how would I be able to determine wether certain aminos contain organic carbon
They are all organic and if IIRC they all have carbon which links the chains together.
To equate them to vodka and vinegar, first consider dilution ,ie, what % of water is in the supplement being used and how does that % compare to other carbon sources, like ; vinegar which is 95% water and 5% carbon source (acetic acid) or 80 proof vodka which is 60% water and 40% carbon source( ethanol) Thus it takes approximately 8 times as much vinegar as vodka for the same carbon amount .
Sugar or other undiluted sources are factored in at 1 =2.5 vodka or 1=20 vinegar.
Finer tuning can be done by looking at the chemical structure of the particular aminos in a mixed supplemnt to determine the relative amount of C atoms vs H and N in each and in the aggregate as compared to other sources. Personally , I'd just account for dilution variances and settle for that.
You are correct that all amino acids contain carbon, both in the bonds that link them together (if they are small peptides) and in the actual structure of the amino acids (either in peptides or as free AA). However, it is best to not even consider AA as a carbon source in your aquarium. Their structures are complicated (relative to ethanol, acetic acid, and even glucose), their composition is heterogenous, and they are expensive.
To demonstrate the problem with their compositions being heterogenous, consider the following example. With a carbon source like Ethanol (EtOH), we know that we will always be dosing about 0.5 grams organic carbon per gram ethanol, and that the carbons in each molecule of EtOH are all chemically equivalent (in the same oxidation state, react with the same enzymes, form the same end-products, provide the same energy). However, in the case of amino acids, let's look at what can happen:
The simplest amino acid, glycine, provides about 0.3 grams organic carbon per gram amino acid, and the most complicated (standard) amino acid, tryptophan, supplies .65 grams of carbon per gram of amino acid, a more than 2 fold difference. However, the real disparity comes in the chemical heterogeneity of these carbons. Between amino acids, the carbons come in such different forms, bonded in many different ways, and will be metabolized by different proteins, may even be used for different purposes (protein synthesis versus energy for example) and provide different amounts of energy to the bacteria, if that particular amino acid can be used for energy in that particular bacteria at all. This makes it difficult if not impossible in a home-aquarium setting to adequately calculate for the carbon dose coming from amino acids.
Also, although bacteria can use some amino acids as a carbon source, many bacteria are restricted with regard those aa that they can use for energy production, and I honestly don't know if that information is known with the kind of bacteria we try to grow in our aquariums with carbon dosing (note, almost any organism can use most AA for protein synthesis, not so for energy production). There is also a lot more known about the simpler carbon sources used in reef aquariums from a practical standpoint, and many people have used them with great success, no reason to reinvent the wheel.
Therefore, IMO, if you want to carbon dose, stick with a simple molecule like ethanol, vinegar, or even a polymeric form like poly-hydroxyalkanoates (the stuff they make biopellets out of), and treat AA as a separate entity entirely, preferably not dosing them at all
