Identifaction of compounds via HPLC

[seamoro]

we have a single wavelenght hplc variable and a LCMSMS. We have already run an extract containing multipe compounds on LCMSMS. The LCMSMS identified a number of compounds by mass spectra comparison..etc. From the results my professor bought in standard compounds for the compounds identified by LCMSMS and wants to run them on hplc and from there retention time varify the compounds in the extract mixture. The reson we cant use LCMSMS again as it damaged in a flood. My question is....can we use the LCMSMS rsults and the hplc results together?? from separate instruments?...is this correct? there is always a possiblity of similar retention times of compounds...!!!

[dreamermario]

hi i think when you run HPLC system of the same make and column it would be similar but it also depends on your sample if its the same extracted batch

[lmh]

I'm not clear on two things: (1) did your LC-MS also have a PDA or UV detector? (2) Do you have any chance of getting UV spectra, or are you stuck with just one wavelength? I assume one wavelength.

I presume your question is: can you confirm the identities suggested by LC-MS by comparison of retention times to authentic standards.

There is little or no chance that you will get identical retention times now to what you got on the LC-MS; your best chance is if the systems are the same model from the same manufacturer. But all is not lost. If you have samples that you ran on the LC-MS and collected UV data, you can run one of those samples now on the HPLC along with your authentic standards. The profile of peaks on the HPLC should be very similar to that from the LC-MS's UV detection (make sure you use the same wavelengths) and will allow you to match up peaks from the original LC-MS runs to the HPLC runs. If you don't have any UV data from the MS runs, and obviously no MS from the HPLC runs, unless your samples are extremely simple, it will be very hard to match up the two at all.

The reason I asked about spectra is that if you can get UV spectra from the peaks now, and have spectra from the peaks in LC-MS, this gives extra certainty that you are looking at the same peaks in each, and matching the data correctly.

[seamoro]

the LCMS was run a on extract from a mushroom......so there was multiple compounds in the sample. The LCMS had PDA yes........it identified compounds by ms spectra ....but since our LCMS is now not working. can identify by independant chromtography with HPLC that the extract peaks are the standard peaks? combining both the data....i.e LCMS and hplc with separate chromtogarphy conditions?

[Gaetan Glauser]

Lmh answered it very clearly: your only chance is to compare the new UV trace on the LC-UV machine with the same UV trace extracted from your previous PDA analyses. If there are many peaks in the UV trace at some given wavelength, you could now use them to align your chromatograms and identify the peaks. You will have to use the same chromatographic conditions (same column, mobile phases, flow rate and gradient) and hope that the possibly different dwell volumes will not affect the separation too much. If the peak order is very similar, there is a good chance that you can still identify your compounds.

So that's good you had a PDA connected to the LC-MS but...did you use it to record a PDA trace when you performed LC-MS?