How to Read an HPLC Flowmeter Calibration Certificate

Accuracy checks on high performance liquid chromatography (HPLC) pump systems should be performed frequently as part of a laboratory’s standard operating procedures.   Uniform and reproducible retention time is extremely important and relies on uniform and reproducible HPLC pump flow rates.

Checking the accuracy of an HPLC system can be done manually – an extremely time consuming and laborious process – or by using the digital FlowCal 5000 liquid flowmeter from Tovatech.   But as we’ve noted in a companion post on traceable calibration flowmeters themselves must be periodically checked for accuracy.

This too is a time-consuming and laborious process involving multiple measurements and calculations for each flow rate being tested.  That’s why we strongly recommend returning the FlowCal 5000 to us on an annual basis to have it tested in conformance to UKAS standards and returned with a calibration certificate traceable to the UKAS (United Kingdom Accreditation Service).  UKAS is equivalent to our National Institute of Standards and Technology.

Labs subscribing to this recalibration service must specify flow rates to be tested in addition to the required 1 ml/min.  Customers may also request “as found” data at rates in addition to 1 ml/min.  Pre-testing includes cleaning, sensor testing and other points that should be addressed to restore the HPLC Flowmeter to tip-top shape.

HPLC Flowmeter Calibration Services Detail

The following table is excerpted from an actual UKAS Certificate of Calibration.  This example shows 4 calibration points. Note that the FDA prefers at least 3 points covering those generally used by the customer.  In this example all readings are within specification, which is what the equipment is designed to deliver.

  • “Nominal” is the requested flow rate for calibration
  • “Actual” is the flow rate of the liquid actually delivered to the flowmeter during the calibration procedure
  •  “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 readout against the actual flow rate
Calibration Details

Point 1

Point 2

Point 3

Point 4


Nominal flow ml/min





Actual flow ml/min





Within ±10% of nominal
Displayed flow ml/min





Within  ±1.0% of actual
Standard deviation ±%





Error %






Among other details the certificate indicates the date of the testing,when the next test is due and that the results were found to meet the manufacturer’s specification.

Contact the scientists at Tovatech for detailed information regarding the FlowCal 5000 liquid flow meter, its operation and maintenance.

About Bob Sandor

Bob began working as a chemist in 1987 and remains a science geek to this day. After his PhD he worked on the bench in materials and inorganic chemistry for 10 years. He then took on a love for marketing and sales. He combined his passion for science and business and took entrepreneur general management positions in large corporations like Hoecsht Celanese now Sanofi Aventis, Bel-Art and Smiths Detection. There he learned what it would take to run a business and finally Tovatech was co-founded in 2006. Bob’s hobbies include playing, listening and composing music, skiing, working out, the internet and all things science. Read More