Ultra‐high performance supercritical fluid chromatography combined with quadrupole time‐of‐flight mass spectrometry for the characterization of pentaerythritol fatty acid esters

Abstract

Rationale Pentaerythritol fatty acid esters are an excellent lubricant oil additive, due to their good biodegradability, thermal ability, anti‐wear, and friction properties. However, to meet the application requirements, fatty acids with different alkyl chain lengths are reacted with pentaerythritol, resulting in complex ester compositions. To reveal the relation between the functionalities and the composition of esters, it is important to develop a method for their analysis. Methods We developed a method using ultra‐high‐performance supercritical fluid chromatography combined with quadrupole time‐of‐flight mass spectrometry (UHPSFC/QTOF‐MS) to separate and characterize pentaerythritol fatty acid esters. This method has the advantages such as short analysis time and high separation efficiency for such weakly polar compounds; high‐resolution mass spectrometry (HRMS) provides exact mass information, enabling the identification of the structure of the pentaerythritol fatty acid esters. Results Based on the exact masses and characteristic ions, the pentaerythritol fatty acid esters and their main fragmentation pathways were identified; the fatty acid composition was also deduced from characteristic product ions. A dihydrogen rearrangement reaction caused the neutral loss of fatty acid fragment; [M + Na‐FA]+ product ions (a stable six‐member ring structure) were produced due to the absence of a γ hydrogen in pentaerythritol fatty acid esters. Conclusions A UHPSFC/QTOF‐MS method was successfully employed for the separation of pentaerythritol fatty acid esters. Exact masses and product ion information were determined using HRMS. The composition of the fatty acids was effectively deduced by characteristic ions and their relative abundances. This method is an effective means for the quality control and process optimization of this type of product, serving as a positive reference for further study on pentaerythritol fatty acid esters.

Environmental risks and toxicity of surfactants: overview of analysis, assessment, and remediation techniques

“…Standard detectors commonly used include flame ionization detector, evaporative light scattering detection, Fourier transforms infrared spectroscopy, corona-charged aerosol detection, and ultraviolet-visible detection (Shah et al 2015 ; Tang et al 2020 ). Tang et al (Tang et al 2020 ) used quadrupole time-of-flight mass spectrometry coupled with SFC to identify different pentaerythritol fatty acid esters. The application of supercritical fluid chromatography marked a notable advance in the study of pentaerythritol fatty acid esters.…”

“…There is a wide range of detectors that can be used with SFC. Standard detectors commonly used include flame ionization detector, evaporative light scattering detection, Fourier transforms infrared spectroscopy, corona-charged aerosol detection, and ultraviolet-visible detection (Shah et al 2015;Tang et al 2020). Tang et al (Tang et al 2020) used quadrupole time-of-flight mass spectrometry coupled with SFC to identify different pentaerythritol fatty acid esters.…”

Identification of chemical constituents in pomegranate seeds based on ultra‐high‐performance supercritical fluid chromatography coupled with quadrupole time‐of‐flight mass spectrometry

“…SFC has been successfully used to analyze TCM for both nonpolar and polar components, such as lipids, carbohydrates, phenolics 23,24 . More importantly, as a new generation of SFC, ultra‐high‐performance supercritical fluid chromatography (UHPSFC) uses sub‐2 μm particles in the stationary phase, allowing for dramatically improved chromatographic performance and analysis speed compared to conventional SFC 20,25,26 …”

“…18 Although SFC is commonly used to analyze nonpolar components, its solvation capacity is improved using a CO 2 -miscible mobile phase containing modifiers and additives, such as ammonium formate and methanol, for eluting polar compounds. 19,20 The solubility of most compounds in mixtures of supercritical fluids is usually better than that in pure organic solvents. 21,22 SFC is highly compatible and interoperable with mass spectrometry (MS).…”

“…23,24 More importantly, as a new generation of SFC, ultra-high-performance supercritical fluid chromatography (UHPSFC) uses sub-2 μm particles in the stationary phase, allowing for dramatically improved chromatographic performance and analysis speed compared to conventional SFC. 20,25,26 UHPSFC coupled with electrospray ionization (ESI) and quadrupole time-of-flight (QTOF)-MS has been used in the analysis of natural compounds and extracts. 27 Compared to single quadrupole, ion trap, and triple quadrupole mass spectrometers, a TOF mass analyzer is advantageous to conduct exact mass measurements, which can confirm or exclude potential molecular formulae.…”