DETERMINATION OF ZINC IN HUMAN-MILK BY ELECTROTHERMAL ATOMIC-ABSORPTION SPECTROMETRY

An electrothermal atomic absorption spectrometric method has been developed for determining zinc in human milk. Milk samples were analysed after 1 + 99 dilution with 0.1% Triton X-100. The within-run precision was found to be 4.6%. The accuracy was ascertained by recovery of standard additions, and was found to be 96 +/- 10% (n = 85 milk samples). The accuracy was also checked against National Institute of Standards and Technology Standard Reference Material 1549 Non-Fat Milk Powder. The results were 713 +/- 35-mu-mol g-1 (n = 38) (certified value: 705 +/- 34-mu-mol g-1). The detection limit was found to be 0.052-mu-mol l-1. The calibration graph was linear up to 3-mu-mol l-1. The choice of experimental parameters (diluent, dilution rate, background correction, graphite furnace tube, etc.) are discussed. Normal values for colostrum and transitional milk varied from 45 to 318 and from 30 to 146-mu-mol l-1, respectively.