Passamonti M, de Roos C, Schoenmakers PJ, Gargano AFG. Poly(acrylamide-
co-
N,
N'-methylenebisacrylamide) Monoliths for High-Peak-Capacity Hydrophilic-Interaction Chromatography-High-Resolution Mass Spectrometry of Intact Proteins at Low Trifluoroacetic Acid Content.
Anal Chem 2021;
93:16000-16007. [PMID:
34807576 PMCID:
PMC8655738 DOI:
10.1021/acs.analchem.1c03473]
[Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
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In this study, we
optimized a polymerization mixture to synthesize
poly(acrylamide-co-N,N′-methylenebisacrylamide) monolithic stationary phases for
hydrophilic-interaction chromatography (HILIC) of intact proteins.
Thermal polymerization was performed, and the effects of varying the
amount of cross-linker and the porogen composition on the separation
performance of the resulting columns were studied. The homogeneity
of the structure and the different porosities were examined through
scanning electron microscopy (SEM). Further characterization of the
monolithic structure revealed a permeable (Kf between 2.5 × 10–15 and 1.40 ×
10–13 m2) and polar stationary phase
suitable for HILIC. The HILIC separation performance of the different
columns was assessed using gradient separation of a sample containing
four intact proteins, with the best performing stationary phase exhibiting
a peak capacity of 51 in a gradient of 25 min. Polyacrylamide-based
materials were compared with a silica-based particulate amide phase
(2.7 μm core–shell particles). The monolith has no residual
silanol sites and, therefore, fewer sites for ion-exchange interactions
with proteins. Thus, it required lower concentrations of ion-pair
reagent in HILIC of intact proteins. When using 0.1% of trifluoroacetic
acid (TFA), the peak capacities of the two columns were similar (30
and 34 for the monolithic and packed column, respectively). However,
when decreasing the concentration of TFA to 0.005%, the monolithic
column maintained similar separation performance and selectivity (peak
capacity 23), whereas the packed column showed greatly reduced performance
(peak capacity 12), lower selectivity, and inability to elute all
four reference proteins. Finally, using a mobile phase containing
0.1% formic acid and 0.005% TFA, the HILIC separation on the monolithic
column was successfully hyphenated with high-resolution mass spectrometry.
Detection sensitivity for protein and glycoproteins was increased
and the amount of adducts formed was decreased in comparison with
separations performed at 0.1% TFA.
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