Atomic absorption spectroscopy (AAS) features which of the following?

• A. Light source: hollow cathode lamp; Atomizer: converts ions to atoms; Chopper: pulses light; All of the above
• B. Light source: deuterium lamp; Atomizer: warms sample; Chopper: modulates beam; None of the above
• C. Light source: hollow cathode lamp; Atomizer: converts atoms to ions; Chopper: pulses light; None of the above
• D. Light source: LED lamp; Atomizer: converts ions to atoms; Chopper: pulses light; All of the above

Answer: (D)

In atomic absorption spectroscopy the key parts are a light source that provides sharp, element-specific lines, an atomizer that creates free atoms from the sample, and a means to modulate the light signal to improve measurement accuracy. The standard light source for AAS is a hollow cathode lamp, which emits the characteristic line(s) of the element being measured. The sample is atomized in a flame or graphite furnace, producing ground-state atoms that can absorb the lamp light; the atomizer’s job is to generate those atoms, not ions. To reduce noise and drift, some instruments use a chopper to pulse the light so the detector can perform rapid on/off comparisons and improve background correction. While deuterium lamps are used for continuous background correction in some UV regions and LEDs are explored for certain elements, they are not the typical primary light source in AAS, and ions are not the form that atoms are in during absorption. So the most accurate description emphasizes hollow cathode lamp as the light source, atomization into atoms, and beam modulation by pulsation of the light.