Operation Tips for Gas Chromatography

1 heating

Due to the different manufacturers and quality of gas chromatographs, the methods of setting the temperature are also different. For setting the temperature using the microcomputer setting method or the dial selection method, it is usually to directly set the number or select an appropriate given temperature value to increase the temperature. And if you use the knob positioning method, there are techniques:

1.1 Over-temperature positioning method

Adjust the temperature control knob to about 30°C lower than the operating temperature. Warm up the gas chromatograph. When the temperature reaches approximately the operating temperature, it is equipped with a temperature indicator and a heating indicator light, and then gradually adjust the temperature control knob to the appropriate position.

1.2 Step-by-step positioning method

Turn the temperature control knob at an angle in the direction of heating. The temperature will start to rise and the indicator light will light up. When the temperature is basically stable, turn the temperature control knob in the same direction. Start to continue to heat up: adjust in this way until the constant temperature is at the working temperature.

2 Adjust the balance of the pool

Adjusting the balance of the pool is actually adjusting the balance of the thermal conductive bridge. To make it have a more suitable output, focus on adjustment skills. In fact, it is for gas chromatographs with adjustment functions such as cell balance, zero adjustment and recording zero adjustment.

Step 1:Use the cell balance or zero adjustment knob to adjust the recorder pointer to the appropriate position;

Step 2:Decay to about 16 times. Observe the movement of the recorder pointer;

Step 3:Use the record zero knob to adjust the recorder pointer back to its original position;

Step 4:Return to attenuation. Observe the movement of the recorder pointer;

Step 5: Use the zero adjustment or cell balance knob to return the recorder pointer to its original position.

3 ignition

The hydrogen flame gas chromatograph needs to be ignited when it is turned on, and sometimes it also needs to be ignited after it is turned off due to various reasons. However, we often encounter problems with ignition. Here are two ignition techniques for colleagues to try.

3.1 Increase hydrogen flow rate method

First increase the hydrogen flow, ignite the fire, and then slowly return to the working condition. This method is universal.

3.2 Method of reducing makeup air flow

First reduce the makeup gas flow, ignite the fire, and then return to the working condition. This method is suitable for using hydrogen as the carrier gas and air as the supporting gas and tail gas.

4. Adjustment of gas ratio

Flow ratio of three gases in hydrogen flame gas chromatograph. Relevant information suggests that: Nitrogen: Hydrogen: Air = l: l: 10. However, due to the inaccuracy of the flow rate indicated by the rotameter. In fact, who would be demanding this ratio? I think it is a good match for each Qi Jing. The purpose is to have both high detector sensitivity and good separation effect. It won't flame out easily. Based on the above principles, the gas ratio should be adjusted as follows:

(1) Adjustment of nitrogen flow

After the chromatographic column conditions are determined, the separation effect of sample components and the flow rate of nitrogen are the decisive factors when adjusting the nitrogen flow rate. Inject a sample to observe the separation of components. Until the nitrogen flow is as large as possible and the sample components are well separated.

(2) Adjustment of hydrogen and air flow

The adjustment effect of hydrogen and air flow can be tested by the size of the base flow. First adjust the hydrogen flow to make it approximately equal to the flow of nitrogen. Then adjust the air flow. When adjusting the air flow, observe the changes in the base flow. As long as the base flow is increasing, you should still adjust it in the opposite direction until the base flow no longer increases. Finally, increase the hydrogen flow a little.