Fireflies generate flashes of visible light via luciferase-catalyzed chemiexcitation of the substrate (luciferin) to the first excited state of the emitter (oxyluciferin). Microenvironment effects are often invoked to explain the effects of the luciferase active pocket on the emission; however, the exceedingly complex spectrochemistry and synthetic burdens have precluded elucidation of the nature of these interactions. To decipher the effects of microenvironment on the light emission, here the hydrophobic interior of cucurbit[7]uril (CB7) is used to mimic the nonpolar active pocket of luciferase. The hydrophobic interior of CB7 induces shifts of the ground-state pKas by 1.9-2.5 units to higher values. Upon sequestration, the emission maxima of neutral firefly oxyluciferin and its conjugate monodeprotonated base are blue-shifted by 40 and 39 nm, respectively, resulting in visual color changes of the emitted light.

Limited work has been done to assess the types and levels of PACs in domestic and treated wastewater in arid and semi-arid countries. In these countries, reuse or artificial recharge of treated sewage effluent is commonly practiced. Thus, the objectives of this study were to quantify the levels of selected PACs in domestic wastewater in the United Arab Emirates (UAE) and to assess the effectiveness of domestic wastewater treatment plants in their removal. An analytical protocol was developed for the analysis of 15 PACs using a UPLC-MS/MS system. Four batches of water and sludge samples were collected from different locations at Al Saad Wastewater Treatment Plant in Al Ain, UAE. Aliquots of each sample were enriched by solid phase extraction. Results show that phenylephrine, dapsone, noscapine, propyl gallate, genistein, and ketoconazole were present in the raw wastewater at low levels (<0.1 μg/L), while acetaminophen and caffeine were present at high levels (>10 μg/L). The overall removal efficiency of the tested PACs from the water stream exceeded 99% for cotinine, acetaminophen, caffeine, naproxen, and ibuprofen, but significantly drops (<50%) for phenylephrine, amoxicillin, dapsone, noscapine, spiramycin, noscapine, genistein and ketoconazole. Analysis of the results indicate that, for highly removed PACs, the main mechanism of removal is possibly aerobic biodegradation. However, for tyramine, dapsone, 9-aminoacridine, noscapine, propyl gallate, and ketoconazole sorption onto the mixed liquor suspended solids first occurs followed by removal by anaerobic digestion. Results of the study should be useful for properly managing treated sewage effluent and sewage sludge.

The guest-host interaction between Dapsone drug and β-cyclodextrin (β-CD) was investigated using fluorescence spectroscopy, 1 H-NMR, and liquid chromatography with fluorescence detection. The optimized conditions for the interaction were investigated by spectrofluorometry and were found to be at 0.2 mg/mL (0.176 mM) of β-CD and pH 8.8. For these conditions, very low concentration of Dapsone drug of 2.4 ng/mL (12.97 nM) can be detected. The standard addition method was utilized to detect Dapsone in influent and effluent wastewater samples in the sub parts per billion concentration range by HPLC-FLD using β-CD as an additive in the mobile phase.

Sensitive spectrofluorometric and liquid chromatography with fluorescence detection methods have been developed for detection and determination of naproxen drug in the presence of cucurbit7uril (CB7). Fluorescence signals have been improved with the addition of CB7 to the drug aqueous solution. Fluorescence spectroscopy, mass spectrometry, 1H-NMR, and liquid chromatography with fluorescence detection were used to investigate the guest-host interaction of naproxen drug and cucurbiturils. Naproxen was found to form a supramolecular complex with CB7 that had a high formation constant. The optimal conditions for the interaction were discovered using spectroflurometry to be 0.2 mg/ml of CB7, 2.4 μg/ml of naproxen drug, and pH10. A 1:1 complex between naproxen and CB7 is revealed by proton NMR and tandem mass spectrometry. Using the standard addition calibration method, an HPLC with a fluorescence detector was used to detect naproxen in influent and effluent wastewater samples. Finally, it was discovered that the measured concentrations of naproxen in the influent and the effluent wastewater were 1.87 × 10−4 ppb and 2.1 × 10−5 ppb, respectively. This was done by sample enrichment, which reduced the 1000 mL into 1 ml.