Degradation Products Of Tetracycline Research Articles

Photocatalytic degradation of tetracycline by g-C3N4/stilbite under visible light: Mechanistic insights and degradation pathways

In this study, the g-C3N4/stilbite composite was fabricated by the in-situ synthesis method, and the photocatalytic performance was investigated by degrading tetracycline (TC) under visible light. The results indicated that the photocatalytic degradation efficiency of g-C3N4/stilbite-6 (86.8 %) was about 2.7 times higher than that of pure g-C3N4 (31.8 %). The introduction of the stilbite carrier effectively resolved the issues of g-C3N4 such as easy self-agglomeration and the difficulty in separating photo-generated carriers, thereby improving the photocatalytic activity of g-C3N4. From the quenching experiment, it was found that h+ and •O2− were main active species for TC degradation. By HPLC-MS analysis, TC degradation products were identified, and three degradation pathways were proposed. In addition, the impacts of solution pH, light intensity, and catalyst dosage on TC degradation performance were also evaluated. Overall, a simple and successful strategy has been proposed to synthesize high-performing visible-light-driven photocatalysts for efficiently eliminating organic contaminants from wastewater.

Transformation of antibiotics to non-toxic and non-bactericidal products by laccases ensure the safety of Stropharia rugosoannulata

The substantial use of antibiotics contributes to the spread and evolution of antibiotic resistance, posing potential risks to food production systems, including mushroom production. In this study, the potential risk of antibiotics to Stropharia rugosoannulata, the third most productive straw-rotting mushroom in China, was assessed, and the underlying mechanisms were investigated. Tetracycline exposure at environmentally relevant concentrations (<500 μg/L) did not influence the growth of S. rugosoannulata mycelia, while high concentrations of tetracycline (>500 mg/L) slightly inhibited its growth. Biodegradation was identified as the main antibiotic removal mechanism in S. rugosoannulata, with a degradation rate reaching 98.31 % at 200 mg/L tetracycline. High antibiotic removal efficiency was observed with secreted proteins of S. rugosoannulata, showing removal efficiency in the order of tetracyclines > sulfadiazines > quinolones. Antibiotic degradation products lost the ability to inhibit the growth of Escherichia coli, and tetracycline degradation products could not confer a growth advantage to antibiotic-resistant strains. Two laccases, SrLAC1 and SrLAC9, responsible for antibiotic degradation were identified based on proteomic analysis. Eleven antibiotics from tetracyclines, sulfonamides, and quinolones families could be transformed by these two laccases with degradation rates of 95.54–99.95 %, 54.43–100 %, and 5.68–57.12 %, respectively. The biosafety of the antibiotic degradation products was evaluated using the Toxicity Estimation Software Tool (TEST), revealing a decreased toxicity or no toxic effect. None of the S. rugosoannulata fruiting bodies from seven provinces in China contained detectable antibiotic-resistance genes (ARGs). This study demonstrated that S. rugosoannulata can degrade antibiotics into non-toxic and non-bactericidal products that do not accelerate the spread of antibiotic resistance, ensuring the safety of S. rugosoannulata production.

Efficient activation of peroxymonosulfate by Co/Cu co-substituted-ferrite and carbon composite for rapid degradation of tetracycline in aqueous phase: Performance evaluation and mechanisms

In this study, a novel Co/Cu co-substituted ferrite-carbon composite CoxCu1-xFe2O4@C (x = 0.1, 0.3, 0.5, 0.7, and 0.9) was prepared by gel-thermolysis to activate peroxymonosulfate (PMS) for tetracycline (TC) removal. The materials were comprehensively characterized using different instruments. Batch experiments were conducted to investigate the effects of different operating parameters on TC removal. Our findings indicated that appropriate amount of Co and Cu substitution was very important. Co0.5Cu0.5Fe2O4@C (CoCF-0.5@C) exhibited the best activity. Using 0.1 g/LCoCF-0.5@C and 0.15 g/LPMS achieved 90.06 % TC removal (0.4091 min−1) in 6 min. Humic acid significantly inhibited TC removal, whereas the impact of coexisting anions varied. Thereinto, CO32− displayed moderate inhibitory effect, Ca2+ and NH4+ showed weak inhibitory effect, and SO42− exhibited insignificant effect. CoCF-0.5@C demonstrated not only excellent activity but also remarkable stability and anti-interference ability, achieving over 60 % TC removal under diverse conditions, such as a wide pH range (pH 3–11), different coexisting ions, and various matrices. Even after 5 cycles, CoCF-0.5@C could maintain 78.4 % TC removal. Compared to other catalysts in previous studies, CoCF-0.5@C combines the dual advantages of high activity and reproducibility. The results of quenching experiments, EPR/ESR and electrochemical tests showed that TC removal mechanism were dominated by non-radical 1O2 and direct electron transfer. The cycling of Cu2+/Cu+, Fe3+/Fe2+, and Co3+/Co2+ in CoCF-0.5@C played a pivotal role in PMS activation, accelerating electron transfer and reactive oxygen species (ROS) generation. The carbon helped to disperse ferrite and avoid its agglomeration, which significantly enhanced electron transfer. Based on the degradation products of TC, two possible pathways for TC degradation were proposed. This study provides a new approach for development of efficient PMS activators to promote TC degradation.

Single-atomic Co-N site modulated exciton dissociation and charge transfer on covalent organic frameworks for efficient antibiotics degradation via peroxymonosulfate activation

Covalent organic framework (COF) materials have received extensive attention in the field of photocatalysis in recent years, but the strong exciton effect in COF has seriously affected the separation of electron-hole pairs so that limiting the enhancement of the photocatalytic performance. It is of great significance to explore suitable ways to regulate the exciton behavior in COF materials and enhance their electron-hole's separation efficiency. By anchoring Co single-atoms within a silver birch leaf-like COF framework (COF-Cox), the exciton in COF is effectively dissociated by forming Co-N sites, producing massive free electrons and holes. Co-N sites also facilitate photogenerated holes aggregation toward Co single-atoms, which effectively drives the carriers' separation in COF framework. The carrier concentration of COF-Co10 is 2.81 times higher compared with the original COF. The reduced exciton binding energy (Eb) further proves that the the formation of Co-N sites promote the exciton dissociation. Consequently, COF-Cox can well activate peroxymonosulfate (PMS) to degrade tetracycline (TC) pollutants, the reaction rate constant of COF-Co10 (3.65 × 10-2 min−1) is 5.27 times higher than COF (6.93 × 10-3 min−1). The possible activation routes and degradation products of TC are also discussed. This study provides a more comprehensive understanding of the exciton behavior for the design of more efficient COF-based catalysts.

Sonocatalytic degradation of tetracycline by Cu2O/MgFe2O4 nanocomposites: Operational parameters, sonocatalytic mechanism, degradation pathways, and environmental toxicity

Cu2O/MgFe2O4 nanocomposites with an S-scheme heterojunction were synthesized successfully and the sonocatalytic degradation effect of tetracycline (TET) by Cu2O/MgFe2O4 nanocomposites was demonstrated. Using the combination of analytical characterization and theoretical estimates, the composition, microscopic shape, comparative surface area and catalysis properties of Cu2O/MgFe2O4 nanocomposite materials were investigated. The experiment results showed that Cu2O/MgFe2O4 had good sonocatalysis performance. Over 91.93±1.07% TET was removed within 90 min at the optimal conditions. The TET sonocatalytic degradation mechanism showed that reactive species such as holes (h+), hydroxyl free radicals (·OH), and superoxide anion radicals (·O2−) produced during the reaction played a vital role in the effective removal of TET. Finally, the possible degradation products of TET were investigated by MS Q-TOF. In conclusion, the sonocatalytic activity, reusability, and stability of the produced Cu2O/MgFe2O4 nanocomposites are excellent, demonstrating that Cu2O/MgFe2O4 nanocomposites will become the focus of research in the field of sonocatalytic removal of pollutants.

Ecotoxicity and resistance genes induction changing of antibiotic tetracycline degradation products dominated by differential free radicals

Studying the ecological risks of antibiotics and their degradation products is of great importance to water environment security and advanced oxidation processes (AOPs) development. This work studied the changes and internal influencing mechanisms of ecotoxicity and the capacity for inducing antibiotic resistance genes (ARGs) shown by the tetracycline (TC) degradation products generated in AOPs with differential free radicals. Under the action of superoxide radicals and singlet oxygen in the ozone system, and sulfate and hydroxyl radicals in the thermally activated potassium persulfate system, TC exhibited differential degradation pathways and resulted in the differential growth inhibition trends on the determined strains. Microcosm experiments combined with metagenomics were also performed to analyze the remarkable changes in the TC resistance genes tetA (60), tetT, and otr(B) induced by the degradation products and ARG hosts in the natural water environment. Microcosm experiments exhibited that the microbial community in actual water have changed significantly with the addition of TC and degradation intermediates. Furthermore, the richness of genes related to oxidative stress was investigated to discuss the effect on reactive oxygen species production and SOS response caused by TC and its intermediates.

Tetracycline photolysis revisited: Overlooked day-night succession of the parent compound and metabolites in natural surface waters and associated ecotoxicity

Despite the extensive study of tetracycline photolysis in aquatic environments, the phototransformation of tetracycline and its metabolites under natural day-night succession has not been examined. In this study, we investigated tetracycline photolysis and associated ecotoxicity in two natural surface waters and one artificial ultrapure water under simulated day/night cycling over two days. Previously unrecognized and highly pH- and temperature-dependent dark interconversions of tetracycline metabolites were observed. The liquid chromatography-mass spectrometry/mass spectrometry analysis identified a range of isomerized, hydroxylated, demethylated, deaminated, and open-ring photoproducts. The hydrolysis of tetracycline, isotetracycline, and several intermediate products was proposed as the major mechanism for the observed dark transformations. Exposure studies employing Escherichia coli indicated that although the tetracycline degradation products had lower bacterial toxicities than the parent compound, increasing toxicity with irradiation time after the near-complete degradation of the parent compound in natural waters implied that product mixtures retain ecotoxicity. The dark transformations also affected the bacterial toxicity and fluorescence properties of irradiated tetracycline solutions. Overall, this study provides new insights into the photochemical behavior of tetracycline and its associated ecological risk in aquatic environments.

Double Z-scheme Co3O4/Bi4O7/Bi2O3 composite activated peroxymonosulfate to efficiently degrade tetracycline under visible light.

Co3O4/Bi4O7/Bi2O3 (CBB) composites were prepared, in which Co3O4 was synthesized from Co-MOF as precursor. The peroxymonosulfate (PMS) activated by CBB catalyst under visible light was used to degrade tetracycline (TC). Owing to the synergistic effect of photocatalysis and PMS activation, 98.4% of TC was removed within 60min. The optimal loading of Co3O4 was determined, and the influence of PMS dosage, initial pH, and disturbing anions on the degradation effect were investigated. The "CBB + Vis + PMS" system showed good reusability, and the degradation was only reduced by 1.7% after 5 cycles. This system also had a good degradation of other five pollutants. The quenching experiment showed that holes (h+), superoxide radicals (·O2-), and singlet oxygen (1O2) were the main active species. The degradation products of TC were determined by liquid chromatography-mass spectrometry, and the degradation pathway was proposed. Finally, a double Z-scheme degradation mechanism was proposed in the "CBB + Vis + PMS" system. The peroxymonosulfate activated by CBB under visible light to degrade organic pollutants has widespread application prospects in environmental remediation.

Biodegradation of Tetracycline Antibiotics by the Yeast Strain Cutaneotrichosporon dermatis M503.

In this study, the Cutaneotrichosporon dermatis strain M503 was isolated and could efficiently degrade tetracycline, doxycycline, and chlorotetracyline. The characteristics of tetracycline degradation were investigated under a broad range of cultural conditions. Response surface methodology (RSM) predicted that the highest degradation rate of tetracycline could be obtained under the following conditions: 39.69 °C, pH of 8.79, and inoculum dose of 4.0% (v/v, ~3.5 × 106 cells/mL in the medium). In accordance with the five identified degradation products of tetracycline, two putative degradation pathways, which included the shedding of methyl and amino groups, were proposed. Moreover, the well diffusion method showed that the strain of M503 decreases the antibacterial potency of tetracycline, doxycycline, and chlorotetracycline. These findings proposed a putative mechanism of tetracycline degradation by a fungus strain and contributed to the estimation of the fate of tetracycline in the aquatic environment.

Activation of peroxydisulfate by bimetal modified peanut hull-derived porous biochar for the degradation of tetracycline in aqueous solution

The sulfate radical-based advanced oxidation processes (SR-AOPs) are considered to be efficient and environmentally friendly for handling persistent organic pollutants issues. The activation of persulfate (PS) by biochar (BC) materials derived from waste biomass is the current research hotspot in SR-AOPs. Herein, we propose bimetal modified peanut hull-derived biochar (BC-Fe-1-Zn) catalysts to activate PS to degrade tetracycline (TC) with a removal efficiency of 90% in 120 min. The physicochemical properties and reaction mechanisms are well studied through the effective combination of various characterization techniques and experiments. SO4•–, •OH and electron transfer are all involved in the degradation of TC and SO4•– is the main reactive oxygen species (ROSs). The Fe and Zn oxides and the oxygen-containing functional groups on the catalyst surface are considered as the active sites for the reaction. Moreover, the influences of different factors (such as pH, catalyst dosage, PS dosage and coexisting ions) on the TC remove efficiency are studied. Simultaneously, the TC degradation products and its reasonable degradation paths are analyzed. This work provides new ideas for the rational design of biochar-supported bimetallic catalysts and revealed that using BC-Fe-1-Zn in AOPs technology to environmental remediation is a promising approach.

Degradation of tetracycline by atmospheric-pressure non-thermal plasma: Enhanced performance, degradation mechanism, and toxicity evaluation

Tetracycline is a common antibiotic and is often carelessly released into the natural environment, thus constantly posing potential threats to the environment. Currently, due to lack of effective methods to remove it from the environmental water system, researchers are still exploring new ways to deal with tetracycline. In this work, we employed atmospheric-pressure non-thermal plasma (NTP) to treat tetracycline in water and investigated the involved degradation mechanism. The enhanced degradation efficiency was acquired and investigated, and the degradation mechanism by the plasma-generated active species were explored. The tetracycline degradation pathways via especially the interactions with plasma-generated hydroxyl radical and ozone were examined by virtue of UV spectroscopy, three-dimensional fluorescence spectroscopy, high performance liquid chromatography-mass spectrometry (HPLC-MS), together with the assistance of theoretical simulations. Moreover, the toxicological evaluation of NTP treatment of tetracycline was also provided, which confirmed that the biological toxicity of tetracycline degradation products was negligible. Therefore, this work provides not only the effective way of treating antibiotics by engineered plasma technology, but also the insights into the mechanisms of degradation of antibiotics by NTP.

Fe/Mn loaded sludge-based carbon materials catalyzed oxidation for antibiotic degradation: Persulfate vs H2O2 as oxidant

Due to the nature of high carbon content in sludge, that is promising to fabricate multi-functional carbon materials with waste activated sludge (WAS). In this study, we report a facile and cost-effective approach to convert waste activated sludge (WAS) into multi-functional sludge-based carbons (Fe/Mn-SBC) through KMnO4-Fe(II) conditioning coupled with pyrolysis strategy. The Fe/Mn-SBC had abundant porous structure and superior catalytic activities towards PS /H2O2, resulting in highly efficient removal of tetracycline (TC) through catalytic oxidation. Meanwhile, •OH radicals played the leading role during TC degradation process in both of Fe/Mn-SBC catalyzed PS and H2O2 systems compared to 1O2 and SO4•- radicals. In addition, the SO4•- produced in Fe/Mn-SBC catalyzed PS system led to higher TC degradation than H2O2 over a wide range of pH, due to its stronger oxidizing and stably properties compared to •OH. Moreover, the different free oxygen radicals were produced from Fe/Mn-SBC catalyzed PS /H2O2, causing formation of different TC degradation products via losing H2O and methyl in amin, or hydroxylation, hydrogenation, and dihydroxylation processes. This study proposed a novel strategy for excess sludge reutilization for preparing carbon-based catalyst with superior oxidative ability for PS /H2O2 activation for organic contaminants degradation.

Tetracycline degradation by persulfate activated with magnetic γ-Fe2O3/CeO2 catalyst: Performance, activation mechanism and degradation pathway

Tetracycline is a typical antibiotic that is eco-toxic and easily causes bacterial resistance, and thus it is necessary to eliminate tetracycline from the water environment. In this work, γ-Fe2O3/CeO2 was prepared and used to activate persulfate for tetracycline degradation. The catalyst was characterized by XRD, VSM and XPS, and results showed that it had excellent crystallinity and magnetism. The low valence metals (Fe (II) and Ce (III)) in γ-Fe2O3/CeO2 benefited persulfate activation. Tetracycline removal efficiency reached 84% with the γ-Fe2O3/CeO2/persulfate system; and the value was 70% in the surface water matrix. In addition, γ-Fe2O3/CeO2 kept high activity from pH 3 to 9. It had high stability and reusability and was easily recycled from solution due to its good magnetism. Mechanism analyses showed that SO4− and OH on catalyst surface catalyst were the major active species, O2− and 1O2 were also produced due to the excess oxygen vacancies of catalyst. Moreover, the degradation products of tetracycline were determined, and the degradation pathway was proposed. Hydroxylation, demethylation, decarbonylation, dehydroxylation, C-N bond cleavage and ring-opening were the main pathway. The cost of wastewater treatment with the γ-Fe2O3/CeO2/persulfate system was estimated to be 0.106 $/m3. This study provided an efficient and stable catalyst for tetracycline degradation.

Effects of rainfall events on behavior of tetracycline antibiotics in a receiving river: Seasonal differences in dominant processes and mechanisms.

Tetracycline (TC) antibiotics are widely used in livestock and poultry breeding. However, limited work has been done on the partition of TCs between suspended sediment (SPS) and overlying water or on the seasonal effects of rainfall events on the behavior of TCs in receiving rivers. Here, we assessed the impacts of rainfall events in different seasons on the concentrations and fate of TCs in a typical watershed. Concentrations of TCs in river water, SPS, and surface sediment were determined before, during, and after rainfall events. Results indicated that the sequence of TC concentration levels in river water was wet season > normal season > dry season. Rainfall events in all seasons increased the concentrations of TCs in river water. The concentration of TCs in SPS reached 104 ng/g. The SPS concentrations were only 22-78 mg/L, while the daily fluxes of TCs in particulate form contributed 39%-62% of the total (dissolved and particulate) daily fluxes in river water. The increases in TCs in river water were mainly attributed to internal release from sediment during rainfall events in the dry season but to external input during rainfall events in the wet season. The degradation products of TCs with higher concentrations and greater toxicity than their parent compounds should be considered in the ecological risk assessment of TCs. This research demonstrated that manure application should not be conducted in the normal season or before rainfall events, especially heavy rainfall.

Simultaneous removal of tetracycline and Cr(VI) by a novel three-dimensional AgI/BiVO4 p-n junction photocatalyst and insight into the photocatalytic mechanism

Simultaneous combination of photocatalytic oxidation of tetracycline (TC) and reduction of Cr(VI) over the AgI/BiVO4 p-n junction photocatalysts were studied systematically. The result showed that the pollutant degradation efficiency of the photocatalyst was greatly enhanced when the system contained both TC and Cr(VI) compared to that containing Cr(VI) or TC alone. It is proposed that the co-existence of oxidizable and reducible species, such as TC and Cr(VI), ensured efficient use of the photoinduced electrons and holes, which leaded high efficiencies for both TC oxidation and Cr(VI) reduction. Among these photocatalysts, the 0.3-AgI/BiVO4 exhibits excellent photocatalytic activity, which is ascribed to the increased lifetime of the charge carriers confirmed by the result of time-resolved fluorescence emission decay spectra. In addition, seven degradation products of TC were found by GC–MS. Moreover, the band structure of the photocatalyst was obtained by the DFT calculation, VB-XPS spectra and the values of the Fermi level obtained by CASTEP. Finally, simultaneous photocatalytic oxidation and reduction enhancing mechanism over the AgI/BiVO4 photocatalyst was discussed in detail. The strategy of forming novel p-n junction photocatalyst for both the Cr(VI) reduction and TC oxidation will benefit the development of the other new photocatalysts for the purpose of controlling and improving the environment.

Toxic effects of tetracycline and its degradation products on freshwater green algae

Tetracycline antibiotics are the most widely used antibiotics in the world and the most common veterinary drugs and feed additives used in livestock, poultry and aquaculture operations. Because antibiotics cannot be completely removed by currently existing sewage treatment facilities, these materials enter the environment directly via sewage treatment plant discharge, where they degrade. Accordingly, the metabolism and the ecological toxicity of tetracycline degradation products are worthy of attention. Herein, we investigated the effects of tetracycline and its degradation products (anhydrotetracycline and epitetracycline hydrochloride) on the growth, cell structure and algal cell oxidative stress of common Chlorella vulgaris. The results showed that the 96h-EC50 values of tetracycline (TC), anhydrotetracycline (ATC) and epitetracycline (ETC) on algal cells were 7.73, 5.96 and 8.42 mg/L, respectively. Moreover, the permeability of algal cells exposed to high concentrations of these three drugs was significantly enhanced. In addition, there were structural changes in the cells such as plasmolysis and starch granule deposition appeared, the thylakoid lamellae in the chloroplasts became blurred and deformed, and the vacuoles became larger. Exposure to higher concentrations (>5 mg/L) of TC and its degradation products ATC and ETC significantly upregulated the activity of ROS, as well as the antioxidants SOD and CAT. The levels of the lipid peroxidation product MDA also showed the same trend. Finally, ATC had the strongest toxicity toward algal cells, followed by TC and then ETC.

Occurrence and transformation of veterinary antibiotics and antibiotic resistance genes in dairy manure treated by advanced anaerobic digestion and conventional treatment methods.

Manure treatment technologies are rapidly developing to minimize eutrophication of surrounding environments and potentially decrease the introduction of antibiotics and antibiotic resistant genes (ARGs) into the environment. While laboratory and pilot-scale manure treatment systems boast promising results, antibiotic and ARG removals in full-scale systems receiving continuous manure input have not been evaluated. The effect of treatment on ARGs is similarly lacking. This study examines the occurrence and transformation of sulfonamides, tetracyclines, tetracycline degradation products, and related ARGs throughout a full-scale advanced anaerobic digester (AAD) receiving continuous manure and antibiotic input. Manure samples were collected throughout the AAD system to evaluate baseline antibiotic and ARG input (raw manure), the effect of hygenization (post-pasteurized manure) and anaerobic digestion (post-digestion manure) on antibiotic and ARG levels. Antibiotics were analyzed by liquid chromatography-tandem mass spectrometry (LC-MS/MS), and the ARGs tet(O), tet(W), sul1 and sul2 were analyzed by quantitative polymerase chain reaction (Q-PCR). Significant reductions in the concentrations of chlortetracycline, oxytetracycline, tetracycline and their degradation products were observed in manure liquids following treatment (p < 0.001), concomitant to significant increases in manure solids (p < 0.001). These results suggest sorption is the major removal route for tetracyclines during AAD. Significant decreases in the epimer-to-total residue ratios for chlortetracycline and tetracycline in manure solids further indicate degradation is desorption-limited. Moreover, sul1 and sul2 copies decreased significantly (p < 0.001) following AAD in the absence of sulfonamide antibiotics, while tetracyclines-resistant genes remained unchanged. A cross-sectional study of dairy farms utilizing natural aeration and liquid-solid separation treatments was additionally performed to compare levels of antibiotics and ARGs found in AAD with the levels in common manure management systems. The concentration of antibiotics in raw manure varied greatly between farms while minimal differences in ARGs were observed. However, significant (p < 0.01) differences in the levels of antibiotics and ARGs (except tet(W)) were observed in the effluents from the three different manure management systems.

Evaluation of Degradation of Antibiotic Tetracycline in Pig Manure by Electron Beam Irradiation

This study was carried out to evaluate the degradation efficiency and intermediate products of the tetracycline from artificially contaminated pig manure using of electron beam irradiation as a function of the absorbed dose. The degradation efficiency of tetracycline was 42.77% at 1 kGy, 64.20% at 3 kGy, 77.83% at 5 kGy, and 90.50% at 10 kGy. The initial concentration of tetracycline (300 mg kg(-1)) in pig manure decreased significantly to 24.2 +/- 5.3 mg kg(-1) after electron beam irradiation at 10 kGy. The radiolytic degradation products of tetracycline were 1,4-benzenedicarboxylic acid, hexadecanoic acid, 9-octadecenamide, 11-octadecenamide, and octadecanoic acid.

Formation of Tetracycline Degradation Products in Chicken and Pig Meat under Different Thermal Processing Conditions

Tetracycline (TC) and 4-epitetracycline (4eTC) degradation, as well as anhydrotetracycline (ATC) and 4-epianhydrotetracycline (4eATC) formation, has been evaluated in thermally treated chicken breast, pig loin, and pig loin with added back-fat. Samples containing TC and 4eTC residues were submitted to microwave or boiling heating, extracted with a mixture of McIlvaine buffer/methanol (75:25), and analyzed by high-performance liquid chromatography-diode array detection on a phenyl-hexyl reverse phase chromatographic column. The formation of ATC and 4eATC, as well as of two unidentified compounds, was described for the first time in edible meat samples submitted to mild thermal treatments, similar to those applied at home to cook foods. Degradation of TC and 4eTC and formation of ATC and 4eATC versus time of treatment fitted satisfactorily a first-order kinetic. Even if the potential toxic effects of these breakdown compounds should be further investigated, their formation in cooked meat should be taken into account when maximum residue limits are established.

Chemical stability of chlortetracycline and chlortetracycline degradation products and epimers in soil interstitial water

Tetracyclines and tetracycline degradation products and epimers end up in the environment. In order to predict the persistence of the potential dominating species of the chlortetracyclines in the environment, the chemical stability of chlortetracycline (CTC) and four major CTC degradation products and epimers (iso-CTC, 4-epi-CTC, anhydro-CTC, and 4-epi-anhydro-CTC) was studied in milliQ water and soil interstitial water (SIW) under environmentally relevant conditions (oxygen, light, pH (3–9), and temperature (6 °C and 20 °C)). The chemical stability of the compounds was evaluated by following the decrease in amount of parent compound over time. In order to compare the results obtained under the varying conditions, apparent pseudo-first-order rate constants ( k obs) for the disappearance of the parent compound and corresponding apparent half-lives were calculated. A statistical evaluation of the data showed that the chemical stability of the chlortetracyclines was generally dependent on photolysis, temperature, and matrix. The presence or absence of oxygen did not influence on the chemical stability. The presence of calcium and magnesium ions in SIW is believed to account for the significant differences in half-lives between milliQ water and SIW, although numerous of other factors are believed to influence as well. Generally, the five compounds were more persistent at pH 3–4 than at pH above 5.