Why should the mobile phase of the liquid chromatograph be degassed What are the commonly used degas

1. Liquid chromatograph.

The necessity of degassing of the mobile phase.

Mobile phase degassing is an effective measure for HPLC systems to obtain reliable data. HPLC pumps generate a lot of force when transporting liquids due to the compression ratio of the gas.

It is much larger than liquids, so when bubbles are present, we see an instantaneous decrease in flow rate and a drop in system pressure. If this bubble is large enough, the liquid phase pump will not be able to deliver any solvent, and if the pressure falls below the pre-set pressure limit, the pump will stop working. When a bubble passes through the infusion pump, the bubble usually dissolves in the mobile phase solution due to the high system pressure, passing through the column with the mobile phase.

However, when the detector flow cell is reached, the system pressure returns to atmospheric pressure.

As a result, bubbles may reappear in the detector flow cell, resulting in irregular burrs on the chromatogram.

Second, the degassing method.

1.Helium blowing degassing method.

Uses helium for solubility in liquids.

The lower than air characteristics, under pressure, at a flow rate of about 60 ml min into the mobile phase reservoir container for 10 to 15 minutes, can effectively remove dissolved air from the mobile phase, can remove nearly 80% of oxygen. Using a distributed jet device, one volume of helium can remove almost all of the same volume of gas from the mobile phase. This means that 1 L of helium can be vented through 1 L of mobile phase.

Although this degassing method is good, it has a high helium ** and is rarely used.

2.Heating reflux method.

The degassing effect of this method is better. Pay attention to the cooling efficiency of the condensing tower during operation, otherwise the solvent will be lost and the proportion of mixed mobile phases will change.

3.Vacuum degassing method.

A vacuum pump can be used for this method.

Reduced pressure to , the dissolved gas can be removed. However, because vacuum degassing will change the composition of the mixed solvent, which will affect the reproducibility of the experiment, it is mostly used for simple analysis of single-solvent systems.

4.Ultrasonic degassing.

The mobile phase to be degassed is placed in an ultrasonic cleaner and used for 10 20 minutes. The degassing effect of this method is poor.

In order to ensure the accuracy of liquid chromatography results, degassing is an important step.

If it is not degassed, it will cause baseline drift, the retention time of the main peak is unstable, and ghost peaks will appear, which will seriously affect the detection results. Commonly used methods are ** degassing, ultrasonic degassing and boiling degassing. **Degassing requires instrument configuration**Degasser, ultrasonic degassing is a more commonly used method.

The mobile phase must not be boiled and degassed.

Summary. The liquid chromatograph components have a unique shape design and flexible combination; system performance indicators; Graphical workstation-friendly interface; The intelligent maintenance system and comprehensive and perfect regulatory certification function are widely used in drug research and development, production, food testing, environmental testing and other fields. Several common degassing methods for liquid chromatography:

1. The degassing effect of the heating reflux method is better. 2. The helium blowing degassing method uses helium with lower solubility than air in the liquid, and under pressure, the mobile phase is passed into the mobile phase at a flow rate of about 60ml min for 10-15min to drive out the dissolved gas. This method is used in all solvents, and the degassing effect is better, but it is less used in China because helium is more expensive.

3. At this time, a miniature vacuum pump can be used to reduce the pressure to the dissolved gas in the removal area. Obviously, using a water pump to connect the suction filter bottle and the G4 microglass funnel can work together to filter mechanical impurities and degass. Since vacuuming will cause changes in the composition of the mixed solvents, this method is suitable for the degassing of single-solvent systems.

The multi-solvent system should be degassed in advance and then mixed to ensure that the proportion of mixed remains unchanged. 4. Ultrasonic degassing method: At present, the laboratory uses a wide range of degassing methods, and the prepared flow is connected to the container and put it into the ultrasonic water for degassing for 10-20min. This method is easy to operate and can basically meet the requirements of daily analysis.

The liquid chromatograph components have a unique shape design and flexible combination; system performance indicators; Graphical workstation-friendly interface; The intelligent maintenance system and comprehensive and perfect regulatory certification function are widely used in drug research and development, production, food testing, environmental testing and other fields. Several common degassing methods of liquid chromatograph: 1. The degassing effect of this method is better.

2. The blowing trace helium degassing method uses helium with lower solubility than air in the liquid, and under pressure, the mobile phase is introduced into the mobile phase at a flow rate of about 60ml min for 10-15min to expel the dissolved gas. This method is used in all solvents, and the degassing effect is better, but this method is less used in China because helium is more expensive. 3. At this time, a miniature vacuum pump can be used to reduce the pressure to the dissolved gas in the removal area.

Obviously, using a water pump to connect the suction filter bottle and the G4 microglass funnel can work together to filter mechanical impurities and degass. Since vacuuming will cause changes in the composition of the mixed solvents, this method is suitable for the degassing of single-solvent systems. The multi-solvent system should be pre-monitored and degassed before mixing, so as to ensure that the proportion of mixed remains unchanged.

4. Ultrasonic degassing method: At present, the laboratory uses a wide range of degassing methods, and the prepared flow is connected to the container and put it into the ultrasonic water for degassing for 10-20min. This method is easy to operate and can basically meet the requirements of daily analysis.

The mobile phase used in HPLC must be degassed in advance, otherwise air bubbles can easily escape in the system and affect the operation of the pump. Air bubbles can also affect the separation efficiency of the column, affecting the sensitivity of the detector, baseline stability, or even making it impossible to detect.

Increased noise, unstable baseline, sudden jumping. In addition, oxygen dissolved in the mobile phase may react with the sample, the mobile phase, and even the stationary phase (e.g., alkyl amines). Dissolved gases can also cause changes in solvent pH, which can lead to errors in separation or analysis results.

Commonly used degassing methods are: heating and boiling, vacuuming, ultrasonic, helium blowing, etc.

High performance liquid chromatography is an important branch of chromatography, using liquid as the mobile phase, using a high-pressure infusion system, a single solvent with different polarity or different proportions of mixed solvents, buffers and other mobile phases are pumped into the chromatographic column equipped with stationary phase, and after the components in the column are separated, they enter the detector for detection, so as to realize the analysis of the sample.

The mobile phase solution often affects the operation performance of liquid chromatography due to dissolved oxygen or mixed with air, and bubbles are generated in the pump to make the flow rate unstable, and holes will be formed in the pump head when the bubbles are large. When air bubbles enter the detector, they can cause sharp noise peaks on the chromatogram, reducing the response or even causing the signal to disappear. Oxygen in the mobile phase has the greatest effect on the photodetector, increasing the UV detector baseline and canceling out the signal at low wavelengths.

In fluorescence detection, dissolved oxygen also quenches fluorescence. Dissolved gases may also cause oxidation of some samples or change the pH of the solution. 2. Methods of mobile phase degassingThere are about four methods of mobile phase degassing used in liquid chromatography

Helium degassing, vacuum degassing, ultrasonic degassing, and thermal degassing.

1.Helium degassing: Helium degassing is a very effective method of degassing.

Helium slowly passes through the mobile phase to remove the dissolved air, and if used properly, it can remove 80% and 90% of the dissolved gas within 10 minutes. Since the solubility of helium in the mobile phase is extremely low, the mobile phase protected by helium degassing can be considered a gas-free dissolved system. Our unit water liquid chromatography is to use helium plum tong gas degassing, and the effect is very good.

The disadvantage is that helium** is more expensive and will increase the cost of inspection.

2.Vacuum degassing: It is also a more commonly used degassing method.

The reservoir is partially vacuumed, and the dissolved gas evaporates to form a bubble overflow, which is second only to helium degassing. Our unit AGILENG1200 liquid chromatography uses a ** degasser. The disadvantage is that it needs to be equipped with an air pump or degasser, which increases the investment in the instrument.

3.Ultrasonic degassing: Put the prepared flow-connected container into the ultrasonic water tank for degassing for 10-20min

This method is relatively simple, and can basically meet the requirements of daily leakage guessing analysis operation, so it is still widely used. This method removes only 30% of the dissolved gas, and sometimes causes an increase in gas solubility. This method should not be used in oxygen-sensitive detectors.

4.Heating reflux degassing: Although this method works well, the scope of application is narrow. This method is not suitable for organic solvents or mixed mobile phases because volatile components are lost, changing the composition of the mobile phase.

3. Precautions Nowadays, most liquid chromatography is a multivariate system, which can deliver several different mobile phases at the same time. However, it should be noted that some mobile phases will produce gases when different components are mixed, and for this flow, the in-system mixing will be changed to off-system pre-mixing. The determination of melamine uses acetonitrile and sodium octane sulfonate as mobile phases, and one of our inspectors put the mobile phases in two bottles after degassing respectively, and the results of the baseline fluctuated greatly and could not be stable. Later, the problem was solved by pre-mixing and degassing.

Correct answer: The solvent needs to be filtered and de-elevated, which can remove mechanical impurities such as insoluble particles and air bubbles dissolved in the mobile phase in the mobile phase to prevent blockage of the infusion tube, injection valve, and chromatographic column, which will affect the separation effect of the chromatographic Lingxiao broad column, the baseline stability of the detector, and the reproducibility of the retention time ruler and peak area.

There should be three kinds: vacuum filtration can remove part of the air leaked from the mountain, ultrasonic can be further degassed, and the instrument can be used to return to Wang Cheng if there is a degassing machine. I haven't seen anything else.

The mobile phase used for HPLC must be degassed beforehand, otherwise air bubbles can easily escape in the system and affect the operation of the pump. Air bubbles can also affect the separation efficiency of the column, the sensitivity of the detector, the stability of the baseline, or even make it undetectable.

Increased noise, unstable baseline, sudden jumps. In addition, oxygen dissolved in the mobile phase can react with the sample, the mobile phase, and even the stationary phase (e.g., alkyl amines). Dissolved gases can also cause changes in the pH of the solvent, which can lead to errors in separation or analysis results.

Commonly used degassing methods include heating boiling, vacuuming, ultrasonic, helium blowing, etc.

High-performance liquid chromatography (HPLC) is an important branch of chromatography. Using liquid as the mobile phase, the high-pressure infusion system pumps single solvents of different polarities or mixed solvents, buffers and other mobile phases with different polarities into the stationary phase chromatography column. After separating the components in the column, they are detected with a detector.

The analysis of the sample was realized.

Filtration has two meanings: one is to filter out insoluble particles in the mobile phase, and the other is to filter out air bubbles dissolved in the mobile phase.

Degassing is all about getting rid of air bubbles.

For the liquid phase, the pump is like the heart, and if there are air bubbles blocking the pump, then the heart is not functioning properly.

In addition, the chromatographic column is composed of packing materials with very small pore size, for example, the traditional chromatographic column has a pore size of 5um, so the filter membrane to be used for filtration ensures that air bubbles or impurities will not block the column.

The bubbles into the column are equivalent to the column drying up part, destroying the column.