Aas (1 Viewer)

[cutemouse]

Hello,

Conquering Chemistry doesn't mention anything about a standard solution with AAS, but Jacaranda and Chemistry Contexts both say that a standard solution is needed...

What is a standard solution for in AAS, and why is it necessary?

Thanks

 

[xiao1985]

I could only assume the standard solution is the Standards prepared to form a calibration graph. Since AAS can only ever determine aborbance, not concentration directly.

For eg, you make up 1.0, 2.0, 3.0, 4.0 and 5.0 ppm solution of Cu, and the AAS give you absorbance of 2, 4, 6, 8, 10 respectively. Now, should your unknown have an absorbance of, say, 7.6, you know the concentration of the unknown is 3.8 ppm.

 

[cutemouse]

Hey thanks for your reply... But he's what Conquering Chem says, it doesn't mention anything about a standard solution:

The experimental arrangement is shown in Figure 6.13. The sample to be analysed is fed into a flame which vaporises it and converts molecules and ions into atoms. The light source is a lamp that emits radiation of a wavelength which is absorbed by the element to be measured. A separate lamp is required for each element. The lamp actually produces the emission spectrum of the element to be analysed so there is an exact match of emitted and absorbed wavelengths. The light passes through the flame and into a prism or monochromator. The monochromator has a photomultiplier as detector. By rotating the prism (or grating) of the monochromator, light of different wavelengths can be focused on to the photomultiplier. By measuring the intensity of the light reaching the detector with and without the sample in the flame, the instrument calculates and displays a function called absorbance. Absorbance is proportional to concentration, so the measured absorbance can be used to calculate the concentration of the particular element being examined.

Thanks