Masaru Ushiro

Hoshi University, Edo, Tōkyō, Japan

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Publications (4)10.64 Total impact

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    ABSTRACT: A simple, rapid and sensitive method termed dispersive liquid-liquid microextraction (DLLME) combined with gas chromatography-mass spectrometry (GC/MS) was developed for the determination of tricyclic antidepressants (TCAs) in human urine sample. An appropriate mixture of methanol (disperser solvent), carbon tetrachloride (extraction solvent), and acetic anhydride (derivatization reagent) was injected rapidly into human urine sample. After extraction, the sedimented phase was analyzed by GC/MS. The calibration curves obtained with human urine were linear with a correlation coefficient of over 0.99 in the range of 2.0/5.0-100 ng mL(-1). Under the optimum conditions (carbon tetrachloride: 10 μL, methanol: 150 μL), the detection limits and the quantification limits of the tricyclic antidepressants were 0.5-2.0 ng mL(-1) and 2.0-5.0 ng mL(-1), respectively. The average recoveries of TCAs were 88.2-104.3%. Moreover, the inter- and intra-day precision and accuracy was acceptable at all concentrations. The results showed that DLLME is applicable to the determination of trace amounts of TCAs in human urine sample.
    Journal of chromatography. B, Analytical technologies in the biomedical and life sciences 12/2011; 879(31):3714-20. DOI:10.1016/j.jchromb.2011.10.012 · 2.73 Impact Factor
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    ABSTRACT: The risk assessment of di(2-ethylhexyl)phthalate (DEHP) migration from polyvinyl chloride (PVC) medical devices is an important issue for patients. The aim of this study was to determine DEHP degradation and migration from PVC sheets. To this end, the method for the simultaneous determination of DEHP and its breakdown products (mono(2-ethylhexyl)phthalate (MEHP) and phthalic acid (PA)) was improved. Their migration levels from 0 to 50 kGy gamma-ray irradiated PVC sheets were determined. DEHP migration level decreased in proportion to the dose of gamma-ray irradiation, while MEHP and PA migration levels increased. The hardness and the elastic modulus of PVC sheets were examined, but no clear relationship between DEHP migration and these parameters was observed.
    International Journal of Pharmaceutics 05/2009; 376(1-2):213-8. DOI:10.1016/j.ijpharm.2009.04.019 · 3.65 Impact Factor
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    ABSTRACT: Tris(2-ethylhexyl)trimellitate (TOTM) is used as an alternative plasticizer of polyvinyl chloride (PVC) medical devices. A method for the determination of TOTM released from PVC medical devices into intravenous preparations was developed, which uses liquid chromatography-tandem mass spectrometry (LC-MS/MS). A PVC tube was filled with an intravenous preparation and extraction was carried out by shaking for 1h at room temperature. LC was performed with an Inertsil-C8 (50 mm x 2.1 mm, 5 microm) column. The isocratic mobile phase was acetonitrile:purified water (90:10, v/v) at a flow rate of 0.2 ml/min. MS detection was accomplished with an MS/MS detector equipped with a turbo ionspray ionization source in the positive ion mode. The limit of detection and the limit of quantification for the standard solution of TOTM was 0.5 ng/ml (S/N=3) and 1.0 ng/ml (S/N > or =10), respectively. When Prograf (tacrolimus) was used, the average recovery of TOTM was 101.1% (R.S.D.=4.72%; n=3). When our method was applied to the determination of TOTM released from unsterilized and gamma-ray-sterilized PVC tubes, we found that a higher concentration of TOTM was released from the unsterilized PVC tube than from the gamma-ray-sterilized one.
    International Journal of Pharmaceutics 08/2008; 360(1-2):91-5. DOI:10.1016/j.ijpharm.2008.04.020 · 3.65 Impact Factor
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    ABSTRACT: The aim of the present study was to establish a liquid chromatography-tandem mass spectrometric (LC-MS/MS) method for the simultaneous determination of di(2-ethylhexyl) phthalate (DEHP), mono(2-ethylhexyl)phthalate (MEHP), and phthalic acid (PA). In the proposed method, the limits of detection of DEHP, MEHP, and PA were 5, 0.5, and 1 ng/mL, respectively, and the limits of quantification with standard solutions were 20, 2, and 5 ng/mL, respectively. Intra- and interday assays showed good accuracy and repeatability. The recoveries of DEHP, MEHP, and PA from respective extraction solvents ranged from 98.9 to 104.2% (relative standard deviation was below 10.3%). DEHP and its breakdown products migrating from gamma-ray irradiated polyvinyl chloride (PVC) sheets were determined simultaneously since DEHP is easily eluted from PVC medical devices. DEHP migration was noted from both gamma-ray irradiated and control PVC sheets. Compared with the migration from the control PVC sheet, MEHP showed significant migration from the gamma-ray irradiated PVC sheet. In contrast, PA migration was noted only from the gamma-ray irradiated PVC sheet.
    Journal of Liquid Chromatography &amp Related Technologies 11/2007; 31(2-2):198-209. DOI:10.1080/10826070701738811 · 0.61 Impact Factor