Can we keep the cost of analysis of haloaceticacids (HAAs) down by using an alternative to Helium?

Importance of the Topic

Haloacetic acids (HAAs) are regulated carcinogenic disinfection byproducts in drinking water. Accurate measurement is essential for public health and regulatory compliance. Rising helium costs and supply restrictions motivate evaluation of hydrogen as a cost-effective carrier gas alternative.

Study Objectives and Overview

The study compares hydrogen and helium carrier gases for GC–ECD analysis of five regulated HAAs, four additional HAAs and dalapon according to EPA method 552.3. It aims to assess performance metrics and potential cost savings when using hydrogen.

Methodology

Sample derivatization and extraction produced a methyl ester mix of HAAs and internal standards. Six-point calibration curves (1–50 ppb) were constructed with quadratic 1/A weighting. Blanks and repeatability standards were analyzed to evaluate system performance and detection limits.

Instrumentation Used

• Shimadzu Nexis GC-2030 with dual split/splitless injectors
• Dual ECD-2030 detectors and dual AOC-20 Plus autosampler
• Analytical column: Rtx-1701 (30 m × 0.25 mm × 0.25 µm)
• Confirmation column: Rxi5Sil-MS (30 m × 0.25 mm × 0.25 µm)
• Carrier gas: hydrogen or helium at constant pressure for linear velocity of 40 cm/s

Results and Discussion

• Chromatograms and retention times were nearly identical with H2 and He carrier gases
• Calibration curves showed coefficients of determination (r²) above 0.995 for all analytes
• Repeatability of 1 ppb injections produced <2% RSD, well below the EPA threshold of 20%
• Accuracy across levels fell within ±30% of expected values; recoveries ranged 76.8–93.8% at the lowest level
• Blank analyses confirmed absence of interfering peaks above one-third the reporting level

Practical Implications

Substituting hydrogen for helium reduces carrier gas cost by approximately 6.2-fold with research grade gas and 2.7-fold with ultra-high purity gas. Laboratories also mitigate helium supply risks while maintaining EPA compliance.

Future Trends and Potential Applications

• Expansion of hydrogen use in additional GC applications and detectors
• Integration with GC–MS for enhanced selectivity and compound identification
• Advancements in gas safety and purity control to address flammability concerns
• Development of greener analytical workflows minimizing reliance on nonrenewable gases

Conclusion

Hydrogen is a practical carrier gas alternative for GC–ECD analysis of HAAs under EPA method 552.3. It delivers equivalent analytical performance to helium while offering significant cost savings and supply stability.