Last spring a client sent me a chromatogram pack from a 96-hour sequence on an Aijiren . The first forty injections looked clean. By injection 70 the peak areas for their target analyte had dropped 18%, and by injection 90 the internal standard response was wandering enough that the reported concentrations were useless. They had replaced the column, re-prepped the mobile phase, and re-calibrated the autosampler. Nobody had looked at the cap. When I asked which septum was on the vial, th...

Last spring I watched a lab burn through three boxes of septa in a week on a single 96-position autosampler. The method was a 60-injection sequence, nothing exotic: 40 °C oven, water/acetonitrile gradient, 10 µL injections. By injection 25 the chromatograms had grown a new, late-eluting ghost peak that nobody could assign. The septa were the cheapest line on the requisition, and that is exactly why they were the last thing anyone suspected. The fix was not a more expensive septum. It was a ...

I still remember the Monday morning when a customer sent back a box of 2 mL autosampler vials with a note taped to the lid: “Your septa are shedding.” Inside were forty vials, each holding a tiny gray disc of silicone floating in the buffer. The instrument had been running a 96-hour sequence over the weekend and the needle had punched each vial six times. By Saturday night, the septum on vial 12 had started to coring, and by Sunday the autosampler was aspirating silicone crumbs ...