A. biochemical tests:
AHL, particularly 3-oxo AHL, which is what we use, reacts strongly with Chlorox. if you mix a known concentration of chlorox with an unknown concentration of AHL, and use the DPD assay to determine levels of chlorox over time, you can figure out your initial concentration of AHL. I haven't figured out exactly what the DPD assay is yet, but the article gives the impression that it's relatively quick and easy. I'll look into this a little deeper later today.
B. biosensor tests:
AHL reduction test by Imperial (Tito) http://openwetware.org/wiki/IGEM:IMPERIAL/Protocols/S01656/AHL_reduction_AHL_reduction
A paper on quorum sensing in E. Coli. The paper seems to indicate that 3-oxo AHL is specific for the Lux system, and so I don't think we will have to worry about cross-talk if we use this AHL for this system. http://www.pnas.org/cgi/reprint/103/7/2386.pdf