Gas chromatograph maintenance eight points introduction

The maintenance of the entire gas chromatograph mainly includes the following aspects:

1 , inlet maintenance standard test

The injection system, commonly known as the gasification chamber or sample port, is a special device that is set before the gasification of the sample into the chromatographic system and ensures that the system does not leak. The inlet is an important part of the instrument and the first pass to introduce pollution and cause interference. If the inlet is contaminated or not, the direct performance is the chromatographic characteristics. Prepare a standard for testing. It can be verified by the standard when it is not sure whether the inlet is contaminated.

2 , regular replacement of the injection septum

Leakage of the inlet septum is a common fault in gas chromatography. When the number of injections is too large, the needle of the injection pad wears out and ages, and it is easy to leak. Leakage on the one hand loses carrier gas, causing waste of resources; on the other hand, the aging degradation of the septum can also cause interference to the analysis, such as ghost peaks. Therefore, it needs to be replaced regularly and in time. Generally, the septum can reach the life of more than 100 times. Different manufacturers have different life spans, such as BTO low loss septum up to 400 times, and red silicone septum is about 100 times.

3 , timely cleaning the syringe

A clean syringe prevents interference with sample memory effects. Wash the sample when it is replaced. When using the same sample for multiple injections, clean the syringe with solvent and sample. Generally, use a solvent such as methanol, dichloromethane, acetonitrile, acetone or n-hexane to clean the needle. Push the rod, inject the cleaning solvent with another syringe, and insert the push rod to gently push the solvent out of the needle.

To thoroughly clean the syringe, it can be washed sequentially with the following solutions, 5% aqueous sodium hydroxide solution, distilled water, acetone, chloroform, and finally drained. It should not be washed with a strong alkaline solution. If it is found that the stainless steel oxide in the syringe affects normal use, a small amount of soapy water can be inserted into the syringe on the stainless steel core, and it can be removed by pulling it back and forth several times, and then cleaning it to avoid residual The sample is stuck to the core, causing the syringe to be scrapped.

Syringes are fragile instruments, so be careful when using them. Wash them when not in use. Do not pull them back and forth, especially if they are dry and dry, otherwise they will wear out seriously and damage their air tightness. , reducing accuracy.

4 , regularly check and clean the inlet and liner

After long-term use of the inlet liner, due to the residual non-volatile components in the sample, it will be found that there are tar-like substances in the liner, in addition to the accumulation of particulate matter, such as septum debris, solid matter in the sample. These will interfere with the normal conduct of the analysis. Therefore, check and clean the inlet and liner regularly. Generally, the cleaning is mainly washed with pure water, methanol or absolute ethanol or ultrasonic cleaning. The pollution can be wiped gently with a cotton swab. The force is not excessive, avoiding damage to the surface to produce active spots, and then drying in an oven at 70 ° C, cooling and sealing. Just fine.

5 , timely replacement of capillary column gasket

Seal gasket leakage is one of the most common faults in gas chromatography. Do not reuse the same seal on different columns, even if the same column is removed for reinstallation, it is best to replace it with a new one. There are three types of gaskets that are most commonly used: graphite, Vespel/graphite (85%/15%), Vespel, which have the highest temperature of use, but the mechanical strength and life are increased in turn, so it should be based on the material and wear of the gasket. Decide if you need to replace it.

6. Use a gas of a standard purity

The carrier gas should be of high purity to avoid interference with analysis, contamination, damage to the column and detector. Because of the relative carrier gas, the column and detector are more expensive, such as the price of a column is more than 20 times that of high purity nitrogen.

7. Regularly change the gas purifier packing

The purifier plays a large role in the gas phase carrier gas system and can help remove contaminated equipment from the gas source and impurities such as moisture, hydrocarbons, and oxygen that affect the analysis results. For the color-changing silica gel used for moisture removal, the performance can be judged according to the color change, and the purifier for adsorbing organic matter such as molecular sieve is not easily judged by the naked eye, and the general experience is changed once every three months.

8 , replacement parts must be carried out one by one

When repairing the inlet, do not replace multiple parts at once, which will cause a judgment error in the cause of the failure. One piece should be replaced at a time, and another piece should be replaced after the test, which may be more accurate.

(Content source Hengtianli Instrument Network)