Specific enrichment of a targeted nitrotyrosine-containing peptide from complex matrices and relative quantification for liquid chromatography-mass spectrometry analysis.

•A novel method to specifically enrich nitrotyrosine-containing peptides from complex biological matrices was developed.•Stringency was validated by highly efficient enrichment of nitrated angiotensin II from 1:100 (w/w) BSA digest and from 1:10 000 (w/w) plasma digest.•Mean recoveries during enrichment from BSA digest and from plasma digest were 49.8% and 41.1%, respectively.•Nitrotyrosine was reduced to aminotyrosine by DTT&hemin to avoid considerable amount of side-products (could be over 50%).