Determination of As, Sb and Se in Difficult Environmental Samples by Hydride Generation

Significance of the Topic

Determination of hydride-forming elements such as arsenic, antimony and selenium in complex environmental samples is critical for regulatory compliance, pollution monitoring and public health assessment. Continuous-flow hydride generation atomic absorption offers high sensitivity, simplified workflows and effective interference control in soils, sludges, sediments and waters.

Objectives and Study Overview

This application note evaluates continuous-flow hydride generation using the Agilent VGA-76 accessory versus traditional batch zinc slurry methods and graphite furnace AAS. The study involved an interlaboratory comparison with Lockheed Engineering and Sciences Company (LESC) under updated USEPA SW-846 guidelines, focusing on spike recovery, precision and interference management.

Methodology and Sample Preparation

Six challenging matrices (river sediment, electroplating sludge, hazardous waste soil, industrial sludge, fly ash and a water blank) were digested following EPA Methods 3050 and 3010 with nitric acid and hydrogen peroxide. Digests underwent controlled evaporation to remove residual peroxide, then acidification and addition of urea and potassium iodide to ensure analyte reduction to the +3 or +4 oxidation state before hydride generation. Predigestion spikes of 100 µg/L Sb, 40 µg/L As and 10 µg/L Se assessed digestion efficiency.

Used Instrumentation

• Agilent VGA-76 continuous-flow vapor generation accessory
• Agilent SpectrAA-20 and SpectrAA-400 AA spectrometers
• PSC-56 programmable sample changer for up to 67 samples plus five standards
• LESC “homemade” four-channel continuous-flow hydride generator for comparison

Main Results and Discussion

Calibration for As, Sb and Se showed excellent sensitivity and precision (RSD ≤1.6%). VGA-76 hydride AAS and graphite furnace AAS yielded comparable concentrations in digests. Blank water spikes recovered 90–105% for all elements, while real sample predigestion recovery varied (As 90–100%, Sb 30–36%, Se 56–74%) due to incomplete solubilization. Continuous-flow VGA-76 data matched LESC results after additional evaporation steps, demonstrating immunity to residual H2O2 interferences without complexing agents.

Benefits and Practical Applications

• High throughput: ~60 determinations per hour with ≤1% RSD
• Low-ppb detection limits despite sample dilutions
• Continuous-flow design reduces operational delays and interferences
• Automated sample handling improves reproducibility and efficiency

Future Trends and Applications

Emerging developments include microfluidic hydride generators, hyphenation with ICP-MS for multi-element speciation, advanced microwave or UV-assisted digestion protocols, and software-driven interference correction. These innovations will expand applications in environmental monitoring, food safety and industrial quality control.

Conclusion

The Agilent VGA-76 continuous-flow hydride generation AAS method provides a robust, sensitive and high-throughput solution for As, Sb and Se determination in difficult matrices. Effective peroxide removal and proper oxidation-state control are key to accurate recovery. This approach aligns with revised EPA SW-846 procedures and eliminates the need for specialized complexing reagents.

References

• K. Brodie, B. Frary, B. Sturman and L. Voth, Varian AA-at-Work No. 38, 1983.
• L. M. Voth-Beach and D. E. Shrader, Spectroscopy 1(11), 60–65, 1985.