[Determination of two perfluorinated compounds in urine by liquid chromatography-tandem mass spectrometry].

Objective: To establish a method for the determination of two perfluorinated compounds in urine by liquid chromatography-tandem mass spectrometry. Methods: In November 2022, urine samples were extracted by acidic methanol, purified by WAX solid phase extraction column, and eluted with methanol water, then Waters ACQUITY UPLC BEH C18 column (100 mm×2.1 mm, 1.7 µm) was used with 1.0 mmol/L ammonium acetate solution and methanol as mobile phase. The gradient elution was carried out, the detection was carried out by electrospray negative ion multiple response monitoring (MRM) mode, and the quantitative method was internal standard method. Results: Perfluorooctanoic acid and perfluorooctane sulfonic acid had a good linear relationship in the concentration range of 0.5-50.0 µg/L, and the correlation coefficient was >0.999. The limit of detection was 0.017 µg/L, and the limit of quantitation was 0.005 µg/L. The average recoveries were 96.3% and 101.8%, respectively. Days of precision were 3.5%-6.2% and 3.1%-7.4%, respectively, daytime precision were 4.3%-6.8% and 4.7%-8.1%, respectively. Conclusion: The established method of liquid chromatography-tandem mass spectrometry is high sensitivity and accuracy, and is suitable for the determination of perfluorooctanoic acid and perfluorooctane sulfonic acid in human urine.

[Determination of triclocarban and triclosan in urine by QuEChERS extraction and ultra-performance liquid chromatography-tandem mass spectrometry].

Objective: To establish a method for the determination of triclocarban (TCC) and triclosan (TCS) in urine by ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) after purification by QuEChERS. Methods: In May 2022, urine samples were extracted by acetonitrile, purified by QuEChERS, separated by Waters Acquity UPLC BEH C18 column (100 mm×2.1 mm, 1.7 µm), and eluated with water-acetonitrile as mobile phase gradient at a flow rate of 0.3 ml/min. The detection was conducted in negative ion mode (ESI(-)) and multiple reaction monitoring (MRM) scanning, it was quantified with a internal standard method, and the methodology was verified. Results: The linear ranges of TCC and TCS were 0.5-100.0 µg/L and 1.0-100.0 µg/L, and the correlation coefficients were 0.9997 and 0.9991, respectively. The limits of detection and quantitation of TCC and TCS were 0.17 and 0.33 µg/L, and 0.5 and 1.0 µg/L, respectively. The recoveries of TCC and TCS were 100.1%-102.8% and 96.7%-108.6%, and the relative standard deviations were 4.9%-6.7% and 4.1%-8.3%, respectively, at 2.0, 10.0 and 80.0 µg/L. Conclusion: QuEChERS-UPLC-MS/MS method is simple, rapid, sensitive and reproducible, and can be used for rapid and accurate simultaneous detection of TCC and TCS exposure levels in occupational population.

[Detection of three metabolites of xylene in urine samples by solid-phase extraction coupled with liquid chromatography-mass spectrometry].

Objective: To establish a method for the rapid determination of the three metabolites of xylene, 2-methylmarmaluronic acid, 3-methylmarmaluronic acid and 4-methylmarmaluronic acid, in urine of occupationally exposed workers by ultra-performance liquid chromatography-high resolution mass spectrometry (UPLC-HRMS) . Methods: In July 2022, urine samples were diluted and extracted with pH=6.86 phosphate cache solution, cleaned up by a MAX solid-phase extraction (SPE) column and separated by an Accucore Ph/Hexyl column (100 mm×2.1 mm, 2.6 µm) with a gradient of 5 mmol/L ammonium formate-0.1% formic acid aqueous solution and methanol as mobile phases. The analysis was carried out in electrospray ionization mode and full mass-data dependent secondary mass spectrometry mode, and quantified by external standard method. The characteristics of each index of this method were analyzed. Results: A good linearity was obtained in the concentration range of 1.0-200.0 µg/L for 2-methylmuramic acid, 3-methylmuramic acid and 4-methylmuramic acid with the correlation coefficients of 0.9979-0.9993. The limits of detection of the method were 0.18-0.24 µg/L. While the spiked recoveries at the three concentrations (1.0 µg/L, 100.0 µg/L, and 180.0 µg/L) were in the range of 83.0%-93.7%, with the relative standard deviations of 2.2%-7.9%. Conclusion: The UPLC-HRMS method is simple, rapid, sensitive and accurate, and is suitable for the simultaneous determination of the three metabolites of xylene in the urine of occupationally exposed workers.

[Effectiveness of snail control by immersion of molluscicides through tide diversion in marshlands: a field evaluation].

OBJECTIVE: To compare the effectiveness of snail control between immersion of molluscicides through tide diversion and mollusciciding by spraying in marshland areas. METHODS: Immersion of 26% suspension concentrate of metaldehyde and niclosamide through tide diversion and spraying 26% suspension concentrate of metaldehyde and niclosamide alone were employed for snail control in two neighboring snail-breeding marshlands, and snails were surveyed before and after mollusciciding. The mortality of snails and the density of living snails were estimated. RESULTS: The density of living snails reduced by 72.19% and 100.00% 1 and 2 years after immersion of 26% suspension concentrate of metaldehyde and niclosamide through tide diversion, and 5.93% and 18.15% 1 and 2 years after spraying 26% suspension concentrate of metaldehyde and niclosamide alone. CONCLUSIONS: Immersion of 26% suspension concentrate of metaldehyde and niclosamide through tide diversion is significantly superior to spraying 26% suspension concentrate of metaldehyde and niclosamide along for snail control, and implementation of immersion of 26% suspension concentrate of metaldehyde and niclosamide through tide diversion for more than 2 successive years may achieve a higher snail control efficiency.