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

Human Metabolism and Urinary Excretion Kinetics of Nonylphenol in Three Volunteers after a Single Oral Dose

“…As already discussed in our recent analytical method publication (Ringbeck et al 2021), quantification of OH-NP and oxo-NP via different mass transitions can result in slightly different concentrations. The monoisomeric analytical standards used (based on the straight chain α,α-dimethyl isomer with oxidative modification introduced in the n – 1 position) represent in reality a very complex mixture of structural and positional isomers which each can favor (or disfavor) certain mass transitions.…”

“…We could not identify any terminal carboxylic acid metabolites of NP (NP-CA) or β-oxidation breakdown products thereof such as heptylphenol carboxylic acid, which might have been expected in analogy to other substances with branched nonyl side chains, such as diisononyl phthalate (DINP) , or diisononyl cyclohexane-1,2-dicarboxylate (DINCH), or with other branched and linear alkyl side chains. − , Qualitatively, we could thus confirm similar metabolic structures [alkyl-chain oxidized metabolites, ring-hydroxylated metabolites (catechols), and mixtures of both] previously reported by Doerge et al (2002) in rat tissues or Ye et al (2007) in rat and human liver microsomes. , However, contrary to Doerge et al (2002) and Ye et al (2007) who found the catechols to be dominant metabolites in their tissues, in our setting (oral dose to volunteers, urinary excretion) the alkyl chain metabolites OH-NP and oxo-NP exhibited highest signal intensities (see Figure S2 for qualitative excretion kinetics). These two NP metabolites had already been chosen as target analytes in our recently published analytical method [Ringbeck et al (2021)] . As analytical standards had not been available, these had to be synthesized.…”

“…The slightly different concentrations of the oxidized metabolites obtained for each MRM transition are a consequence of the quantitation approach using monoisomeric α,α-dimethyl-derived, n – 1-oxidized standards representing the entirety of all 211 possible constitutional NP isomers multiplied by various oxidation positions in the alkyl chain. For a more detailed description of quantitative differences in mass spectrometric fragmentations, see Section II of the Supporting Information and the detailed discussion in Ringbeck et al (2021) . In the case of non-oxidized, parent NP, this does not apply because the full mixture of isomers was used as the analytical standard.…”

“…The single-isomer analytical standards 4-(6-hydroxy-1,1-dimethylheptyl)­phenol (6OH-[4-NP 9 ] [nomenclature for NP isomers according to Guenther et al (2006)]; purity >95%), 4-(6-oxo-1,1-dimethylheptyl)­phenol (6-oxo-[4-NP 9 ]; purity >95%), and the internal standard 4-(6-hydroxy-1,1-dimethyl­(6,7,7,7- 2 H 4 )­heptyl)­phenol (6OH-[4-NP 9 ]- d 4 ; chemical purity >95%, isotopic purity >98%) were synthesized as described in Section . For further information on the chemicals and reagents used for the quantification of oxidized NP metabolites, see Ringbeck et al (2021) . Ethanol (≥99.8%) for the oral dosing study was purchased from Honeywell Riedel-de Haën (Seelze, Germany).…”

Advances in Plant Metabolomics and Its Applications in Stress and Single-Cell Biology

“…During nano-electrospray (nESI), a decrease in evaporative volume leads to a rise in the desolvation rate, allowing more metabolite ions to generate and enter MS [44,45]. Comparative results from nLC-MS and regular LC-MS showed that the former provided a much higher metabolite coverage in human urine, sweat and glioma cells [46,47]. Although nLC-MS/MS has become routine in proteomics research, there are only a few nLC-MS applications in plant metabolomics.…”