Hello,

Does anybody please have an LC method for methyl salicylate and menthol?

I have seen an unpublished piece which uses isopropyl alcohol:KH2PO4 buffer (0.1M):formic acid at 540:1000:1 to separate the methyl salicylate. However when I injected the sample (made in mobile phase) the system pressure increased dramatically due to precipitation of the buffer salt I assume. can anybody please explain why this is occuring since I am using solvents which should be miscible with the buffer.The pH is around 3.8 by the way.

Thanks for your help!

Why use HPLC for menthol as it does not contain a good UV-chromophore; GC probably better for menthol only or for the combination in an external analgesic? Over 20 years ago, my company assayed both simultaneously by GC (packed column in those days on DEGS but would try modern cyanopropyl silicone capillary today such as SP-2330 from Supelco, which we have found to have similar characteristics to DEGS with fatty acid methyl esters but much more stable). Back then (before automatic samplers became readily available and reliable) we also used n-octanol as internal standard. Now if you want to do menthol by GC and methyl salicylate by HPLC, use acetic acid water and either ACN, methanol, or THF on RP-18 column with UV at 313 nm.

Update to above: 313 nm good for sunscreen components like octyl salicylate, but may need to drop down to 280 nm or so for methyl salicylate(run UV scan on standard).

These days I'd likely make trimethylsilyl derivatives with BSTFA+1% TMCS (sample and standards dissolved in DMF) and do by capillary GC on nonpolar column. Easy.