Production of imported large precision PE atomic absorption hollow cathode lamps

PE atomic absorption hollow cathode lampUsage:

It is a large precision instrument, and the laboratory should always pay attention to the changes of the hollow cathode lamp when using this instrument.

1. Discrimination of Normal Operation of PE Atomic Absorption Hollow Cathode Lamp

Most hollow cathode lamps are filled with neon gas, while a few lamps are filled with argon gas. After being powered on, any normal hollow cathode lamp should have a clear orange meridian light when observed from the brightness tone of the lamp filled with neon gas; A lamp filled with argon gas should emit purple light. If the neon lamp emits pink or even white light, and the argon lamp emits white light, it indicates the presence of impurity gases in the lamp and should be treated with degassing.

A normally functioning hollow cathode lamp should emit light inside the hollow cathode. If the cathode port and anode emit light, it indicates that the polarity of the lamp pins is incorrect or reversed.

2. Selection of Current for PE Atomic Absorption Hollow Cathode Lamp

The atomic absorption spectrophotometer uses pulsed square wave power supply. Therefore, the lamp current displayed by the instrument is the average value rather than the peak value of the lamp power supply. For the same average current value, the peak current size is related to the duty cycle of the pulse power supply. Duty cycle refers to the ratio of the duration of a pulse power supply to the entire cycle.

The duty cycle of the square wave pulse in an atomic absorption spectrophotometer is 1:5. The peak value of the lamp current can be estimated using the above method. Because the duty cycle is 1:6 (i.e. duty cycle 1:5, which refers to the ratio of the power on time to the power-off time during one cycle of pulse power supply). If the current value is set to 2mA, the peak current of the hollow cathode lamp is approximately 12mA. Therefore, for this type of instrument, the selected lamp current value (i.e. average value) should be appropriately small. Choose approximately one-third of the current value when powered by DC.

The general principle for selecting the current of PE atomic absorption hollow cathode lamp is that it should not be too high to avoid the influence of spectral line self absorption on the analysis results; It should not be too small to avoid unstable light emission. But under the premise of sufficient energy and high signal-to-noise ratio, it should be as small as possible. By improving sensitivity, expanding the linear range, and extending the service life of the lamp.

*The current value of the hollow cathode lamp should be determined based on the actual analysis and measurement results.

3. When adjusting the lamp position to find the maximum energy value of the lamp, attention should be paid to using an orange red spot to deviate from the center position of the monochromator entrance light bar in order to reach the maximum energy value. This is due to the hollow cathode of the lamp not being aligned with the center of the light window during manufacturing. This situation does not affect the use.

4. The degassing process

The polarity of the pins of PE atomic absorption hollow cathode lamps is uniform. For lamps with abnormal glow color tone and impurities in the lamp, degassing treatment (i.e. reverse connection treatment) should be carried out. The method is to connect the cathode of the lamp to positive and the anode to negative, and apply 20mA of electricity until the glow color is normal.