I spent three weeks chasing a 0.9% carryover on a 2 mL vial method last year. The wash cycle ran 6 seconds of methanol, the needle rinsed on the outside, the injection port was clean, and the blank still came back with a peak at the retention time of the analyte. The instrument was not the problem. The vial was. Specifically, the vial was acting as a reservoir, holding a few microlitres of sample in a place the wash solvent never reached, and then releasing it into the next injection. That ...