Determination of tetracyclines in surface water and milk by the magnesium hydroxide coprecipitation method

Tetracyclines uptake from irrigation water by vegetables: Accumulation and antimicrobial resistance risks

Wastewater irrigation may introduce antibiotic residues in the soil-plant systems. This study aimed to investigate the uptake of tetracyclines by spinach and collard greens and assess associated ecological and human health risks. Synthetic wastewater spiked with 1 ppm and 10 ppm of oxytetracycline, doxycycline, and tetracycline was used to grow vegetables in a greenhouse pot experiment. The uptake and accumulation of the tetracyclines were low and residual concentrations in the soil were negligible. All the tetracyclines were detected at concentrations ranging from 1.68 to 51.41 μg/g (spinach) and 1.94-30.95 μg/g (collard greens). The accumulation rate was in a dose-response scenario with a bioconcentration factor of 6.34 mL/kg (spinach) and 2.64 mL/kg (collard greens). Oxytetracycline had the highest accumulation in leaves, followed by doxycycline and tetracycline, and the residual concentrations followed the same order. The highest residual concentration was in soils receiving 10 ppm oxytetracycline. Residual concentrations in the soil were lower than accumulated levels and exerted negligible ecological risks. Tetracyclines accumulation in spinach significantly differed between the vegetables demonstrating a subspecies difference in uptake and accumulation. Ecological risk quotient (RQ) and human health risk quotient (HQ) were below thresholds that would exert toxicity and resistance selection impacts. Although RQs and HQs are low (<0.1), this study shows that the vegetables accumulate tetracyclines from irrigation water, posing plausible human health risks to allergic individuals. Similarly, the ecological risks cannot be ignored because the synergistic and antagonistic effects of sublethal concentrations can perturb ecosystem processes.

High-efficiency removal of tetracycline from water by electrolysis-assisted NZVI: mechanism of electron transfer and redox of iron

A low-cost, stable and non-precious metal catalyst for efficient degradation of tetracycline (TC), one of the most widely used antibiotics, has been developed. We report the facile fabrication of an electrolysis-assisted nano zerovalent iron system (E-NZVI) that achieved TC removal efficiency of 97.3% with the initial concentration of 30 mg L^-1 at an applied voltage of 4 V, which was 6.3 times higher than the NZVI system without an applied voltage. The improvement caused by electrolysis was mainly attributed to the stimulation of corrosion of NZVI, which accelerated the release of Fe²⁺. And Fe³⁺ in the E-NZVI system could receive electrons to reduce to Fe²⁺, which facilitated the conversion of ineffective ions to effective ions with reducing ability. Moreover, electrolysis assisted to expand the pH range of the E-NZVI system for TC removal. The uniformly dispersed NZVI in the electrolyte facilitated the collection and secondary contamination could be prevented with the easy recycling and regeneration of the spent catalyst. In addition, scavenger experiments revealed that the reducing ability of NZVI was accelerated in the presence of electrolysis, rather than oxidation. TEM-EDS mapping, XRD and XPS analyses indicated that electrolytic effects could also delay the passivation of NZVI after a long run. This is mainly due to the increased electromigration, implying that the corrosion products of iron (iron hydroxides and oxides) are not formed mainly near or on the surface of NZVI. The electrolysis-assisted NZVI shows excellent removal efficiency of TC and is a potential water treatment method for the degradation of antibiotic contaminants.

A simple co-precipitation sorbent-based preconcentration method for the analysis of fungicides in water and juice samples by high-performance liquid chromatography coupled with photodiode array detection

A magnesium hydroxide co-precipitation sorbent-based method in the presence of an anionic surfactant (e.g., sodium dodecylbenzenesulfonate) and high-performance liquid chromatography were used to preconcentrate and analyze fungicides in water and apple juice samples. The preconcentration procedure can be accomplished in a single step based on the co-precipitation of target fungicides and magnesium chloride in the presence of surfactant in a sodium hydroxide solution (pH 11) and a white precipitate gel was simply obtained after centrifugation. The property of precipitate phase was subsequently characterized using Fourier-transform infrared spectroscopy, scanning electron microscopy, and X-ray diffractometry. Under the optimum conditions, the developed method exhibited good sensitivity, with an enrichment factor of 11–18 and limits of detection of approximately 1–5 μg/L for water samples and 7–10 μg/L for apple juices. High reproducibility was achieved with a relative standard deviation of less than 11%, and a good recovery range of 72% to 120% was also obtained. The proposed method was shown to be a simple preconcentration procedure for concentrating fungicides in the samples investigated.

Determination of seven tetracyclines in milk by dissolvable layered double hydroxide-based solid-phase extraction coupled with high-performance liquid chromatography

A dissolvable layered double hydroxide-based solid-phase extraction combined with high-performance liquid chromatography was developed for the analysis of minocycline, oxytetracycline, tetracycline, demeclocycline, metacycline, chlortetracycline and doxycycline in milk samples. In situ formation of the layered double hydroxide was achieved by the addition of MgCl₂-AlCl₃ solution to alkaline deproteinized milk. The analytes were efficiently extracted by the Mg/Al layered double hydroxide. After centrifugation, the co-precipitates were dissolved in 0.1 mol L^-1 Na₂EDTA-McIlvaine buffer prior to HPLC analysis. Under optimized conditions, the method achieved low detection limits of 0.414-0.986 μg L^-1 and quantification limits of 1.38-3.29 μg L^-1, and good recoveries of 93.5-100% with intra- and inter-day RSDs of 0.498-4.08% and 1.23-10.0%, respectively. This method is convenient, accurate, sensitive, rapid, cost-effective, eco-friendly, and suitable for the determination of seven tetracycline antibiotics in milk samples.

Single-component and competitive adsorption of tetracycline and Zn(ii) on an NH4Cl-induced magnetic ultra-fine buckwheat peel powder biochar from water: studies on the kinetics, isotherms, and mechanism

Single-component and competitive adsorption of tetracycline (TC) and Zn(ii) on an NH₄Cl-induced magnetic ultra-fine buckwheat peel powder biochar (NH₄Cl-BHP-char/Fe₃O₄) was investigated in batch experiments.

Stability of antibiotics in drinking water: An advanced approach towards the impacts of water quality parameters on doxycycline bioavailability

Objective:

This study was considered to explore the possible impacts of drinking water quality from different sources on the bioavailability of doxycycline.

Materials and Methods:

Sixty-four tap and ground drinking water samples collected from poultry farms were scrutinized for their water quality limits (TH, pH, total dissolved solids, electrical conductivity, Cl⁻, Ca⁺², Na⁺, and Mg⁺²) and heavy metals concentrations (Zn, Fe, Cu, and Ni). An in vitro study was conducted by adding the therapeutic concentrations of doxycycline to all tested water samples, and allowed to interact for 1 h, 3 h, 5 h, and 8 h followed by re-estimation of doxycycline concentrations after each contact time using thin layer chromatography.

Results:

The therapeutic concentration of doxycycline was decreased in tap water samples by 1.92%, 9.63%, 22.42%, and 30.83% for the aforementioned contact times, respectively, while the corresponding reduction percentages in ground water samples were 2.14%, 17.14%, 28.57%, and 40.09%. However, the control samples had never showed any recorded decrease in their doxycycline concentrations overall contact times. All measured concentrations of doxycycline were significantly lower in tap and ground water than those of control at all times of contact. Both pH, Mg⁺² showed significant positive correlations with decreasing values of doxycycline in water.

Conclusion:

Different drinking water sources reduce the concentrations of doxycycline in vitro in a time dependent manner, which can be attributed to their different physico-chemical parameters, i.e., pH and Mg⁺² ions. This emphasizes the role of water quality on the stability of antibiotics concentrations administrated via drinking water.

Determination of three tetracyclines in bovine milk using magnetic solid phase extraction in tandem with dispersive liquid-liquid microextraction coupled with HPLC

A novel analytical method namely magnetic solid phase extraction in tandem with dispersive liquid-liquid microextraction was developed and used for the extraction/preconcentration of tetracycline (TCN), oxytetracycline (OTC) and doxycycline (DC) from bovine milk sample before HPLC-UV analysis. The β-cyclodextrin functionalized silica-coated magnetic graphene oxide (Fe₃O₄@SiO₂@GO-β-CD) was used as an adsorbent. The adsorbent was fully characterized using FT-IR, SEM, EDX and Zeta potential techniques. The effective parameters on the performance of the method such as extraction solvent type and volume, adsorbent amount, desorption solvent type and volume, disperser solvent type, desorption time, ionic strength and pH value were investigated. The limit of detection (LOD) and limit of quantification (LOQ) were obtained in the ranges of 1.8-2.9 μg L^-1 and 6.1-9.7 μg L^-1, respectively. The linearity was in the range of 10.0-200.0 μg L^-1 with satisfactory determination coefficients (R²) higher than 0.9929 and a good precision (RSD < 8.8%). The recovery percentages for the analytes in real samples (bovine milk and water) were achieved in a range from 70.6 to 121.5%.

Trace determination of tetracyclines in water samples by capillary zone electrophoresis combining off-line and on-line sample preconcentration

In this work, a sensitive and reliable method using capillary zone electrophoresis with UV detection has been developed for trace determination of tetracycline antibiotics in river, spring, and ground waters. A solid-phase extraction method using Oasis HLB was applied for off-line preconcentration and cleanup of water samples, in combination with an on-line preconcentration methodology named large volume sample stacking with polarity switching. Different parameters were optimized in order to obtain an adequate separation combined with the highest sensitivity, using 75 mM sodium carbonate (pH 10) and 1 mM EDTA as separation buffer, applying a voltage of 25 kV at 25°C. The samples were injected in water at 1 bar for 1 min, applying then -25 kV and starting the sample stacking. Sample matrix removal from the capillary was controlled by monitoring the electric current (when the 95% of the separation current is reached the stacking process is completed). The applied voltage was then switched from negative to a positive value of 25 kV in order to separate the compounds. Under optimum conditions, sensitivity enhancement factors ranged from 303 to 428 for the studied compounds. The combination of both off-line and on-line preconcentration procedures provided a total sensitivity enhancement factor about 20 000, obtaining detection limits from 67 to 167 ng/L. The precision (intra- and interday), expressed as %RSD was below 12%. Recoveries obtained from river, spring, and ground waters ranged from 87 to 96%. Thus, this procedure is suitable for monitoring these compounds in water samples.

Ultrasound-assisted dispersive extraction for the high pressure liquid chromatographic determination of tetracyclines residues in milk with diode array detection

Ultrasound assisted matrix solid phase dispersive extraction was applied for the selective isolation and clean-up of tetracyclines (oxytetracycline, tetracycline, epi-chlorotetracycline, chlorotetracycline and doxycycline) from milk. Target analytes were determined by an accurate and sensitive chromatographic analytical method, which was validated to meet the European Legislation criteria. The separation was performed on a LiChroCART-LiChrospher® 100 RP-18 (5μm, 250×4mm) analytical column, operated at ambient temperature, followed by diode array detection. Validation included investigation of linearity, selectivity, stability, limits of detection and quantitation, decision limit, detection capability, trueness, precision and ruggedness according to the Youden's approach. Limits of quantitation of examined tetracyclines were from 14.5 to 56.6μg/kg significantly lower than respective Maximum Residue Limits, whereas recoveries ranged from 82.0% to 108%. The applicability of the method was evaluated using milk samples purchased from local market. Accuracy of the method was additionally proved by analysis of bovine milk certified reference material (BCR®-492).