Analytical Sciences

Reversed Phase Column HPLC-ICP-MS Conditions for Arsenic Speciation Analysis of Rice Flour

Tomohiro NARUKAWA,* Eri MATSUMOTO,** Tsutomu NISHIMURA,** and Akiharu HIOKI*

*National Metrology Institute of Japan (NMIJ), National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba Central 3, 1-1-1 Umezono, Tsukuba, Ibaraki 305-8563, Japan
**Japan Food Research Laboratories, 6-11-10 Nagayama, Tama, Tokyo 206-0025, Japan

New measurement conditions for arsenic speciation analysis of rice flour were developed using HPLC-ICP-MS equipped with a reversed phase ODS column. Eight arsenic species, namely, arsenite [As(III)], arsenate [As(V)], monomethylarsonic acid (MMAA), dimethylarsinic acid (DMAA), trimethylarsine oxide (TMAO), tetramethylarsonium (TeMA), arsenobetaine (AsB) and arsenocholine (AsC), were separated and determined under the proposed conditions. In particular, As(III) and MMAA and DMAA and AsB were completely separated using a newly proposed eluent containing ammonium dihydrogen phosphate. Importantly, the sensitivity changes, in particular those of As(V) and As(III) caused by coexisting elements and by complex matrix composition, which had been problematical in previously reported methods, were eliminated. The new eluent can be applied to C₈, C₁₈ and C₃₀ ODS columns with the same effectiveness and with excellent repeatability. The proposed analytical method was successfully applied to extracts of rice flour certified reference materials.

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