Combining UHPLC-HRMS targeted and suspect screening for a comprehensive analysis of nisin A and its variants in cow milk

A liquid chromatography method coupled with an Orbitrap analyser was used to detect nisin A and its variants in partially skimmed and raw cow milk. A suspect screening method enabled the identification of F, Q and Z variants. Adequate linearity was achieved (r(2) = 0.9998-1 up to 250 mu g/L) with a limit of quantitation for nisin A of 2.5 mu g/L. Method accuracy (at 2.5, 25 and 250 mu g/L) in milk ranged from 94 to 98% and precision in the range 0.4-1.9%. Nisin Z was abundant in partially skimmed samples. The method was suitable for determining these bacteriocins in cow milk.