Analysis of non-fat soybean powder for the mass fractions of three elements: Copper and zinc by isotope dilution ICP–MS and calcium by ICP–AES

Isotope dilution inductively coupled plasma–mass spectrometry with “approximate match” approach was developed for the measurement of mass fractions of Cu and Zn. An “approximate match” (within 10%) was made between calibration and sample blends. The method was validated against two certified reference materials, namely NIST SRM 1515 (Apple Leaves) and IAEA-359 (Cabbage). Inductively coupled plasma-atomic emission spectrometry with bracketing technique was developed for the measurement of mass fraction of Ca. NIST RM 8412 (Corn Stalk) was employed for method validation purposes. The validated methods were applied to the measurement of Cu, Zn and Ca in a sample of non-fat soybean pertaining to the international comparison CCQM-P64. The results submitted for the comparison were in excellent agreement with the mean values of all participants’ results. Relative standard uncertainties of about 4% (k = 2, which gives a level of confidence of approximately 95%) were achieved in the measurement of the three elements concerned.