Determination of specific urinary nonylphenol metabolites by online-SPE-LC-MS/MS as novel human exposure biomarkers

•Determination of two oxidized metabolites of nonylphenol in human urine.•LC-MS/MS coupled with turbulent flow chromatography for online sample clean-up.•Stable isotope dilution analysis using custom synthesized standards.•Pilot study detects widespread NP exposure in the general German population (n = 34)•OH-NP & oxo-NP quantifiable in 94% and 47% of urine samples of this pilot study.