Mass spectrometric study of persistent acid metabolites of nonylphenol ethoxylate surfactants

• Published in: Journal of mass spectrometry. Vol. 35; no. 7; pp. 818 - 830
• Main Authors: Hao, Chunyan, Croley, Timothy R., March, Raymond E., Koenig, Brenda G., Metcalfe, Chris. D.
• Format: Journal Article
• Language: English
• Published: Chichester, UK John Wiley & Sons, Ltd 01-07-2000; Wiley
• Subjects: chemical ionization; Chemistry; Chromatography, High Pressure Liquid - methods; Detergents - chemistry; electron ionization; electrospray ionization; Ethylene Glycols - chemistry; Ethylene Glycols - pharmacokinetics; Exact sciences and technology; Gas Chromatography-Mass Spectrometry - methods; General and physical chemistry; mass chromatogram; Mass Spectrometry - methods; nonylphenol ethoxylates; nonylphenoxy carboxylic acids; selected reaction monitoring; Surface physical chemistry; Surface-Active Agents - chemistry; Surface-Active Agents - pharmacokinetics; Surface-active agents: properties; tandem mass spectrometry; Biodegradation; Electron impact; Collisional activation; Chemical analysis; Coupled method; Non ionic surfactant; Surfactant polymer; Derivatization; Electrospray; Esterification; Chemical ionization; Gas chromatography; Carboxylic acid; Mass spectrometry MS/MS; Degradation product; Quantitative analysis; Structural analysis
• ISSN: 1076-5174; 1096-9888
• DOI: 10.1002/1096-9888(200007)35:7<818::AID-JMS6>3.0.CO;2-P

A mass spectrometric study was carried out on two nonylphenoxycarboxylic acids, NP1EC and NP2EC (where 1 and 2 indicate the number of ethoxylate units attached to the nonylphenoxy moiety), that are persistent metabolites of widely used nonionic surfactant nonylphenol ethoxylates. In a gas chromatographic/mass spectrometric (GC/MS) study of the methyl esters of NP1EC and NP2EC, two series of fragment ions were observed in electron ionization (EI) mass spectra; m/z (179 + 14n, n = 0–7) and m/z (105 + 14n, n = 0–4) for NP1ECMe and m/z (223 + 14n, n = 0–7) and m/z (107 + 14n, n = 0–5) for NP2ECMe. Similarity indices were used to compare quantitatively the mass spectra of isomers. The mass spectra of two isomers were found to be similar whereas those of the remaining isomers were readily distinguishable from each other. The abundant fragment ions of the two NPECMes were investigated further by GC/MS/MS; product ions resulting from cleavage in the alkyl moiety, cleavage in the ECMe moiety and cleavage in both moieties were detected. Possible structures of the nonyl groups in the two esters were inferred. GC/chemical ionization (CI) mass spectra of the NPECMes with isobutane as reagent gas showed characteristic hydride ion‐ed fragment ions shifted by 1 Da from those in the corresponding EI mass spectra. The sensitivity of a selected ion monitoring quantitation method for the NPECMes is enhanced under CI conditions compared with that under EI conditions. With electrospray ionization MS/MS, [M − H]− ions of NP1EC (m/z 277) and NP2EC (m/z 321) were observed and, upon collision‐induced dissociation of [M − H]− of each of the two acids, fragment ions of m/z 219 corresponding to deprotonated nonylphenol, were observed in each case. Based on this observation, a rapid, simple and reliable selected product ion quantitation method is proposed for NP1EC and NP2EC. Copyright © 2000 John Wiley & Sons, Ltd.