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- Joined: Mon Apr 11, 2022 12:44 am
I have been working on the analysis of carotenoids for the last 2-3 years for my PhD using UPLC-UV-HRMS. I used an analytical standard of lycopene (extracted from tomato) to detect the presence of this compound in bacteria. During all my tests I consistently found that there are 3 peaks in my chromatogram matching the mass of lycopene. One peak matches the exact retention time of the standard (RT: ~20.3 min). The other two peaks have the mass of lycopene but elute at around 16.3 and 17.6 min respectively.
The person who is helping me with the analysis has told me that I can refer to these other two peaks as lycopene isomers. I was wondering with which certainty I can say that these other peaks are lycopene isomers. I haven't found a lot of information in the literature about other lycopene isomers retention times, there are actually so many isomers that is hard to find possible matches just based on RT. Also this compound has been extensively studied in food matrixes but not in bacteria. It is interesting because I see different proportion of these 3 isomers/peaks in my bacteria depending on the growth conditions.
I just want to be certain while writing my thesis that I am not making a mistake when I refer to these other peaks as "isomers". It is possible that these products are maybe some degradation product of lycopene? I guess in that case the mass should be different? I ran the samples on a UPLC-DAD to check the absorbance spectra of the different peaks. One of the isomers have almost identical peaks than the lycopene from the standard while the other one differers a bit more. Is this any indication of what type of isomer/difference in structure?
Any advice will be greatly appreciated. Thank you