Magnetic solid phase extraction as a nonchromatographic method for the quantification of ultratrace inorganic arsenic in rice by inductively coupled plasma-optical emission spectrometry (ICP OES)

An alternative analytical method was developed for the quantification of inorganic arsenic (iAs) in rice by ICP OES. Iron nanoparticles modified with an organophosphorus compound were used as the solid phase for MSPE of iAs from the plant matrix. The MSPE procedure was performed using 4 mL of a buffer solution with pH 4.0, 20 mg of the nanomaterial, and a 15-min extraction time. The total As (tAs) by ICP OES was also quantified using the same MSPE procedure after solubilization of the samples by a block digester. The accuracy of tAs and iAs quantification was verified using CRM NIST 1568b (97 % and 101 % recovery, respectively). The precision (RSD < 15 %) and LOD and LOQ (1.08 and 3.70 µg kg-1, respectively) of the proposed method were satisfactory. The rice samples had tAs contents between 0.090 and 0.295 mg kg-1 and iAs mass fractions between 0.055 and 0.109 mg kg-1.