Preparation and evaluation of certified reference materials for crude protein, crude fat, and crude ash in feed

Abstract

Three new certified reference materials (CRMs) for crude protein, crude fat, and crude ash in animal feed were developed and characterized according to ISO 17034:2016 and ISO Guide 35:2017. The Kjeldahl, Soxhlet extraction, and ashing methods were employed to quantify these three components in candidate CRMs for swine feed, poultry feed, and fish feed. To improve the precision, the measurement methods were optimized on the basis of Directive 93/28/EEC, Directive 98/64/EC, and Directive 71/250/EEC and further validated using two existing CRMs (BCR-708 and BCR-709). The homogeneity, short- and long-term stability, and moisture content were evaluated. The certified values and their expanded uncertainties (k = 2.00) were determined through nine laboratories. The results for crude protein, crude fat, and crude ash were 14.7 ± 0.4, 5.19 ± 0.24, and 6.23 ± 0.14% for swine feed CRM; 22.7 ± 0.7, 5.16 ± 0.39, and 5.74 ± 0.18% for poultry feed CRM; and 35.6 ± 0.9, 9.29 ± 0.40, and 8.70 ± 0.25% for fish feed CRM, respectively. These three CRMs have been used in the comparison of Chinese feed quality testing laboratory systems and proved suitable for evaluating quality control in laboratories.