identification

[RAMESH JANGA]

Dear all

How to indentify the elution pattern in HPLC while injected same sample in LC-MS for mass numbers indentification.

[Don_Hilton]

Ramesh,

If I understand your question, you want to match the peaks between two types of LC detctors? This is tricky because some compunds appear with one kind of detection, but not with another. Detection changes on LC-MS depending on method of ionization and polaritiy.

What type of detector are you using on the HPLC that you want to match up with the LC-MS?

And, I assume that you are using the same chromatographic condisitons with each detector. If there are differences, that is important to know as well. A bit more detail may help someone to help you out on this one.

[lmh]

Two ideal situations:

(1) Install a detector on your LC-MS that is as similar to the HPLC detector as possible (typically, use an LC-MS that also has a PDA detector if you are using PDA or UV detectors on HPLC). That way, you will have nearly identical chromatograms on both instruments, so it is easier to see which peaks are which.

(2) Install a fraction collector on your HPLC, and analyse the collected fractions by direct infusion MS on the LC-MS system (you can replace the column with a back-pressure regulator, or possibly just a union, and autoinject all the fractions).

The situation is extremely intractable if you have a form of chromatography that cannot easily be used on LC-MS (for instance ion exchange with strongly salty buffers) and therefore you are forced to carry out chromatography on the MS that is totally different to that on the HPLC. It will really help if you can duplicate your HPLC method exactly on the LC-MS.

[sassman]

It would help to know what compounds you are analyzing and the details of your method (column, mobile phase, etc.). If it is possible to use the exact same chromatographic conditions, then all compounds will have the same retention time. Your chromatogram, however, will NOT look the same since some compound will show up on the MS that do not show up with UV and vice versa.