Increased formation of halomethanes during chlorination of chloramphenicol in drinking water by UV irradiation, persulfate oxidation, and combined UV/persulfate pre-treatments.

Ultraviolet/persulfate (UV/PS) has been widely used to generate sulfate radicals for degradation of water organic pollutants in previous studies. However, its impacts on disinfection byproduct formation during post-chlorination of degraded compounds is unclear. The objective of this study was to evaluate the impacts of UV irradiation, PS oxidation, and the combined UV/PS advanced oxidation process (AOP) pre-treatments on halomethane formation during the following chlorination of chloramphenicol (CAP), a model antibiotic commonly found in wastewater-impacted water. Results showed that CAP could be transformed to more trichloromethane (TCM) than monochloromethane (MCM) and dichloromethane (DCM) in the presence of excess chlorine. UV photolysis, PS oxidation and UV/PS AOP all directly decomposed CAP to produce halomethanes (HMs) before post-chlorination. Moreover, UV and UV/PS pre-treatments both enhanced the formation of all the HMs in the subsequent chlorination. PS pre-oxidation decreased the TCM formation during post-chlorination, but increased the yields of MCM, DCM and total HMs. UV pre-irradiation significantly increased the bromide utilization of HMs, whereas UV/PS pre-oxidation decreased the bromine incorporation and utilization of HMs from the chlorination of CAP in a low-bromide water. UV irradiation, PS oxidation, and UV/PS AOP can inactivate pathogens and degrade organic pollutants, but this benefit should be weighed against a potential risk of the increased halomethane formation from degraded organic pollutants with and without post-chlorination.

Detoxification of the veterinary antibiotic chloramphenicol using electron beam irradiation.

Electron beam irradiation has shown potential as an alternative process for the treatment of industrial effluents that contain toxic organic chemicals. This study investigated the effectiveness of electron beam in degrading chloramphenicol (CAP) in aqueous solution. The degradation efficiency was 32.4% at 1 kGy, 86.9% at 5 kGy, and 100% at 10 kGy. The total organic carbon (TOC) of CAP in aqueous solution declined 4.6% at 1 kGy, 12.1% at 5 kGy, and 17.1% at 10 kGy of irradiation with electron beam. The CAP degradation products after irradiation were CAP1 ([M + H] m/z 307.1), CAP2 ([M + H] m/z 291.1), and CAP3 ([M + H] m/z 321.1). The degradation products were tested for microbial toxicity against Escherichia coli, Pseudomonas putida, and Bacillus subtilis and did not show any toxic antimicrobial effects caused by the CAP degradation products after irradiation with electron beam. The results of this study suggest that electron beam irradiation is the best technology for the comprehensive treatment of veterinary antibiotics at wastewater treatment plants.

Photocatalytic degradation and drug activity reduction of Chloramphenicol.

The photocatalytic degradation of Chloramphenicol, an antibiotic drug, has been investigated in aqueous heterogeneous solutions containing n-type oxide semiconductors as photocatalysts. The disappearance of the organic molecule follows approximately a pseudo-first-order kinetics according to the Langmuir-Hinshelwood model. It was observed that, with TiO(2) P-25 as photocatalyst, quantitative degradation of the organic molecule occurs after 4h of illumination. During this time, the dechlorination of the substrate is complete, while the organic nitrogen was recovered in the form of nitrate and ammonium ions. The effect of temperature on the degradation rate of Chloramphenicol shows similar apparent activation energies for both TiO(2) P-25 and ZnO photocatalysts. The initial apparent photonic efficiency (zeta(0)) of the photo-oxidation and the mineralization under various experimental conditions have been calculated, while the Kirby-Bauer disc diffusion method showed a 100% reduction of the drug activity after 90 min of photocatalytic treatment.

[Application of photochemically activated ointment based on polyethylene oxides for treatment of peritonitis].

There was given evidence, using the complex of morphological, morphometrical, biochemical and microbiological investigations in experiment, of the peritonitis treatment efficacy applying photochemically activated laevomecol ointment. The experiment was performed in 120 adult male white mongrel rats, following the recommendations of Vancouver's convention for biomedical investigations.

Determination of assay and impurities of gamma irradiated chloramphenicol in eye ointment.

A sample preparation method was developed to isolate chloramphenicol and its radiolytic products from an oily ointment base. The isolation method suspended the eye ointment in n-hexane at 45 degrees C, and isolated the target compounds as residue by centrifugation. It was found that the main element to ensure a satisfactory isolation was keeping the sample solution at 45 degrees C during sample preparation. Linearity, precision, accuracy and suitability of the method were confirmed valid for both assay and impurity tests. This isolation method was ideal for assay, unique for extraction of unexpected and complex radiolysis products, and had a number of advantages compared to the pretreatment methods described in The United Stares Pharmacopoeia and British Pharmacopoeia, in terms of accuracy, precision, and easy handling. The effect of gamma-irradiation on chloramphenicol eye ointment was studied by HPLC, after applying the developed sample preparation method. The present assay and impurity test methods with HPLC were confirmed to be suitable for irradiated chloramphenicol in eye ointment. Formation of radiolytic products induced by gamma-irradiation was evidenced by the impurity test. The assay test showed that active ingredient of chloramphenicol eye ointment decreased by 3.3% at an irradiation dose of 25 kGy and by 11.1% at 50 kGy.

[Decomposition of chloramphenicol in eyedrops--irritation in the eyes]. / Spaltning av kloramfenikol i øyedråper--svie i øynene.

Chloramphenicol single dose eyedrops 0.5% (Nycomed Pharma) have been found to be very sensitive to exposure to light. We could detect approximately 15% decomposition after six hours of exposure to diffuse daylight. One of the decomposition products is the extremely irritant dichloroacetic acid. This may explain why some patients complain of a burning sensation in the eyes. In one of the samples of light yellow eyedrop received together with the complaints our analysis revealed 17% of the end-cleavage product p-nitrobenzaldehyde. The Norwegian Medicines Control Authority will suggest to the producers of these preparations that they market the product in special light-proof containers.

Photoreactivity of chloramphenicol in vitro and in vivo.

The negative side effects of chloramphenicol (CAP) mostly involve blood dyscrasias (e.g. irreversible non-dose-dependent aplastic anemia), allergic skin reactions and eye damage. To learn the cause of these side effects, most research focuses on metabolically formed nitroso- and hydroxylamino derivatives in the predisposed patient. In previous investigations it was demonstrated that photochemical decomposition of CAP in vitro by UV-A leads to formation of p-nitrobenzaldehyde (pNB), p-nitrobenzoic acid (pNBA) and p-nitrosobenzoic acid (pNOBA); the latter comprises up to 45 mol% of the starting amount of CAP. Incubation of these photoproducts in rat blood showed that pNB and pNOBA rapidly react and that PNBA is stable under these conditions. Reaction products from pNB (half-life 1.7 min) proved to be pNBA and p-nitrobenzyl alcohol (pNBOH) while pNOBA (half-life 3.7 min) was converted into p-aminobenzoic acid (pABA). Exposure of CAP in rat blood to UV-A yielded the same end products: pNBA, pABA and pNBOH. To estimate the amount of oxidative stress generated in vivo by these compounds, the ability to form methemoglobin (MetHb) in erythrocytes was tested; only pNOBA and p-hydroxylaminobenzoic acid (pHABA), a possible intermediate in the decomposition of pNOBA, proved to be reactive. Ultraviolet-A exposure of rats, after intraperitoneal injection of CAP, led to 3.6 times the basic level of MetHb. In addition, covalent binding of 3H-labeled CAP photoproducts to the skin of the back and to the ears was found, which was 9.1 and 3.2 times higher, respectively, than the dark values.(ABSTRACT TRUNCATED AT 250 WORDS)

Pulse radiolysis study of the reactivity of chloramphenicol, diazepam and clonazepam with the electron and the hydroxyl radical.

Chloramphenicol (CAP), diazepam (DIAZ) and clonazepam (CLONA) have been irradiated in aqueous and methanolic solutions by pulsed electrons (Febetron 707). Spectra of the species formed by the attack of the solvated electron and of OH radical have been determined. The kinetics of reaction of CAP, DIAZ, and CLONA with the solvated electron have been measured. Reactions of radical-radical recombination have also been studied. All these reactions are limited by the diffusion of the reactive species.

Photo-induced affinity labeling of Escherichia coli ribosomes by chloramphenicol.

In order to obtain more information about the binding site for chloramphenicol (D-threo diastereoisomer) on the bacterial ribosome, photo-affinity labeling experiments of this receptor have been performed with [3H]chloramphenicol itself. Control experiments show that this drug can be split photochemically by ultraviolet irradiation, whereas the ribosome is not modified structurally or functionally by such a treatment. When photolysis of a mixture of chloramphenicol and ribosomes is performed under critical conditions, some proteins like L1, L11, S3 and S4 are radiolabeled. L11, S3 and S4 are radiolabeled specifically as demonstrated by photo-incorporation experiments with isotopically diluted [3H]chloramphenicol or by comparison of the results obtained here with reversible experiments performed by the isotopic dilution method. When the D-erythro diastereoisomer of chloramphenicol is photo-incorporated into the bacterial ribosome, proteins are radiolabeled only in a non-specific way. These results show that this material could be used as an efficient scavenger. When finally D-threo [3H]chloramphenicol is photo-incorporated in the presence of a large amount of the D-erythro diastereoisomer, the radiolabeling pattern obtained for the proteins is quite different from that expected: while L11 is still labeled fairly extensively, L27 is the most radiolabeled protein found.

Light sensitive chloramphenicol analogues.

Some chloramphenicol analogues have been prepared in order to find reagents which could be used in a photoaffinity labelling study of the peptidayl transferase center of the E. coli ribosome. The compounds were tested for antibiotic activity in vitro in the "fragment reaction" assay, and for their ability to generate very reactive species upon irradiation.