SPE HG-AAS method for the determination of inorganic arsenic in rice—results from method validation studies and a survey on rice products

• Published in: Analytical and bioanalytical chemistry Vol. 405; no. 24; pp. 7851 - 7857
• Main Authors: Rasmussen, Rie R., Qian, Yiting, Sloth, Jens J.
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.09.2013; Springer; Springer Nature B.V
• Subjects: Analytical Chemistry; Arsenates; Arsenic; Biochemistry; Cartridges; Characterization and Evaluation of Materials; Chemical properties; Chemistry; Chemistry and Materials Science; Chromatography; Composition; Food; Food Science; Hydrochloric acid; Identification and classification; Laboratories; Laboratory Medicine; Liquid chromatography; Markets; Mass spectrometry; Monitoring/Environmental Analysis; Rapid Detection in Food and Feed; Reproducibility; Research Paper; Rice; Scientific imaging; Seafood; Separation; Testing; Validation studies; Denmark; China; Germany; SPE HG-AAS; Rice samples; Food control; Inorganic arsenic; Water bath extraction; Speciation
• ISSN: 1618-2642; 1618-2650
• DOI: 10.1007/s00216-013-6936-8

The present paper describes the development, validation and application of a method for inorganic arsenic (iAs) determination in rice samples. The separation of iAs from organoarsenic compounds was done by off-line solid-phase extraction (SPE) followed by hydride generation atomic absorption spectrometry (HG-AAS) detection. This approach was earlier developed for seafood samples (Rasmussen et al., Anal Bioanal Chem 403:2825–2834, 2012 ) and has in the present work been tailored for rice products and further optimised for a higher sample throughput and a lower detection limit. Water bath heating (90 °C, 60 min) of samples with dilute HNO 3 and H 2 O 2 solubilised and oxidised all iAs to arsenate (As V ). Loading of buffered sample extracts (pH 6 ± 1) followed by selective elution of arsenate from a strong anion exchange SPE cartridge enabled the selective iAs quantification by HG-AAS, measuring total arsenic (As) in the SPE eluate. The in-house validation gave mean recoveries of 101–106 % for spiked rice samples and in two reference samples. The limit of detection was 0.02 mg kg −1 , and repeatability and intra-laboratory reproducibility were less than 6 and 9 %, respectively. The SPE HG-AAS method produced similar results compared to parallel high-performance liquid chromatography coupled to inductively coupled plasma mass spectrometry (ICP-MS) analysis. The SPE separation step was tested collaboratively, where the laboratories ( N  = 10) used either HG-AAS or ICP-MS for iAs determination in a wholemeal rice powder. The trial gave satisfactory results (HorRat value of 1.6) and did not reveal significant difference ( t test, p  > 0.05) between HG-AAS and ICP-MS quantification. The iAs concentration in 36 rice samples purchased on the Danish retail market varied (0.03–0.60 mg kg −1 ), with the highest concentration found in a red rice sample.