Low-speed centrifuge selection and technical parameter determination method
Low-speed centrifuges are widely used in clinical medicine, radioimmunity, biochemistry, food hygiene, environmental protection and other scientific research fields. Today, I will introduce you to the desktop low-speed centrifuge for your reference. Due to the wide variety of products and the different occasions, we can't blindly choose the model when purchasing a desktop centrifuge. Generally, there will be a parameter index, use, speed requirement, capacity requirement, temperature control range and timing range before purchase. And different types of products, different parameter indicators. After determining the parameter indicators, we can test the parameters such as the maximum speed and temperature control of the machine to see if it meets the standard requirements.
The selection of low-speed centrifuges is mainly based on sample composition, rotational speed requirements, capacity requirements, and temperature control requirements.
First, the sample composition:
There are certain rules for the types of laboratory centrifuges used for samples of different compositions.
Second, the speed requirements:
The high speed of the laboratory centrifuge zui represents the separation capacity of the centrifuge, which is divided into the high speed of the main engine and the high speed of the rotor. The high speed of the host zui is not necessarily the high speed of each rotor.
Third, the capacity requirements:
Refers to the capacity of the centrifuge tube and the maximum number of centrifuge tubes that can be placed at one time.
Fourth, temperature control requirements:
Refers to the need to freeze when separating samples.
Five, precision control test:
Because the desktop low-speed centrifuge is a precision instrument, we generally test its control accuracy. We can test according to the accuracy of the medical device standard, including temperature control accuracy, time control accuracy, and speed control accuracy. There are also some special applications that require higher precision control for benchtop low-speed centrifuges, so we can test them according to our own precision.
6. Determination of the speed and centrifugation time of the centrifuge
The effect of centrifugal separation is not only related to the type of centrifuge, centrifugation method, centrifugal medium and density gradient. In actual operation, the determination of the speed and centrifugation time of the main centrifuge, the pH value of the centrifugal medium and the temperature are also crucial. .
(1) Centrifuge speed
The magnitude of the centrifugal acceleration depends on the rotational speed of the rotor and the radius of rotation of the particles. When describing the centrifugation conditions, it is often also expressed by the relative centrifugal force field. In actual work, the data of the centrifugal force field refers to the average value. That is, the centrifugal force field of the particles at the point in the centrifugation solution.
(two) centrifugation time
The centrifugation time varies depending on the centrifugation method. For differential centrifugation, it refers to the time when a certain particle completely settles to the bottom of the centrifuge tube; for iso-density gradient centrifugation, the centrifugation time refers to the equilibrium time at which the particle completely reaches the iso-density point; Time refers to the time when a well-defined zone is formed. For zone formation time or equilibration time required for density gradient centrifuges and equal density gradient centrifugation, the influencing factors are complex and can be determined after testing.
The settling time of the particles, also called the clarification time, refers to the time required for the particles to completely settle from the liquid level of the centrifuged sample to the bottom of the centrifuge tube. The settling time is determined by the particle settling velocity and settling distance.
(3) Temperature and PH value
In order to prevent agglomeration, denaturation and deactivation of the separated substances, in addition to the attention in the selection of the centrifugal medium, it is necessary to control the temperature and the centrifugal conditions such as the pH of the medium solution. The centrifugation temperature is generally controlled at about 4 degrees. For some enzymes with good thermal stability, centrifugation can also be carried out at room temperature. However, in the case of overspeed or high-speed centrifugation, the high-speed rotation of the rotor generates heat and causes an increase in temperature. Therefore, a refrigeration system must be used to keep the temperature within a certain range.
The pH of the centrifuged medium solution should be in the pH range where the enzyme is stable, and a buffer may be used if necessary. In addition, peracid or overbase may also cause corrosion of the rotor and other parts of the centrifuge and should be avoided as much as possible.