Chromatography Forum

Hello!
I am trying to quantify the steroid acids using IS, on Agilent 1260, Q-TOF MS, C-18 column. I made a standard of docosanol (1 mg/ml in MeOH), but the peak was very low (I diluted it to 0.1 mg/ml, but still peak height has to be much higher). In addition, I found that the IS got solid after being stored in a refrigerator. I knew that the problem will appear, as melting point is even above room temperature.
Thus, I am wondering if there are internal standards that meet several requiements:
1. Highly soluble in MeOH, MeCN or water;
2. After being dissolved, keep liquid in room temperature;
3. Suitable for LC-MS.
4. Not pricy.

I realize that my attempt to use docosanol sounds strange, but my supervisor said that first I shall try to use existing supplies rarther than purchase something.

I am not surprised docosanol ionizes very poorly in LC-MS. I think your supervisor is wrong, you should not lose time trying to test any unrelated product e in your stocks, but rather 1) do the litterature and check which ISs have been used by other researchers, 2) see if among them some may be useful to you, 3) check prices, 4) ask your supervisor if you can purchase them.

For instance, one can buy cholic acid-d4 on the market for a very reasonable price.
https://www.trc-canada.com/product-detail/?C432603

Thanks a lot, I started with that, haha. All authors use isotopically labeled standards of my target analytes. I thought of testing other approaches before purchasing isotopically labelled standards.