Dilute-and-shoot enhances sensitivity of phthalate urinary concentrations for assessing the exposure in children

Phthalates are not covalently bound to plastics. They can leach from experimental plastic devices. Due to the development of sensitive techniques, exogenous sources that interfere with the accuracy of phthalate monoester analysis can be easily detected. Here, we propose the simple and rapid dilute-and-shoot method to minimize sample handling and limit contact with laboratory apparatus, which efficiently reduced phthalate interferences mainly from experimental plasticware and improved the accuracy of analysis. Chemical additives in the mobile phase and modifiers in reconstituted solution were evaluated to improve peak shape and liquid chromatography separation. Under optimal conditions, the limit of detection ranged from 0.01 to 0.5 ng/mL. No phthalate monoesters were detected above the limit of detection in blank water while the leached concentrations of MMP, MEP, MiBP, MnBP and MEHP from the conventional solid phase extraction procedure were 1.9, 2.7, 0.9, 2.0 and 1.1 ng/mL, respectively. In 304 samples collected from primary school children aged 9-10 years, we observed a positive association between body mass index (BMI) and urinary MMP and MiBP concentrations in boys, while MEOHP and MEHHP were inversely related to BMI in girls. Furthermore, detectable phthalate monoesters may be considered potential chemical obesogens related to BMI in children.