evaluation. The subtraction method was based on subtracting every impurity detected from 1. Since the detection of every impurity is impossible, validation of the subtraction method is necessary. To validate our subtraction method based on chromatographic techniques, the purities of 4-n-nonylphenol, 4-n-heptylphenol, and 2,4-dichlorophenol were determined using both the subtraction and freezing point depression methods, and then compared. The purities obtained by the subtraction method were comparable, within the range of uncertainties, to the purities determined using the freezing point depression method. Moreover, validation of our subtraction method was confirmed using international comparisons, which play an important role in ensuring mutual recognition of national reference materials, related to purity evaluation. Therefore, these data suggest that our subtraction method used for purity evaluation of alkylphenols is a reliable technique.

In this dissertation, advanced flow-based analysis systems for biological and environmental samples are proposed, and their novel techniques are discussed. A spectrophotometric flow injection analysis (FIA) for formaldehyde (HCHO) using hydroxylamine and iron(III)-ferrozine complex was investigated. HCHO was condensed with hydroxylamine, and then the residual hydroxylamine reduced iron(III)-ferrozine complex. As a result, iron(II)-ferrozine complex was formed and detected at 562 nm. A new HCHO standard gas generator based on gravitational dispensing-vaporization and an automated FIA equipped with a diffusion scrubber for breath HCHO were developed. The proposed system could determine trace breath HCHO at 3-min intervals. An automatic stopped-in-dual-loop flow analysis (SIDL-FA) system for the determination of vanadium was proposed. The detection reaction for vanadium is based on its catalytic effect on the oxidation of p-anisidine by bromate in the presence of Tiron as an activator. A fully automated pre-concentration system coupled with graphite furnace atomic absorption spectrometry (GFAAS) was developed. The proposed system showed high sensitivity comparable to ICP-MS. Cadmium and lead at the level of ppt in the leached solutions was detectable utilizing this system. A simple and economic lab-on-chip was contrived for an acidity assay. This system was small compared with other FIA and SIA systems, and it could reduce reagent consumption and waste generation extremely. In addition, an extract of a flower was used as a natural reagent. Therefore, this method was environment-friendly.