DETERMINATION OF CALCIUM, POTASSIUM, MAGNESIUM, IRON, COPPER AND ZINC IN MATERNAL MILK BY INDUCTIVELY-COUPLED PLASMA-ATOMIC EMISSION-SPECTROMETRY

A simple and rapid method was developed for the determination of Ca, P, Mg, Fe, Cu and Zn in maternal milk samples by inductively coupled plasma atomic emission spectrometry. Milk samples were emulsified with ethoxy nonylphenol to 0.03% m/v. The emulsified samples were diluted 10-fold with nitric acid and to 1% v/v. Aqueous solutions with the same amount of emulsifier and acid were used as calibration standards. The accuracy of the proposed method was assessed using the National Institute of Standards and Technology Standard Reference Material 1549 Non-Fat Milk Powder. No significant difference at the 95% confidence level was observed. The precision of the method when applied to real samples was in the range 0.3-2% expressed as %RSD, with no internal standard. Maternal milk samples from 50 women residing in Caracas, Venezuela, collected at three different lactation stages (on the third, seventh and twenty-first days postpartum) were analysed.