Diagnosis and Maintenance of Common Failure Phenomenon in Atomic Absorption Spectrophotometer
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Check whether the fuse is loose or blown first. Then check the power cord for open circuit or poor contact. Normally, the insulation resistance between the power supply line and the chassis should be greater than 20 MΩ.
Second, the failure phenomenon: hollow cathode lamp does not shine.
It may be that the lamp power supply is broken or not turned on; the lamp wiring is disconnected or the lamp head is in poor contact with the lamp holder. Check the lamp power supply, connection, and related connectors separately.
Third, the phenomenon of failure: hollow cathode lamp flashover discharge phenomenon.
This is the cause of oxide or impurities on the cathode surface of the lamp. The lamp current can be increased to a dozen milliamps until the spark discharge stops. If it is not valid, you need to change the lamp.
Fourth, the phenomenon of failure: hollow cathode lamp glow color is not normal.
This is an impure gas in the lamp. The power can be reversed at operating current until the glow color is normal.
Fifth, the failure phenomenon: the output energy is too low.
It may be that the wavelength is out of tolerance; the cathode lamp is aging; the external light path is not correct; the lens or monochromator is heavily contaminated; the gain of the amplifier system decreases. If the output energy is low in the short wave or part of the wavelength range, check the failure of the light source and the light path system. If the output energy is reduced in the full wavelength range, it is important to check whether the photomultiplier tube is aging or not, and whether the amplifier circuit has a fault.
Six, failure phenomenon: electrical zero is not good This may be caused by the following reasons:
1, cathode lamp aging. Replace the new lamp.
2, waste liquid is not open,
3, atomization indoor water. Should be ruled out in time.
4, gas instability, so that the measurement conditions change. Gas can be adjusted to meet the conditions.
5. There is dirt on the surface of the cathode lamp window and the quartz window or the condenser lens on both sides of the burner. Check one by one to clear.
6, the capillary is too long. Excess capillaries can be cut off.
Seven, failure phenomenon: low sensitivity.
May be caused by
1. Cathode lamp operating current is large, resulting in broadening of the spectral line and self-absorption. In the case where the light source emission intensity meets requirements, a low operating current should be used as much as possible.
2, atomization efficiency is low. If the pipe is clogged, the flow of scavenging gas can be increased, and the nozzle can be blocked by hand to open it. If the relative position of the impact ball and the nozzle is not adjusted properly, it should be adjusted to the best when the mist is smoke-like liquid particles.
3. The ratio of gas to oxidizer is not properly selected. The ratio of gas to oxidizer gas is generally less than lean flame, and intermediate and intermediate flames are greater than flames.
4, the burner and the outer light path are not parallel. The optical axis should pass through the center of the flame, and the slits should remain parallel to the optical axis.
5, analysis of spectral lines did not identify. A more sensitive resonance line can be selected as the analysis line.
6. Samples and standard solutions are contaminated or stored for too long. Rinse the container immediately and reconstitute it.
Eight, fault phenomenon: poor stability.
May be caused by
1, the instrument damp or warm-up time is not enough. Use hot air blower to remove moisture or preheat for a specified time before operation.
2. The pressure of gas or oxidant gas is not stable. If it is not caused by insufficient gas source or pipeline leakage, a valve control switch can be added to the gas source pipeline to stabilize the flow.
3, waste liquid flow is not smooth. Stop the inspection, clear or replace the waste pipe.
4, improper choice of flame height, resulting in abnormal changes in the number of atoms in the ground state, resulting in instability in absorption.
5, photomultiplier tube negative pressure is too high. Although increasing the negative high voltage can increase the sensitivity, there is a problem of large noise and poor measurement stability. Only by properly lowering the negative high pressure can the measurement stability be improved.
Nine, failure phenomenon: large background correction noise
1. The light path is not adjusted to the best position. Re-adjust the position of the xenon lamp and the hollow cathode lamp so that the two spots coincide.
2. The pressure is too high. Decrease the energy of the xenon lamp appropriately and increase the width of the slit when the analysis sensitivity allows.
3, the atomization temperature is too high. Appropriate atomization conditions can be selected.
Tenth, failure phenomenon: calibration curve linear difference
1. The aging of the light source lamp or the use of a high lamp current results in the weakening or widening of the analytical line. Replace the light source lamp or turn down the lamp current in time.
2. The slit is too wide, making more than one analytical line passed. The slit can be reduced.
3, the concentration of the sample is too large. Due to the disproportionate ground-state atoms generated by the high-concentration solution in the atomizer, the calibration curve is curved. Therefore, it is necessary to narrow down the range of measured concentrations or to use analytical lines with lower sensitivity.
Eleven, failure phenomenon: high detection limit
1, the scale expansion is not enough. Should be expanded to a suitable value.
2. The integration time is too short. Can be lengthened to an appropriate value.
3, the analysis sensitivity is low. Analyze and solve the problems one by one according to the previous troubleshooting methods.
4, capillary blockage or aging corrosion. The capillary should be cleaned or replaced.
5. The gas path is unstable. Check whether there is any problem such as air leakage or water in the gas system; check if the gas source is stable.
XII. Failure phenomenon: This phenomenon occurs when tempering occurs. The speed of the air flow is less than the burning speed. It is extremely easy to cause fire and explosion during tempering. Therefore, in the event of a sudden power outage or failure of the oxy-fuel gas compressor, and when it is found that the effluent discharge pipe seal is not good or the safety plug in the spray chamber is loose, or if the gas path is not replaced for a long time and aging occurs, it should be immediately shut down. Gas gas path to ensure the safety of people and property. Then return the instrument's control switches to their pre-open state and check the cause of the tempering.