The solvent degassing instrument is a device that removes dissolved gases from solvents through physical or chemical methods. It is widely used in fields such as analytical chemistry, biomedicine, and materials science. Its core objective is to enhance the purity of the solvent and prevent gases from interfering with experiments or production processes. The degassing effect is influenced by multiple factors and requires a comprehensive consideration of equipment parameters, solvent characteristics, operating conditions, etc. The following systematically analyzes its influencing factors from eight dimensions:

I. Temperature Control

The relationship between gas solubility and temperature

According to Henry's Law, the solubility of gases decreases as the temperature rises. For example, the solubility of oxygen in water is 9.1 mg/L at 20℃ and drops to 6.7 mg/L at 40℃. Appropriate temperature increase can accelerate the escape of gas, but excessively high temperatures may cause solvent evaporation (for example, the boiling point of ethanol is 78℃), and the operating temperature should be selected based on the characteristics of the solvent.

2. Thermal stability limitations

High temperatures may damage heat-sensitive samples (such as proteins and high-molecular polymers), and precise regulation needs to be achieved through a temperature control system (such as PID temperature control), usually within the range of 2060℃.

Ii. Pressure Conditions

1. Vacuum degree and degassing efficiency

A low-pressure environment can reduce the partial pressure of gas and promote the release of gas. For instance, during vacuum degassing, the partial pressure of oxygen drops from atmospheric pressure (21kPa) to below 1kPa, and the degassing rate increases several times. However, a vacuum degree that is too low may cause the solvent to boil (for example, the boiling point of water at 20kPa is approximately 60℃), and a threshold should be set based on the vapor pressure of the solvent.

2. Inert gas displacement

When using the nitrogen or argon displacement method, the gas flow rate and pressure need to be balanced: a flow rate that is too fast may cause the solvent to atomize, while a flow rate that is too slow will prolong the degassing time. The gas flow rate is usually controlled at 15 L/min, and the pressure is maintained at a slightly positive pressure (520kPa).

Iii. Degassing Time

1. Dynamic equilibrium

The degassing rate is fast in the early stage and slows down in the later stage. For example, 80% of the gas in the water sample can be degassed within 10 minutes, while the remaining 20% takes a longer time. In actual operation, efficiency and cost need to be combined, and it is usually set at 2060 minutes.

2. Side effects of excessive degassing

Excessive processing may lead to solvent evaporation loss (such as acetone evaporation rate reaching 30% per hour), or introduce new contaminants (such as vacuum pump oil mist). It is recommended to terminate degassing in real time through online monitoring (such as gas sensors).

Iv. Physical and Chemical Properties of Solvents

Vapor pressure and volatility

Highly volatile solvents are prone to loss during the degassing process, so the temperature needs to be reduced or the time shortened. Low-volatile solvents (such as glycerol) can withstand high temperatures but have high viscosity and need to be stirred in combination.

2. Surface Tension and Bubble behavior

High surface tension solvents (such as mercury) require ultrasonic assistance to break bubbles. Low surface tension solvents (such as ethanol) are prone to foaming, and defoamers need to be added or the stirring intensity controlled.

3. Chemical activity

Strong polar solvents (such as concentrated sulfuric acid) may react with the materials of the equipment, and corrosion-resistant materials (such as polytetrafluoroethylene coating) should be used.

V. Equipment Design and Parameters

1. Container shape and stirring efficiency

The conical container is conducive to the aggregation and discharge of gas. When combined with magnetic stirring (300 to 800 RPM), it can accelerate mass transfer. Turbine stirring is suitable for high-viscosity systems, but the shear force may damage sensitive samples.

2. Sealing performance and dead volume

Minor leakage (such as 1μL/min) will significantly reduce the vacuum degree, and fluororubber sealing rings need to be adopted. Dead volume areas (such as pipe corners) are prone to residual gas, and the flow path design needs to be optimized.

3. Detection method

Optical sensors (such as infrared spectrometers) can monitor gas concentrations in real time, while electrochemical sensors (such as Clark electrodes) are suitable for trace oxygen detection and should be selected based on requirements.

Vi. Optimization of Operating Parameters

Stirring speed and gas diffusion

Low-speed stirring (<200rpm) may cause gas retention, while high-speed stirring (>1000rpm) intensifies turbulence. Generally, 400 to 600 RPM is selected to balance mass transfer and shear force.

2. Gas flow control

When purging inert gas, if the flow rate is too low (<0.5L/min), it cannot be effectively replaced; if it is too high (>10L/min), solvent splashing will occur. Precise adjustment through a mass flow controller is required.

3. Multi-stage degassing strategy

First, vacuum remove most of the gas, and then purge and replace the residual gas to improve efficiency. For example, first evacuate to 1kPa and maintain it for 15 minutes, then introduce nitrogen to normal pressure and circulate it three times.

Vii. Influence of Sample Characteristics

1. Types and concentrations of dissolved gases

The oxygen content in air-saturated water is approximately 8mg/L, while the CO₂ content in carbonated beverages reaches 300mg/ L. The degassing method needs to be adjusted specifically (for example, CO₂ requires alkaline pretreatment).

2. Sample uniformity

Suspended particles or emulsions may encapsulate gases and require pre-centrifugation (such as 10,000rpm for 10 minutes) or the addition of surfactants to improve mass transfer.

3. Bioactive samples

Degassing of cell culture medium should avoid mechanical damage. It is advisable to use mild ultrasound (20kHz, 10 seconds per time) or membrane filtration (0.22μm hydrophobic membrane).

Viii. Interference from environmental factors

Fluctuations in temperature and humidity

For every 1℃ increase in ambient temperature, the solubility of gases decreases by approximately 2%, and a constant temperature room (±1℃) needs to be configured. Excessive humidity may cause condensation on the equipment. Dehumidification is required to reduce the RH to less than 60%.

2. Changes in air pressure

For every 1,000 meters increase in altitude, the atmospheric pressure drops by approximately 10kPa. It is necessary to calibrate the vacuum gauge and extend the degassing time. For example, degassing in plateau areas requires an increase of 20% in duration.