Development of a Combined Standard Additions/Internal Standards Method to Quantify Residual PEG in Ethoxylated Surfactants by MALDI TOFMS

Abstract

Measuring the residual polyethylene glycol (PEG) in polyethylene oxide (PEO)-based surfactants is important to fully understanding the performance of these materials. Traditional methods of quantitating PEG in PEO-based surfactants can be time-consuming and struggle with low amounts or overlapping molecular mass distributions. This paper describes a matrixassisted laser desorption/ionization (MALDI) mass spectrometry method developed to quantitate residual PEG in a series of ethoxylated surfactants. The technique addresses the difficulties faced in doing quantitative MALDI experiments by utilizing both internal standard and standard additions protocols. The method produces excellent straight line standard addition plots, and the quantitative results are verified using both a constructed standard and an independent traditional chromatographic separation.

Quantitative Analysis of Polymer Additives with MALDI-TOF MS Using an Internal Standard Approach

“…Trimpin and coworkers [22] have shown that the latter limitation can be overcome by the use of a solvent-free sample preparation method, which has already been proven valuable in several applications [14,[16][17][18][19][20][21][22]. In addition, a few experiments were made concerning the possibility to quantify certain synthetic polymers [14,[23][24][25][26].…”

Citric Acid Capped Iron Oxide Nanoparticles as an Effective MALDI Matrix for Polymers

“…In the literature, several parameters have been used to quantify mass spectrometry responses, including the sum of peak area, ΣI iarea [17]; the sum of peak intensity multiplying the number of repeating units in each oligomer, Σn i I i [16]; and the sum of peak intensity multiplying mass of each oligomer Σm i I i, [18,68]. Linear response has been observed using all three parameters within a narrow sample/internal standard gravimetric ratio range [16][17][18]68].…”

“…Thus, the measured mass distribution by MALDI does not necessarily reflect the true gravimetric (mass) concentration of each oligomer [12,13], which is particularly problematic for broad molecular mass distribution (MMD) polymers [14]. Nonetheless, a few studies have examined narrow MMD polymer MALDI quantitation with a closely related polymer as an internal standard [15][16][17][18]. Among these works [15][16][17][18], within a narrow analyte/internal standard gravimetric concentration ratio (~0.5-2), a linear relationship between MS signal and gravimetric concentration is reported.…”

“…Nonetheless, a few studies have examined narrow MMD polymer MALDI quantitation with a closely related polymer as an internal standard [15][16][17][18]. Among these works [15][16][17][18], within a narrow analyte/internal standard gravimetric concentration ratio (~0.5-2), a linear relationship between MS signal and gravimetric concentration is reported. A Taylor expansion mathematical model to determine absolute MMD distribution from measured intensities for narrow disperse polystyrenes has also been proposed [18].…”

“…In improving signal reproducibility between replicates, sample preparation homogeneity is the key. Generally, electrospray deposition is preferred [17,18] and, when using dried-droplet method, a fast evaporative solvent is used (e.g., tetrahydrofuran) that helps to form homogenous sample/matrix spots [16].…”