Validation of the Sample Preservation and Analysis of Dimethyl Disulfide and Dimethyl Trisulfide in Tap Water and Source Water

Abstract

Taste-and-odor occurrence has extensive socio-economic impacts on drinking water, which is now a public health concern. Sulfur odorants can significantly affect the esthetic quality of drinking water and arouse unpleasant organoleptic experience of consumers, which can also harm the human body at high concentration levels. Researches on analysis of sulfur odorants in air and environmental water are numerous, while the reports on analysis of them in tap water are few. The analysis of sulfur odorants in tap water is quite different with it in environmental samples owing to the treatment of the water plant, such as the introduction of disinfectants. In this paper, a novel and practical method for determining the dimethyl disulfide (DMDS) and dimethyl trisulfide (DMTS) in tap water and source water by purge-and-trap coupled to gas chromatography–mass spectrometry (GC–MS) analysis was proposed. The evaluations of sample preservation were performed due to the adverse impact caused by the remaining disinfectant in tap water on the analysis of DMDS and DMTS, including the investigation on the selection and the dosage of preservatives. Besides, aspects affecting the preconcentration procedure and GC–MS analysis of DMDS and DMTS were investigated as well. Moreover, the proposed method was validated by five independent laboratories from different regions of China, representing a good linearity with correlation coefficients (r) ranged from 0.9990 to 0.9999 for both DMDS and DMTS between the concentrations of 10 ng L−1 and 100 ng L−1. The method detection limit (MDL) and limit of quantification (LOQ) of DMDS and DMTS were 3 ng L−1 and 10 ng L−1, respectively. Meanwhile, satisfactory precision and accuracy were also obtained when the method was applied to detect DMDS and DMTS in tap water and source water. The relative standard deviation (RSD) was 0.90–7.3% for DMDS and 1.1–7.6% for DMTS, and the recovery was 81.2–120% for DMDS and 73.6–118% for DMTS. Furthermore, the repeatability limits and reproducibility limits of DMDS and DMTS were acquired, ranging from 0.631 to 5.71 at low, medium and high concentrations. The proposed method is an effective, environmentally friendly, and promising approach for routine monitoring of DMDS and DMTS in tap water and source water.