Carbon dioxide incubator use points and precautions

The carbon dioxide incubator is an indispensable equipment for scientific research in modern large and medium-sized hospitals, and is distributed in various laboratories of hospitals. It simulates the formation of a cell-like growth environment in a living organism such as a constant pH (pH: 7.2-7.4), a stable temperature (37 ° C), and a high relative humidity (in the inside of the incubator). 95%), a stable carbon dioxide level (5%), a device for in vitro culture of tissues, cells, and bacteria. There are two types of commonly used carbon dioxide incubators: air jacketed and water jacketed. Carbon dioxide incubators have two basic requirements: one is the requirement

The carbon dioxide incubator provides the most accurate and stable control of temperature, carbon dioxide concentration and humidity for the progress of its research work. Second, it requires the carbon dioxide incubator to effectively prevent microbial contamination in the incubator and eliminate pollution regularly. To protect research results and prevent sample loss.

1 Basic working principle of carbon dioxide incubator

The temperature of the water jacketed carbon dioxide incubator is heated by the water in the water jacket of the heating wire, and then the temperature change is detected by the temperature sensor inside the tank, so that the temperature in the tank is constant at the set temperature. The heating of the gas-capped carbon dioxide incubator is directly heated by the heaters in the gas jacket of the tank, which is also called direct heating on six sides. Compared with the water jacket type, the gas-sleeve type has the characteristics of quick heating and rapid recovery of the temperature than the water-type incubator, which is particularly advantageous for short-term cultivation and the need for frequent switching of the door. The temperature inside the box is generally set at about 37 °C. The concentration of carbon dioxide in the carbon dioxide incubator is controlled by a carbon dioxide concentration sensor. The carbon dioxide sensor is used to detect the concentration of carbon dioxide in the tank, and the test result is transmitted to the control circuit and the control device such as the solenoid valve. If the concentration of carbon dioxide in the tank is detected to be low, the solenoid valve is opened and the carbon dioxide enters the tank.

Inside, until the carbon dioxide concentration reaches the set concentration, the solenoid valve is closed and the carbon dioxide in the tank is cut off to reach a steady state. The carbon dioxide sampler samples the carbon dioxide and air mixed in the tank to the sampling port on the external panel of the machine to detect the concentration of carbon dioxide at any time by using a carbon dioxide concentration meter. At present, most carbon dioxide incubators generate moisture through the evaporation of the humidification disk (the relative humidity level is about 95%, but the humidity recovery rate is very slow after opening the door). Because the humidity evaporation area is larger, it is easier to reach the maximum relative saturation humidity and the recovery time after the door is opened is shorter. Therefore, the incubator with a large evaporation area is easier to maintain than the incubator with a small evaporation area.

Hold the maximum relative saturation humidity.

2 Be sure to prepare for use before use

The carbon dioxide incubator should be used by a special person. Do not twist any switch and adjustment knob on the operation panel once it is fixed, so as not to affect the temperature, carbon dioxide concentration and humidity fluctuation of the box, and reduce the sensitivity of the machine. Place the box horizontally, avoid direct sunlight and dust, etc., to ensure that the airflow around the instrument circulates, leaving a clearance of 5 cm on the rear and sides. Install a regulated power supply to ensure that the power supply voltage fluctuation does not exceed 220 V ± 10%. The water to be added must be distilled water or non-ionized water to prevent the mineral deposits from corroding in the water tank. Always check whether the water in the tank is sufficient. The water level should be added until the “water level indicator” is turned off. Use a sterile alcohol or iodine solution in the front box to thoroughly scrub to prevent other micro-production

Material pollution caused the experiment to fail. Install air conditioning in the room to keep the ambient temperature around 25~C. The carbon dioxide used must be pure, otherwise the sensitivity of the carbon dioxide sensor and the contamination of the carbon dioxide filter unit are reduced.

3 Proper inflation to extend the life of the CO2 sensor

The pressure in the carbon dioxide incubator is controlled by a carbon dioxide gas sensor. Normal feedback of carbon dioxide sensor requires intake pressure to Medical Equipment Vo1.22, No. 4 0.06 MPa. When the air pressure in the box is lowered, the carbon dioxide sensor is rhythmically opened and closed under low-pressure stimulation, and is slowly inflated into the tank. When the intake pressure reaches 0.1 MPa, the adjustment is automatically stopped. If the inflation method is improper, the intake pressure will increase, and when the pressure exceeds 0.1 MPa or even 0.2 MPa, the carbon dioxide sensor will be damaged. At the beginning of this damage effect is not obvious, it is not easy to detect, repeated error operation, the carbon dioxide sensor damage accumulation eventually fatal damage, making the air pressure regulation malfunction. Therefore, the life of the carbon dioxide sensor is related to the size of the carbon dioxide intake pressure. As long as the intake pressure is adjusted, the performance of the carbon dioxide sensor can be protected. Carbon dioxide sensors are expensive and difficult to replace.

It is necessary to adjust the intake pressure to extend the service life of the carbon dioxide sensor.

4 Pay attention to the incubator humidity when doing culture

The humidity inside the box is a very important but often overlooked factor for the training work. Because the saturated humidity environment can avoid the escape of carbon dioxide in the culture solution, the pH value in the culture solution is stable, which is good for cell growth, sufficient humidity level and fast enough humidity recovery speed (such as after opening and closing the door) to ensure that it will not be excessive. Drying causes the culture to fail. Therefore, during the use of the carbon dioxide incubator, a certain amount of sterilized water (3/2 to full plate) is placed in the tray inside the box to make the inside of the box a saturated humidity environment. If the user forgets to add water, so that the cultured cells are in low humidity or even dry heat environment, the carbon dioxide gas in the culture liquid is volatile, the pH value of the liquid rises, affecting cell growth, and efforts should be made to avoid this problem in the work. When the sample is used for a long time, the box is stored in the compartment, and the culture is stored in a basket or a porcelain plate, so that the access is fast, the opening time is shortened, the gas and humidity in the box are reduced, the gas is saved, and the cell growth environment is stabilized.

5 Preventing contamination of carbon dioxide incubator Doing pollution in the tank to disinfect carbon dioxide incubator is a major factor leading to cell culture failure. Therefore, to reduce and prevent pollution, the main way is to minimize the area and surface where microorganisms can grow and take disinfection measures. . For example, for the problem of bacteria in the hot and humid environment inside the box, we use 2 mL of neostigmine solution in 1000 mL of water, regularly disinfect the air inside the box with alcohol and ultraviolet light, and wipe the water in the box with the culture alcohol. The water in the dish should be at least one week. Change once, control pollution, maintain the adaptive evaporation, reduce the rate of microbial growth in the box. In order to protect the tank from contamination and to ensure bio-cleanability in the instrument cabinet, some carbon dioxide incubators are designed with automatic decontamination devices to effectively prevent contamination. There are a variety of sterilization methods, such as CO2 incubators with UV disinfection. Other designs and production of HEPA filters can filter the air inside the incubator, can remove 99.97% of the particles above 0.3/an, and also design the environment to achieve high temperature and heat inside the box to kill Deadly contaminated microorganisms, incubators for sterilization purposes.

6 Monitoring of zero drift of carbon dioxide incubator and adjustment of zero point During the use of the incubator, the carbon dioxide zero will naturally drift. This phenomenon cannot be expressed in the box gas display box, and the user is not easy to perceive the drift result. Whether the zero point of carbon dioxide drifts, the carbon dioxide gas tester can be used to collect the gas in the incubator from the sampling port on the control panel, and then the carbon dioxide concentration can be measured by the gas chromatograph. The step of adjusting the zero point of the carbon dioxide incubator (usually zeroing with air as the standard, once every six months, taking the Thermo3111 as an example):

(1) Set the carbon dioxide concentration setting to zero in order to prevent carbon dioxide from entering the tank.

(2) Open all the doors for 5 min, add water to the basin, close all the doors, and stabilize for more than 12 h.

(3) After the isothermal humidity is fully stabilized, observe whether the carbon dioxide concentration display value is zero. If it is not zero, correct it to zero (by Mode)

Press the key to the Cal file, press the left button or right button to select “C02 CALX.X”, use the up or down button to adjust the value to zero, then press the Enter button to confirm).

(4) Re-set the carbon dioxide concentration setting (for example, 5.0%).

(Article source: Medical Equipment 2009 No. 4 29 Wang Chuanzheng )