Parallel Detection and Quantification of Thin-Film Peptides with Dynamic-Secondary Ion Mass Spectrometry (D-SIMS) Excited by C60+-Ar+ Co-Sputtering
Date Issued
2011
Date
2011
Author(s)
Chang, Chi-Jen
Abstract
Using pulsed primary cluster ions, especially for C60+ cluster ion, time-of-flight secondary ion mass spectrometry (ToF-SIMS) has been shown to be a promising technique for analyzing biological specimens. With molecular secondary ions of high mass, multiple molecules can be identified at the same time without prior separation or isotope labeling. While current reports are based on static-SIMS that makes depth profile more complicated, a dynamic-SIMS based technique is reported in this work. Mixed trehalose and peptides were used as a model for evaluating the parameters that lead to parallel detection and quantification of biomaterials. Trehalose is mixed with different peptides separately with varied concentrations of peptides. It is found that the normalized secondary ion intensity of peptide as respect to trehalose is direct proportional to its concentration in the matrix. Therefore, by plotting the percentages of peptides exist in trehalose versus their normalized SIMS intensities, calibration curves of each peptide are obtained. Using these curves, it is shown that parallel detection, identification, and quantification of multiple peptides in the matrix can be achieved. To suppress the associated carbon deposition with high energy C60+ bombardment that leads to suppressed ion intensity in prolonged profiling, a low energy Ar+ is used to co-sputter the peptide-doped trehalose thin film. It is shown that the co-sputtering technique yields more steady molecular ion intensity than single C60+ beam. In other words, the co-sputtering is more suitable for analyzing thick specimens. Furthermore, because the C60+ is responsible for generating the molecular ions, it is found that the does of the auxiliary Ar+ does not change calibration curve for quantification.
Subjects
surface analysis
dynamic-SIMS
C60+-Ar+ co-sputter
depth-profile
biological detection
Type
thesis
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