Hi: I hear questions similar to yours every week from investigators. There are no single or simple answers to your questions. You are hearing "mixed answers" to your questions, because of a profound level of missing information needed to make constructive suggestions. A 'universal' extraction method will not be sample specific (often leaving behind actual sample or even changing or degrading it). None exist. There is no "single" analytical method which is applicable to the range of compounds you list ( but there is a technique and please keep in mind that to detect and measure such compounds, they will always be in mixtures with many other chemical compounds too, perhaps hundreds or thousands). There is no single "best" solution to use for LC-MS analysis. One first has to develop a high quality, sample specific, HPLC method for use (millions of possible methods. Experience and experimentation helps an expert narrow down the choices).

• The "best" or most appropriate analytical technique to use must be sample specific.

Pick one to start with, then research what types of other materials may also be found in the same sample which need to be extracted and/or resolved from and which methods are applicable ("Google it"). Get an idea of how much material (concentration) might be expected. Determine what solvents these compounds are soluble in and under what conditions they may become unstable.

*Your teachers are in the best position to help you. Ask them to help you simplify the project and also get help from experienced scientists. Focus on how you can specify detailed goals and then manage the process of finding the answers. 'We' do not need to do all of the work ourselves (critical to learn as a student). Where possible, hire or utilize other experts to work on the parts of the project that you do not have a decade of extra time to study. To develop just a basic level of proficiency in using HPLC and/or developing methods requires a minimum of five years (emphasis on "basic" level, as in after 5 years of training you will NOT have enough experience to develop reliable methods). HPLC coupled to MS (a quad or Orbitrap) requires far more hands-on training and industrial experience. Save time by finding local experts with industrial experience in using these techniques for the sample types YOU are most interested in. Make sure the proposed techniques really are 'best' for your research. HPLC and LC-MS may not be the right tools (but probably are based on your sample names). This way you can spend your time collecting and researching samples and the analytical experts can work out the details needed to extract and measure the compounds.

Methanol or acetonitrile.

I agree with Mr. William Letter. Developing such a sophisticated LC/MS procedure is not an easy task and likely will take lots of time and effort. No one will be able to provide a method that works on the spot. Nevertheless, here are some general ideas: Find methods, where one of the compounds has been analyzed and try to find similarities. Biomolecules are often separated via reversed phase LC/MS with a C18 column. A typical mobile phase would be acetonitrile and water (with 0.1% of formic acid). The higher the share of acetonitrile in your mobile phase, the earlier the compounds will elute.

Caffeine is routinely analyzed under these conditions (works very well in my personal experience). If you use 10-15% acetonitrile, caffeine will elute as early as 1-1.5 minutes, as you can see in the following 2 papers.

Article LC-MS/MS analysis of acetaminophen and caffeine in amniotic fluid

Article UPLC-MS-MS Method for Simultaneous Determination of Caffeine...

Theobromine being very similar to caffeine is often analyzed in the same procedure. Since theobromine elutes even early than caffeine, you would clearly need to start with lower acetonitrile in your mobile phase and than gradually increase its concentration. Please see the conditions of the following paper.

Article Validation of an LC-MS/MS Method for the Quantification of C...

With 75% acetonitrile in the mobile phase, elution of nicotine is expected after 1.2 minutes, so it will elute much later, than caffeine or theobromine, as you can see in the following publication.

Article A LC-MS/MS Method for Concurrent Determination of Nicotine M...

Capsaicin has been eluted with either 70% or 50% acetonitrile and should take even longer than nicotine.

Article A sensitive LC-MS/MS method for quantifying capsaicin and di...

Article HPLC Determination of Capsaicinoids with Cross-Linked C18 Co...

So in general all 4 compounds have been successfully analyzed in C18-LC/MS with water and acetonitrile as mobile phase, making it plausible to separate all at once. I would suggest you read the relevant parts of these papers to get a feeling yourself.

Extraction can also be challenging. I have no experience working with ceramic samples, so my help might be of little value here. Since capsaicin only is sparingly soluble in water, high water concentrations might lead to inefficient extraction. A simple approuch would be to try extraction with your mobile phase, so a mixture of acetonitrile and water. In pure acetonitrile, capsaicine is soluble, the only problem would be, that your sample would be soluted in your "strong" solvent for the chromatography which might (not neccessarily must) cause your compounds to elute even earlier than they should be. So you might want to add as much water, as you can without impeding the solubility of capsaicin. Another guess might be using water:methanol (30:70), as this should also be sufficient for extraction of capsaicin and methanol is a "weaker" solvent than acetonitrile.

https://www.longdom.org/open-access/an-alternate-solvent-for-the-determination-of-capsaicin-content-in-chillies-by-hplc-method-2329-6836-1000342.pdf

Of course, none of these insights can guarantee, that your procedure will succeed, as there are many unknowns, that could impede the method. I hope, my suggestions provided you with a helpful starting point, from which you can elaborate your strategy.

Good luck and best regards!

Since methanol is a harmful solvent, it's preferable to replace it with another solvent of the same polarity.

https://www.epa.gov/sites/default/files/2016-09/documents/methanol.pdf

It seems that one of the most useful tools has been completely missed. Do a literature search for the extraction and separation of each of the individual compounds that you are looking for. Don't just look for the specific technique that you are using, in your case LC-MS, just look for extraction and analysis of the specific compounds. Once you have this information, you can more easily reconcile the differences between the methods. You may need to use multiple methods.

"Those that do not learn from history are bound to repeat it."

Since dichloromethane is not miscible with aqueous liquid chromatography solvents this may cause poor reproducibility as a solvent for injection on the LC-MS. The analytes you are looking to observe have strong UV chromophores, so you should be able to see them at wavelengths above 220 nm with no interference from your extraction solvent. Methanol is a good general solvent for dissolution of moderately polar compounds like the ones you're working with.

This document may help you.

Acetonitrile or Methanol or another solvent with the same polarity.

Based on type of sample your using the compound can be extracted the best chromatography avalible in the pharmaceutical labs is hplc and Gas chromatography even and your using hyphenated two way method LC-Ms the combination of chromatography and spectroscopy yeilds better results no doubt but here if want to determine how much yeild present in the sample is taken into consideration you have to chose the technique but LC-Ms is an expensive methods and you can face challenges in performing extraction my way is how much you have to show Lc-ms can detect ultra trace level but it has also some limition to prove compounds present you can use hplc method