Chromatography-mass spectrometric determination of highly toxic and carcinogenic N-nitrosamines in water

Abstract

Introduction. In Russia, the current condition regarding water quality in the water bodies of the Russian Federation used for drinking purposes “continues to remain unfavourable (according to the Strategy of the Environmental Safety of the Russian Federation until 2025). It takes place primarily due to the discharges of industrial and domestic wastewater.” Thus, 19% of wastewater is discharged into water bodies without purification, 70% - insufficiently purified, and only 11% - purified to the established acceptable discharge standards. Therefore, 30-40% of the country’s population regularly uses water that does not correspond to the hygienic standards, which leads to an increased risk of morbidity among the population of Russia. This study aims to execute chromatography-mass spectrometric determination of highly toxic and carcinogenic N-nitrosamines in drinking water. Materials and methods. Within the framework of the study, we reviewed standard samples of N-nitrosamines Mix, 1X1ML, 2000 ug/ml, methanol, experimental diagrams of solid-phase extraction. The practical charts of solid-phase extraction were tested with the help of a susceptible and accurate analytical mass-spectrometric method, a gas chromatograph with a mass selective detector (MSD). An internal laboratory control was carried out according to CIS standardization recommendations 76-2014 of the State System for Ensuring Uniform Measurement to ensure the reliability of the analytical results obtained to determine N-nitrosamines in water. The quality indicators for the analysis results were experimentally established: the accuracy, correctness, precision of the analysis technique, and the methods for their assessment according to GOST R ISO 5725-2002 standards. Results. In the course of the performed experimental studies, it was found that the degree of N-nitrosamines extraction from water samples of 100 ml volume, through scavenging analytes on a carbon cartridge (Coconut 6 cm3) and using four optimal diagrams of solid-phase extraction - SPE for N-dimethyl nitrosamine, N-diethyl nitrosamine, N-dipropyl nitrosamine, N-piperidine nitrosamine was 73.9%, 90.8%, 100 and 95.4% respectively. Optimal elution scheme 4: stage 1 - conditioning the cartridge to activate it: 5 ml methylene chloride for 3 seconds, 5 ml ethyl acetate for 3 seconds, rinsing the cartridge with 5 ml water for 10 seconds. Stage 2 - adsorption of a 100 ml water sample on a 6 ml Coconut cartridge for 1 minute; stage 3 - rinsing the cartridge with 5% sodium chloride solution of 10 ml for 30 seconds; stage 4-elution of N-nitrosamines from the cartridge with methylene chloride of 3 ml for 3 min. into a test tube in position 1 of the carriage of the automatic TFE system. The method for the determination of N-nitrosamines in water is based on the concentration of the analyzed compounds of water samples on a carbon cartridge - solid-phase extraction (SPE), identification of substances by library mass spectra and retention time, quantitative determination according to the calibration graph on a high polarity capillary column HP-FFAP-50 m • 0.32 mm • 0.50 μm. Conclusion. The developed guidelines for measuring the N-nitrosamines content in the water of centralized water supply systems let us determine highly toxic compounds at the lower limit of 0.00004 μg/cm3 with an error of more than 35.0%.