As a phenothiazine derivative, Promethazine may undergo structural modifications when it is exposed to light. This process consists in the degradation of the initial compound and in the generation of new photoproducts with possible anti-infectious qualities. Stability studies are necessary in order to establish the proper use of drug solutions in different applications. At the same time, these investigations are important in the context of the generation of side-products induced by environmental conditions that bring new benefits to the compound.
This study reports the stability of Promethazine aqueous solutions, based on their absorption spectra acquired before and after Nd:YAG laser irradiation sessions or under different temperature and illuminating storage conditions. Samples of Promethazine solutions in ultrapure water, at a concentration range between 10-6 M – 10-2 M, were kept in dark at 22°C, and 4°C as well as at 22°C in ambient light up to a time interval of three months. Absorption spectra were recorded periodically in order to determine any changes of the optical properties. Also, solutions of 20 mg/mL were exposed for different time intervals to laser radiation emitted at 266 nm by the Nd:YAG laser. The stability of the optical properties of irradiated Promethazine solutions for 4 h was investigated up to two months.
The laser irradiated samples show similar but more rapid and intense changes compared to solutions exposed to ambient light, suggesting molecular modifications that could be due to the production of more polar phenothiazine derivatives.
The extensive use of pharmaceuticals became a worldwide environmental issue. Most of these compounds are not
completely removed in wastewater treatment plants and, as a result, they are found in surface and ground water.
In this report the behavior of two drugs, Thioridazine and BG1188 were investigated after their exposure in aqueous
solutions to laser radiation. The degradation processes were monitored using spectroscopic techniques (Absorption
Spectroscopy, Laser Induced Fluorescence, NMR Spectroscopy) and chromatographic methods (HPLC-MS).
The Thioridazine 5x10-2 M solution was irradiated up to 11 min and, respectively, BG1188 10-3 M solution was irradiated up to 30 min, both with 355 nm Nd:YAG pulsed laser beam, with 30 mJ average pulse energy on the sample.
The exposure of Thioridazine solution to laser radiation leads to the appearance of new VIS/NIR absorption peaks, while
the 1H NMR spectrum of 11 min irradiated Thioridazine 5x10-2 M solution indicates modifications both in aliphatic and in aromatic protons regions. The HPLC-MS measurements highlight a change of Thioridazine in two metabolites:
Mesoridazine in the first instance and Sulphoridazine finally. The behavior of the irradiated BG1188 10-3 M solution according to the evolution of the absorption and laser inducedfluorescence spectra highlights a photodecomposition of the initial solution and the appearance of new photoproducts. All the investigated solutions exhibit the photodegradation of the initial compounds, which allows us to consider that the exposure of solutions containing pharmaceutical products to laser beams may constitute a possible mean to remove these kinds of pollutants from different wastewater sources.
Besides the biochemical action of methotrexate (MTX) and 5-fluorouracil (FU) their effect in destroying cancer tumours could be enhanced by exposure to light at different doses. Absorption, excitation and emission spectra of 10-4M - 10-5M MTX solutions in natural saline and sodium hydroxide at pH = 8.4 were measured, while their exposure to coherent and uncoherent light in the visible and near ultraviolet (UV) spectral ranges was made (Hg lamps and Nitrogen pulsed laser radiation were used). Absorption spectra exhibit spectral bands in the range 200 nm - 450 nm. The 200 - 450 nm excitation spectra were measured with emission centered on 470 nm; MTX fluorescence excitation was measured at 390 nm and the emission was detected between 400 nm and 600 nm showing a maximum at 470 nm. Spectra modifications, nonlinearly depending on exposure time (varying from 1 min to 20 min), evidenced MTX photo-dissociation to the fluorescent compound 2,4 diamino-formylpteridine. In the 5-FU case the absorption spectra exhibit bands between 200 nm and 450 nm. The emission fluorescence spectra were measured between 400 nm and 600 nm, with λex = 350 nm for UV Hg lamp and with λex = 360 nm for laser irradiated samples; at irradiation with N2 laser emitted radiation the excitation spectra were measured in the range of 200 nm - 400 nm, with λem = 440 nm. New vascularity rapid destruction was observed for conjunctive impregnated with 5-FU solution whilst exposed to incoherent UV and visible light.
Pesticides monitoring at low concentrations using optical absorption, laser induced fluorescence (LIF), fluorescence lifetime measurements and gas chromatography are reported. The studied pesticides were chlortriasines (athrasine, propasine and simasine) and organophosphoric pesticides (dichlorvos and parathion). Since in normal conditions the chlortriasines show absorption spectra in ultraviolet (around 250 nm), to obtain fluorescence spectra in the visible they were treated with pyridine and ethyl ester of cyanoacetic acid in basic medium. The LIF spectra of chlortriasines are measured at concentrations of pollutants between 5 ppm and 20 ppm. The molecular complex fluorescence spectrum induced by pulsed laser radiation at 545 nm, available from a tunable dye laser, exhibited a maximum of 577 nm; it remained unchanged for three hours, following which the intensity decreases as a consequence of the complex destruction (decomposition). The fluorescence lifetime of the molecular complex measured using a fast photodetector was 2.6 ns, immediately after complex formation. The organophosphoric pesticides were monitored using a rather different initial chemical treatment, at the end of which a quinino-vanado- molibdophosphoric complex (PMo10V2O39)2(C20H24O2N2H2)3 was formed. The fluorescence spectra of these pesticides induced by pulsed laser radiation at 337.1 nm available from a pulsed nitrogen laser (700 ps pulse time width, 300 (mu) J/pulse energy) exhibited a maximum at 445 nm with a FWHM of 80 nm. The low concentration detection limits were 0.2 ppm for P in dichlorvos (dichlorvos concentration 14.18 ppm) and 0.2 ppm for P in parathion (parathion concentration 17.8 ppm). These methods in correlation with optical absorption, classical fluorescence and gas chromatography methods were applied to monitor pesticides in water samples collected from the North Pole zone following two expeditions dated March-April 1995 to Severenaia Zemlia Archipelago and July-August 1996 to Spitzbergen Archipelago. Comments about the monitoring of pesticides content of these samples are made.
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