MONITORING FOR HALOACETIC ACIDS IN TREATED WATERS USING DIRECT AQUEOUS INJECTION ON THE AGILENT 6460 LC/QQQ

Significance of the Topic

Haloacetic acids (HAAs) are persistent disinfection by-products formed when chlorine and other disinfectants react with organic and inorganic precursors in drinking water. Due to their potential health risks, regulatory bodies such as the US EPA set maximum contaminant levels (MCLs) for key HAAs. Reliable, sensitive, and rapid analytical methods are essential for monitoring these compounds to ensure water safety and regulatory compliance.

Objectives and Study Overview

This study aimed to develop a streamlined analytical procedure for simultaneous determination of nine HAAs plus Dalapon in treated drinking water. The approach employs direct aqueous injection on an Agilent 6460 triple quadrupole LC/MS system to achieve detection limits below 0.25 µg/L without derivatization or extensive sample preparation. The method targets a calibration range up to 50 µg/L to support routine water quality monitoring.

Methodology and Instrumentation Used

The procedure eliminates extraction steps by injecting untreated water directly into an Agilent 1200 Series HPLC coupled to a 6460 QQQ with a Jet Stream interface. Key parameters include:

• Column: C18, 2.0 × 250 mm, 5 µm, maintained at 40 °C
• Mobile phase A: 0.05 % formic acid; B: methanol; 23 min gradient run
• Injection volume: 15 µL
• Mass spectrometry: negative-ion ESI in MRM mode with optimized transitions for each analyte

Main Results and Discussion

The method delivered limits of detection from 0.07 to 0.21 µg/L for all target compounds. Spike recoveries at 5 µg/L and 37.5 µg/L ranged between 88 % and 102 %, demonstrating accuracy and reproducibility. Chromatograms of a 5 µg/L standard showed clear resolution of all analytes, and calibration curves were linear across the full concentration range. A real sample analysis detected 9.8 µg/L of dichloroacetic acid with consistent quantitation.

Benefits and Practical Applications

This direct injection LC/QQQ method reduces analysis time and costs by removing extraction and derivatization steps. It minimizes solvent use, lowers sample volume requirements, and improves reproducibility by avoiding variable extraction efficiencies. The high sensitivity and selectivity suit routine compliance testing and QA/QC programs in drinking water treatment facilities.

Future Trends and Potential Applications

Advancements may include expanding the analyte panel to emerging disinfection by-products, integrating online sampling and automation for real-time monitoring, and coupling with high-resolution MS for non-target screening. Broader adoption of direct injection techniques can streamline environmental analysis across diverse water matrices.

Conclusion

The presented method using direct aqueous injection on an Agilent 6460 LC/QQQ offers a fast, sensitive, and robust solution for quantifying nine HAAs and Dalapon in treated drinking water. With detection limits well below regulatory thresholds and excellent recovery performance, it delivers a practical tool for routine monitoring and ensuring water safety.

Reference

1. Doris Smith and Ken Lynam, Determination of Haloacetic Acids in Water by GC/µECD Using Agilent J&W DB-35ms Ultra Inert and DB-XLB Columns, Agilent Technologies publication 5990-8765EN, August 2011.