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Chemistry Forums for Students => Analytical Chemistry Forum => Topic started by: hapi001 on March 09, 2011, 02:08:33 AM

Title: about HPLC..
Post by: hapi001 on March 09, 2011, 02:08:33 AM

i am just a lab report question on determination of paracetamol and caffeine in tablet by hplc..

Would it be suitable for monitoring the active ingredients at the UV absorbance wavelength of 190nm instead of 254nm? Why?

Thanks...

Title: Re: about HPLC..
Post by: enahs on March 10, 2011, 12:17:12 PM

Maybe (most likely not). It depends on your solvent system. Solvents also absorb UV light, and there is a UV Cutoff wavelength, which means at some wavelength the solvents have an absorbance of 1 or higher, meaning, you can not really blank them properly and they will interfere with the absorbance of your compounds of interest.

A random internet search and first results turns up this: http://macro.lsu.edu/HowTo/solvents/UV%20Cutoff.htm
So, if you trust LSU, you can use that data to determine if you could use a wavelength of 190nm.