Figure 7: Peak deterioration with varying urine concentrations. Sample: urine percentages from 0 to 5 % in a mobile phase, keeping constant the concentration of the analyte, PFPP column: Discovery HS F5 (5μm, 2.1x50 mm), mobile phase: 5mM ammonium formate buffer (pH 2.9) in 80 % acetonitrile, flow rate: 0.2 mL/min, column temperature: 40°C