Figure 1.

Representative total ion chromatogram of the BSA digest spiked with synthetic peptides used in this study for evaluation of system suitability. The intra-scan peptides (highlighted in red) were spiked in pairs consisting of one light peptide and one heavy isotope labeled peptide (schematic mass spectrum representation shown in insert). The light peptides were present at signal normalized concentrations corresponding to 0.1% to 100% of the heavy peptide concentrations in each pair. The inter-scan peptides (highlighted in blue) are closely related synthetic peptides eluting at similar retention times around 30 min. The other peaks in the chromatogram correspond to BSA peptides. The signal from the inter-scan peptides present at signal normalized concentrations of 1% and 0.1% are too low to be directly observed on the total ion chromatogram.