ANALYTICAL & LAB EQUIPMENT
Figure 3. Example output from the Biotech Liquid Flow Meter during two minutes of high frequency data collection from a pump delivering a pulsating flow pattern
FLOW RATE DETERMINATION A more recent technology for determination of flow rate is thermal conductivity [4]. This non-invasive principle involves two temperature sensors on a quartz glass tube, with a heating element positioned in-between, as depicted in Figure 1. With a built-in algorithm that converts heat difference to flow rate using internally stored calibration data, devices based on this principle can determine flow rate with a high frequency. The Biotech Liquid Flow Meter is constructed on this principle and produced into a handy physical size (see Figure 2). This flow meter can deliver readings every 78 milliseconds, thereby enabling high- resolution flow monitoring to detect variations and pulsating behaviour from pumps, as shown in Figure 3. The specifications of this flow
meter have been independently verified by a European accredited calibration laboratory using traceable standards. Their report concluded that the deviation from the reference value was below ±0.17% for all five tested flow rates within the range 0.15 to 5.0 mL/min. The uncertainty was determined to be 0.2% full scale deviations at the highest flow rate
but lower within the rest of the tested range. These tests verify that the Biotech Liquid Flow Meter match the specifications from the manufacturer while also fulfilling the requirements for operational qualification of HPLC & UHPLC equipment and other fluidic systems where the quality of the results depend on a reliable flow rate.
A STANDARDISED PROTOCOL When used within the Advanced Pump Validation Kit, i.e., with a standardised and automated protocol for data collection and calculation, the Biotech Liquid Flow Meter will provide a full data set plus a report for qualification of HPLC & UHPLC equipment within 10 minutes. This validation test report contains information about the average flow rate and its deviation from the nominal flow of the pump, plus relative standard deviation from five independent determinations, and a traceable reference to the stored raw data file. Unique to the Biotech Liquid Flow
Meter with the Advanced Pump Validation Kit is that it provides an independent assessment of flow pulsation. This can be used as an additional quality parameter for
pumps to follow their wear and thus plan ahead for maintenance actions. The pulsation parameter is calculated as a relative max-min value within two minutes, which corresponds to how noise typically is defined and measured in analytical measurements including liquid chromatography.
REFERENCES: [1] GEON Quality Management Document PA/ PH/OMCL (11) 04 R7 (2005) “Qualification of Equipment Annex 1: Qualification of Liquid Chromatography Equipment”, General European Network of Official Medicines Control Laboratories, Strasbourg, France.
[2] United States Pharmacopeia General Chapter <1058> (2017) “Analytical Instrument Qualification”, Unted States Pharmacopeial Convention, Rockwille, Maryland, USA.
[3] P. Uthaiwat, T. Leeudomwong, T. Sanponpute, “The comparison of flow rate calibration methods for high-performance liquid chromatography (HPLC) pump”, Accreditation and Quality Assurance (2024) 29:205-214.
[4] Biotech Liquid Flow Meters, https://
biotechfluidics.com/products/sensors/biotech- liquid-flowmeter/ (accessed 2025-03-10).
AUTHORS: Dr. Tobias Jonsson, CEO, Diduco AB, Umeå, Sweden
Anders Grahn, Chairman & Founder, Biotech Fluidics AB, Onsala, Sweden
For more information visit:
www.biotechfluidics.com
www.scientistlive.com 17
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