Eluent passing through HPLC pump systems can, over time, impact the accuracy of the system and result in inaccurate flow rates. HPLC pump system impellers, valves, seals, injectors and other components in direct contact with analytes carried in an eluent are subject to wear as well as possible deposition of damaging salts and other substances that interfere with flow rates.
That’s why HPLC pump system flow rates should be checked on a regular basis. Regular accuracy checks contribute to meeting FDA standards for system OQ and PQ validation as well as ongoing performance verification. There are different ways to do this. One we call the hard way, the other the easy way.
An example of the hard way is repeatedly and manually collecting and measuring by weight or volume the solvent as it exits the HPLC system. This is extremely work-intensive and highly subject to operator error.
An easier and far more accurate and reproducible method is to place a FlowCal 5000 digital liquid flow meter at the end of the line. The unit is compatible with all HPLC brands.
The FlowCal 5000 Operating Procedure
A compact 5.4 x 3.0 x 1.8 inches in size and weighing only 12 ounces the FlowCal 5000 operates by repeated and accurate measurement of the time it takes the solvent to fill a 140 microliter flow tube. As the solvent fills the tube the meniscus passes two optical sensors. These sensors are connected with an internal timer to monitor the transit time of the meniscus.
Simply stated, when the solvent enters the flowmeter it activates the first sensor and timer. When it reaches the second sensor a valve is opened and the tube is drained. This process is repeated many times.
Flow rates are displayed on a 4-digit LCD and data are transferred via an RS-232 interface for a 6-digit (xx.xxxx) reading to a thermal printer or computer. The measured flow rate is independent of the liquid type up to a 10 centipoise viscosity.
Equipped with a single chip micro-controller, FlowCal 5000 digital HPLC flowmeter units are supplied gravimetrically calibrated at 1.0 (+10%) ml/min. Calibration at multiple points is available as the equipment has guaranteed linearity from 0.05 to 25ml/minute accurate to 1% of the reading. They are shipped with a mounting kit, a cleaning kit, a traceable calibration certificate and instructions, all packed in a carrying case. Annual recalibration is required to conform to GLP.