Liquid chromatograph common fault problem processing method

The liquid chromatograph is a commonly used analytical instrument that can be used to separate and analyze the identified mixtures. The products are widely used in many industries.

The liquid chromatograph is a commonly used analytical instrument that can be used to separate and analyze the identified mixtures. The products are widely used in many industries. The liquid chromatograph also has certain fault problems in use, which will have certain influence on the user's use. Today we will introduce and explain the common faults and treatment methods of the liquid chromatograph, hoping to help users better apply the product.

1, 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 enters the mobile phase. 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.

2, peak area repeatability is not good

(1) The injection valve leaks;

(2) The sample needle is not in place.

(3) Insufficient liquid volume. Handle the injection valve gasket for the first case; for the second case, ensure that the needle is inserted to the end, and the sample solution must be quickly and smoothly switched from the LOAD state to the INJECT state after the injection of the sample solution to ensure The injection volume is accurate. In daily work, the maintenance of the liquid chromatograph is very important. If you are careful not to let the air enter the infusion system and the high pressure pump, the solution in the reservoir should be cleaned and replaced with a solution if it has not been used for a long time. After the chromatograph is finished, the buffer should be rinsed with pure water to prevent precipitation or deposition of inorganic salts. The pretreatment of the sample is also important. Any sample should be removed as much as possible, completely dissolved, and the contamination of the column should be minimized. Extend the service life of the column while avoiding the injection of the concentrated sample solution to prevent the residual liquid from clogging in the injection valve. The column is marked and the column for different analysis purposes should not be mixed.

3, high column pressure reasons

(1) a buffer salt such as (ammonium acetate or the like) is deposited in the column;

(2) Sample contamination deposition. For the first case, first use 40~50°C pure water, and rinse the column at a low speed. After the column pressure is gradually decreased, the flow rate is 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). (The length of the rinsing time is determined by the contamination of the sample), then rinsed with methanol, then rinsed with pure water, and finally the methanol rinse is rinsing the column for more than 30 minutes.

4, 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 gasket; for the second case, use a 50 ml glass syringe to help extract air at the pump outlet while the pump is acting.

5, 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 a foreign object between the check valve and the valve seat, remove the check valve and put it into the beaker containing acetone for ultrasonic cleaning.

6, the peak is not good, 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) (depending on the contamination of the sample) Rinse with 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 the 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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