recalibration
Recalibration is checking and resetting an instrument's calibration after time has passed, because instruments drift. Think of a clock that runs a few minutes fast each week: it was right when you set it, but it slowly wanders, so you reset it against an accurate reference. Recalibration is that reset for an analytical instrument.
Concretely, you re-measure known standards and, if the instrument no longer reproduces their expected values within tolerance, you build a fresh calibration curve or adjust the existing one. Many labs also run a quick mid-batch "calibration check" with a single standard to see whether a full recalibration is needed before continuing.
It matters because lamps age, columns wear, baselines shift, and temperatures change — yesterday's calibration may no longer be true today. Recalibrating keeps results trustworthy over a long run of samples. The balance to strike: too rarely and undetected drift biases results; too often and you waste time and standards. Validated methods specify how often and against what criteria to recalibrate.
Midway through a 200-sample run, the analyst re-measures a 5 mg/L check standard. It now reads 4.6 mg/L — outside the ±5% tolerance — so the instrument is recalibrated before continuing.
A drifting check standard signals it is time to recalibrate.
Recalibration restores agreement with standards but does not validate the whole method — it cannot reveal a problem common to both standards and samples, such as a contaminated reagent. Routine blanks, control charts, and check standards work alongside recalibration.