Routine maintenance of the gel permeation chromatograph

1. Cleaning of gas pipelines, injectors and syringes.

When cleaning the gas connection pipe, the joints at both ends of the pipe should be removed first, and then the section of the pipeline should be taken out of the chromatograph, and the dust on the outer wall of the pipe should be scrubbed clean first, so as to avoid pollution when the inner wall of the pipe is cleaned. When cleaning the inner wall of the pipeline, it should be dredged with absolute ethanol first, which can remove most of the granular blockages in the pipeline and the organic matter and water that are easily dissolved by ethanol. In this dredging step, if it is found that the pipeline is not passable, you can use the ear wash ball to blow under pressure, and if it is still ineffective after pressurization, you can consider using a thin steel wire needle to dredge the pipeline.

This method can not make the pipeline unblocked, and the alcohol lamp can be used to heat the pipeline to carbonize the blockage at high temperature to achieve the purpose of dredging.

After cleaning the gas line with absolute ethanol, consider whether there are contaminants on the inner wall of the line that are not easily dissolved by ethanol. If not, the line can be heated and purged with dry gas, and the line can be installed back into the original gas circuit for later use. If it is determined that there may be other contaminants on the inner wall of the gas path that are not easily dissolved by ethanol during the analysis of the sample, other cleaning solutions can be selected according to the dissolution characteristics of the specific substance.

The order in which the cleaning solution is selected should be to use a high-boiling solvent first, followed by a low-boiling solvent for immersion and cleaning. The cleaning solutions available are naphthalene, N, N-dimethylamide, methanol, distilled water, acetone, ether, freon, petroleum ether, ethanol, etc.

Cleaning of the injector, including the vaporization chamber, should be preceded by dredging. Blockages that are typically found in the injector are fragments of the injection septum, carbonized high boiling points in the sample, and these solid impurities can be unblocked with a stainless steel poke needle before rinsing with ethanol or acetone. For a more thorough cleaning, 2:

The 1:4 H2SO4 HNO3 H2O mixture was washed with the injector, then with distilled water, and finally with acetone or ethanol. After cleaning, drying, install the instrument with carrier gas for half an hour, heat it to 120 hours, and work normally after a few hours.

Be careful not to break the heater leads or cause them to touch the housing when disassembling the injector; The temperature measuring element should also be installed back in the original temperature measuring point after it has been put back into the injector. Often, the temperature measuring element and the injector heater are in close contact, and too much distance will result in too high vaporization temperatures.

The syringe can be cleaned with acetone before use to avoid staining the sample, but it is best to clean the syringe itself once or twice with the sample to be injected. Only the sample should be aspirated during cleaning, and the sample should be discharged outside the vial. The syringe should be cleaned immediately after use to avoid contamination by the high boiling point of the sample.

Generally, the following solutions are commonly cleaned sequentially: 5% sodium hydroxide aqueous solution, distilled water, acetone, chloroform, and finally drained with a vacuum pump. The analysis and testing encyclopedia is happy to answer all kinds of questions encountered in the experiment for you, if you have any questions, you can find me, search up and down.

Gel chromatography can not only be used to separate and determine the relative molecular weight and relative molecular weight distribution of polymers, but also to separate fat-soluble and water-soluble substances according to the gel fillers used, and the relative molecular mass of the separation can range from several million to less than 100. In recent years, gel chromatography has also been widely used for small molecule compounds. Substances with similar molecular mass but different chemical structures cannot be completely separated and purified by gel permeation chromatography.

Gel chromatography cannot distinguish compounds of similar molecular size, and the relative molecular weight difference needs to be more than 10% to be separated.

Gel Permeation Chromatography (GPC) was first studied in 1964. It can not only be used for the separation and identification of small molecule substances, but also for the analysis of polymer homologues with the same molecular volume and different molecular volumes. (The polymers are separated on the separation column according to the volume of molecular fluid forces).