Measurement of Arsenic and Selenium in White Rice and River Water by Hydride Generation-Atomic Absorption Spectrometry (HG-AAS) with Electric Cell Heating

Significance of the Topic

The hydride generation atomic absorption spectrophotometric technique provides a highly sensitive approach for trace-level quantification of arsenic (As) and selenium (Se). By converting analytes into volatile hydride species, HG-AAS minimizes interferences from alkaline metals and complex matrices, making it valuable for environmental monitoring and food safety assessments.

Objectives and Study Overview

This application demonstrates the use of a Shimadzu AA-7000 atomic absorption spectrophotometer combined with an HVG-1 hydride vapor generator and SARF-16C electric cell heater to measure As and Se in certified white rice and river water reference materials. The goal was to validate method sensitivity, accuracy, and reproducibility without relying on flame heating.

Methodology and Instrumentation

Sample pretreatment involved acid digestion of approximately 1 g white rice with nitric and perchloric acids, followed by reconstitution in hydrochloric acid to obtain a 25 mL stock solution. River water samples (10 mL) underwent a similar acidification and dilution to 20 mL. Pre-reduction steps using HCl, KI, and ascorbic acid (for As) or HCl alone (for Se) generated hydride-forming species.

The analytical system comprised:

• AA-7000 atomic absorption spectrophotometer
• HVG-1 hydride vapor generator
• SARF-16C electric cell heater set to 800 °C
• Carrier gas: argon at ~0.1 L/min
• Reagent: 0.4 % NaBH₄ in 0.4 % NaOH, mixed with 5 M HCl
• Wavelengths: 193.7 nm for As, 196.0 nm for Se; slit width 0.7 nm
• Background correction: deuterium lamp
• Integration: 5 s per replicate, n=5

Key Results and Discussion

Calibration curves yielded detection limits of 0.05 ppb for As and 0.09 ppb for Se at 1 % absorbance. White rice analysis produced As 0.101 mg/kg (certified 0.109 mg/kg, RSD 1.7 %) and Se 0.010 mg/kg (RSD 8.5 %). Unspiked river water measured As 0.21 µg/L (certified 0.20 µg/L, RSD 7.4 %), Se below 0.2 µg/L. Spiked water showed As 5.1 µg/L (certified 5.2 µg/L, RSD 1.5 %) and Se 5.3 µg/L (certified 5.0 µg/L, RSD 1.0 %). These results confirm method accuracy and precision.

Benefits and Practical Applications of the Method

• Enhanced sensitivity (~1.5× higher vs. flame AAS)
• No need for acetylene or air gas supplies
• Robust performance in complex food and water matrices
• Applicable to trace monitoring in QA/QC and environmental labs

Future Trends and Potential Applications

Advances may include coupling HG-AAS with ICP techniques for multi-element analysis, miniaturization of hydride generation modules for field use, and integration into automated platforms for high-throughput QA/QC in industry and environmental surveillance.

Conclusion

Electrically heated hydride generation AAS on the AA-7000 platform provides a reliable and sensitive approach for arsenic and selenium determination in food and water samples, streamlining workflows by eliminating flame gases while delivering accurate, reproducible results.

References

• Shimadzu Corporation. Application Note A495: Measurement of Arsenic and Selenium in White Rice and River Water by Hydride Generation-Atomic Absorption Spectrometry with Electric Cell Heating. Oct. 2015.