Why is fluorescence a more sensitive technique than absorption?

Answer 1

Answer- Flames in atomic emission are more sensitive to flame instability because optimum excitation conditions vary widely from element to element. High temperatures are needed for excitation of some elements and low temperatures for others. The region of flame that gives rise to optimum line intensities varies from element to element. Flame is rarely use in atomic emission because atomization is more complete when using a plasma due to the production of high temperatures. Also the plasma helps reduce the ionization interference effects. In flame absorption, after the sample is nebulized by a flow of gaseous oxidant, mixed with a gaseous fuel and carried into the flame it is then atomized. Then some of the atoms in the gas ionize to form cations and electrons. In flame emission the sample is introduce with argon, carries the sample into the flame. The flame is suppose to atomize the sample, while the flow of gas takes the ions and electrons to be detected.

Answer 2

Okay either this question is just a coincidence or you are in my lab methods II class but ... Imagine your on a football field in the dark and theres a bunch of people with flashlights on, and one person turns theirs off, you might be able to tell where that person was but it would be difficult (absorption). On the other hand if you're on a dark football field and everyone has their flashlights on, if one person turns theirs on you can easily find them (fluorescence). So basically fluorescence is more easily detectable making it more sensitive than absorption.

(metaphor courtesy of Dr. Louise Sowers)

Bald daddies are awesome!

Answer 3

AAS is more sensitive because it excites more atoms from the ground state to excited state compared to AES. It does this by using the specific wavelengths of electromagnetic radiation that a certain element absorb at (the wavelength an element absorbs reflects the energy needed by the electrons in the outer shell of that element to make the appropriate jump to an excited state).

AES on the other hand just heats the metal in a flame and records the characteristic wavelengths of electromagnetic radiation that element emits as the excited electrons move back down from different excitational states to their relaxed (ground) state.

Answer 4

Atomic emission spectroscopy is less sensitive than atomic absorption spectroscopy as the background emission from flames and the sample matrix leads to interference in atomic emission spectroscopy.

Answer 5

It is not a generale rule.