Analysis of free nucleotide monophosphates in human milk and effect of pasteurisation or high-pressure processing on their contents by capillary electrophoresis coupled to mass spectrometry.

A simple, efficient and green analytical method for the determination of free nucleotide monophosphates in human milk is proposed. It involves centrifugal ultrafiltration (CUF) as sample treatment and capillary electrophoresis-electrospray mass spectrometry (CE-ESI-MS) for separation and simultaneous quantification. The optimised method, applied to the analysis of human milk samples, included their dilution (1:5) with water followed by CUF treatment. No matrix effects were found. The method provided limits of detection between 0.08 and 0.13 μg mL(-1) and limits of quantification between 0.26 and 0.43 μg mL(-1). The intralaboratory repeatability and reproducibility afforded relative standard deviation values lower than 10%. The method was applied to the study of the effects of Holder pasteurisation and high-pressure processing on the nucleotide contents in samples from a human milk bank. The results showed concentration values between 0.5 and 10 μg mL(-1), with higher concentrations for the samples treated by pasteurisation. The effect of freezing time on the content of nucleotides was also assessed.