Determination of molecular weight distributions of tert-octyephenol ethoxylate surfactant polymers by laser desorption Fourier transform ion cyclotron resonance mass spectrometry and high performance liquid chromatography

Abstract

Triton polymers are commercial surfactants whose molecular weight distributions are conventionally determined by means of high-performance liquid chromatography (HPLC). However, in the case of the important octylphenol ethoxylates [p-C8H17-C6H4-O-(CH2CH2O)n-H], HPLC cannot resolve individual oligomers of high molecular weight Triton surfactants (e.g., greater than 2000 u or so; u = unified atomic mass unit). In this paper, we show that laser desorption Fourier transform ion cyclotron resonance mass spectrometry (LD/FT/ICR/MS) provides a simple and accurate measure of such Triton surfactant molecular weight distributions up to at least 3500 u, based on a single-shot laser pulse measurement of a few seconds duration. Comparison of LD/FT/ICR/MS and HPLC molecular weight distributions of low molecular weight surfactants shows that laser desorption/ionization produces minimal fragmentation and thus offers an accurate measure of the relative abundances of the neutral oligomers, without the need for prior chromatographic separation of the components. Moreover, for all Triton polymer molecular weight distributions (700-3000 u), LD/FT/ICR/MS provides much more highly resolved profiles of oligomer relative abundances. Finally, LD/FT/ICR/MS reveals the presence of poly(ethylene oxide) side products of the polymerization process, which are not observed by HPLC with conventional ultraviolet absorption detection.

Detailed Characterization of Petroleum Sulfonates by Fourier Transform Ion Cyclotron Resonance Mass Spectrometry

“…These advantages have allowed for introduction of this technique into the study of industrial surfactants of high molecular weight, which are mostly obtained from complex mixtures as raw materials. The average molecular weight of Titron surfactants ( tert -octylphenol ethoxylate surfactant polymers) has been studied by means of laser desorption FT-ICR MS …”

“…27 These advantages have allowed for introduction of this technique into the study of industrial surfactants of high molecular weight, which are mostly obtained from complex mixtures as raw materials. The average molecular weight of Titron surfactants (tert-octylphenol ethoxylate surfactant polymers) has been studied by means of laser desorption FT-ICR MS. 28 In this work, a detailed characterization of petroleum sulfonates was achieved by means of negative electrospray ionization [(−) ESI] FT-ICR MS analysis. Compositional differences were observed between the water-and oil-soluble petroleum sulfonate extracts.…”

Applications of 1.06-μm IR Laser Desorption on a Fourier Transform Mass Spectrometer

“…The focus of this investigation is the analytical potential of a Nd:YAG laser at its fundamental frequency output corresponding to 1.06 μm. This wavelength has been evaluated by several laboratories for direct desorption, using pulse widths between 10 ns and 100 ms. − Others have reported the use of harmonic frequencies with Nd:YAG lasers. − Use of the fundamental wavelength is simpler, and it provides a wider range of energy per pulse, since frequency conversion is accompanied by energy loss. The compact, relatively inexpensive laser used here has a pulse width of 6 ns.…”

Composition to Interfacial Activity Relationship Approach of Petroleum Sulfonates by Fourier Transform Ion Cyclotron Resonance Mass Spectrometry

“…Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) has emerged as a prominent analytical tool that allows for analyzing complex mixtures, including crude oil and petroleum derivative samples, at a molecular level and performing a detailed analysis of their chemical structure (molecular weight, aromaticity, etc.). 35,36 These advantages have motivated us to introduce negative-ion electrospray ionization [(−) ESI] FT-ICR MS into the study of petroleum sulfonates synthesized from high-vacuum gas oil (HVGO), affording structural information that aims to explain their performance in enhanced oil recovery (EOR) formulations. 37,38 In the present work, the synthesis of petroleum sulfonates from different atmospheric residues (ARs) obtained from three crude oils was performed.…”