Copper has many world-wide applications from jewellery to the electronics indust

Question

Copper has many world-wide applications from jewellery to the electronics industry. AN atomic emission spectroscopy experiment is set up to determine copper concentration. The copper level is detected at 216.6 nm. In this experiment a blank sample with the same matric as standard and unknown samples provided an emission intensity of 0.5. A 5.00 ppm standard sample provided an emission intensity of 25.0. An unknown sample, treated the same way in the instrument, provided an emission intensity of 20.0. What is the concentration of copper in the unknown sample?

Explanation / Answer

This is a quantitative determination of Cu by Atomic emission spectroscopy. It is detected at 216.6nm.

Given data:

Blank sample intensity emission=0.5au       au: arbitrary units

Standard of 5.00ppm intensity emission=25.0au

Unknown sample intensity emission= 20.0au

Concentration (ppm) of Cu=?

In atomic emission spectroscopy the intensity of the emitted light is proportional to the number of atoms of the element.

First you have to subtrac the blank value to standard and sample:

Standard of 5.00ppm intensity emission corrected by lank=25.0-0.5= 24.5au     au: arbitrary units

Unknown sample intensity emission corrected by blank= 20.0-0.5=19.5au

Now you can calculate Cu concentration:

Cu concentration =Concentration of standard)(Intensity emission of sample)/Intensity emission of standard)

Concentration of Cu = (5ppm)(19.5au)/(24.5au) = 4 ppm Cu.

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