# A Purge-and-Trap Gas Chromatography–Mass Spectrometry Method for the Quantitative Determination of Six Haloacetonitriles in Drinking Water

## TL;DR

This paper introduces a new method to accurately measure harmful haloacetonitriles in drinking water using gas chromatography-mass spectrometry.

## Contribution

A novel, optimized purge-and-trap GC/MS method for quantifying six haloacetonitriles in drinking water without pH adjustment or quenching.

## Key findings

- The optimized method achieved high sensitivity with LODs as low as 0.007 μg/L and recoveries between 89.5–111.0%.
- Bromochloroacetonitrile and dibromoacetonitrile were the dominant HANs in Kunshan tap water samples.
- Sand filtration and activated carbon effectively removed HANs, while chloramination increased brominated HANs.

## Abstract

Haloacetonitriles (HANs), toxic disinfection by-products, are unregulated in China, with no standardized analytical methods. This study established a simultaneous quantitative method for six typical HANs in drinking water using an optimized purge-and-trap gas chromatography–mass spectrometry (P&T-GC/MS) system. Key parameters, including sorbent trap selection, purge time, and moisture control settings, were systematically optimized. The OI No. 7 trap and a 13 min purge time were selected to maximize sensitivity while minimizing moisture interference. Under optimal conditions, all target analytes showed good linearity (R2 > 0.999). The method detection limits (LODs) ranged from 0.007 to 0.202 μg/L, and the limits of quantitation (LOQs) ranged from 0.2 to 2.0 μg/L. Average spiked recoveries in tap water were 89.5–111.0%, with relative standard deviations (RSDs) below 5% (n = 7). A core optimization was omitting pH adjustment and ascorbic acid quenching to avoid non-target degradation of brominated HANs and ensure accurate in situ concentration determination. Application to 16 Kunshan tap water samples showed total HAN concentrations of 0.59–3.03 μg/L (average: 1.62 μg/L), dominated by bromochloroacetonitrile (BCAN) and dibromoacetonitrile (DBAN). Process analysis indicated significant synergistic HAN removal by sand filtration and activated carbon, while chloramination significantly increased brominated HANs via enhanced bromination. This efficient, sensitive P&T-GC/MS method is suitable for trace HAN monitoring and provides technical support for HAN control in water treatment.