Fig. 3

PRM analysis of tryptic digests of cTnI spiked serum. A MS/MS spectrum of targeted precursor ion TLLLQIAK²⁺ (selected product ions y₅⁺ and y₆⁺ for quantification in red); B MS/MS spectrum of targeted precursor ion NITEIADLTQK²⁺ (selected product ions y₆⁺ and y₉⁺ for quantification in blue); C EICs obtained when quantifying cTnI-free human serum spiked with a cTnI at LOQ level (1.8 µg/L) and SIL-cTnI at 15 µg/L showing coelution of the TLLLQIAK peptide and its isotopically labeled counterpart; D EICs obtained when quantifying cTnI-free human serum spiked with a cTnI at LOQ level (1.8 µg/L) and SIL-cTnI at 15 µg/L showing coelution of the NITEIADLTQK peptide and its isotopically labeled counterpart. Precursor ions were isolated using an isolation window of 0.6 m/z