Journal of Surfactants and Detergents

, Volume 2, Issue 4, pp 503–513

Analysis of ethoxylated fatty amines. Comparison of methods for the determination of molecular weight

  • Russell F. Lang
  • Dennisse Parra-Diaz
  • Dana Jacobs
Article

DOI: 10.1007/s11743-999-0099-y

Cite this article as:
Lang, R.F., Parra-Diaz, D. & Jacobs, D. J Surfact Deterg (1999) 2: 503. doi:10.1007/s11743-999-0099-y

Abstract

Specific lengths of the fatty and polyoxyethylene chains of ethoxylated fatty amines are critical to their performance in specific applications, and thus the ability to characterize these surfactants accurately is crucial. Normal-phase high-performance liquid chromatography (HPLC) and matrixassisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry methods were developed to determine with accuracy the molecular weight and degree of ethoxylation of ethoxylated fatty amines. Ethoxylated fatty amines were analyzed using these methods, and comparison was made to molecular weight determinations using proton nuclear magnetic resonance (NMR), neutralization equivalent weight, and hydroxyl value methods. Molecular weight results from normalphase HPLC analyses were in very good agreement with MALDI-TOF results, typically varying less than one ethylene oxide unit. A reversed-phase HPLC method was developed to determine concentrations of polyethylene glycols (PEG) and fatty homologs. PEG interfered with molecular weight determinations by NMR, neutralization equivalent weight, and hydroxyl value methods. PEG caused no interference with molecular weight determinations by normal-phase HPLC and MALDI-TOF methods.

Key Words

Degree of ethoxylationethoxylated fatty aminesHPLChydroxyl valueMALDI-TOFmolecular weightneutralization equivalent weightH NMR

Copyright information

© AOCS Press 1999

Authors and Affiliations

  • Russell F. Lang
    • 1
  • Dennisse Parra-Diaz
    • 1
  • Dana Jacobs
    • 1
  1. 1.Beckman-Coulter Inc.Miami