Interlaboratory comparison of simmondsin analysis

Abstract Eleven samples containing various amounts of simmondsin (S), simmondsin ferulate (SF), demethyl simmondsins (DMS) and didemethyl simmondsins (DDMS) were analyzed by five different laboratories. The samples were made from chromatographically pure simmondsin, animal feed formulations containing jojoba meal, defatted jojoba meal, water extracts of jojoba meal and combinations of these ingredients. Where mixes were made, all materials were ground together in a coffee mill and sieved. Four laboratories analyzed for simmondsin and related components and one laboratory analyzed for only S. The means of the S, SF, DMS and DDMS percentages in the samples were determined to be: high performance liquid chromatography (HPLC) purified simmondsin, 94.1% S, 0 SF, 6.30% DMS, 0.52% DDMS; recrystallized simmondsin, 99.6% S, 0 SF, 1.01% DMS, 0 DDMS; water extract of jojoba meal 1, 29.2% S, 2.62% SF, 3.45% DMS, 9.47% DDMS; water extract of jojoba meal 2, 20.6% S, 2.00% SF, 2.81% DMS, 8.66% DDMS; formulated pet food with simmondsin, 0.59% S, 0 SF, 0 DMS, 0.01% DDMS; defatted jojoba presscake 7.05% S, 1.55% SF, 1.34% DMS, 3.48% DDMS. Using a Rank-Sum test, no laboratory demonstrated a consistently higher or lower bias compared to other laboratories for simmondsin analysis. Simmondsin analysis had less variability (C.V.=44) than other component analyses. Reproducibility for a blind duplicate sample of defatted jojoba presscake demonstrated that four of the five laboratories were consistent in simmondsin analysis. Water extracts of jojoba meal were shown to be highly variable in simmondsin content.