DETERMINATION OF ARSENIC IN RICE AND COOKED RICE USING X-RAY FLUORESCENCE METHOD

• Main Author: Yatu Niken Syahfitri, Woro
• Format: Theses
• Language: Indonesia
• Subjects: Kimia
• Online Access: https://digilib.itb.ac.id/gdl/view/57293
• Institution: Institut Teknologi Bandung

Rice is a staple food consumed by more than half of the world's population, as a source of carbohydrates, vitamins, and minerals. However, the rice can contain heavy metals, especially As (arsenic) which originate from natural and anthropogenic activity. The release of As into the environment can cause As accumulation in waters and soils, thus causing the entry of As in rice plants. Several rice varieties have been reported to contain high levels of arsenic (As) in various countries. This has become a worldwide concern because of the high level of consumption of rice and its processed products and the long-term effects it can cause, so it is necessary to regularly control the quality of rice. Therefore, an advanced, accurate, fast, relatively easy, and environmentally friendly As analysis method is needed such as X-ray fluorescence (XRF). The activities carried out include sampling, initial sample preparation, method selection, instrument performance evaluation, optimization of sample preparation methods both suspension and acid digestion using microwave digestion, and method validation with selectivity, linearity, precision parameters including repeatability and internal repeatability, accuracy, detection limit, and ruggedness/robustness using NIST 1568b Rice Flour as a primary standard reference material (SRM). The Total X-ray fluorescence (TXRF) method was chosen because it has a specific configuration with a critical angle of ~ 0,10, which minimizes background and has a low detection limit. The quality control of the TXRF instruments on the FWHM (full width at half maximum) parameter based on testing during the period from July 2020 to May 2021, was obtained at 130.7±0.3 eV. This shows good conformity with the standard specification, which is < 149 eV so that the detector performance can be categorized as good. The validation results obtained indicate that the TXRF method is selective for the determination of As with a ratio value between As/Pb of 0.97-1.06 and linear in the concentration range of 0.020-4.0 mg/L, with a coefficient of determination (R2) of 0,9991. In addition, the results showed that the optimization of the suspension sample preparation method and acid digestion had the same potential, with accuracy, repeatability, internal repeatability, and detection limits in accordance with the acceptability limit, namely for an accuracy of 77.0- 96.4%, %RSD repeatability < 0.5CV Horwitz, internal repeatability %RSD < 0.67 %CV Horwitz, and detection limit of 0.002-0.0099 mg/Kg. The results of the t-test for the ruggedness/robustness parameter and the comparison of the two preparation methods showed that the value of t count < t table, where there was no significant difference in the two methods with a 95 % confidence level between the values obtained. The results of the analysis of the sample using the TXRF method were compared with the neutron activation analysis (NAA), the ratio between TXRF/NAA was 0.96. Based on the evaluation of validation parameters and comparison with the NAA method, TXRF can be used in determining As in rice and its processed products with a good level of validity. The results of the analysis of the content of As in the rice samples and their processed products were in the range of <0.0099-0.104 mg/Kg. This result is still below the maximum limit of the Food and Drug Supervisory Agency (BPOM) and the World Health Organization (WHO), which is 0.1-0.2 mg/Kg. Furthermore, the As content in processed rice can be used to estimate the potential for As toxicity by determining the estimation daily intake (EDI) of As exposure to the body. The estimated daily intake value is strongly influenced by the As content in the sample, which is then carried out to estimate the toxicity level of As exposure by determining the hazard quotient (HQ) and lifetime cancer risk (LCR). The results obtained are expected to be used as a scientific-based reference in minimizing As pollution.