Figure 1From: Method optimization and validation for the simultaneous determination of arachidonic acid metabolites in exhaled breath condensate by liquid chromatography-electrospray ionization tandem mass spectrometrySix-port switching valve arrangement for the clean-up and enrichment step (Valve position A, left side) and the chromatographic separation step (Valve position B, right side). P1 correspond to the isocratic and P2 to the gradient pump.Back to article page