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Chemistry Forums for Students => Analytical Chemistry Forum => Topic started by: Bob Sacamano on February 12, 2011, 03:28:38 PM

Title: AAS question
Post by: Bob Sacamano on February 12, 2011, 03:28:38 PM

Why do unique lamps have to be used in AAS determinations? Why couldn't you simply use white light?

I know the beam of light is that of the metal being analyzed, but why? Wouldn't the intensity of the light change if the light was not monochromatic and simply white light?

Title: Re: AAS question
Post by: Stepan on February 12, 2011, 11:02:11 PM

You are right, it can be done, but such modification makes it more expensive, and then it will not be able to compete with ICP, which uses similar technology.

Most AA's can be used in emission mode, where you do not need a lamp at all, but you loose sensitivity 10-100 fold.

Title: Re: AAS question
Post by: Bob Sacamano on February 13, 2011, 12:51:41 AM

So using a lamp that is specific to the metal being analyzed increases the sensitivity of the instrument?

Why?

Title: Re: AAS question
Post by: Stepan on February 13, 2011, 01:37:20 AM

Because it emits exactly the same line as the element that you need to detect. Thus you do not need any optical device at the source end of the instrument. You can achieve the same selectivity effect by using a sophisticated spectrometer at the source and another one at the detection end, but it will cost you a fortune.