Development of a simple and fast method for the determination of total arsenic and its species in rice husked by ICP-MS and LC-ICP-MS

Abstract

Arsenic (As) is a naturally occurring toxic element in the earth´s crust, with mutagenic, teratogenic, genotoxicity, and neurotoxicity capabilities. It is well-known that the food route is the main source of contamination by humans [1]. In this context, the rice is considered one of the main sources of As intake in the human diet, due to its plant has high capacity to accumulate this element, mainly in the grain [2]. Therefore, this work aimed to develop a simple and high-throughput analytical procedure based on ultrasound highfrequency assisted extraction with diluted acid for the determination of total As and speciation of As for ICPMS/MS and HPLC-ICP-MS/MS. The multivariate optimization approach to optimize and develop the extraction procedure was performed using the Box-Behnken experimental design, varying the HNO3 concentration, time (min), and ultrasound power (W). The best experimental condition was chosen from the recovery of total As. Therefore, a CRM Rice flour 1568ª was used and recoveries ranging from 70 to 100%, were obtained through the process of optimizing the extraction of As. In this sense, the optimized conditions for ultrasound-assisted extraction were the HNO3 of 0.08mol L-1 , sonication time of 5 minutes, and power of 100 % applied to the ultrasonic. The proposed method allows an increase in the analytical frequency of analysis, reducing the sample preparation time. Furthermore, the developed method matches with the green chemistry principles, essentially due to significantly reducing the nitric acid amount. Regarding the analytical figure of merits, the use of ICP-MS/MS, provided low LOD and LOQ values for tAs (0.39 and 1.29 µg kg−1). After checking the method’s trueness, the proposed procedure was successfully employed for the determination of total Arsenic in sixty-five rice husked samples of ten different varieties from the province of Corrientes, Argentina. Values higher than the maximum allowed concentration of As in rice by some regulatory agencies (FAO,WHO and ANVISA) were found in some samples, with a minimum of 75.6 and a maximum of 2679 µg kg-1 of total As, and an average of 257 ug kg-1 , being this value similar to others found in studies that analyzed arsenic in South American rice [3]. The proposed extraction method was also applied to identify the organic species of As, being found the species monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA). Overall, the present method of sample preparation based on extraction via high-frequency ultrasound allows the use both for total analysis of As and for chemical speciation of As species keeping the integrity of the native arsenic species of As(III), As(V) MMA and DMA. Therefore, the proposed procedure for the extraction of As in husked rice samples using ultrasound high frequency and diluted HNO3 was an adequate strategy showing advantages such as simplicity, high analytical frequency, and low cost.