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Your location: Home > Related Articles > There are several points for QINSUN to interpret common troubleshooting methods of gas chromatographs-

There are several points for QINSUN to interpret common troubleshooting methods of gas chromatographs-

Author:QINSUN Released in:2023-05 Click:26

1. Incomplete separation

(1) Multiple peaks overlap and cannot be separated. Treatment method: reduce carrier gas flow, reduce injection volume, and lower column temperature. For those that can be completely separated after a while, it cannot be completely separated, which indicates that the fixer has been lost, the life of the chromatographic column is over, and the fixer needs to be replaced.

(2) The separation time is too long to flatten the peak of the late distillation. Solution: It can be solved by increasing the temperature of the column.

(3) The sensitivity of the detector is too low, so that low-content components cannot be detected. Treatment method: It can be solved by improving the sensitivity of the detector through the injection volume.

2. Irregular peak shape

(1) Tail peaks appear. Method ofTreatment: Use a strong polar fixer, eliminate support activity, and increase the column temperature to resolve the issue.

(2) A flat top or peak appears. Workaround: Solve the problem by reducing the injection volume and increasing the column temperature and carrier gas flow. Additionally, flat peaks also form when the amplifier input is saturated.

3. The influence caused by the detector

Taking TCD as an example, the thermal conductivity detector TCD uses the difference in thermal conductivity between the carrier gas and the measured gas to detect the difference in the bridge circuit. The equilibrium voltage is proportional to the concentration of the measured component to obtain the measurement of the measured component.

(1) The TCD detector is polluted and the baseline drifts or a staggered baseline appears, and high noise may occur.

(2) The resistance wireTCD thermal nce is blown and the baseline drops to zero.

(3) The power supply of the TCD is unstable and there are pulse interference spikes.

4. The influence of carrier gas

The carrier gas transports the analysis sample through the stationary phase, and the separated gas is discharged from the chromatographic column one by one by the carrier gas over time and sent to the detection of the detection part. Operating conditions such as carrier gas flow rate, nature of carrier gas and influence of carrier gas pressure will affect the chromatographic separation performance.

(1) If the amount is too small, the retention time will increase, the sensitivity will decrease, or round peaks and trailing peaks will appear.

(2) If the carrier gas flow is too high, it will cause high noise or component separation without carrier gas control instability, resulting in drift of the carrier gas.uneven baseline or wavy baseline drift.

In the above cases, check whether the pressure reducer exceeds the operating range. If necessary, replace the pressure reducer, then check for a carrier gas leak.

5. Circuit fault

Circuit faults are usually easier to judge, such as power supply does not start, detector and injection port do not heat up not, the thermostat cannot maintain the temperature, etc. wave in the baseline, it is caused by the failure of the amplifier circuit; the treatment method is usually to replace the damaged electronic components.

Other problems not discussed above will be encountered in the daily scan, such as the hydrogen flame detector does not turn on, first confirm if the is on and empty, then confirm if the ignition coil is working. If theIf all three conditions are met or if ignition fails, it may be due to an air leak at the joint between the detector and the chromatographic column; the polarity of the processor is reversed. In this case, first check the polarity of the instrument; if the injection volume does not match the integral area, the output signal line may be incorrectly connected.