The GC column is the core of the gas chromatograph, so the use, maintenance and maintenance of the column is very important. This article mainly introduces the knowledge about the GC column.
First, the installation of gas chromatography column
First of all, of course, the installation of the column. Installation of the column can be said to be an entry-level operation for gas chromatography, and everyone is generally familiar with it. However, there are a few issues that still need to be brought to the attention:
1. Put the gasket on the column head first. At this time, the column head should be facing down to prevent the gasket debris from entering the column and causing blockage.
After the graphite pad is placed over the column head, the column head should be cut off 1-2 cm. Special column cutters can be used. It can also be opened with AMB bottles, scratched on the column, and then cut off. This ensures that the end of the column is clean and avoids interference with the analysis of the stigma contaminants, as it removes contaminants that may enter the stud when passing through the seal, or the end of the column that may be damaged during transport.
2, the length of the column end protruding from the seal different instruments have different regulations, should be determined in strict accordance with the instrument manual.
The general principle is that after one end of the inlet is installed, the column end should be above the diversion point and be in the center of the liner. At one end of the detector is the column outlet as close as possible to the detection point to avoid extra-column effects caused by dead volume. In order to ensure the length of the end of the column is accurate, after the end of the column can be cut off, first measure the length of the column head, then mark the column below the joint, and tighten the street to ensure that the mark is located at the end of the joint. This avoids inaccurate protrusion lengths caused by column movement during tightening.
3. Do not screw the joint too tightly to avoid fracturing or crushing the column.
Generally, the new graphite pad is hand-tightened and then 1/4 turn with a wrench. If it is a repetitive graphite pad, tighten the point until it is pulled gently by hand. In principle, a new graphite pad should be used each time the column is installed. However, when the same column is removed and installed, the graphite pad can be reused, but the number of repeated use should not exceed 3 times, otherwise the sealing will be lost.
Second, the maintenance of the gas chromatographic column
Second, it is the maintenance of the column.
Aging is performed before each injection after each new column is installed. The general method is to increase the column temperature from 60 ° C at a rate of 5-10 ° C / min to 30 ° C below the maximum operating temperature of the column, or 30 ° C above the actual analysis operating temperature, and thermostat at 30-120 min at high temperature until The recorded baseline is stable. If the baseline is difficult to stabilize, it can be repeated several times of programmed temperature aging, or it can be constant for a longer period of time at high temperatures. Note that you must wait until the baseline is stable before doing a blank run or sample analysis. After the column has been used for a period of time, some high-boiling components will remain in the column. At this time, the baseline may have fluctuations or ghost peaks, and the aging method can also be used to solve the problem.
After the unused column is removed, the ends of the column are blocked with silica gel and stored in a box to avoid contamination. The oven temperature should be reduced to below 50 °C before each shutdown, and then the power and carrier gas should be turned off. Cutting off the carrier gas at high temperatures may cause air to diffuse into the column and cause oxidative degradation of the fixative.
Third, the simple maintenance of the GC column
Finally, let's talk about the simple maintenance of the column, which is how easy it is to block the block.
Generally, the column is aged first. If it does not work, the column can be removed, the column head can be cut off 10 cm or longer, and the test is installed. If it still does not work, it can be washed by repeated injection of solvent. The common solvents are acetone, methanol, ethanol, chloroform and dichloromethane. If it still does not work, the column may have failed and needs to be scrapped.
(content source gas chromatography home)
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