Dear All
Pertaining on the title, I would like to know, how do you double check the result to ensure all compound identified is correct. Here I attached the lc-ms result for perusal. I don't have authentic standard to check it. Can I just use Nmr or FTIR to double check the structure and compound. please advise
Usually high-resolution mass-spectra data is fairly reliable and can be used for identification. If you want to confirm the identity of the detected compounds, then using standards is the most straightforward method (you will have a combination of HRMS and retention time data, which is pretty unique).
IR would be useful for identification of functional groups, and of course NMR is the best tool to determine the structure. However, for taking the IR or NMR spectra you will have to isolate each component is sufficient amount and purity, which is (usually) not practical.
In any case, having LC-HRMS data is a good starting point; perhaps you may need to confirm the presence of only few compounds of interest. If, for example, it is critical to confirm the presence of only one, let's say, unusual compound, I would make efforts to isolate it and collect all possible data, including NMR, IR, etc.
you have to collect enough amount from the components (hplc peaks) of the sample, about 10 mg, and confirm the structure using nmr
To be reasonably secure you need both a retention time match and a mass spectral match. If you don't have a standard, then you could try doing some experiments fragmenting your compound in the MS and comparing the fragmentation to what is in the literature, or what you might expect based on your proposed structure. Without a retention time match and a second identifier, I think you should regard the identity of your peak as tentative. If it is a known compound then even 1H NMR (maybe with a COSY or TOCSY) would be sufficient for confirmation of identity when taken together with the mass from the LC-MS. Usually 100 ug is more than enough for with a modern NMR spectrometer, but the sample needs to be reasonably pure.
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