Speciation of Inorganic Arsenic in Baby Rice Cereals Using HPLC-ICP-MS

Significance of the topic

Inorganic arsenic is a recognized carcinogen and early exposure through rice-based infant cereals raises concerns due to rice’s capacity to accumulate arsenic. Monitoring and speciation are critical to assess health risks for vulnerable populations such as infants.

Objectives and study overview

This study applies the FDA Elemental Analysis Manual Section 4.11 HPLC-ICP-MS protocol to both speciation and total arsenic determination in 31 commercial baby rice cereals produced by seven manufacturers. The aim is to quantify individual arsenic species, compare cereal formulations, and evaluate compliance with existing data.

Methodology

Sample preparation and analysis followed a hot block acid extraction with nitric acid digestion, centrifugation, filtration and pH adjustment. Speciation employed isocratic anion-exchange HPLC using a 10 mM ammonium phosphate mobile phase at pH 8.25. Detection of As(III), DMA, MMA and As(V) occurred by Agilent 7700x ICP-MS in helium collision cell mode monitoring m/z 75. Limits of detection ranged from 0.9 to 1.8 ng/g and quantitation limits from 7 to 14 µg/kg. Quality control used NIST SRM 1568a and 1568 rice flour with certified values for total and speciated arsenic.

Instrumentation used

• An Agilent 1200 Infinity LC system with vacuum degasser, binary pump, autosampler and a 10-port valve plus external Shimadzu LC-20AD pump for post-column internal standard addition.
• An Agilent 7700x ICP-MS with MicroMist nebulizer, Scott double-pass spray chamber, and helium collision gas.

Main results and discussion

All 31 rice cereals contained detectable total and inorganic arsenic. Total arsenic ranged from 80 to 277 µg/kg (average 174 µg/kg), and inorganic arsenic from 55 to 158 µg/kg (average 101 µg/kg), representing about 58 percent of total arsenic. Mixed grain cereals showed lower levels (average total 105 µg/kg and inorganic 63 µg/kg). Method mass balance averaged 96.7 percent. Calibration was linear (R2=1.00), recoveries 99–113 percent, and repeatability below 7 percent RSD. Compared with FDA 2012 data, this study recorded lower average inorganic arsenic per serving (1.5 µg vs. 2.7 µg).

Benefits and practical applications

HPLC-ICP-MS speciation provides reliable, sensitive profiling of arsenic species in infant foods, supporting risk assessment efforts and regulatory compliance. The streamlined workflow facilitates routine quality control in food safety laboratories.

Future trends and potential applications

Advances may include high-resolution mass spectrometry for non-targeted speciation, microfluidic chromatography for faster throughput, coupling mass spectrometry imaging to visualize arsenic distribution, and automation with online sample preparation. Continued improvement in detection sensitivity and broader speciation of other toxic elements will enhance dietary exposure assessment.

Conclusion

The FDA EAM 4.11 HPLC-ICP-MS method effectively quantifies inorganic and organic arsenic in baby rice cereals with high sensitivity and precision. Study results underscore the necessity for ongoing monitoring of arsenic species in infant foods to protect consumer health.

References

• B. Jackson et al. Arsenic, Organic Foods, and Brown Rice Syrup. Environmental Health Perspectives. 2012;120:623–626.
• B. Jackson et al. Arsenic concentration and speciation in infant formulas and first foods. Pure and Applied Chemistry. 2012;84(2):215–225.
• A. Carey et al. Phloem transport of arsenic species from flag leaf to grain during grain filling. New Phytologist. 2011;192(1):87–98.
• A. Meharg et al. Arsenic & Rice. Springer. 2012. ISBN 978-9400729469.
• A. Meharg et al. Geographical variation in total and inorganic arsenic content of polished (white) rice. Environmental Science & Technology. 2009;43(5):1612–1617.
• G. Sun et al. Inorganic arsenic in rice bran and its products is an order of magnitude higher than in bulk grain. Environmental Science & Technology. 2008;42(19):7542–7546.
• N. Vela & D. Heitkemper. Total arsenic determination and speciation in infant food products by ion chromatography–ICP-MS. Journal of AOAC International. 2004;87(1):244–252.