A Primer on HPLC FlowmetersMarch 4th, 2013
High performance liquid chromatography – HPLC – is very often the method of choice for analyzing pharmaceutical compounds starting with R&D and continuing into manufacturing. Among other things it is used to
- Check candidate drugs for purity
- Monitor changes in pharmaceutical intermediates during chemical synthesis scale up
- Test the stability and dissolution of formulations in development and
- Support quality control in final drug products
Identifying an analyte by HPLC is based on accurate and reproducible column retention time as it passes through an HPLC system. Reproducible retention time is critical and depends on uniform, reproducible HPLC pump flow rates. A leak developing or other malfunction in the HPLC system will result in analysis errors. Obviously, then, continuous testing is necessary to insure that the HPLC system is properly calibrated. This is called operational qualification. OQ starts before the HPLC system is put into use and as part of ongoing system calibration checks.
Researchers can perform calibration tests by using a timer and either volumetric or gravimetric measurement of collected solvent. This is time consuming, tedious and prone to operator error. A far superior method of HPLC operational qualification uses the FlowCal 5000 digital liquid flow meter available from Tovatech.
How the FlowCal 5000 Works
These digital liquid flowmeters collect solvent exiting the HPLC system via a 1/16-inch PEEK (Polyetheretherketone) flow meter inlet tube. The flow rate is measured volumetrically.
The principle of operation is recording the time it takes the solvent to fill a glass tube equipped with two optical sensors. When the liquid enters the flowmeter at the bottom and begins to fill the measuring tube the meniscus passes the bottom sensor which activates a timer. When the meniscus reaches the top it activates the second sensor that opens a valve and drains the tube. The valve closes and the process repeats itself. Each new measurement refreshes the reading on the liquid crystal display.
The FlowCal 5000 has a low internal volume of 0.13 ml enabling it to quickly measure very low flow rates with high accuracy and repeatability. The mode of operation limits the viscosity of liquids that can be measured.
Consistent readings indicate that the HPLC pump is operating correctly. A variance signals that there may be a leak or other malfunction that requires attention.
The FlowCal 5000 is accurate to 1% of the reading with a guaranteed linearity from 0.05 to 25.00 ml/minute and is compatible with any HPLC pumping system. Flow data are shown on the liquid crystal display and can be transferred via an RS 232 interface to a computer or to an optional battery powered mini printer for archiving.
Contact the scientists at Tovatech answer your questions on the application and use of our FlowCal 5000 digital liquid flow meter.
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