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Shimadzu liquid chromatograph maintenance Daquan
First, the installation requirements of the instrument for the environment
1, power supply voltage (220V):
In the case of conditions, it is best to use lighting, this voltage is relatively stable, and the performance stability of the instrument is good. When there is no way, when power supply must be used, it is necessary to take corresponding measures to overcome or reduce The motor starts frequently and affects the grid voltage fluctuation when the operation is stopped (the motor is an inductive load, and the stop and start can generate a strong interference spike voltage). If the electrician is asked to separate the power transformer from the power line and the lighter wire to the laboratory, this can greatly reduce the interference to the instrument. When economically allowed, it is best to use an AC voltage regulator. In short, the voltage should not exceed 198V at the minimum, and the maximum is not more than 230V.
2. Requirements for the laboratory:
A. It is best to have dust-proof facilities in the room. When the instrument works, it generates a lot of heat and dissipates heat through the fan of the instrument. This makes it possible to bring the surrounding dust into the machine. Under the action of static electricity, it is attached to the circuit for a long time. Especially in the south, the rainy season is relatively humid, which may have adverse effects on the instrument work.
B. The requirement for laboratory temperature is that the temperature change is relatively small. In particular, the sun's rays should not be directed at the instrument, otherwise the instrument will be unstable. If bubbles are not visible to the naked eye in the mobile phase, the baseline stability deteriorates when entering the system. The temperature change of the column will change the retention time and have a certain influence on the analysis results. The stabilization time of the UV detector and the stability during operation are strongly related to the constant ambient temperature. When conditions permit, it is best to install an air conditioner. Note that the air conditioner should not be powered by the same line as the instrument.
C. Ground wire to eliminate interference. Improve the stability of the instrument and ensure personal safety.
Second, the high voltage constant current pump in the work of some common faults and troubleshooting methods (a total of six questions)
1. The pressure display value is high and low. The main reason for this phenomenon is that there are bubbles in the system. At this point, it is necessary to carefully check whether the valve under the infusion tube and the pump head is tightened, whether the PTFE tube has cracks, etc., because the liquid will generate a slight negative pressure when flowing, and the air will enter the system.
After checking the confirmation, turn the vent valve counterclockwise for about one turn, then press and hold the traversing button. At this time, the pump flows out from the venting valve at the highest flow rate, and the air bubbles flow out. This phase must be performed when the pump head has been cleaned or when the mobile phase has been replaced.
When the effect of this method is not good, the pressure cap of the valve on the main pump head can be loosened a little (about one-third of a turn) and the air bubbles in the check valve can be eliminated. When the instrument is newly purchased or not used for a long time, sometimes such a phenomenon occurs. When it is confirmed that the infusion tube is all normal, the above situation is also outdated, the effect is still not good, and the pump can be operated for a period of time to achieve the purpose. This is because the gem valve ball and the seat surface are not fully wetted by the mobile phase, and the sealing is not strict during the liquid absorption and drainage processes, and the backflow phenomenon causes the pressure and flow rate to be unstable.
For the mobile phase, full degassing (ultrasonic) is required. It is best to use the current degassing. Do not leave it for too long, otherwise the air will slowly dissolve into it. The bottle containing the mobile phase should not be exposed to direct sunlight. It is best to place it in a higher position (higher than the pump), but it is difficult for bubbles to enter the system (bubbles rise).
2. After the pump is running, the pressure is displayed as zero (ie no flow). If such a situation occurs, it is necessary to consider whether there is a problem with the operation method. If the infusion tube is connected to the inlet of the pump, whether the tube is filled with the mobile phase, whether the joint is tightened, whether the filter head is blocked, or whether it is inserted into the mobile phase. It is also possible to withdraw the liquid from the outlet of the vent valve by means of a syringe or the like. Also, when the infusion tube is transferred from one mobile phase bottle to another, it must be noted that the pump should be stopped and the pump must be stopped during operation.
3, constant flow pump leakage: divided into two parts
a. When the mobile phase flows out from the flushing pipe of the main and auxiliary pump heads, most of the reasons are that the inner wall of the sealing ring is dirty, and the gemstone is attached with dirt to cause leakage. At this time, the liquid leakage can be eliminated after cleaning. If the leakage phenomenon is not serious and the retention time has not changed, it can continue to be practical, but it should be processed in a short time. The mobile phase must be filtered to remove minute impurities (which are difficult to distinguish with the naked eye). If the filter used for filtration is of poor quality, flocculation may occur in the mobile phase. For a long time, when it is attached to the seal ring or the gemstone, it may cause liquid leakage. If the buffer is used, it will not be washed or rinsed after the work is not complete. The crystal salt will cause the pump to leak due to the wear of the seal ring and the gemstone, which cannot be repaired. Therefore, it is necessary to rinse after use. Before the flushing is completed, the mobile phase in the flushing tube of the pump head is flushed with a syringe. The constant current pump takes a long time, and when the normal wear and tear occurs, the corresponding parts need to be replaced.
b. The mobile phase leaks from the connection between the pump head and the pump body. The gasket between the pump head and the pump body is made of PEEK material. Due to long-term high pressure and low pressure (normal pressure), the elasticity is reduced and the sealing performance is poor. Another reason is that repeated cleaning of the pump head can cause liquid leakage. However, this phenomenon rarely occurs. You can use an Allen key to evenly tighten the two screws, no leakage.
4. The pressure display (pre-column pressure) is too high. The factors are as follows:
A. The sintered stainless steel mesh in the in-line filter is blocked and the resistance is increased. The mobile phase is not ideally treated or the bottle is unclean and formed over a long period of time. If the column is removed, the normal pressure will be zero, and the pressure can rise to more than 20Mpa after blocking. At this time, a layer of dirt on the inlet surface of the stainless steel mesh can be seen, and 6%--10% nitric acid solution can be used. Ultrasonic cleaning can be performed in 20 minutes.
B. The injection valve is blocked and the pressure display is increased: the material of the injection valve rotor is relatively soft, and the analyzed sample is improperly processed (with particles), and the channel is blocked for a long time. The powder generated by the friction between the rotor and the stator, the surface of the injection needle can be cleaned, causing the rotor and stator to wear and leaking when it is severe. The column is removed, and the valve outlet (connected to the column end) flows in a linear manner (flow rate is above 1 ml/min). If it is one drop and one drop outward, the hole is blocked and ultrasonic cleaning is required.
C. The pressure of the column itself increases: the column is used for a long time, and the pressure will rise to different degrees. This is normal. When the sample being analyzed has not been treated (filtered), for a long time, the magazine will accumulate on the screen at the end of the column (sintered stainless steel) causing an increase in pressure. Judgment method: remove the column, the pressure shows zero, otherwise you should consider the column has a problem. Solution: Remove the screen ultrasonic cleaning.
D. The UV detector tube or the blockage of the cell body causes the pressure to rise. The main reason is that the column with poor quality is selected, and the pipe outflow blocks the pipe. The solution to the problem is ultrasonic cleaning.
Note: The basic inspection steps for the pre-column pressure display are too high:
1. Remove the column and observe the pressure display. If zero is not displayed, the problem may appear on the injection valve or on the line filter.
2, remove the injection valve, not showing zero, you can conclude that the problem appears on the online filter.
E, the flow setting display, sometimes rises to 4.99ml / on its own, in three cases:
1. The direct cause of this situation is that the power supply voltage is too low for too much time, causing the circuit to work abnormally. If the power supply and the power line are the same line, the motor or the device with a large load starts and stops, and the instantaneous current is large, causing the voltage to drop, which causes the above phenomenon. It is best to use the lighting power to supply power, if necessary, use an AC voltage regulator for voltage regulation.
2. If the above situation caused by low voltage is excluded, it is likely to be a problem of the instrument itself. The internal power supply voltage is reduced due to component damage or poor performance. At this time, professionals are required to perform the test.
3. The panel film setting button is used for long-term use to make the contact surface concave, resulting in poor contact results.
F, the constant current pump starts and stops working, and it is divided into three kinds of situations:
1. The running key and stop button on the constant current pump are repeatedly pressed and recessed for a long time, causing the internal contacts to be turned on and off due to slight vibration. This phenomenon can also occur if the lead end is dirty and causes leakage.
2. The instrument circuit itself is working abnormally, which is caused by good or bad time.
3, 220V power supply voltage instantaneously has a large interference pulse caused by this phenomenon. The above three conditions need to be carefully judged to confirm. In the first case, replace the new mask switch or wipe the lead strip conductive strip with alcohol cotton ball; in the second case, professional maintenance is required; in the third case, the power supply voltage needs to be improved. The quality of the lighting is powered by lighting. Do not share a power supply with a larger load.
Article source: Beijing Jingke Ruida Technology Co., Ltd.