Abstract: To address the frequent occurrence of odor incidents in drinking water sources and effectively ensure the safety and stability of water supply quality, this study established and systematically optimized an analytical method based on purge and trap coupled with gas chromatography-triple quadrupole tandem mass spectrometry (P&T-GC-MS/MS), aiming at the simultaneous detection of 88 typical volatile organic compounds and common odor compounds in raw water. A series of core instrument operating conditions were systematically screened and optimized through repeated comparative experiments. The optimal experimental conditions were finally determined as a purge time of 11 minutes, a desorption temperature of 250 ℃, an inlet temperature of 220 ℃, and a split ratio of 10:1. Under these optimized experimental conditions, all 88 target compounds were successfully analyzed with good chromatographic separation and accurate quantitative analysis, which laid a solid foundation for the subsequent method validation and practical application. The results of methodological validation showed that all 88 target compounds exhibited excellent linear relationships in the range of 0.2-60.0 μg/L, with correlation coefficients (R²) all greater than 0.99, indicating high linearity and reliability of the method. The method detection limits (MDLs) of the target compounds ranged from 0.02 to 0.22 μg/L, and the method quantification limits (MQLs) ranged from 0.2 to 0.87 μg/L, which fully met the requirements for trace analysis of volatile organic compounds and odor compounds in drinking water. In addition, the relative standard deviations (RSDs) of the method, which reflect the precision and repeatability of the detection results, were between 0.01% and 10.6%. The average spiked recoveries of the 88 target compounds ranged from 70.8% to 112%, further confirming that all performance indicators of the established method were in line with the strict requirements of trace environmental analysis. Eight representative sampling sites were set along the main stream of the Beijiang River, which serves as an important drinking water source for Qingcheng District and Sanshui District in Guangdong Province. Collected surface water samples were determined by the optimized method, and a total of seven target compounds were detected in the actual water body, mainly including trans-1,2-dichloroethylene, dichloromethane and the typical odor substance 2-ethyl-5,5-dimethyl-1,3-dioxane (2-EDD). The concentration of detected pollutants ranged from not detected to 0.77 μg/L. Among them, the 2-EDD concentration at site 3 reached 365 ng/L, which far exceeded the local standard limit of 0.02 μg/L with an over-standard multiple up to 18 times and caused obvious odor in local source water. Other detected pollutants complied with water quality limits, and no obvious illegal industrial discharge was found along the river. Ecological and human health risks were further evaluated. Only site 3 presented low ecological risk to aquatic systems, while other sites showed no potential ecological risk. Carcinogenic risk indexes were all below safety thresholds, and non-carcinogenic hazard quotients stayed within safe ranges, proving detected substances posed no threat to residents’ health. This method provides a technical reference for drinking water safety control.

Key words: purge and trap, gas chromatography-tandem mass spectrometry (GC-MS/MS), volatile organic compounds, odor compounds