# How can I detect a specific molecule on a surface?

Based on the comments and answers, this question wasn't very clear, so I have completely overhauled this question to make it much clearer in another post: How to create the equivalent of luminol for a compound?

Original Post/Question:

I'd like to be able to detect trace amounts of the chemical 'monomorine I' (5-methyl-3-butyloctahydroindolizine) on a surface. (It is an ant pheromone)

Is there an easy way to determine if the molecule is visible in IR or UV? (before I spend the money on this equipment)

Is there a strategy for causing a visible reaction? or even a reaction visible by IR or UV?

Advice on where to even begin would be a huge help.

(I do not have a chemistry lab with a Mass Spectrometer at my disposal)

• Perhaps a fluorescently labelled monoclonal antibody? – canadianer Aug 22 '14 at 3:23
• In dx.doi.org/10.1007%2FBF01926645 they obtained the structure from spectral analysis: MS, IR and NMR. You can find more about this compound here, quite possibly also a full spectrum. From your question I really do not understand what you are trying to accomplish. Will you wash the substance of the surface, is ich chemically or physically adsorbed to it? All in all, I guess GCMS would be your best bet to figure out trace amounts... – Martin - マーチン Aug 22 '14 at 4:32

Simple UV spectroscopy is not an option.

You won't find anything at all above 254 nm - probably just a a weak band in the 220 nm range. Indolizidines are pretty dead in UV.

Derivatisation towards a fluorescent compound would require clevage of a $\ce{C-N}$ bond, formally a dealkylation of the tertiary bridgehead amine.

I have no idea if a reagent like 2-naphthyl chloroformate, which does form fluorescent carbamates upon heating with tertiary amines will work here and honestly, I wouldn't bother to try.

As pointed out in Martin's comment, GC/MS after washing/extraction probably is the way to go.

Is it possible? Sure. Could you, considering practical issues, use it here? No.

There is definitely one spectroscopic technique but it's fairly difficult to do and requires the use of ultrafast lasers. Such lasers require vibration-damped tables, constant (and low) relative humidity as well as a constant temperature—this is not therefore a field approach. Furthermore, the whole set up (optical parametric amplifiers etc.) costs hundreds of thousands of pounds.

For those interested anyway, Sum Frequency Generation spectroscopy only works for non-centro-symmetric systems. So if you have a bulk solution, on average the system is symmetric and no spectrum is obtained. At surfaces however this symmetry is broken and molecules even along with their orientations can be observed. This works for both UV/vis and IR. Because the lasers are ultrafast, transient species can often be tracked as a given chemical transformation is occurring, whatever that may be (as long as there is a given chemical signature to lock onto).

A short review of this technique can be found here.