Arsenic content of various types of rice as determined by plasma-based techniques

The determination of total As in rice is of special importance because rice forms a major dietary staple for many populations and contains a relatively high amount of this element as compared to other foodstuffs. Arsenic is in fact abundant in many minerals and its compounds are frequently employed in the chemical industry for producing pharmaceuticals, agricultural chemicals (herbicides, fungicides, wood preservatives, insecticides, rodenticides and sheep-dips) or as pig and poultry growth-promoters. Ingestion of As with food is one major route for this element to enter the human organism. Moreover, As in general, and its chemical forms in particular, are well known to cause acute and chronic toxicity, which may range from minor disorders to cancer and even death. In consideration of the above, the Community Reference Laboratory for Residues at the Istituto Superiore di Sanita (ISS-CRL) has undertaken a study aimed at quantifying the total content of As in eight different types of rice produced in northern Italy, seven of which belong to the variety Japonica and one to the variety Indica. Prior to analysis the rice samples were subjected to grinding and mineralized by acid-assisted microwave digestion. Determinations were performed by means of inductively coupled plasma atomic emission spectrometry (ICP-AES), quadrupole inductively coupled plasma mass spectrometry (Q-ICP-MS) and magnetic sector high resolution inductively coupled plasma mass spectrometry (HR-ICP-MS). The As concentration intervals found for the eight types of rice investigated are as follows (in ng g(-1)): 205 +/- 16 (Arborio, Japonica, very fine); 80.7 +/- 1.0 (Baldo, Japonica, very fine); 136 +/- 4 (Carnaroli, Japonica, very fine); 283 +/- 9 (Ribe, Japonica, fine); 121 +/- 4 (Ribe Parboiled, Japonica, fine); 223 +/- 12 (Vialone Nano, Japonica, semi-fine); 187 +/- 1 (Originario, Japonica, common) and 133 +/- 4 (Thaibonnet Parboiled, Indica). Other trace elements were also quantified, the concentrations of which spanned the ranges (in ng g(-1)): Cd, 15.6-228; Co, 4.40-30.9; Cr, 2.1-4.7; Cu, 1958-3165; Fe, 2378-5014; Mn, 4656-11847; Pb, 4.57-17.3; V, 2.48-5.16 and Zn, 7510-20529. Grinding of rice prior to digestion caused no detectable effects on the actual values of As and of the other trace elements. (C) 2002 Elsevier Science B.V. All rights reserved.