Determination of Microelements in Human Milk and Infant Formula Without Digestion by ICP-OES

The concentrations of zinc (Zn), iron (Fe) and copper (Cu) in both human milk and infant formula were determined using a new sample preparation method, by inductively coupled plasma – optical emission spectometry (ICP-OES) and flame atomic absorption spectrometry (FAAS). Human milk samples were diluted in ultrapure water. The infant formula of powder samples (suitable for an infant 1-6 months of age) and standard reference material (SRM-1849) were analyzed in parallel . The results have shown that FAAS method was more sensitive for Fe determination in human milk while ICP-OES was more sensitive for both Zn and Cu detection. The limit of quantification for both Zn and Cu was 5 µg L -1 and 10 µg L -1 for Fe and the recovery for Zn, Fe and Cu was ranged from 90 % to 94 %, 97 % to 103 % and 90% to 102 %, respectively. Mean concentrations of Zn, Fe, and Cu in human milk samples were 5.35, 0.47 and 0.83 mg L -1 , respectively while these values in infant formula were ranged from 3.52 - 4.75 mg L -1 , 3.37 - 4.56mg L -1 and 0.28 - 0.41 mg L -1 , respectively. Despite the sample complexity, the proposed method using dilution of milk samples with waterwas simple, rapid, effective and accurate. ICP-OES was a better method for Zn determination while FAAS was a better method for Fe determination. In the case of Cu both methods were comparable.