Direct Mass Spectrometry with Online Headspace Sample Pretreatment for Continuous Water Quality Monitoring

Abstract

This study investigates the use of selected ion flow tube mass spectrometry with an automated headspace pretreatment system for the continuous surveillance of water quality at wastewater treatment plants (WWTPs) and rivers. The reaction rates of the target compounds introduced using the headspace method were similar to those of the mass scan library, with a margin of error of <10%. Novel quantitative formulae were derived for the water samples of the target compounds, and the linearity of the calibration curves for both the purified and effluent matrix (0.1–2.0 mg/L) showed a coefficient of determination of 0.98–0.99 for most compounds. The detection limit for 74% of the target substances was 0.02–0.10 mg/L, and the average recoveries were 111.6% and 104.7% for the low- and high-concentration spiked samples, respectively, which are comparable to those of the headspace gas chromatography-mass spectrometry system. However, the variability in individual concentrations was still large, due to the unstable control of sample injection flow and pressure. Herein, 79% of the 28 compounds met one-tenth of the proposed method detection limit criteria for emergency operations in WWTP. Field experiments showed that the system was easy to maintain and could be used to monitor chemical accidents.

Keywords

• direct mass spectrometry
• selected ion flow tube mass spectrometry
• headspace method
• online water quality monitoring
• chemical leaks