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. 2013;4(3):172.
doi: 10.4172/2157-7064.1000172. Epub 2013 Mar 27.

Human C-peptide Quantitation by LC-MS Isotope-Dilution Assay in Serum or Urine Samples

Alexander V Stoyanov  1 , Shawn Connolly  1 , Curt L Rohlfing  1 , Eduard Rogatsky  2 , Daniel Stein  2 , Randie R Little  1
Affiliations

Human C-peptide Quantitation by LC-MS Isotope-Dilution Assay in Serum or Urine Samples

Alexander V Stoyanov et al. J Chromatogr Sep Tech. 2013.

Abstract

In this communication we report a simple and efficient approach to C-peptide quantitation using isotope dilution mass-spectrometry analysis. The method facilitates quantitation of C-peptide levels at least one order of magnitude lower compared to concentration levels achieved with an IDA method reported previously. The improvement was due to more intensive sample preparation procedure that, in turn, makes it possible to increase the sample load without a corresponding increase in matrix effects. We also show the results of a comparison study with a second laboratory using a similar previously reported method for C-peptide quantitation.

Keywords: C-peptide/Mass spectrometry; Ion Exchange chromatography; Isotope dilution assay; Sample preparation.

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Figures

Figure 1:
Figure 1:
Purified C-peptide MS characterization. A: SIM for 1007.7 (native) and B: 1013.0 standard are shown. Retention time for C-peptide is 14.7min.
Figure 2:
Figure 2:
Method comparison between the MO and NY laboratories; n=47, y=0.941x+0.047, R2=0.9647. Solid line is the regression line; dashed line is y=x.
Figure 3:
Figure 3:
Comparison of C-peptide internal standard (IS) mass spectrograms for pure IS (A) and IS mixed with the serum sample (B). A: 50 pg of pure stable isotope labeled C-peptide (retention time 13.5 min, S/N 165) B: 50 pg on column of the same isotope as in A spiked in serum (retention time 13.6 min, S/N 86). The lower signal intensity observed for IS (Mw/z=1017.7) mixed with serum is due to both matrix effect and analyte losses during purification steps.
See this image and copyright information in PMC

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