Question

if you are analying caffeine, aspirin and acetaminophen. what advantage of quantifyig these actives using a diode array detector for HPLC instead of a UV detector set at 254nm?

Answer 1

ADVANTAGES ARE:

1. Both UV and DA detectors are used to detect the absorption in UV-VIS region. But the difference is that a UV-VIS detector has only one light-receiving section from the sample side while a DAD has multiple photodiode arrays to obtain information over a wide range of wavelengths at one time. Thus, caffeine, aspirin and acetaminophen can be easily analysed as well as quantified using DAD.

2. In UV detector, since the measurement is performed at a fixed wavelength (254nm)and as per the retention time, a minor deviation in retention time can make identification of components difficult. While in DAD, the spectra are measured at intervals of 1 second or less during separation by HPLC. so even during minor deviation in retention time, caffeine, aspirin and acetaminophen can be identified by a comparison of their spectrum.