I need help with calculating the amount caffeine in a sample tablet. From the ca

Question

I need help with calculating the amount caffeine in a sample tablet. From the calibration curve, I've determined the caffeine concentration of the tablet to be 26 ug/mL.

The mass of the sample tablet was 0.650g

The prep of the sample solution was this:

1. 0.650g table dissolved in 50 mL of HPLC solvent.

2. 10 mL of the sample solution was diluted to 100 mL with HPLC solvent

3. 10 uL the diluted sample solution was injected into the HPLC

What is the calculation for determining the amount of caffeine in the sample tablet?

Explanation / Answer

You determined that you have 26 micrograms / ml, this concentration was gotten from a 10 microliters of solvent

The concentration of 10 microliters comes from a volume of 100 ml so the 100 ml has a concentration of 26 ug/ml

this concentration comes after diluting 10 ml to 100 ml apply dilution equations

C1 V1 = C2 V2, c1 is the concentration we know, V1 is concentration of 100 ml , c2 is the concentration we want to know and V2 is the volume of 10 ml

26 ug / ml * 100 ml = C2 * 10

C2 = 26 * 100 / 10 = 260 ug / ml

This concentration for 10 ml was taken from the original sample of 50 ml, so the sample of 50 ml must have the same concentration

so how many micrograms do yo have in 50 ml with a concentration of 260 ug / ml? apply formula concentration = mass / volume

mass = concentration * volume

260 ug / ml * 50 ml = 13000 micrograms

13000 micrograms is equal to 0.013 grams or 13 miligrams

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