December 04, 2020, 12:17:26 PM
Forum Rules: Read This Before Posting

Topic: HPLC Concentration calculations  (Read 7382 times)

0 Members and 1 Guest are viewing this topic.

Offline Zel

  • Very New Member
  • *
  • Posts: 2
  • Mole Snacks: +0/-0
  • Gender: Male
HPLC Concentration calculations
« on: October 11, 2012, 10:24:43 PM »
Hi there,
I completed a practical which involved HPLC of two known solutions, and two unknown solutions. From this, we have to calculate the concentration of the unknown solutions.

Paracetamol Stock solution: 20ppm concentration
Average Retention time = 3.3695 min
Average Peak Area = 437630.5

Caffeine Stock Solution = 5ppm
Average Retention time = 4.5125 min
Average Peak Area = 200423.5

Unknown Solution 1 (weight capsule = 0.3516g)
(1) Average Retention time = 3.239 min
(1) Average Peak Area = 592642
(2) Average Retention time = 4.406 min
(2) Average Peak Area = 302820

Unknown Solution 2 (weight capsule = 0.2314g)
Average Retention time = 3.3485 min
Average Peak Area = 484653.5

It can be seen that US 1 has both caffeine and paracetamol, where US 2 has paracetamol.
How do I go to calculate the concentration of each component in each US?
We got each Unknown solution by weight a capsule, dissolving it into a 200mL flask, then diluting in a 1:50 ratio into a 100mL flask, so this has to be taken into consideration when calculating the concentration.
I understand I might need to plot a calibration curve, but what will I use? The ratios? Or just use the concenration vs. averages?
Any help will be appreciated. Thank you.
« Last Edit: October 11, 2012, 11:14:16 PM by Zel »

Offline Borek

  • Mr. pH
  • Administrator
  • Deity Member
  • *
  • Posts: 26159
  • Mole Snacks: +1703/-402
  • Gender: Male
  • I am known to be occasionally wrong.
    • Chembuddy
Re: HPLC Concentration calculations
« Reply #1 on: October 12, 2012, 03:23:19 AM »
Signal should be directly proportional to the concentration. You don't need a calibration curve here, although drawing one won't be incorrect - it is just much faster to calculate just using proportions. That would be equivalent to use a calibration curve going through 0,0 point.

Then take care of dilutions.
ChemBuddy chemical calculators - stoichiometry, pH, concentration, buffer preparation,,

Sponsored Links