Would there be a spot test/tests that can detect either/both of the following molecules at low concentrations?

The likely concentrations are in the $10{-}\pu{50 mg/L}$ range in an aqueous solution. Ideally, I'd want something that does not need an exotic/expensive instrument. e.g. a color change or precipitation or conductivity/pH change.

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The background interference: The sample is Terrific Broth which has the following composition:

$\pu{12 g}$ Bacto tryptone
$\pu{24 g}$ Bacto yeast extract
$\pu{4 mL}$ Glycerol
$\pu{100 mL}\ \pu{0.17M}\ \ce{KH2PO4}$ and $\pu{0.72M}\ \ce{K2HPO4}$, sterile, to be prepared separately from the tryptone, yeast extract, and glycerol solution.

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    $\begingroup$ Any sort of such a spot test would depend heavily on what else might be in the solution. So what other "stuff" could be in the water? I wouldn't expect either of those molecules to be very water soluble. $\endgroup$ – MaxW Jun 22 '16 at 19:28
  • $\begingroup$ Thanks @MaxW I've added info about what else could be in the sample. And yes you are right these are not very water soluble although at the low conc. I am expecting they very well might be. This is a conc. of less that 0.01%. $\endgroup$ – curious_cat Jun 22 '16 at 19:34
  • $\begingroup$ In any case, I want to brainstorm possible test options. At which point I can test them out on control samples of the broth to see what reaction I get. $\endgroup$ – curious_cat Jun 22 '16 at 19:36
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    $\begingroup$ >Bacto yeast extract || yeah, forget about any meaningful spectroscopy for such low concentrations with this unholy mix in the media. Theoretically speaking, a highly selective molecular recognition agent such as specifically tailored antibody may work, but the R&D required would be quite costly, so unless your needs do not exceed thousands of samples, it is not even worth considering. Other than thatn, GS/GSMS is your best bet. $\endgroup$ – permeakra Jun 22 '16 at 19:39
  • $\begingroup$ @permeakra Thanks for the insight. That's what I feared. GCMS works well, just that it is slow as number of samples scale. $\endgroup$ – curious_cat Jun 23 '16 at 2:37

Do you have the pure compounds on hand? If you do, the two target compounds can be crudely isolated by extracting the broth with diethyl ether, concentrating it down, and spotting on SiO2 TLC plate. Compare RF with that of the pure compounds. Alternatively, the same general extraction methodology could prepare a sample for GC-MS or crude NMR, if such instrumentation is available

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