# Atomic absorption spectroscopy

#### gordda

I am having major trouble trying to figure the concentration of a substance that is given by the AAS. Here's the question:
To determine the iron content in a 'Milo' milk drink, a 5ml sample was diluted to 50ml. the absorption of the diluted solution and of several standard solution were measured using AAS.

What mass of iron would you consume by drinking 250ml glass of Milo?

It is given that the concentration of iron, in ppm, in the diluted milo is 2.57ppm hence the concentration of iron, in ppm, in the undiluted milo is 25.7ppm.

If anybody could work this out it would be greatly appreciated

Thanx:)

#### Borek

Mentor
V = 250 mL, C = 25.7 ppm - AAS doesn't mean anything here, you know the volume, you know the concetration, go ahead. The problem is that IMHO the formulation is stupid - ppm is mass of substance per mass of sample but mass of sample is not given. Assume density of water (1 g/mL).

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#### gordda

but i can't just use the forumla n=cv because i need to change ppm into mol/L. and i have no idea how to do that? how do u change ppm into mol/L.

#### Gokul43201

Staff Emeritus
Gold Member
gordda said:
but i can't just use the forumla n=cv because i need to change ppm into mol/L. and i have no idea how to do that? how do u change ppm into mol/L.

1 ppm means there's 1 gm of Fe in a million gms of milk. Convert the first number into moles (from the atomic wt of Fe) and the second into a volume (assuming the density as above), and you are done.

#### Borek

Mentor
There is no need for any conversions! You are asked about mass of iron so you don't need molar concentration for anything.

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#### Gokul43201

Staff Emeritus
Gold Member
Borek said:
There is no need for any conversions! You are asked about mass of iron so you don't need molar concentration for anything.
Ummm...yes; didn't look carefully. Still need to convert volume of solution into a mass, but that's the only one.

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