How to read the HPLC flowmeter calibration certificate

Accuracy checks of efficient liquid chromatography (HPLC) pump systems should be performed frequently as part of a laboratory's standard operating procedure. Consistent and reproducible retention times are extremely important and depend on consistent and reproducible HPLC pump flow.

The accuracy of an HPLC system can be checked manually, a very time-consuming and laborious process, but, as we point out in our companion article on traceably calibrating the flow meter itself, it needs to be checked periodically for accuracy. It is also a time-consuming and labor-intensive process involving multiple measurements and calculations for each measured flow.

Laboratories for recalibration services need to specify the flow rate to be tested in addition to the required 1ml/min. Clients can also request "found" data at a rate of 1ml/min. Pre-tests include cleaning, sensor testing and other actions that should be taken to restore the HPLC flow meter to top shape.

HPLC Flow Meter Calibration Services Details

The table below is taken from an actual UKAS calibration certificate. This example shows 4 calibration points. Note that FDA wants to cover at least 3 points to cover those typically used by customers. In this example, all readings are within specification, which is what the device is intended to deliver.

• "Nominal" is the flow rate required for calibration

• "Actual" is the flow rate of liquid that is actually delivered to the flowmeter during calibration

• "Displayed" is the average of the readings displayed on the FlowCal 5000 Digital Readout

• "Standard Deviation" indicates the precision of the unit

• "Error" shows the accuracy of the reading relative to the actual flow