Realtime monitoring of GPC/SEC flow rate

A new technical study from Testa Analytical demonstrates the importance of continuous monitoring of current flow rate in GPC/SEC experiments.

Flow rate is one of the most important parameters in any liquid chromatography system, it determines retention time or volume and therefore has a major influence on reproducibility. In this new study, the Testa Analytical Liquid Chromatography Flowmeter is shown to provide a valuable tool for continuous, non-invasive measurement of flow rate in GPC/SEC systems.

The popularity of using GPC/SEC to characterise natural and synthetic polymers is inherently connected to its simplicity. A pump to push the solvent through the instrument, an injection port to introduce the test sample onto the column, a column to hold the stationary phase, and one or more detectors to detect the components as they leave the column. Results obtained rely on a calibration curve obtained by running a set of reference standards with known molecular weight and narrow molecular weight distribution. In GPC/SEC experiments - the determination of molecular weight of an unknown sample is based on the determination of its elution volume and then obtaining the corresponding value from the calibration curve.

In the study, researchers investigated the effect of a +/- 1% deviation in flow rate on results for an unknown sample determined with both a standard calibration and a universal calibration. This small variation in flow rate was selected as it might arise due to backpressure in a typical GPC/SEC system which is often below the detection limit of the pump pressure transducer and is thus undetectable with on-board means. The investigation was conducted by running a sample right after calibration, performing calculations and subsequently manually changing the flow rate parameter used for calculation. This was then repeated for a second sample using a viscosity detection and universal calibration.

The reported results from the study showed that a 1% deviation in flow rate resulted in a change of over 20% in calculated molecular weight results. These simple experiments underline the necessity for a suitable method of constant monitoring of current GPC/SEC flow rates and correction of running chromatogram.

The HPLC flowmeter range from Testa Analytical sets the benchmark for continuous non-invasive monitoring of the performance of pumps serving liquid chromatography systems. Compatible with all common solvents, the compact liquid chromatography flowmeter powers itself from a USB connection. At the heart of this flowmeter is a high-resolution thermal flow sensor that is both extremely accurate and sensitive. This non-invasive sensor enables the device to operate over a wide dynamic range. Each Testa flowmeter is supplied with an easy-to-use PC based App that allows users to continuously record, and store measured flow rate data from a liquid chromatography system. Current flow rate is displayed on the devices integral high-resolution OLED display.

To request a copy of the technical study please contact Testa Analytical.

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