Article pubs.acs.org/est
Matrix Normalized MALDI-TOF Quantification of a FluorotelomerBased Acrylate Polymer Keegan Rankin and Scott A. Mabury* Department of Chemistry, University of Toronto, 80 St. George St., Toronto, Ontario Canada, M5S 3H6 S Supporting Information *
ABSTRACT: The degradation of fluorotelomer-based acrylate polymers (FTACPs) has been hypothesized to serve as a source of the environmental contaminants, perfluoroalkyl carboxylates (PFCAs). Studies have relied on indirect measurement of presumed degradation products to evaluate the environmental fate of FTACPs; however, this approach leaves a degree of uncertainty. The present study describes the development of a quantitative matrix-assisted laser desorption/ ionization time-of-flight (MALDI-TOF) mass spectrometry method as the first direct analysis method for FTACPs. The model FTACP used in this study was poly(8:2 FTAC-coHDA), a copolymer of 8:2 fluorotelomer acrylate (8:2 FTAC) and hexadecyl acrylate (HDA). Instead of relying on an internal standard polymer, the intensities of 40 poly(8:2 FTAC-co-HDA) signals (911−4612 Da) were normalized to the signal intensity of a matrix-sodium cluster (659 Da). We termed this value the normalized polymer response (PN). By using the same dithranol solution for the sample preparation of poly(8:2 FTAC-co-HDA) standards, calibration curves with coefficient of determinations (R2) typically >0.98 were produced. When poly(8:2 FTAC-co-HDA) samples were prepared with the same dithranol solution as the poly(8:2 FTAC-co-HDA) standards, quantification to within 25% of the theoretical concentration was achieved. This approach minimized the sample-to-sample variability that typically plagues MALDI-TOF, and is the first method developed to directly quantify FTACPs.
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INTRODUCTION Fluorinated polymers are the largest class of commercial fluorochemical products. Despite this fact, there is little known about their environmental fate and potential impact due to difficulties in developing analytical methods to directly measure changes in the formal polymer structure. Fluorotelomer-based acrylate polymers (FTACPs) are a class of fluorinated polymers widely used as antiwetting and antistaining agents in the textile, upholstery, carpet, and paper industries.1 Specifically, FTACPs are copolymers prepared from fluorotelomer acrylates (FTACs), hydrocarbon acrylates, and often other nonfluorinated monomers.2,3 Similar to other fluorinated polymers, FTACPs benefit from improved repellency, lubricity, and chemical and thermal stability through the replacement of hydrogen with fluorine.4 Consequently, the properties that make FTACPs ideal for industrial applications have also raised concern about their environment fate. Recent studies suggest that the degradation of FTACPs is likely an indirect source of the ubiquitous and persistent perfluoroalkyl carboxylates (PFCAs).5,6 Because long-chain PFCAs (>7 perfluorinated carbons) have been demonstrated to accumulate in biota,7,8 and the desired antiwetting and antistaining properties of the original FTACP formulation required fluorotelomer acrylates having ≥8 perfluorinated carbons,9−11 there is significant interest in directly assessing the environmental fate of FTACPs. Previous efforts have aimed at © 2015 American Chemical Society
evaluating the degradation of FTACPs indirectly by measuring the transformation products (i.e., PFCAs) by high performance liquid chromatography tandem mass spectrometry (LC-MS/ MS).12,13 However, PFCAs are also known transformation products of other fluorotelomer-based material such as FTACs and fluorotelomer alcohols (FTOHs),14−20 which have been reported as residuals in the crude FTACP material at levels 0.97; Figure 4). The calculated PN for each poly(8:2 FTAC-co-HDA) standard had relative standard deviations (RSDs)
