Nontargeted analysis of the urine nonpolar sulfateome: a pathway to the nonpolar xenobiotic exposome

Abstract

RATIONALE Testing the urine nonpolar sulfateome can enable discovery of xenobiotics that are most likely to be bioactive. This is based on the fact that nonpolar xenobiotics are more likely to enter cells where they tend to undergo metabolism, in part, to sulfates that are then largely excreted into the urine. METHODS The following sequence of steps, with conditions that achieve high reproducibility, was applied to large human urine samples: (1) competitive nonpolar extraction with a porous extraction paddle; (2) weak anion exchange extraction with strong organic washing; and (3) UHPLC/negative ion-MALDI-TOF/TOF-MS with recording of ions with S/N ≥ 20 that yielded M-1-80 (loss of SO3) or m/z 97 (HSO4−) upon fragmentation. RESULTS From a collection of urine samples from six pregnant women, the masses of 1129 putative sulfates were measured. Three lists of candidate compounds (preliminary hits) from these masses were formed by searching METLIN, especially via MATLAB, yielding putative xenobiotic contaminants (35 compounds), steroids (122), and flavonoids (1582). CONCLUSION A new way to reveal some of the nonpolar xenobiotic exposome has been developed that applies to urine samples. The value of the method is to suggest xenobiotics for subsequent targeted analysis in the population of people under study, in order to relate the environment to health and disease.

Trends in the application of high-resolution mass spectrometry for human biomonitoring: An analytical primer to studying the environmental chemical space of the human exposome

“…Other applications of neutral loss filtering are monitoring the loss of one or two water molecules ([M-H 2 O+H] + , [M-2H 2 O+H] + ) in the identification of anabolic steroids that form adducts with mobile phase such as methanol and acetonitrile (Diaz et al, 2012), and a water molecule loss from glucuronide conjugates of 2-ethylhexyl diphenyl phosphate (Ballesteros-Gomez et al, 2014). Notable applications are to detect metabolites from phase II detoxification pathways that show characteristic neutral loss of 176.0321 for glucuronide conjugates, 129.0426 for glutathione conjugates, and 79.9568 for sulfate conjugates (Wu et al, 2010; Yao et al, 2016). …”

Porous extraction paddle: a solid‐phase extraction technique for studying the urine metabolome

“…Some other considerations were as follows. (1) It was important to collect large urine samples both to measure an average exposure and to establish, for each urine, a corresponding abundant repository sample (especially for the purpose of scaling up selected unknown compounds in the future for identification). Each urine is to be collected at a designated point (first trimester) in the pregnancy, making each corresponding repository sample unique and precious, so we wanted to have plenty of this sample from each pregnant women.…”

“…4(B). (In a companion article, [1] LC/MS was employed to avoid the excessive complexity of Fig. 4(A).)…”

“…Our initial interest in employing a PEP for competitive adsorption as part of a strategy for nontargeted analysis is explained in a companion article. [1] Potential to resist clogging SPE becomes more complicated when particulates are present. Commonly a sample is centrifuged or filtered to remove particulates prior to SPE, usually because the particulates are not of interest, or because they tend to clog the extraction device.…”

“…This minimal degree of purification, as intended here, means that one or more subsequent sample cleanup steps will usually be required to adequately minimize matrix effects in a subsequent detection step. For example, in a companion article, [1] we describe a subsequent weak anion-exchange step to enable the detection of nonpolar sulfates in urine. Thus, as practiced here, the PEP mainly is providing a broad-scope extraction.…”