Question

Explain how the following background correction techniques work: (a) beam chopping: (b) deuterium lamp; (c) Zeeman.

Short answer

a)A beam chopper alternately exposed and blocked the light to the flame and detector. The signal is created by the backdrop when the bulb is obscured. When the light is switched on, the background signal is added to the signal from the analyte. The difference between these two is the needed analytical signal.

b)The furnace or flame is alternately exposed by the deuterium lamp and the hollow cathode lamp. Light from the deuterium lamp is absorbed by the background, but light from the hollow cathode lamp is absorbed by the analyte plus background. The difference between these two is the needed analytical signal.

c) When the magnetic field is parallel to the viewing direction applied to the furnace, the analytical signal is split into two. Because of its polarisation, the component at the analytical wavelength is invisible. The wavelength of two more components is incorrect. When a magnetic field is introduced, the Analyte becomes "invisible" to the detector, leaving just the backdrop visible. Without a field, the corrected signal is visible, however with the field, it is visible.

Step-by-step solution

Definition of wavelength.

The distance between any two successive identical spots on the waveform is denoted as the wavelength.

The working of beam chopping.

a)

The light was alternately exposed and blocked to the flame and detector by a beam chopper. When the bulb is obstructed, the signal is caused by the backdrop. When the light is turned on, the signal from the analyte plus the background. The required analytical signal is the difference between these two.

The working of deuterium lamp.

b)

The deuterium lamp and hollow cathode lamp alternately expose the furnace or flame. The background absorbs light from the deuterium lamp, whereas the analyte plus background absorbs light from the hollow cathode lamp. The required analytical signal is the difference between these two.

The working of Zeeman.

c)

When the magnetic field supplied to the furnace is parallel to the viewing direction, the analytical signal is split in two. Because of its polarisation, the component at the analytical wavelength is not visible. Two more components have the incorrect wavelength. When a magnetic field is applied, the analyte is "invisible" to the detector, and only the background is seen. Without a field, the corrected signal is detected, less the signal that is observed with the field.