Analytical, toxicological and kinetic investigation of decomposition of the drug diclofenac in waters and wastes using gamma radiation.

A Bojanowska-Czajka,S Borowiecka,A Koc,G Nałęcz-Jawecki,G Kciuk,D Solpan Ozbay,M Gumiela,J F Garcia-Reyes,M Trojanowicz

doi:10.1007/s11356-015-5236-6

Abstract

The radiolytic decomposition of the drug diclofenac (DCF), and in limited extent, also two other widely used drugs, ibuprofen and carbamazepine, was examined using liquid chromatography (LC) methods. The efficiency of DCF decomposition was examined in function of the absorbed dose of gamma radiation, and also in the presence of selected scavengers of radicals, which are commonly present in natural waters and wastes. Three different tests were employed for the monitoring of toxicity changes in the irradiated DCF solutions. The LC/mass spectrometry (MS) was used for the determination of products of DCF radiolysis. Using pulse-radiolysis method with the spectrophotometric detection, the rate constant values were determined for reactions of DCF with the main products of water radiolysis: hydroxyl radicals (1.24 ± 0.02) × 1010 M−1 s−1 and hydrated electrons (3.1 ± 0.2) × 109 M−1 s−1. Their values indicate that both oxidative and reductive processes in radiolytic decomposition of DCF can take place in irradiated diluted aqueous solutions of DCF. The possibility of decomposition of all examined analytes was investigated in samples of river water and hospital waste. Compared to the previous studies, the conducted measurements in real samples were carried out at the concentration levels, which are close to those reported earlier in environmental samples.Graphical abstractᅟ

Highlights

The wide use of pharmaceuticals by the contemporary society results in an important side effect, which is an increasing danger for the natural environment by pharmaceutical residues
For the examined level of the initial DCF concentration 50 mg/L, it was showed that the DCF decomposition in aerated aqueous solution requires dose 4.0 kGy, while in the process carried out with the scavenging of the solvated electron by saturation of the irradiated solution with N2O, leading to substantial increase of hydroxyl radicals according to Eqs. (2) and (3), the required dose drops down to 1 kGy
The deaeration of irradiated solution by saturation with argon and irradiation in the presence of tert-butanol decreases yield of DCF irradiation only in the range of doses from 0.5 to 3 kGy, whereas above 3 kGy, it has no effect. This shows that the radiolytic degradation is more efficient in the oxidative conditions, and this is confirmed by the calculated G values and evaluated rate constant values for reactions of DCF with hydroxyl radicals and hydrated electron, which are reported below

Summary

Introduction

The wide use of pharmaceuticals by the contemporary society results in an important side effect, which is an increasing danger for the natural environment by pharmaceutical residues. A fast increase of interest in different aspects of the presence of pharmaceutical residues in environmental waters is observed. This problem was a subject of several published books, e.g., [Kümmerer 2008], and numerous valuable review articles in scientific journals, e.g., [Fatta-Kassinos et al 2011, Mompelat et al 2009, Luo et al 2014]. A common presence of pharmaceutical residues in the aquatic environment, and in finished drinking water, is a source of concern about their impact on public health, a commonly encountered opinion in the literature is that our current knowledge about the effects of low-dose mixture of pharmaceuticals on human health is very limited.

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