Pharmaceutical drugs, drugs of abuse and/or their metabolites are emerging environmental pollutants. The identification of their degradation/photodegradation processes is of interest in the so called “sewage epidemiology,” for estimating drug consumption in a community by wastewater analysis, and in toxicity studies for understanding their toxic effects in the aquatic environment.
The UVA and UVB light-induced behaviour of 6-monoacetylmorphine (6-MAM) and morphine, the two main metabolites of heroin, was studied in methanol, aqueous solution and in the dry state. Irradiation was performed at 365 (UVA) and 312 (UVB) nm, for different times, achieving radiant energies of 20-300 J/cm2. UV spectra of irradiated samples, at selected dosages, were compared with the spectra of the same samples kept in the dark. In order to estimate the extent of photolysis, positive ion electrospray ionization experiments were performed on the irradiated samples by High Resolution, High Accuracy Mass Spectrometry (HRMS) and by liquid chromatography-HRMS. Tentative identification of photoproducts was performed on the basis of their elemental formula as calculated by HRMS results. Morphine and 6-MAM demonstrated to be quite stable under UVA light but very sensitive to UVB irradiation. The production of singlet oxygen was also evidenced under UVB exposure. In methanol solutions, they undergo a similar pattern, both reaching 90 % photodegradation after 100 J/cm2 of UVB irradiation, with a slightly faster kinetic for morphine at lower doses. In water, the yields of photodegradation are nearly one third lower than in methanol. In the solid state, the yields of photodegradation is lower than those in solution. The structures of some UVB-induced degradation products, based on HRMS measurements, are proposed. Photoaddition of the solvents and photooxidation seem to be the main pathways of phototransformation of the two molecules. Cocaine and metabolites were studied in an analogous way. Solar light was demonstrated to alter molecular structures of drugs when irradiated in solutions.
In human hair, where drugs of abuse are known to accumulate with chronic use and do not undergo metabolic degradation, drug concentrations are affected by cosmetics or chemical treatments (dying, perming or bleaching) as well as by environmental exposure. Solar light was demonstrated to alter molecular structures of drugs when irradiated in hair, decreasing the concentrations of drugs and/or producing new compounds/metabolites. Studies were performed for different classes of compounds and metabolites by exposure of true positive hair to controlled UVA and UVB light (cocaine, opiates, methadone) or to the whole sunlight spectrum (cannabinoids, cocaine, ethylglucuronide)