A Direct Aqueous Injection Method for Contaminants in Drinking and Nonpotable Water

Importance of the topic

Water quality monitoring is critical for public health and regulatory compliance. Emerging contaminants such as acrylamide, haloacetic acids (HAAs) and β-estradiol present analytical challenges due to their polarity, low regulatory limits and matrix interferences. A rapid, reliable method enables laboratories to support drinking water safety and environmental surveillance more efficiently.

Objectives and study overview

This study aimed to develop and validate a direct aqueous injection LC-MS/MS method for simultaneous quantitation of acrylamide, a set of five HAAs and β-estradiol in drinking, surface and ground water. Key goals included minimization of sample preparation, achievement of sub-µg/L detection limits and demonstration of method robustness across different water matrices.

Methodology and instrumentation

Sample Preparation

• Addition of 0.2 M EDTA and formic acid to 1 mL water samples to chelate metals and improve retention.
• Sodium thiosulfate added to drinking water to quench residual chlorine.
• No internal standards used, although available for future implementation.
• Direct injection of 10 µL sample into LC system.

Chromatography and Detection

• Agilent 1290 Infinity II LC with Poroshell 120 Aq-C18, 3.0 × 150 mm, 2.7 µm column.
• Gradient elution over 12 minutes at 0.4 mL/min, column temperature 45 °C.
• Agilent 6495D triple quadrupole with Jet Stream ESI in dynamic MRM mode and fast polarity switching.
• Data acquired and processed using Agilent MassHunter software.

Main results and discussion

Calibration curves were linear (R² ≥ 0.995) across relevant ranges: acrylamide 0.03–3 µg/L, HAAs 0.1–10 µg/L, β-estradiol 0.001–0.5 µg/L. Instrument detection limits achieved were 0.013–0.19 µg/L for polar analytes and 0.003–0.005 µg/L for β-estradiol. Precision over 12 replicates in ultrapure, ground, surface and drinking water yielded RSDs < 3.6% and recoveries within 75–125%. Chromatographic peaks were well resolved with minimal matrix effects. Drinking water contained a background level of trichloroacetic acid (~17 µg/L), raising its method detection limit accordingly.

Benefits and practical applications

The direct injection approach eliminates lengthy extraction and concentration steps, reducing turnaround time and solvent consumption. The method supports routine monitoring of emerging contaminants at low regulatory levels with high throughput. Its adaptability allows addition of further analytes via dynamic MRM without extensive reoptimization.

Future trends and potential applications

Large-volume injections (40–100 µL) can further lower detection limits, particularly for ultra-trace targets like β-estradiol. Integration of isotope-labeled internal standards may enhance quantitation accuracy. Expansion of the analyte panel and coupling with high-resolution MS or screening workflows will address evolving regulatory requirements and broaden environmental surveillance capabilities.

Conclusion

The developed direct aqueous injection LC-MS/MS method on Agilent 1290 Infinity II/6495D delivers rapid, sensitive and reproducible quantitation of acrylamide, HAAs and β-estradiol in diverse water matrices. Its simplicity and performance make it an excellent tool for routine water quality testing and emerging contaminant monitoring.

Reference

Powell D., Agilent Technologies, Inc. A Direct Aqueous Injection Method for Contaminants in Drinking and Nonpotable Water. Agilent Application Note, January 2025.