Removal and detoxification of pentahalogenated phenols using a photocatalytically induced enzymatic process.

Poly-halogenated phenols generated from a range of industrial processes can find their way into rivers and ground water. Here we report on a potential treatment for reducing the toxicity of these aqueous pollutants using two highly toxic penta-halogenated phenols (pentachlorophenol (PCP) and pentabromophenol (PBP)) as surrogates. Solutions were passed through a glass column packed with a silica support fused with titanium dioxide (TiO2) and horseradish peroxidase (HRP) immobilized on its TiO2/glass surface (HRP-Tglass). TiO2 photocatalysis was activated through irradiation with UVB (320 nm) which in turn activated the HRP. Two operational flow rates (0.5 and 1.25 mL min-1; hydraulic retention times (HRTs) of 20 and 8 min, respectively), tested the effect of retention time on the extent of degradation and reduction in toxicity of the treated effluent. Microtox® was used to measure the toxicity of the substrate and its by-products at both flow rates. At the highest flow rate, dehalogenation was limited (removal of 37 % chlorine and 22 % bromine) and the toxicity of the reaction products increased. At the lowest flow rate, the longer exposure time resulted in approximately 97 % and 96 % transformation of PCP and PBP, respectively, a greater degree of dehalogenation (removal of 65 % chlorine and 70 % bromine) and a substantial decrease in toxicity of the treated solutions. The higher toxicity of effluent from the higher flow rate was attributed to the initial degradation products being more toxic than the substrates. With a longer HRT, these were then further broken down to less toxic products. Additional toxicity tests (Hydra hexactinella (Hydra) and Chinese Hamster Ovary (CHO) cell toxicity were conducted on the effluent from the lowest flow rate. Both were less sensitive than the Microtox test, with Hydra proving more sensitive than CHO. The novelty of this work is the toxicity risk assessment of the products resulting from the use of a spatially separated immobilized enzyme and photooxidation system. The system was robust and showed no decrease in treatment efficacy over 10 h.

Quantification of tapentadol in canine plasma by HPLC with spectrofluorimetric detection: development and validation of a new methodology.

Tapentadol (TAP) is a novel opioid pain reliever drug that is unusual in its possession of dual mechanism of action (mu opioid-receptor agonist and noradrenaline reuptake inhibitor), this feature makes the active ingredient an attractive potential progenitor of a new pharmacological class. A liquid chromatography-mass spectrometry (LC-MS) method exists to measure TAP in urine and saliva, but the aim of the present study was to develop and validate a simple HPLC-FL based method to quantify TAP in plasma. Several parameters both in the extraction and detection method were evaluated. The applicability of the method was determined by administering TAP orally to two dogs; the protocol yielded the expected pharmacokinetic results and plasma collected by jugular venipuncture at regular intervals. The mobile phase consisted of acetonitrile (A):acetic acid (B) (33 mM), delivered in gradient mode (5-95% B [0-20 min], 95-5% B [20-25 min] and finally 5% B isocratically [25-32 min]) with a flow rate of 1 mL min⁻¹. Excitation and emission wavelengths were of 273 and 298 nm, respectively. TAP was extracted from the plasma using a mixture of Et2O:CH2Cl2 (7:3, v/v), which gave a recovery of 98.0-107.8% and a limit of quantification of 1 ng mL⁻¹. The chromatographic runs were specific with no interfering peaks at the retention times of the analyte and IS (O-desmethyltramadol), as confirmed by HPLC-DAD experiments. In conclusion, this was a simple and effective method using HPLC-FL to detect TAP in plasma, which may be useful for future pharmacokinetic studies.

Continuous enzymatic treatment of 4-bromophenol initiated by UV irradiation.

Horseradish peroxidase (HRP) can be used for the treatment of halogenated phenolic substances. In the presence of hydrogen peroxide phenols are oxidized to form polymers which undergo partial dehalogenation. However, when immobilized, the peroxidase is subject to inactivation due to blockage of the active sites by the growing polymers and to deactivation by elevated levels of hydrogen peroxide. When HRP immobilized on a novel glass-based support incorporating titanium dioxide is subjected to UV irradiation, hydrogen peroxide is produced and the nascent polymer is removed. In this work a reactor was constructed that utilized HRP immobilized on the novel support and the in situ production of hydrogen peroxide to treat 4-bromophenol as a model substrate. The system was operated for almost 17 hours with no apparent decline in activity.