Development and investigation of a QuEChERS-based method for determination of phthalate metabolites in human milk

Phthalates are commonly used as plasticizers and are known as risk factors toward several conditions such as cancer, birth defects, and endocrine disruption. Biomonitoring of phthalates is necessary to assess the potentially harmful effects of long-term exposure. In this work, we have developed a novel QuEChERS method to determine eight phthalate metabolites-mono-(3-carboxypropyl) phthalate, mono-(2-ethyl-5-carboxypentyl) phthalate, mono-(2-ethyl-5-hydroxyhexyl) phthalate, mono-(2-ethyl-5-oxohexyl) phthalate, mono-n-butyl phthalate, mono-benzyl phthalate, mono-(carboxyloctyl) phthalate, and mono-(carboxynonyl) phthalate-in human milk. The extraction process was optimized by comparing three different QuEChERS methods, and a further purification step was used to eliminate interferential lipid. In this process, several factors, such as the pH based on QuEChERS additive salts, acid dissociation constant, and distribution coefficient of the analyte, were found to have a significant effect on the extraction efficiency of the QuEChERS method. Target compounds were determined using liquid chromatography-tandem mass spectrometry equipped with electrospray ionization in the multiple-reaction monitoring mode. The developed method was verified by evaluating the selectivity, linearity, lower limit of quantification, accuracy, precision, and recovery, and applied to monitor real milk samples from 26 people. It is expected that the established method can be utilized not only to monitor phthalate metabolites in biological samples but also to identify the correlation between phthalate concentrations observed for the mother and the newborn.