Production and Characterization of Rice Flour as Reference Material for Chemical Analysis

Proper application of reference materials (RMs) is one of the key components of the quality assurance procedure used to validate analytical methods and ensure that test data is traceable to a fundamental standard. This study was conducted to develop rice flour as an RM. Locally available commercial rice (Oryza sativa) was sampled from a locally available supermarket, ground, mixed with zinc fortificant, pulverized, and homogenized. Homogeneity of the RM was established following ISO Guide 35:2017. The RM property values for proximate and minerals were obtained through an interlaboratory comparison collaborated by 20 local testing laboratories. Continuous analysis of selected measurands by a credible subcontractor was conducted periodically to monitor its stability. The property values of the spiked rice flour RM, expressed as mean ± expanded uncertainty, were as follows: moisture (9.67 ± 0.87 g/ 100 g), protein (7.06 ± 0.46 g/ 100 g), ash (0.37 ± 0.08 g/ 100 g), potassium (64.03 ± 8.09 mg/ 100 g), and zinc (6.40 ± 1.57 mg/ 100 g). The mean was obtained by ANOVA of the laboratories’ result, whereas the expanded uncertainty was derived from the standard uncertainty associated with heterogeneity, short-term and long-term stability, and characterization of the property value of the RM. Spiked rice flour RM was successfully developed for use by testing laboratories as internal QCTM and for method validation purposes. It is highly recommended that the DOST- FNRI strengthen more its qualification in providing quality yet affordable RMs, following international guidelines.