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, 3.37-4.56 mg L-1 and 0.28-0.41 mg L-1, respectively. Despite the sample complexity, the proposed method using dilution of milk samples with water was 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.

Zinc concentrations in human milk and infant serum during the first six months of lactation.

Normal supply of zinc to the newborn via milk is essential for normal development. Using ICP-OES, we analyzed changes in the level of Zn in milk and infant serum in the neonatal period (Day 1 and Day 28 post partum) and at 6 months after delivery, in the cohort of 60 mothers and exclusively breastfed babies. Zn level in the serum showed increase (significant at 6 months) during this period (mg/mL): Day 1: 0.52±0.12; Day 28: 0.59±0.19; 6 months: 0.68±0.28. The concentration of Zn in the milk showed an opposite (decreasing) trend during the follow up: Day 1: 4.70±1.74mg/L; Day 28: 2.65±1.06; 6 months: 0.46±0.36. A significant negative correlation was established between serum and milk [Zn] at day 28 (R=-0.338; p=0.008), whereas a positive correlation was found at 6 months between these parameters (R=0.306; p=0.018). There was no significant correlation between [Zn] in the milk and serum and infants' body mass, mothers' age and mass at delivery. The level of Zn in the milk at 6 months of lactation is not sufficient to meet the recommended values. This implies that in Serbian population, Zn supplementation might be needed in the later phase of lactation.