Internal Standard Stable Carbon Isotope Ratio Method for Determination of C-4 Plant Sugars in Honey: Collaborative Study, and Evaluation of Improved Protein Preparation Procedure
A collaborative study of the internal standard isotope ratio method for measuring C-4 plant sugars in honey Is reported. For 5 Youden pairs of samples containing 2-14% C-4 sugars, analyzed by 9 laboratories, mean sr was 1.92% and SR was 2.19%. Improved performance parameters for determination of δ13C in honey are also presented. The method was adopted first action by AOAC International. Also presented Is an improved purification procedure for the honey protein required for the Internal standard method. The dialysis-precipitation procedure described is considerably less demanding of analyst's time and eliminates possible contamination of the preparation by Indigenous yeasts and molds. No difference In δ13C values was found between the collaboratively studied method and the method when used with the improved procedure to analyze 10 known pure honeys. The dialysis- precipitation procedure is recommended as a substitute for the repeated washing procedure described In the collaboratively studied method.