chemistry- Dr.Bob, can you help me out please?
posted by ~christina~ .
If I had two unknown chemicals (in solid form) mixed together, how could I go about identifying the individual components of the mixture?
Is it possible, by UV, IR, GC, or HPLC?
The problem I have is that with:
GC= sample is destroyed &
if you don't know what compound
you have, you cannot compare
retention times & sample has to be
HPLC= same problem as GC except that
compound (s) don't have to be
IR= not sure how to identify two
unknown samples in a mixture with
IR because of the combined
UV= I know that two compounds will mix
and the spectras will add, but I
only know how to find the
concentration of each compound, if
the identity of the two compounds
are known. If the identities of
the compounds are not known, how
can I use the spectra to
find the identity of each?
Not really? With both IR and UV, it is difficult to superimpose one fingerprint on another, then definitely identify each separately. Either, but mainly IR, would be helpful in determining what kinds of compounds you had in the mixture (ketones, alkenes/alkanes, etc) and that gives you a handle that could be used for separating them. Usually one has enough sample to perform HPLC or TLC or something like that and have enough left over to do sample retention times. My experience, depending upon how much sample I have and what I'm dealing with, is to try to separate the mixture, then work with pure samples. That makes UV, IR, HPLC and all of the other tools MUCH more valuable. Then one can talk about individual. fingerprints. I know I've not answered your question explicitly but I hope I've give you some direction.
Now that you state it, I realise I have a problem with the separation part. I'm not sure how much sample I'm going to be given.
I may come across as going backwards in a sense, but how would I separate two mixtures?
Actually you have only one mixture; it happens to have two components. There is a more or less standard procedure for separating complete unknowns (that's where you know nothing about it) and if you know nothing about it that is where you start. You have either had such a procedure already or you will be given one soon. Or consult a standard organic qualitative analysis book to see how to do it. I doubt, at the level you are, that anyone would expect you to go through the entire procedure. I'll bet that you will be give some directions as well as some glimmer of information that will help you determione what to do. I also expect you will be given more than enough sample to allow you to run a number of tests. I know I've talked in general terms, only, but with nothing more to go on, that's about the best I can do.