Rapid determination of five arsenic species in polished rice using HPLC-ICP-MS

Importance of the topic

Arsenic contamination in rice poses significant health risks because inorganic arsenic forms are toxic and regulated. Speciation analysis is crucial to distinguish hazardous inorganic species from less toxic organic forms, enabling accurate risk assessment and compliance with safety standards.

Objectives and study overview

This work presents a rapid HPLC-ICP-MS method to quantify five arsenic species in polished rice: arsenate (As(V)), arsenite (As(III)), monomethylarsonic acid (MMA), dimethylarsinic acid (DMA) and arsenobetaine (AsB). The study covers method validation, analysis of certified reference materials and application to commercial rice samples.

Methodology and instrumentation

Polished rice from various provinces was milled, extracted with 0.15 M nitric acid under heat and agitation, centrifuged and filtered. Extracts were analyzed within 24 hours to minimize species interconversion.

Instrumental setup

• HPLC: Agilent 1260 system with ZORBAX SB-Aq reversed-phase column, isocratic elution using 20 mM citric acid and 5 mM sodium hexane-sulfonate at pH 4.3, 1.2 mL/min flow, 5 μL or 100 μL injections.
• ICP-MS: Agilent 7900 with Octopole Reaction System (ORS4) in helium mode to remove polyatomic interferences on m/z 75.

Main results and discussion

Five arsenic species were fully separated within 4 minutes. Calibration curves (1–200 ppb) showed excellent linearity. Detection limits ranged from 0.01 ppb (100 μL injection) to 0.67 ppb (5 μL injection). Analysis of NIST 1568a and 1568b CRMs agreed with certified or literature values. Spike recoveries (1–10 ppb) were 85–110%. Precision tests (n = 10) yielded RSDs below 4% (inorganic As < 2%). Twenty commercial rice samples all contained inorganic As and DMA but stayed below the 0.2 mg/kg Codex guideline.

Benefits and practical applications

The method delivers rapid throughput, high sensitivity and reliable quantification of arsenic species in rice. It supports routine food safety monitoring, regulatory compliance and quality control in analytical laboratories.

Future trends and potential applications

• Automation and miniaturization of sample preparation to boost throughput.
• Extension to diverse food matrices and environmental samples.
• Integration with high-resolution mass spectrometry to discover new arsenic compounds.
• Development of portable HPLC-ICP-MS systems for field testing.

Conclusion

The validated HPLC-ICP-MS method enables fast, accurate and sensitive determination of five arsenic species in polished rice. Its performance makes it suitable for regulatory, research and quality-control applications in food safety.

References

• Narukawa T Inagaki K Kuroiwa T Chiba K The extraction and speciation of arsenic in rice flour by HPLC-ICP-MS Talanta 77 2008 427-432
• Huang JH Ilgen G Blank value adsorption preconcentration and preservation for arsenic speciation of environmental water samples Analytica Chimica Acta 512 2004 1-10
• Caruso JA B’Hymer C Heitkemper DT An evaluation of extraction techniques for arsenic species from freeze-dried apple samples Analyst 126 2001 136-140
• Llorente-Mirandes T A fully validated method for the determination of arsenic species in rice and infant cereal products Pure Appl Chem 84 2012 225-238