[jvm208]

I would like to confirm the volume  of internal standard (theophylline) and 5 standard solutions (caffeine) I have calculated to analyze caffeine levels in unknown samples...

Final total volume = 10ml
Stock concentration(caffeine) = 0.4% ; Stock concentration (thophylline) = 0.4%

Standard #1: 0.005% caffeine + 0.03% theophylline
Standard #2: 0.01% caffeine + 0.03% theophylline
Standard #3: 0.015% caffeine + 0.03% theophylline
Standard #4: 0.02% caffeine + 0.03% theophylline
Standard #5: 0.025% caffeine + 0.03% theophylline

My calculated volumes are..

Standard#1 = 0.125ml caffeine (C) + 0.75ml theophylline (T)
Standard#2 = 0.25ml caffeine (C) + 0.75ml T
Standard#3 = 0.375 caffeine (C) + 0.75ml T
Standard#4 = 0.5ml caffeine (C) + 0.75ml T
Standard#5 = 0.625ml caffeine (C) + 0.75ml T

Thank you.

[Arkcon]

What do you get, when you multiply each volume, by each percentage, and divide B total volume.

[jvm208]

Thank you for your reply..

I have checked my calculation and initial volumes are correct.

Using V1 = (C2 x V2)/ C1

e.g. theophylline initial volume = (final concentration % x total volume)/ inital concentration %
                                             = (0.03 x 10)/0.4
                                             = 0.75ml