Arsenic Speciation in Rice and Rice Products using LC-ICP-MS: A Sensitive and Reliable Approach by Shimadzu

Importance of the topic

Arsenic contamination represents a critical public health challenge, as inorganic arsenic species are highly toxic and can accumulate in staple foods such as rice. Speciation analysis enables accurate risk assessment and ensures compliance with stringent regulatory limits.

Objectives and study overview

The primary aim of this work is to demonstrate a robust LC-ICP-MS method for arsenic speciation in rice and rice-based products. The study showcases performance metrics, validation data, and practical applicability of Shimadzu’s LC-ICP-MS-2050 LF system under EU maximum residue level requirements.

Methodology

Samples (white rice, brown rice, crackers, cakes, beverages) are milled and extracted using a modified Nishimura protocol: 0.5 g sample with 2 mL 0.15 M HNO3, heated at 120 °C for 2 h, diluted, centrifuged, and filtered. Calibration employs seven mixed standards (0.2–20 µg/L) with 1/x weighted regression. Duplicate analyses and two spiked levels (25 and 50 µg/kg) assess repeatability and recovery.

Instrumentation Used

Shimadzu Nexera inert UHPLC system with a pentafluorophenyl column (250 × 4.6 mm, 5 µm). Mobile phase: 0.1% formic acid, 1% methanol, 0.025% ion-pair reagent; flow rate 0.75 mL/min; column at 40 °C; 10 µL injection. Detection by Shimadzu ICP-MS-2050 LF (mini-torch, helium cell gas) managed via LabSolutions ICPMS TRM software.

Main Results and Discussion

Calibration curves for As(III) and As(V) show linearity across 0.2–20 µg/L with recoveries within 80–120%. In rice samples, As(III) ranged from 31.8 to 112 µg/kg; As(V) was often below detection in white rice but present up to 21.6 µg/kg in brown rice. Rice products exhibited varied inorganic arsenic levels. Spike recoveries averaged 96.7–119.8%, demonstrating effective extraction and quantification.

Benefits and Practical Applications

The method combines high sensitivity and selectivity of LC-ICP-MS for four arsenic species, requiring minimal user optimization thanks to Shimadzu’s Method Package. It supports regulatory monitoring, quality control in food safety laboratories, and routine screening of rice commodities.

Future Trends and Potential Applications

Advancements may include automation of extraction, miniaturized sample preparation formats, expanded speciation to other toxic elements, integration with high-throughput screening platforms, and data analytics driven by machine learning to further improve laboratory efficiency.

Conclusion

Shimadzu’s LC-ICP-MS-2050 LF coupled with Nexera inert provides a sensitive, reliable, and user-friendly approach for arsenic speciation in rice and related products. The validated protocol meets accuracy and precision requirements for regulatory compliance and consumer safety.

Reference

1) T. Nishimura, M. Hamano-Nagaoka, N. Sakakibara, T. Abe, Y. Maekawa, T. Maitani, Food Hygiene and Safety Science 51 (2010) 178.