RATIONALE
Quantifying polymers by matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOFMS) with a conventional crystalline matrix generally suffers from poor sample‐to‐sample or shot‐to‐shot reproducibility. An ionic‐liquid matrix has been demonstrated to mitigate these reproducibility issues by providing a homogeneous sample surface, which is useful for quantifying polymers. In the present study, we evaluated the use of an ionic liquid matrix, i.e., 1‐methylimidazolium α‐cyano‐4‐hydroxycinnamate (1‐MeIm‐CHCA), to quantify polyhexamethylene guanidine (PHMG) samples that impose a critical health hazard when inhaled in the form of droplets.
METHODS
MALDI‐TOF mass spectra were acquired for PHMG oligomers using a variety of ionic‐liquid matrices including 1‐MeIm‐CHCA. Calibration curves were constructed by plotting the sum of the PHMG oligomer peak areas versus PHMG sample concentration with a variety of peptide internal standards.
RESULTS
Compared with the conventional crystalline matrix, the 1‐MeIm‐CHCA ionic‐liquid matrix had much better reproducibility (lower standard deviations). Furthermore, by using an internal peptide standard, good linear calibration plots could be obtained over a range of PMHG concentrations of at least 4 orders of magnitude.
CONCLUSIONS
This study successfully demonstrated that PHMG samples can be quantitatively characterized by MALDI‐TOFMS with an ionic‐liquid matrix and an internal standard. Copyright © 2014 John Wiley & Sons, Ltd.