Abstract
Quantification of bradykinin peptides in limited amounts of rat muscle tissue dialysate has been performed using a packed capillary LC‐ESI‐TOF‐MS method. The micro dialysate samples (450 μL) with added internal standard were loaded onto a 1 mm×5 mm loading column packed with 5 μm Kromasil C~18~ particles by a carrier solution of 0.1% formic acid in ACN/water (5:95, v/v) at a flow rate of 250 μL/min for online preconcentration of the analytes. Back‐flushed elution onto a 150 mm× 0.5 mm Zorbax C~18~ column packed with 5 μm particles was conducted using a linear solvent ACN/H~2~O gradient containing 0.1% formic acid. (Tyr^8^)‐bradykinin was used as an internal standard and was added to the dialysis sample prior to injection. Baseline separation of bradykinin, arg‐bradykinin and (tyr^8^)‐bradykinin was achieved within 10 min. Positive ESI was performed in the m/z range of 200–1300. The method was validated in the range 0.2–1.0 ng/mL dialysate, yielding correlation coefficients of 0.995 and 0.990 for bradykinin and arg‐bradykinin, respectively. The within‐assay and between‐assay precisions were between 4.3–9.6% and 6.2–10.6%, respectively. Both arg‐bradykinin and bradykinin were detected in dialysate from rat muscle tissue, tws=0ptwb=.18wat concentrations of 0.1 and 0.4 ng/mL for bradykinin and arg‐bradykinin, respectively, confirming the presence of arg‐bradykinin in rat muscles.