Hiroshi Taoda

Qualitative analysis of some carboxylic acids by ion-exclusion chromatography with atmospheric pressure chemical ionization mass spectrometric detection

A simple, selective and sensitive method for the determination of carboxylic acids has been developed. A mixture of formic, acetic, propionic, valeric, isovaleric, isobutyric, and isocaproic acids has been separated on a polymethacrylate-based weak acidic cation-exchange resin (TSK gel OA pak-A) based on an ion-exclusion chromatographic mechanism with detection using UV-photodiode array, conductivity and atmospheric pressure chemical ionization mass spectrometry (APCI-MS). A mobile phase consisting of 0.85 mM benzoic acid in 10% aqueous methanol (pH 3.89) was used to separate the above carboxylic acids in about 40 min. For LC-MS, the APCI interface was used in the negative ionization mode. Linear plots of peak area versus concentration were obtained over the range 1-30 mM (r2=0.9982) and 1-30 mM (r2=0.9958) for conductimetric and MS detection, respectively. The detection limits of the target carboxylic acids calculated at S/N=3 ranged from 0.078 to 2.3 microM for conductimetric and photometric detection and from 0.66 to 3.82 microM for ion-exclusion chromatography-APCI-MS. The reproducibility of retention times was 0.12-0.16% relative standard deviation for ion-exclusion chromatography and 1.21-2.5% for ion-exclusion chromatography-APCI-MS. The method was applied to the determination of carboxylic acids in red wine, white wine, apple vinegar, and Japanese rice wine.

Development of TiO2 photocatalysts suitable for practical use and their applications in environmental cleanup

Recently, environmental disruption is proceeding on a global scale through the consumption of huge amounts of fossil fuels and the emission of various chemical substances. However, these substances resist bio-treatment. TiO2 generates electrons and holes by irradiation with light. Most organic micro-pollutants, including dioxins, are decomposed into carbon dioxide and water by the effect of the holes with high oxidative potential. By using such a photocatalytic reaction, various applications are feasible for environmental cleanup. In general, TiO2 powder has been utilized as photocatalyst, although TiO2 powder photocatalyst has several disadvantages: (1) it is difficult to handle, (2) photocatalytic reaction is slow and it takes a lot of time for treatment and (3) it is difficult to apply to plastics and textiles, because the photocatalyst decomposes them. We have developed a photocatalyst suitable for practical use and have developed high-activity photocatalysts such as TiO2 photocatalytic transparent film, photocatalytic silica-gel, apatite-coated TiO2 photocatalyst usable for plastics and textiles, photocatalytic paper, photocatalytic blue charcoal and photocatalytic oxygen scavenger. The application of these high-activity photocatalysts has been studied in deodorization, anti-bacterial, self-cleaning, anti-stain, water treatment, air purification such as photocatalytic decomposition of dioxins and VOC, and NOx removal. Now various photocatalytic articles using these new photocatalyst materials are on the market in Japan. Photocatalytic technology can create many valuable products for environmental use all over the world.

Ion-exclusion/adsorption chromatography of dimethylsulfoxide and its derivatives for the evaluation to quality-test of TiO2-photocatalyst in water

Ion-exclusion/adsorption chromatography of dimethylsulfoxide (DMSO) and its derivatives, i.e., methanesulfinic acid (MSI), methanesulfonic acid (MSA) and sulfuric acid (SA), was developed in order to clear the decomposition mechanism of DMSO on quality-test of TiO(2)-photocatalyst in water. The separation was achieved by the adsorption effect for DMSO and ion-exclusion effect for MSI, MSA and SA under optimum conditions, using a weakly acidic cation-exchange resin column with 20mM succinic acid as the eluent. In this system, DMSO and MSI with UV at 195nm and MSA and SA with conductivity detection were consecutively determined by single injection and single separation column. This method was used to monitor the artificial decomposition of DMSO induced by a photocatalyst. The concentration of DMSO by active oxygens (e.g., OH radical) generated from surface of photocatalyst was found to be decreased through the stoichiometric reaction in the order of MSI, MSA and SA.

Vacancy ion-exclusion chromatography of carboxylic acids on a strongly acidic cation-exchange resin

A new approach to ion-exclusion chromatography (IEC) is proposed to overcome the relatively poor conductivity detection response which occurs in IEC on when acids are added to the eluent in order to improve peak shape. This approach, termed vacancy IEC, requires the sample to be used as mobile phase and a sample of water to be injected onto a polystyrene/divinylbenzene (PS/DVB)-based strongly acidic cation-exchange column (TSKgel SCX). Vacancy peaks for each of the analytes appear at the retention times of these analytes. Highly sensitive conductivity detection is possible and sharp, well-shaped peaks are produced, leading to efficient separations. Retention times were found to be affected by the concentration of the analytes in the eluent, and also by the presence of an organic modifier, such as butanol in the mobile phase. Detection limits for oxalic, formic, acetic, propionic, butyric and valeric acids at S/N=3 were 0.04, 0.1, 0.47, 0.66, 0.71 and 0.82 μM, respectively, and linear ranges for some acids extended over two-orders of magnitude. Precision values for retention times were <0.57% and for peak height were <2.06%.

VOC Decomposition by Photocatalytic Wall Paper

Sick house syndrome caused by volatile organic compound (VOC) in the room is a serious problem in Japan. A photocatalytic wall paper was developed which is a wall paper coated with a visible light type of photocatalyst. When irradiated by light, the photocatalyst generates strong oxidative potential and decomposes almost all organic substances to water, carbon dioxide, and others. As a result of our experiment using the photocatalytic wall paper, toluene and acetaldehyde were decomposed efficiently even under a fluorescent lamp, and the photocatalytic wall paper had also strong anti-bacterial effect under the fluorescent lamp.

Ion-exclusion chromatography with conductimetric detection of aliphatic carboxylic acids on a weakly acidic cation-exchange resin by elution with benzoic acid–β-cyclodextrin

In this study, an aqueous solution consisting of benzoic acid with low background conductivity and beta-cyclodextrin (beta-CD) of hydrophilic nature and the inclusion effect to benzoic acid were used as eluent for the ion-exclusion chromatographic separation of aliphatic carboxylic acids with different pKa values and hydrophobicity on a polymethacrylate-based weakly acidic cation-exchange resin in the H+ form. With increasing concentration of beta-cyclodextrin in the eluent, the retention times of the carboxylic acids decreased due to the increased hydrophilicity of the polymethacrylate-based cation-exchange resin surface from the adsorption of OH groups of beta-cyclodextrin. Moreover, the eluent background conductivity decreased with increasing concentration of beta-cyclodextrin in 1 mM benzoic acid, which could result in higher sensitivity for conductimetric detection. The ion-exclusion chromatographic separation of carboxylic acids with high resolution and sensitivity was accomplished successfully by elution with a 1 mM benzoic acid-10 mM cyclodextrin solution without chemical suppression.

Generation of low-molecular-weight organic compounds in water by titania photocatalyst under UV-Vis light radiation

We attempted to develop a new type titania photocatalyst that, when activated, responded in not only the ultraviolet rays region but also visible light radiation region by the new titania photocatalyst with the zirconia and nitrogen simultaneously introduced in the titania lattice. The decomposition performance of the standard organic compound in water by this new type titania photocatalyst nanoparticle was compared with the conventional type under both the ultraviolet ray and visible light radiation conditions. It was suggested that the low-molecular-weight organic compounds were also generated from the organic compound in water by the new type titania photocatalyst activities under the visible light radiation.

Organism Resolution Ability of Titania Photocatalyst in Water

The evaluation of the TiO 2 photocatalyst resolution ability of organism in water is studied. The amount of emergence of halogen in water, which was one of the resolution products of the organism with the TiO 2 photocatalyst, was identified and measured. It has been found that the evaluation of TiO 2 photocatalyst activity by the leaching rate of halogen after constant time in water is appreciable.

Test Method for Skin Damage of Titania Photocatalyst Nanoparticles In Vitro

Nanoscale TiO2 is widely used in consumer products like sunscreen and cosmetics. The establishment of damage evaluation test method was attempted to examine the potential neurotoxicity of nanoscale TiO2 to human body skin in vitro model. The emergence amounts of carbon dioxide, which was expected one of the generation products from the skin according to the titania photocatalyst nanoparticles activity under UV / visible light radiation, were identified and measured by the gas analyzer. It was found that it could evaluate the degrees of damage to skin with the photocatalysts activity by using the new evaluation test method considered.

Characteristic of Titania Photocatalyst Fine Particles Added Zirconia

Recently, the titania photocatalyst has been widely used in the environmental fields. However, because the past titania photocatalyst used only the range of ultraviolet rays, the usage has been limited. We attempted to develop a new type of titania photocatalyst that activates to respond not only in the ultraviolet rays region but also in the visible radiation region. The titania photocatalyst fine particles that zirconium oxide was uniformly added in the titania fine particles, and introduced simultaneously nitrogen into the crystal lattice in addition were synthesized. It was showed the high photo-absorption ability of the titania photocatalyst added the zirconium compared with not done by the absorption spectrum. Furthermore, it was found that the titania fine particles that introduced nitrogen colored to yellow, had also the high photo-absorption ability in the visible range of 600nm to 400nm in addition to the range of ultraviolet rays. It was thought that this depended on the reason based on the difference of the amount of the nitrogen introduction in the titania that originated in the zirconium. Moreover, it was compared the stability maintenance for the titania introduced nitrogen with it not done by the bleaching test of heating. As a result, the stability of the titania added the zirconium was higher than not added.