Diluting for Atomic Absorption Spectroscopy

[d0minicz]

Hey I was just wondering why some samples are diluted in order to measure the absorbance of an element? Thanks

[polky]

They need to be diluted because sometimes it is too concentrated.  This would lead to an absorbance that is off the charts, and the calibration curve cannot be used to determine concentration because the absorbance value doesn't lie between the bounds of the calibration curve!

[d0minicz]

Thanks alot 
How would i find the mass of an element in xxxmL of something, given ppm and the volume of the undiluted sample ?

[Mao]

1 ppm = 1 mg / L

[dekoyl]

1 ppm = 1 mg / L

Which is the same as ppm = gram per million gram right?

[vce08]

1 ppm = 1 mg / L

Which is the same as ppm = gram per million gram right?

one is w/v whilst the one u talked about is w/w

[dekoyl]

1 ppm = 1 mg / L

Which is the same as ppm = gram per million gram right?

one is w/v whilst the one u talked about is w/w

Ah right thanks a lot. Just there was a bit of confusion in the other thread.

[/0]

1 ppm = 1 mg / L

According to Heinemann and wikipedia, 1 ppm = 1mg/kg

%w/v = gram per 100 mL

[shinny]

1 ppm = 1 mg / L

As table said, depends whether you want w/w or w/v. Because we tend to deal with solutions, the two are interchangeable as 1mL of water is 1g.
According to Heinemann and wikipedia, 1 ppm = 1mg/kg

%w/v = gram per 100 mL

[/0]

oh ok I understand

[d0minicz]

5.0 mL of Iron, diluted to 50.0 mL. In the diluted sample = 2.59 ppm, in the undiluted sample = 25.9 ppm.
What mass of iron would you consume in a 250 mL glass of drink ?
I need to see the steps, thanks heaps.

[Wizard]

I think that the question is wrong. It most likely should be
"5ml of a drink is diluted to 50ml. In the diluted sample, the iron has a concentration of 2.59ppm. What mass of Iron would you consume in a 250ml glass?"

If it was, i think this is how to do it: (pls correct me if im wrong)
2.59mg/L is the concentration of iron in the diluted drink.
= 2.59 x 10^-2mg x 5/50ml   (just to get it in terms of the 50ml)
The same number of grams of iron is present in both samples. Therefore,
0.1925mg/5ml of drink

In 250ml, there must be 50 times more iron.
Therefore, .1925 x 50 = 6.48mg of Iron in the drink.