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

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 HNO 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), 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.