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Home ›› About Speciation ›› Speciation News

Arsenic speciation analysis in rice milk

(11.05.2020)

Brazilian researchers have developed an analytical method for arsenic species in rice milk using LC-ICP-MS. Its main features are fast analysis, simple sample preparation and adequate accuracy and precision.

Background:

Photo: a glass of rice milk
(Spinoiziano CC BY-SA 3.0)

Rice milk is an alternative product, mainly consumed by individuals intolerant to lactose or allergic to cow milk. Unfortunately, arsenic concentration in rice milk is much higher than in cow milk, and even worse, rice milk usually contains the more problematic inorganic arsenic species. Inorganic arsenic is a carcinogen and therefore daily consumption of contaminated rice milk is a health risk especially for infants, for which milk is their basic food. In order to evaluate the health risks from the consumption of rice milk, not only the total arsenic concentration but also the arsenic species distribution has to be determined.

Liquid chromatography (LC) coupled with inductively coupled plasma mass spectrometry (ICP-MS), is the most often used technique for arsenic speciation analysis. LC-ICP-MS is combining the high selectivity of LC with the impressive sensitivity of ICP-MS. Sample pretreatment should consist of a minimum of steps, avoiding any conversion of species.

The new study:

Researchers from Brazil now developed a simple and fast method for the speciation analysis of arsenic in rice milk. The separation was based on the use of an anion exchange column (Hamilton, PRP-100, 250 x 4.1 mm) under isocratic elution mode. Rice milk samples were diluted 3-fold or 5-fold and filtrated through a 0.45 µm pore size filter before analysis. Aliquots of 200 µl of the so prepared samples were injected to the LC system. The eluent from the column was transported to a quadrupole-based ICP-MS via PEEK tubing. The four species detected (As(III), dimethylarsinic acid (DMA, monomethylarsonic acid (MMA) and As(V)) were processed in peak area mode using external calibration.

The accuracy of the method was validated by using diluted rice milk spiked with each investigated arsenic species at two concentration levels (1.0 or 5.0 µg/L). The recoveries were between 85 and 116%. The obtained detection limits were below 0.15 µg/L and the quantification limits were below 0.45 µg/L for all species.

The obtained results showed that the total arsenic and the As speciation varied in view of the type of rice used for preparing the milk. Milk from brown rice contained more As than rice milk obtained from polished rice.

The authors believe that the method could be adopted as a routine method for regulatory bodies because of the adequate sample throughput and the simple sample preparation.

The original study

Francisco Cunha da Rosa, Matheus Augusto Gonçalves Nunes, Fábio Andrei Duarte, Érico Marlon de Moraes Flores, Flávia Brito Hanzel, Agnes Souza Vaz, Dirce Pozebon, Valderi Luiz Dressler, Arsenic speciation analysis in rice milk using LC-ICP-MS, Food Chem. X., 2 (2019) 1000028. DOI: 10.1016/j.fochx.2019.100028

Analytical instrumentation:

PerkinElmer SCIEX - ELAN DRC II

PerkinElmer Inc. - Series 200 LC Micro Pump

Related studies (newest first)

Zhuyun Gu, Shamali de Silva, Suzie M. Reichman, Arsenic Concentrations and Dietary Exposure in Rice-Based Infant Food in Australia, Int. J. Environ. Res. Public Health, 17 (2020) 415. DOI: 10.3390/ijerph17020415

G.M. Santos, D. Pozebon, C. Cerveira, D.P. Moraes, Inorganic arsenic speciationin rice products using selective hydride generation and atomic absorption spectrometry (AAS). Microchem. J., 133 (2017) 265–271. DOI: 10.1016/j.microc.2017.03.025

T. Pedron, F.R. Segura, F.F. Silva, A.L. Souza, H.F. Malteza, B.L. Batista, Essential and nonessential elements in Brazilian infant food and other ricebased products frequently consumed by children and celiac population. J. Food Compos. Anal., 49 (2016) 78–86. DOI: 10.1016/j.jfca.2016.04.005

A.J. Signes-Pastor, M. Carey, A.A. Meharg, Inorganic arsenic in rice-based products for infants and young children. Food Chem., 191 (2016) 128–134. DOI: 10.1016/j.foodchem.2014.11.078

S. Munera-Picazo, F. Burló, A.A. Carbonell-Barrachina, Arsenic speciation in rice-based food for adults with celiac disease. Food Addit. Contam. Part A., 31/8 (2014) 1358–1366. DOI: 10.1080/19440049.2014.933491

Ron Shannon, Jose M. Rodriguez, Total arsenic in rice milk, Food Addit. Contam. Part B., 7/1 (2014) 54-56. DOI: 10.1080/19393210.2013.842941

A.A. Meharg, C. Deacon, R.C. Campbell, A.M. Carey, P.N. Williams, J. Feldmann, A. Raab, Inorganic arsenic levels in rice milk exceed EU and US drinking water standards, J. Environ. Mon., 10/4 (2008) 428–431. DOI: 10.1039/b800981c