Pipettes are used to transport or measure a volume of liquid. The key to quality processes is ensuring pipette readings are accurate and do not vary. While laboratory managers or technicians can check the instrument for accuracy, many accrediting bodies require third party pipette calibration. Many wonder if the process differs between in-house and third party calibration testing. Below, we outline the pipette calibration process.
Standard Operating Procedure & Documentation
An ISO/IEC 17025 accredited calibration laboratory will have a documented standard that details the pipette calibration procedure. The technician will use this documentation during testing to ensure process conformance. The technician will prepare a form or digital spreadsheet to record results. Many laboratories that use a paper form will later enter results into a digital spreadsheet to calculate variance.
The equipment required for pipette testing includes an analytical balance, a beaker, NIST calibrated thermometer, volumetric flask, gloves, and pipette tips.
Pipette Calibration Testing
For each pipette, the calibration technician will record the make, model, and serial number of the instrument. The model number field may also include information on the minimum and maximum volume setting. The technician will record the values that will be measured on the pipette. Most calibration testing will require readings for the minimum, mid-point, and maximum volume. The technician will record the temperature of the liquid being measured.
The liquid receptacle will be placed on the analytical scale, then the scale is set to 0. This is done so that the only component being measured is the liquid from the pipette. The technician will fit a new pipette tip securely to the instrument. Testing will typically begin with the minimum measurement.
The pipette is set to the selected measurement. The first measurement is taken and recorded. The process is repeated five to ten times, dependent on the Standard Operating Procedure. The process is repeated in the same fashion for the other volume readings. Any conversions that are used will also be noted.
If the pipette fails calibration testing, the technician will check instrument condition. If needed, the technician will clean and lubricate the pipette. The instrument is tested again after this process.
The process listed above is common for an air displacement type pipette. The procedure may vary due to manufacturer requirements, usage, or quality program specifications. If you have any questions about pipette calibration, or would like a quote, contact e2b calibration.