June 18, 2021, 11:05:44 PM
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### Topic: Help with calculations for quantification using HPLC  (Read 170 times)

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#### pestolover

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##### Help with calculations for quantification using HPLC
« on: May 15, 2021, 10:56:32 AM »
I'm so stuck with the maths! I just feel like I'm doing it wrong

Here is my data:

Using calibration curve, obtained a concentration of 22.7 ppm. This was for a 10 mL solution containing a 1mL aliquot of my sample. Concentration of aliquot = 227 ppm. Converting this to mg/L and then mg/mL = 0.227 ppm.

Now, my sample was just instant coffee brewed in water (my 1 mL aliquot which was diluted to 10 mL was directly from this).

We dissolved 0.68g of coffee in 100 mL of water.

My end goal is to find how much caffeine (mg) is in 1.7g of coffee sample

So with my 0.227 mg/mL, I multiplied by 100 to get 22.7 mg/100 mL, which is then 22.7 mg in 0.68 mg

Now to find how much is in 1.7g, I did (22.7/0.68)*1.7

Is this correct?!

Thanks in advance. I've been moving numbers around and it's all blurred into one at this point

Edit: I also want to find the % of caffeine in 1.7 g. Do I then take the above mass: 0.05685 g / 1.7 g * 100 = 3.3% ?
« Last Edit: May 15, 2021, 11:09:32 AM by pestolover »

#### Orcio_Dojek

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##### Re: Help with calculations for quantification using HPLC
« Reply #1 on: May 15, 2021, 11:24:28 AM »
Correct....