proper way for detecting misoprostol

Discussions about GC-MS, LC-MS, LC-FTIR, and other "coupled" analytical techniques.

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pls guys i need help in detecting misoprostol by gc-ms!!

this is the structure
Image

i try but gives spectrum of Amtriptyline!!
Derivatize with PFPA & still nothing change!!

I'd dissolve in DMF acidified with maybe 1% concentrated HCl and derivatize with BSTFA. Acidifying gets that carboxylic acid or salt to derivatize.

I would check the literature. A quick look on line shows some work referencing previous GC/MS work - but does not cite it (http://humrep.oxfordjournals.org/cgi/reprint/20/12/3414.pdf) And there is more than one vendor for internal standards for GC/MS and LC/MS methods. I suspect that with a bit of digging you can find a literature method.

I doubt the spectrum you see is for amtriptylene. The spectrum may look similar to amtriptylene - but it is probably something else. Remember that high match scores are not proof of chemical identity.

Tell us about the conditions under which you handle the standard. You could be degrading the standard to some other compund.

the standard is dissolve in methanol & inject directly to gc-ms with hp-1 and hp-5ms @ 250C, oven was @ 70C for 2 min then increased 20C/min to 300C and hold for 5min.

I tried consumer products guy suggest but no reaction is occure

I used MSTFA directly without DMF and got 2 peaks,

peak 1 ions are: 328, 313, 145, 132, 117, 73
peak 2 ions are: 356, 341, 146, 132, 117, 73

NIST 2008 identfied them as hexadecanoic acid TMS and Octadecanoic acid TMS

Fatty acids are common background in the laboratory, so this is a start - you are getting something derivatized and down the column. And, I would expect derivatized misoprostol to elute after these. Next question: How much mistoprostol are you derivatizing? And are you doing a split or splitless injection? In looking for the peak it would be nice to get something over 100 pg analyte on the column.

And, what kind of mass spec are you running? What is your tune voltage and what is your detector voltage in the analysis? (I assume EI, given library search results.)

What liner are you using? What column dinensions, carrier and flow rate?

Another literature lead - the experimental is a bit weak but: http://humrep.oxfordjournals.org/cgi/reprint/17/2/332.pdf

And in an edit,m I'm adding a link to an article which references what should be a published method.: http://www.geburtshilfe.usz.ch/Documents/LehreUndForschung/Publikationen/MisoprostolAJOG.pdf

10mg misoprostorl

splitless injection

ms is agilent 5975b

single tappered splitt/splitless liner

hp-1 30m , 0.32mm, 0.1um

helium @ 1.4mL/min

if you are putting 10 mg analyte in a GC vial and derivatizing it, you should be seeing a lot of signal - if not of your analyte, at least of degredation products. If you are derivatizing 10 mg analyte in a larger volume container and transfering the derivitization mix to the GC vial - the transfer would be part of the problem.

Tell about you misoprostorl. What kind of source and what kind of purity? (Is this a certified commercial standard? Synthesized in house? Are you using a pharmeceutical preparation and using the compounding information provided with the preparation?)

Describe your derivitization procedure from the point where you weigh the sample. There are some places where sample handling can get in the way. When you used DMF was it anhydrous (purchased as anhydrous and kept in a desicator after opening). Given that there are two hydroxyl groups, and they are not particularly acidic, you could use anhydrous pyridine in the derivitization with BSTFA to drive the equilibrium.


If you have methanol in the derivitization, your derivitizing reagents are likely to be lost by reaction with methanol.

one cytotec tablet is containg 200mg misoprostol which dissolve in 20ml methanol, 1ml of that is transfering to reacti-vial and evaporated under straem of N2 to dryness. 0.1mL of MSTFA was added and incubated at 60C for 30 min. 1 microlitter is injected in gc-ms.

A cytotec tablet contains much more than misoprostol. And, I suspect that when you disolved the tablet in methanol there was some solid residue? While misoprostol may be soluable in methanol, it may partition into that solid residue. Given that the tablet contains hydrogenated castor oil, hypromellose, microcrystalline cellulose, and sodium starch glycolate, I would expect that misoprostl would partition into the hydrogenated castor oil - which may not be soluable in methanol. And even if soluable, may remain partitioned into the cellulose, and other stuff present.

I STRONGLY reccomend that you purchase pure misoprostol or a comercially prepared standard solution for your work. You will be sure of exactly what is in the GC vial when you derivatize it.

thanks Don but do you expect that misoprostol can be detect by gc-ms?
becuase i didn't found any litrature on that all of them using lc-ms!!
only one paper on gc-ms-ms but it was NCI and it required three derivatization agents: PFBHA, PFBB & BSTFA !!

I expec that misoprostol should be detectable by GC-MS. The question is what kind of matrix isues you are dealing with.

From what was in the abstract of that paper, the procedure goes throught quite a few steps and I would expect losses along the way. GC-NCI-MS-MS could be addressing sensitivity issues and/or problems with remaining interferences.

If you are working with complex matrices, the extraction and preparation process may be an issue. If you are working with less complex matricies, the only question is how hot to you need to heat the GC column and will the compound survive? The GC-NCI-MS-MS work would lead you to believe that the compounds can survive the GC column. And, I would expect simple derivitization wiht BSTFA/Pyridine or MSTFA Pyridine to be adequate.
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