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ToF‐SIMS quantification of albumin adsorbed on plasma‐deposited fluoropolymers by partial least‐squares regression
Author(s) -
Ferrari Sandro,
Ratner Buddy D.
Publication year - 2000
Publication title -
surface and interface analysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.52
H-Index - 90
eISSN - 1096-9918
pISSN - 0142-2421
DOI - 10.1002/1096-9918(200012)29:12<837::aid-sia937>3.0.co;2-o
Subject(s) - x ray photoelectron spectroscopy , chemistry , analytical chemistry (journal) , secondary ion mass spectrometry , adsorption , matrix (chemical analysis) , mass spectrometry , oxygen , nitrogen , static secondary ion mass spectrometry , chromatography , nuclear magnetic resonance , physics , organic chemistry
Albumin adsorbed on a radiofrequency glow discharge (RFGD) thin film from hexafluoropropylene was characterized by x‐ray photoelectron spectroscopy (XPS) and time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS). The amount of protein adsorbed as a function of the protein concentration was estimated with XPS by following the atomic percentage nitrogen compared to fluorine, carbon and oxygen. The amount of albumin increases steeply between 10 −4 and 10 −3 mg ml −1 and very slowly thereafter. Intensities of protein‐related peaks in the ToF‐SIMS spectra are influenced by a matrix effect induced by the fluorinated surfaces. This effect is most pronounced at the lowest protein concentrations. The logarithms of the intensities of the fluorine‐containing peaks decrease linearly with increasing protein concentration. Multivariate analysis was used to correlate the data obtained from ToF‐SIMS and XPS. Partial least‐squares regression was applied using the nitrogen content from XPS as the dependent variable and ToF‐SIMS data as the independent variable. A good linear relation is observed using the logarithm of the ToF‐SIMS intensities. The ToF‐SIMS limitations for quantitative analysis due to the matrix effect, instrumental drift and surface sensitivity are discussed. A comparison of XPS data at different take‐off angles with ToF‐SIMS data confirms the surface sensitivity of the latter, but also demonstrates that some fluorinated fragments are sampled at depths deeper than might be expected from ToF‐SIMS. Copyright © 2000 John Wiley & Sons, Ltd.