Carbon dioxide incubator
As an important instrument for cell culture, the carbon dioxide incubator can maintain a stable temperature (37 ° C) during in vitro experiments CO2 concentration (5%) and relatively high saturation humidity (90%) are used to simulate the growth environment of cells or tissues in living organisms, improving the success rate and efficiency of cell or tissue culture. This is an irreplaceable ordinary electric constant temperature incubator. How to choose from the numerous carbon dioxide incubators on the market? At this point, it is important to pay attention to an important component - the sensor!
sensor
CO2 is a cellular metabolite and also a necessary component for cells. In the process of cell culture, as the amount of CO2 released increases, the pH value of the culture medium will decrease. Therefore, NaHCO3 is often added to regulate the pH (NaHCO3 has a tendency to release CO2, and the addition of CO2 can inhibit this reaction). Sensors with high sensitivity and accuracy can accurately detect the concentration of incoming CO2.
At present, CO2 incubators on the market mainly use three types of sensors: ultrasonic sensors, thermal conductivity (TC) sensors, and infrared (IR) sensors.
ultrasonic sensor
Measurement is based on the different propagation speeds of ultrasound in different air media.
Thermal conductivity (TC) sensor
Detect CO2 concentration through changes in resistance value. However, frequent opening and closing of the box door, as well as changes in humidity and temperature, can affect the sensor's judgment. And the reaction is slow and the drift rate is high. At least one correction is needed after each high-temperature sterilization to reduce the error.
Infrared (IR) sensor
Based on the absorption of infrared radiation by CO2, the reduction in infrared radiation is detected to determine its concentration. Composed of an infrared emitter and a detector.
During detection, gas will be sucked into the chamber, with one end of the chamber equipped with an infrared light source and the other end equipped with a filter and detector. Infrared light will pass through the same chamber and pass through a filter before reaching the detector. The light flux received by the detector depends on the gas concentration within the effective volume of the measured environment. Although IR sensors have a complex structure, they have good linearity and high sensitivity, are not affected by temperature and humidity, and can reduce the impact of temperature or device aging on sensor accuracy. They are more accurate than thermal conductivity (TC) sensors and have a smaller drift rate.
Different gases will absorb light of different wavelengths. Measurement based on the principle of non divergent infrared gas detection in CO2 gas chambers can be divided into single beam single wavelength measurement, dual beam dual wavelength measurement, and single beam dual wavelength (NDIR) measurement. NDIR measurement is a way to ensure the accuracy of the sensor, avoiding the instability of a single beam and errors caused by asynchronous arrival of two beams at the detector.
Most IR sensors have thermal stack detectors that can withstand a maximum temperature of about 80 ℃, and the entire probe needs to be removed during ordinary high-temperature sterilization. To avoid cross contamination, an IR sensor that can withstand high temperatures of 180 ℃ can be selected. Even if it is not removed during high temperature cycle sterilization, there is no need to worry about being damaged due to poor heat resistance, ensuring the cleanliness of the incubator chamber.
The IR sensor detects the amount of infrared absorption, and particles inside the box can also reflect or absorb infrared radiation. Therefore, in order to reduce errors caused by suspended particles, an IR sensor with a HEPA high-efficiency filter can be chosen.
