Analysis of Chloral Hydrate and Haloacetonitriles

Importance of the topic

Chlorination byproducts such as chloral hydrate and haloacetonitriles form during water disinfection and pose health concerns. Monitoring their concentrations is critical to ensure tap water safety and regulatory compliance.

Goals and overview of the study

This study demonstrates a gas chromatography–mass spectrometry method using an internal standard to simultaneously quantify chloral hydrate and five haloacetonitrile species in drinking water samples.

Methodology

The internal standard method was applied: each 2 mL water sample was spiked with 50 µL of 10 mg/L 1,2,3-trichloropropane. The mixture was analyzed by GC/MS in selected ion monitoring (SIM) mode. Calibration curves (10–1000 µg/L) were constructed using peak area ratios relative to the internal standard. Chromatographic separation was achieved using a DB-1 column with splitless injection and a temperature program optimized for volatile disinfection byproducts.

Instrumentation

• Gas chromatograph–mass spectrometer: Shimadzu GCMS-QP2010
• Autosampler: AOC-20i
• Column: J W DB-1 (30 m × 0.25 mm I D, 1 µm film)
• Carrier gas: Helium, constant linear velocity 43 cm/s
• Injection: Splitless, 1 µL at 250 °C
• Oven program: 40 °C (10 min) → 200 °C at 20 °C/min (3 min hold)
• Interface: 250 °C; Ion source: 200 °C
• Detection: SIM mode with target ions for each analyte

Main results and discussion

Calibration curves were linear over the 10–1000 µg/L range for all analytes, with correlation coefficients between 0.99994 and 0.999999. SIM chromatograms at 10 µg/L showed well-resolved peaks for chloral hydrate, chloroacetonitrile, dichloroacetonitrile, trichloroacetonitrile, bromochloroacetonitrile and dibromoacetonitrile. Characteristic mass fragments matched expected values, confirming compound identity and purity.

Benefits and practical applications

• Simultaneous quantification of multiple disinfection byproducts in one analysis
• High sensitivity and selectivity through SIM acquisition
• Robust correction using an internal standard for accurate results
• Suitable for routine drinking water monitoring and regulatory compliance testing

Future trends and potential applications

Future developments may include automated sample preparation, online preconcentration, and coupling with high-resolution mass spectrometry for broader screening of emerging disinfection byproducts. Improvements in detection limits and throughput will support real-time water quality surveillance and comprehensive risk assessment.

Conclusion

The described GC/MS internal standard method offers a reliable, precise, and efficient approach to monitoring chloral hydrate and haloacetonitriles in drinking water. Its excellent linearity, sensitivity, and reproducibility make it well suited for environmental laboratories and regulatory testing.