Development of an Ultrasound-Assisted Slurry Sampling-Based Method for Determination of Metals in Rice Samples Using...

The present work addresses the development of a green analytical method based on slurry sampling to determine Ca, Fe, and Zn in rice. Multivariate optimization techniques (two-level fractional factorial design and Doehlert design) were used to find the experimental conditions that offer the best characteristics for the method. The slurry was made with 0.25 g of the sample in a liquid phase composed of 0.7 mol L^-1 HNO₃ and 0.31% Triton X-100 and submitted to an ultrasound bath for 7.5 min. The method has presented analytical characteristics, such as limit of quantification (4.9, 1.6, and 0.22 mg kg^-1), precision expressed as repeatability (4.4, 3.6, and 2.2%, for N = 7) respectively for Ca, Fe, and Zn, suitable for the determination of these metals in rice samples. Additionally, accuracy has been assessed by spike tests (obtaining recoveries between 90 and 108%) and comparing the values obtained by the new methodology with the standard method of acid decomposition in a digester block. The paired t-test revealed that there are no statistically significant differences (95% confidence level) between the slurry sampling method and the method adopted as standard.