Development and Application of a HPLC-PDA-FL Method for the Determination of Melatonin and its Precursors in Infant Formulas

It is well known that the secretion of melatonin begins after the first months of life and is necessary to be supplied through mother's milk or infant formula. It is also important to know the concentrations of compounds involved in the synthesis of melatonin in the pineal gland from the composition of infant formula. Therefore, an HPLC method with UV and fluorescence detection was developed which enables the simultaneous determination of melatonin, serotonin, L-tryptophan, and vitamins B-3 and B-6 in 30 min. The chromatographic method was validated in terms of selectivity, linearity range of the response (R > 0.9997), detection limit (0.0011-0.01 mg L-1), limit of quantitation, precision, accuracy, and robustness and has been proved that it may be used as a tool for evaluating these compounds in infant formulas and also in the manufacture of baby foods. The chromatographic method was applied for the quantification of analytes of interest and for the first time, it has proven the existence of melatonin (0.00045-0.00824 mg/g) and serotonin (0.00002-0.00056 mg/g) in infant formulas from birth onwards.