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#1
06-29-2012, 10:38 AM
 Unregistered Guest Posts: n/a
Calculating a solution from mg/l to mg/kg based on a solid or liquid

If I make a calibration curve with HPLC. On the X ax is mg/l and on the Y-ax is the area.

I dilute for example 0,5 gram solid or liquid in a 10 ml volumetric flask and make it up to volume with eluent. After some sample prep I inject the solution into the HPLC and found a area which has a concentration of 4 mg/l compared to the calibration curve. If we suggest that the slope goes through zero it makes a concentration of area unknown/slope.

After this I want to calculate the concentration in mg/kg. Am I right if I do it in this way.

Area/slope = concentration 4 mg/l absolute

But the sample weighted was in 10 ml volumetric flask so 1000 ml/10 = 100

4mg/l / 100 = 0.04 mg in 0,5 gram

1000 gram / 0.5 gram = 2000

2000*0.5 = 1000 mg/kg

Is this the right way to do it?
#2
06-29-2012, 01:26 PM
 Mrs X can't count, can't spell! Join Date: Feb 2006 Location: New Zealand Posts: 2,433 Rep Power: 12
Re: Calculating a solution from mg/l to mg/kg based on a solid or liquid

Quote:
 Originally Posted by Unregistered If I make a calibration curve with HPLC. On the X ax is mg/l and on the Y-ax is the area. I dilute for example 0,5 gram solid or liquid in a 10 ml volumetric flask and make it up to volume with eluent. After some sample prep I inject the solution into the HPLC and found a area which has a concentration of 4 mg/l compared to the calibration curve. If we suggest that the slope goes through zero it makes a concentration of area unknown/slope. After this I want to calculate the concentration in mg/kg. Am I right if I do it in this way. Area/slope = concentration 4 mg/l absolute But the sample weighted was in 10 ml volumetric flask so 1000 ml/10 = 100 4mg/l / 100 = 0.04 mg in 0,5 gram 1000 gram / 0.5 gram = 2000 2000*0.5 = 1000 mg/kg Is this the right way to do it?
You end up with .04mg in 0.5g of sample, Yes.

The amount of substance of interest in 1kg is 1000g/0.5g x 0.04mg = 80 mg/kg

When you write it out, make sure you know what each number stands for.
#3
06-30-2012, 07:48 AM
 Unregistered Guest Posts: n/a
Re: Calculating a solution from mg/l to mg/kg based on a solid or liquid

Quote:
 Originally Posted by Mrs X You end up with .04mg in 0.5g of sample, Yes. The amount of substance of interest in 1kg is 1000g/0.5g x 0.04mg = 80 mg/kg When you write it out, make sure you know what each number stands for.
I was forgotten to write down the last step (1000 gram / 0.5 gram) x 0.04 mg = 80 mg/kg

Thanks so I am calculating in the right way!
#4
06-30-2012, 01:03 PM
 Mrs X can't count, can't spell! Join Date: Feb 2006 Location: New Zealand Posts: 2,433 Rep Power: 12
Re: Calculating a solution from mg/l to mg/kg based on a solid or liquid

yes definitely calculating it correctly! Keep up the good work.

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