In food analysis, HPLC has become an indispensable analytical instrument for both residue analysis and component analysis. Degassing the mobile phase is a very effective measure for obtaining reliable data from HPLC systems. The following analysis, the necessity of high performance liquid chromatography degassing, and summarized the commonly used methods of degassing.
First, the necessity of degassing Mobile phase degassing is a very effective measure for HPLC systems to obtain reliable data. The HPLC pump generates a lot of force when transporting liquid. Since the compression ratio of the gas is much larger than that of the liquid, when the bubble is present, we find that the instantaneous flow rate decreases and the system pressure drops. If the bubble is large enough, the liquid pump will not be able to deliver any solvent, and if the pressure is below the pre-set pressure limit, the pump will stop working. When a bubble passes through the infusion pump, the bubble is usually dissolved in the mobile phase solution as it passes through the column due to the high system pressure. However, when the detector flow cell is reached, the system pressure returns to atmospheric pressure, so bubbles may appear again in the detector flow cell, and irregular burrs may appear on the chromatogram.
Second, the degassing method
1. Blow the degassing method.
Utilizing the lower solubility of helium in the liquid than air, it can be effectively removed from the mobile phase by passing it into the mobile phase storage container at a flow rate of about 60 mL/min for 10 to 15 minutes at a pressure of 0.1 MPa. Can eliminate nearly 80% of oxygen. With a highly efficient distributed jet flow device, one volume of helium gas can remove an equal volume of almost all of the gas from the mobile phase. This means that 1L of helium can complete the exhaust through the 1L mobile phase. Although this degassing method is good, the price of helium is high and it is rarely used.
2. Heat the reflux method.
This method has a better degassing effect. Pay attention to the cooling efficiency of the condensing tower during operation, otherwise the solvent will be lost and the proportion of the mixed mobile phase will change.
3. Vacuum degassing method.
This method can remove the dissolved gas by using a vacuum pump and reducing the pressure to 0.05 to 0.07 MPa. However, since vacuum degassing changes the composition of the mixed solvent, which affects the reproducibility of the experiment, it is often used for simple analysis of a single solvent system.
4. Ultrasonic degassing method.
The mobile phase to be degassed was placed in an ultrasonic cleaner and shaken with an ultrasonic wave for 10 to 20 minutes. This method has the worst degassing effect.
5. Online degassing method.
The HPLC instrument can be equipped with an online degasser developed by our company. Online degassing is simple to use, low in failure and effective.
In order to ensure the accuracy of high performance liquid chromatography results, degassing is an important part.
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