High throughput determination of inorganic arsenic in rice using hydride generation-ICP-MS

Significance of the topic

Arsenic speciation in rice is critical to food safety because inorganic arsenic species are toxic and carcinogenic while organic forms are less harmful.
Accurate, rapid, and high-throughput analysis supports regulatory compliance and public health monitoring.

Objectives and study overview

This application note presents a hydride generation ICP-QQQ method for the determination of inorganic arsenic in rice products.
Comparison with conventional HPLC-ICP-QQQ is conducted to assess performance, throughput, and detection limits.

Methods and instrumentation used

Sample preparation:

• Rice samples (commercial and controlled arsenic-exposed) ground and extracted for total As and speciated As.
• Total As: microwave digestion with HNO3 and H2O2, diluted to 30 mL.
• Speciation: 1 % HNO3 and 1 % H2O2 extraction at increasing temperatures, centrifuged.

Instrumentation applied:

• Agilent ICP-QQQ 8800 with Hydride Generation Integrated Sample Introduction System (ISIS).
• Hydride generation accessory using 5 M HCl and 2 % NaBH4 with antifoam.
• Gas–liquid separator and argon flow to ICP torch.
• Rhodium internal standard introduced via nebulizer.
• Comparison: HPLC-ICP-QQQ with anion exchange column and ammonium carbonate mobile phase.

Main results and discussion

• Limits of detection for inorganic As: ~1.5 µg/kg (HG-ICP-QQQ) and ~0.3 µg/kg (HPLC-ICP-QQQ).
• QC on reference materials NIST 1568a and IMEP-107 showed agreement with certified values (total As and iAs).
• Commercial rice products (31): all iAs levels below Chinese maximum level (150 µg/kg) and proposed Codex ML (200 µg/kg).
• Total As alone would overestimate risk: 32–42 % of samples exceed limits if total As used.
• Hydride generation method converts iAs quantitatively to AsH3, while organic species yield negligible response.
• Sample throughput: 4 min per sample for HG method vs 5–10 min per replicate with HPLC.

Benefits and practical applications

• Rapid screening of rice and rice products for inorganic arsenic.
• High throughput with minimal data processing, no chromatographic separation.
• Suitable for routine QA/QC, regulatory monitoring, and large-scale biomonitoring studies.

Future trends and potential applications

• Extension to other food matrices with inorganic arsenic concerns (e.g., seafood, cereals).
• Automation and integration with laboratory information management systems (LIMS).
• Integration with speciation workflows for additional toxic elements (selenium, antimony).
• Further miniaturization and field-deployable HG-ICP-MS platforms.

Conclusion

Hydride generation ICP-QQQ provides a fast, sensitive, and robust alternative to HPLC-based speciation for inorganic arsenic in rice.
The method achieves low detection limits and high throughput, facilitating regulatory compliance and public health protection.

References

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