Title : Simultaneous determination of total As and Cd in Columbian Oryza sativa L. rice by ICP-OES
Abstract:
Heavy metals such as Arsenic (As) and Cadmium (Cd) are considered toxic at trace levels, their accurate quantification in rice is quite complex due to their low concentration and interfere with other elements. The aim of this work was to develop, adjust and validate a methodology for As and Cd content quantification in rice stem and grain matrices of rice (Oryza sativa L.) from two production systems “Irrigated Rice Ecosystems” (IRE) and “Rainfed Rice Ecosystems” (RRE) in Colombia. The mineralization process was carried out by acid digestion using an open system with a heating plate. Metals detection was performed by inductively coupled plasma optical emission spectrometry (ICP?OES). The acid digestion was realized using heating plate mineralization. The adjustment, calibration and validation of the method was in accordance with the AOAC standards, considering the sensitivity, precision, accuracy, and selectivity parameters. The linearity equation was constructed in the range from 0.01 to 1 mg L-1. A linear fit was obtained with values of correlation coefficients (R) for As and Cd of 0.9994 and 0.9992, respectively, limits of detection (LOD) and quantification and (LOQ) were 0.0336 1 and 0.1120 ug mL-1 for As and 0.0068 and 0.0227 ug mL-1 for Cd. Recovery percentages of As and Cd using a certified reference material (rice flour NIST-SRM 1568b) were 96.8% and 107.1%, respectively. The accuracy of the method was evaluated using two types of addition with As and Cd in matrices of brown rice grain; the first was the construction of twelve As and Cd levels at laboratory, in the range of 0.001 to 1 mg L-1 and the second was done using matrices of grain of brown rice from plants grown in artificially enriched soils in greenhouse with CdCl? at four levels: 0, 5, 10 and 15 mg L-1. Method application was carried by quantifying 259 rice stem and 443 grain samples. The concentration ranges obtained for As were 0.04 to 0.68 mg kg-1 in rice grain and 0.09 to 1.16 mg kg-1 in rice stem for IRE and 0.01 to 3.29 mg kg-1 in grain and 0.02 to 5.14 mg kg-1 in rice stem for RRE. While for Cd the ranges were from 0.05 to 0.81 mg kg-1 in whole grain and 0.04 to 1.43 mg kg-1 in rice stem for IRE and 0.04 to 2.33 mg kg-1 in grain and 0.01 to 6.04 mg kg-1 in rice stem for RRE.
Key words: Heavy metals, rice, mineralization, IRE, RRE, arsenic, cadmium
Acknowledgments: The authors would like to thank the Colombian Ministry of Agriculture and Rural Development (MADR) and the Corporación Colombiana de Investigación Agropecuaria AGROSAVIA for supporting this study through the Project entitled ‘Study of As and Cd in rice producing areas′. Grant No. 1001231. Rice samples were collected according to the Colombian Resolution No. 1466 of 3rd December 2014, by which Agrosavia has permission to collect biological diversity samples (including soil samples) for non-commercial and scientific research purposes.
Audience Take Away:
- The audience will be able to reproduce the validated methodology to detect total As and Cd levels in samples of rice using ICP-OES.
- This method offers a practical solution for laboratories that do not have a microwave system, as the use of a heating plate for the mineralization process is both suitable and cost-effective for determining As and Cd concentrations in the rice matrix.
- The obtained results showed a high biosorption capacity, especially in relation to the elevated As and Cd contents in the artificially enriched matrix from the greenhouse experiment. These could be used to expand research on topics related to the translocation of heavy metals in plant tissues, not only in rice but also in other crops.
