In this study, we simultaneously analyzed chlornitrofen (CNP) and CNP-amino in tap water by solid-phase extraction-LC-APCI-MS/MS, through the generation of the phenoxide ion of CNP using the negative mode of atmospheric pressure chemical ionization (APCI). As a result, the detection limit for CNP could reach as low as 1/100th of the target value (0.0001 mg/L) of a complementary item in the Japanese Waterworks Act by concentrating the sample water 100 times using solid-phase extraction. The calibration curve generated with this method showed higher accuracy and precision, and the results of the tap water spike and recovery test proved that this method met the accuracy, repeatability, and intermediate precision targets standardized by the Japanese validation guideline concerning tap water analysis, thereby supporting the validity of our method.

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The upper limit of the concentration range of test water in the measurement of volatile organic compounds has been expanded by the amendments of the method (Ministry of Health, Labor and Welfare Notification No. 261) established by the Minister of Health, Labor and Welfare based on the provisions of the Ministerial Ordinance on Water Quality Standards in 2018. However, as the standard sample concentration in the calibration curve increased, the sensitivity of fluorobenzene and 4-bromofluorobenzene, which were internal standard substances, was sensitized. When the sensitization of the internal standard substance was investigated, it was speculated that the competitive adsorption of the volatile organic compounds and the internal standard substances to the “active sites” existing in the analysis channel was the cause of the sensitization. In addition, it has been found that the accuracy of the quantitative results decreases if the amount of adsorbed components at the “active sites” contained in the test water is significantly different from the standard sample used for the calibration curve.

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[in Japanese]

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