I am detecting Ca with an AAS Method using an Perkin elmer AAnalyst800. The resulsts are satisfying. Nevertheless I have no Idea why I don´t have to use any kind of background correction, furthermore the flame is a bright yellow, which is due to the soium content of my samples. I have to add that my samples should be completely organic free.
You don't have to do background correction even in UV, there is no rule per se. Background correction is required when you have some idea beforehand that there will be an interference from your sample. For example, you run a certain standard with known concentration, and your concentration is significantly lower than expected. Chances are then, that there are other absorbing species being formed in the flame. In flame AAS, you monitor the absorption of very (very) specific wavelengths. Background correction becomes important when you are working with very short wavelengths since shorter wavelengths scatter more than longer wavelengths. Secondly, the chances of intereferences absorbing visible light, such as that coming from a hollow cathode lamp of Ca, are very low. If it were a short UV (Around 220 nm), background absorbance can be high.
It´s really that simple. I´m surprised because I though you needed background correction anyways - mostly because of interferences with glowing particles and scattering. Sadly none of the instrumental analysis works I´ve read gave a clear statement like your comment. with best regards Michael Wenzel
The backround correction of a deuterium lamp is effective in a range between 180 and 420 nm.
Micheal, The point you raise about glowing particles and scattering is correct. Imagine a high temperature flame (2700 oC). In a high temperature blue flame combustion is quite complete. You don't have to worry about particles and smoke. However, when your oxidant level is low, the so called yellow flame, you certainly have glowing particles but there is still no smoke. There is another technique called graphite furnace atomization. Instead of a flame, you electrically heat a small volume of the sample. Under these conditions, smoke can exist and background correction becomes compulsory.
It is true that scattering is lower at longer wavelengths and, therefore, correction will be less needed but there are still other types of background interferences such as products from the combustion of the flame combustible or concomitant species of the matrix, that can appear at low or high wavelengths, so I still have the doubt on why it is not required the correction at high wavelengths
- Badges
- Science topic
- Similar topics
- Chemistry
- Organic Chemistry