Fumio Okada's research while affiliated with Hoshi University and other places

A method for determining perfluorochemicals (PFCs) such as perfluorooctanesulfonic acid (PFOS), paerfluorooctane slufoneamide (PFOSA), perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA) and perfluorodecanoic acid (PFDA), in human plasma samples was developed by online solid-phase extraction-HPLC/MS/MS, only after deproteination with acetonitrile. The limits of detection of PFOS, PFOSA, PFOA, PFNA and PFDA in human plasma at a signal to noise (ratio of 3) were 0.08-0.14 ng/ml, and the limits of quantitation of PFOS, PFOSA, PFOA, PFNA and PFDA in human plasma were 0.50 ng/ml. The average recoveries of PFOS, PFOSA, PFOA, PFNA and PFDA ranged from 93.3 to 105% (RSD, 3.0-8.9%; n = 6). This method is more rapid and accurate, compared with the column-switching HPLC/MS method presented in previous reports 18)19). The developed method can be applied to the determination of PFOS, PFOSA, PFOA, PFNA and PFDA in human plasma samples for monitoring human exposure.

We report a method for determining fluorinated organic compounds such as perfluorooctane sulfonate (PFOS), perfluorooctanoate (PFOA) and perfluorooctanesulfonylamide (PFOSA) in human blood samples by column-switching liquid chromatography-electrospray mass spectrometry. The sample preparation prior to solid phase extraction (Waters Oasis HLB extraction column) involved simply mixing plasma sample with internal standard followed by centrifugation and extraction. The compounds were separated by reversed-phase chromatography with a C(8) column, and detected by mass spectrometry using selected ion monitoring in the negative mode. The average recoveries of PFOS, PFOA and PFOSA ranged from 82.2 to 98.7% (R.S.D.: from 2.0 to 5.2%, n = 6). The limits of quantitation of PFOS, PFOA and PFOSA at signal to noise (S/N = 10) were 0.5, 0.5 and 1.0 ng ml(-1). The method enables the precise determination of standards and can be applied to the detection of PFOS, PFOA and PFOSA in human plasma samples for monitoring human exposure.

Fluorinated organic compounds (FOCs), such as perfluorooctane sulfonate (PFOS), perfluoro-octanoate (PFOA), and perfluorooctane sulfonylamide (PFOSA), are widely used in the manufacture of plastic, electronics, textile, and construction material in the apparel, leather, and upholstery industries. FOCs have been detected in human blood samples. Studies have indicated that FOCs may be detrimental to rodent development possibly by affecting thyroid hormone levels. In the present study, we determined the concentrations of FOCs in maternal and cord blood samples. Pregnant women 17-37 years of age were enrolled as subjects. FOCs in 15 pairs of maternal and cord blood samples were analyzed by liquid chromatography-electrospray mass spectrometry coupled with online extraction. The limits of quantification of PFOS, PFOA, and PFOSA in human plasma or serum were 0.5, 0.5, and 1.0 ng/mL, respectively. The method enables the precise determination of FOCs and can be applied to the detection of FOCs in human blood samples for monitoring human exposure. PFOS concentrations in maternal samples ranged from 4.9 to 17.6 ng/mL, whereas those in fetal samples ranged from 1.6 to 5.3 ng/mL. In contrast, PFOSA was not detected in fetal or maternal samples, whereas PFOA was detected only in maternal samples (range, < 0.5 to 2.3 ng/mL, 4 of 15). Our results revealed a high correlation between PFOS concentrations in maternal and cord blood (r2 = 0.876). However, we did not find any significant correlations between PFOS concentration in maternal and cord blood samples and age bracket, birth weight, or levels of thyroid-stimulating hormone or free thyroxine. Our study revealed that human fetuses in Japan may be exposed to relatively high levels of FOCs. Further investigation is required to determine the postnatal effects of fetal exposure to FOCs. Key words: cord blood, fluorinated organic compounds, human, PFOA, PFOS, PFOSA, pregnancy.

We report a method for determining 4-nonylphenol (NP) and 4-tert-octylphenol (OP) levels in human urine samples by column-switching liquid chromatography–electrospray mass spectrometry after enzymatic deglucuronidation. The method involves enzymatic deconjugation by β-glucuronidase and correction by the stable isotopically labeled internal standard, 4-(1-methyl)octylphenol-d5. The compounds were separated by reversed-phase chromatography with a C18 column, and detected by selected ion monitoring in the negative mode. After adding an internal standard to urine samples, a direct analysis was carried out. The average recoveries of OP and NP were above 85.0% with correction using the added internal standard. The quantitation limit in the urine samples was 0.3 ng ml−1. The method enables the precise determination of standards and may be applied to the detection of trace amounts of OP and NP in human urine samples.

Health Canada reported recently that medical devices containing di(2-ethylhexyl) phthalate (DEHP) should not be used in the clinical treatment of infants, young boys, pregnant women, and nursing mothers. The risk assessment of DEHP released from PVC medical devices is an important issue for hospitalized patients. In this study, a simple, accurate, low-contamination and high-throughput analytical technique for the determination of DEHP in intravenous (IV) solution was developed using column-switching liquid chromatography/mass spectrometry (LC/MS) with an extraction mini-column. The sample preparation for on-line extraction involved simply mixing IV solution with internal standard as DEHP-d(4) in LC glass vials. The IV fat emulsion drug sample cannot be analyzed directly, hence this sample spiked with DEHP-d(4) solution was extracted by hexane and measured by column-switching LC/MS yielding an average recovery of 92.2% (C.V.=7.8%, n=5). A linear response was found for a variety of drugs tested within the validated range of 0.1 or 0.5-10 microg/ml with correlation coefficients (r) greater than 0.99. These results suggest that this method can assay background exposure to DEHP released from PVC medical devices in the patients. The method was applied to various IV solution samples to establish the first screening method for DEHP released from medical devices with respect to their safety.

A novel method based on column-switching high-performance liquid chromatography-electrospray mass spectrometry (LC-MS) coupled with an on-line extraction column containing conjugated avidin has been developed for direct injection analysis of di(2-ethylhexyl) phthalate (DEHP) and its metabolite, mono(2-ethylhexyl) phthalate (MEHP), in blood samples. The sample preparation for on-line extraction involved the mixing of blood samples with internal standards, DEHP-d(4) and MEHP-d(4), in LC glass vials. A linear response was found for column-switching LC-MS when tests were conducted within the validated range of 25 to 1000 ng mL(-1) for DEHP and 5 to 1000 ng mL(-1) for MEHP, with correlation coefficients (r) greater than 0.999. In addition, the recoveries of DEHP and MEHP from human plasma were calculated by using this method with on-line extraction, yielding recoveries of up to 91.2% (RSD<5%). We measured the background levels of DEHP and MEHP in six human plasma samples from healthy volunteers and three fetal bovine serum samples for cell-line culture. DEHP and MEHP were not detected in all human plasma samples (N.D. is <25 ng mL(-1) for DEHP, and N.D. is <5.0 ng mL(-1) for MEHP). In contrast, high DEHP contamination of commercially available fetal bovine serum samples was found by this method.

Studies on short fiber reinforced materials have been made to investigate the reinforced mechanism. Matrices used in this study consisted of acrylonitrile-styrene (AS) resin as the brittle materials and polycarbonate (PC) resin as the ductile materials. Glass fibers mixed in pellets were used as the short fibers and the volume fraction was varied from 0 to 10%. The cracking strain and the debonding strain are evaluated.