A 12-position autosampler tray ran 96 injections of a method using 30% acetonitrile in 0.1% TFA at 40 °C. By injection 60, peak areas for the internal standard had drifted 11.4% below the start, and the system suitability RSD on five replicates had climbed from 0.6% to 3.8%. The column was new. The detector lamp had 1,800 hours on it. What had changed was the vial lot: the previous lot used a silicone/PTFE septum, the new one used a plain silicone septum because the distributor was out of t...