Liquid chromatograph is a commonly used analytical instrument, which is mainly composed of pump, sample introduction system, temperature control system, column, detector, signal recording system, etc. It is widely used in biomedicine, environmental chemistry, petrochemical, etc. In the field. Today we mainly introduce the five common fault problems and treatment methods of the liquid chromatograph, hope to help everyone.
1. High column pressure
(1) a buffer salt such as (ammonium acetate or the like) is deposited in the column;
(2) Sample contamination deposition. For the first case, use 40~50°C pure water first, and rinse the column at low speed forward. After the column pressure is gradually decreased, the flow rate will be increased accordingly. After the column pressure is greatly reduced, rinse with normal temperature pure water, then use pure The column was rinsed with methanol for 30 minutes; for the second case, the C18 column was contaminated by the deposition of the sample, and the column was rinsed back with pure water, then replaced with methanol, followed by washing the column with methanol isopropanol (4 6) (rinsing The length of time depends on the contamination of the sample. It is then rinsed with methanol, then rinsed with pure water, and finally the methanol rinse is flushing the column for more than 30 minutes. [1]
2, bubble overflow
There are bubbles in the mobile phase, the pump is turned off, the pressure relief valve is opened, the purg button is turned on, the degas is cleaned, the bubbles are continuously ejected from the filter, and the mobile phase is entered. No matter how many times the purge button is turned on, the continuously generated bubbles cannot be removed. The filter is immersed in a buffer such as ammonium acetate for a long time. The inside of the filter grows due to the growth of mold, forming a cluster of bacteria, blocking the filter. The buffer is difficult to smoothly pass through the filter, and the air enters the filter under the pressure of the pump. Mobile phase. The treatment filter is immersed in a 5% nitric acid solution and ultrasonically cleaned for a few minutes. The filter can also be immersed in a 5% nitric acid solution for 12 to 36 hours, gently vortexed several times, and then the filter is washed several times with pure water. Open the pressure relief valve, open the purge button to clean the degassing. If there are still bubbles emerging from the filter, continue to soak the filter in a 5% nitric acid solution. If there are no bubbles, the filter will emerge from the filter. The internal mold flora has been destroyed by nitric acid and the mobile phase can pass through the filter smoothly. Open the pressure relief valve, turn on the pump, adjust the flow rate to 1.0 ~ 3.0ml / min, rinse the filter with pure water for about 1 hour. The filter can be cleaned. Close the pressure relief valve and rinse with pure methanol for half an hour.
3, no pressure indication, no liquid flow
(1) The pump seal gasket is worn;
(2) A large amount of air bubbles enter the pump body. Treatment For the first case, replace the ferrule; for the second case, use a 50 ml glass syringe to help draw air at the pump outlet while the pump is acting.
4, pressure fluctuations, flow instability
Cause There is a foreign matter between the gem ball and the valve seat with air or check valve in the system, so that the two cannot be sealed. Pay attention to the amount of mobile phase in the treatment work, ensure that the stainless steel filter sinks into the bottom of the reservoir, avoid inhaling air, and the mobile phase should be fully degassed. If there is foreign matter between the check valve and the valve seat, remove the check valve and put it into the beaker containing acetone for ultrasonic cleaning.
5, poor peak, peak fork
(1) The column is contaminated;
(2) The stigma packing collapses. Treatment For the first case, first flush the column with pure water, then switch to methanol, then rinse the column with methanol isopropanol (4 6) (the length of the rinse time is determined by the contamination of the sample), then change Rinse into methanol, rinse with pure water, and finally rinse with methanol for more than 30 minutes. If the peak is still poor after rinsing, consider the second case. In the second case, unscrew the column head and check that the column packing is indented or collapsed. Remove the indurated part (contaminated packing), fill in a new packing, drop a drop of methanol, fill the packing, refill, press with a smooth stainless steel rod with the same inner diameter of the column, fill it again, drop the methanol, and then press it again. Once, until it is filled and filled. Rinse the column head with methanol, wipe the packing on the outer wall of the column, tighten the column head, and rinse with pure methanol for more than 30 minutes.
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