A 12-point drift in the internal standard response on a 60-injection sequence is not a mystery. It is a paper trail, and it usually starts in the receiving dock. The last time I chased one, the septa lot had changed three weeks earlier: same part number, same vendor, but the incoming certificate showed a different batch of chlorobutyl compound and a cure time shortened by 90 seconds. The method had never been revalidated against that lot, because nobody had flagged the change as a change. T...

The run died at injection 47 with “Autosampler error: vial not found” on the , and the tray had 96 vials in it. The lab had swapped to a new case of 2 mL wide-mouth vials the week before. The septa were the same part number as always, 11 mm, 1.0 mm thick, silicone/PTFE. Nothing about the septum had changed. What had changed was that the new vials sat 1.4 mm lower in the tray than the old ones, and the gripper on that instrument has a vertical pickup window of roughl...

A 2 mL HPLC vial filled to 1.5 mL will lose roughly 0.9 mL of its headspace the moment you pierce a 22-gauge needle through a 10 mm septum, and if that septum has already taken 40 injections, the coring debris from that single pierce can plug a 0.25 mm ID column in under 200 µL of mobile phase. I have watched that exact sequence destroy a $600 column on a Tuesday afternoon. The root cause was not the septum material, and it was not the vendor. It was that somebody sized the septum for the v...