Simple and clean determination of tetracyclines by flow injection analysis

Automated method for the solid phase extraction of tetracyclines in wastewater followed by fluorimetric determination

This work presents a multisyringe flow injection analysis (MSFIA) system for the automatic extraction and determination of tetracyclines in wastewater samples. The sample was adjusted with Na2EDTA buffer before solid-phase extraction with an Oasis HLB column used for the analyte preconcentration. The europium (Eu3+)-based and citrate-mediated method (using Tris-HCl buffer) was selected for the fluorimetric analysis (λexc/em = 400/612 nm). For fluorescence detection, a low-cost system consisting of an USB 2000 CCD detector and a 3D-printed support that holds a LED light source was used. Under optimized conditions, the proposed method provided low limits of detection (9.4 μg L-1) and quantification (31 μg L-1), and good values for intra-day (<4 %) and inter-day precisions (<6 %). Recoveries of spiked TCs in wastewater samples ranged from 87 to 106 %. The results of this work were in good agreement with the measurements obtained by liquid chromatography coupled to a fluorescence detector.

Synergy of iron-natural phenolic microparticles and hydrophobic ionic liquid for enrichment of tetracycline residues in honey prior to HPLC-UV detection

Iron-natural phenolic microparticles were developed as absorbents for dispersive micro solid phase extraction (D-μSPE) synergistic with hydrophobic ionic liquid (IL) for dispersive liquid-liquid microextraction (DLLME) to enrich tetracycline residues, including tetracycline, doxycycline, oxytetracycline and chlortetracycline. In situ iron microparticles synthesized from betel nut natural reagent were employed as an adsorbent for D-μSPE. The hydrophobic IL [Hmim][PF6] was synergistically utilized as an extraction solvent to extract and accumulate adsorbents bound with tetracyclines before quantitation by HPLC-UV. The synergistic combination of DLLME with D-μSPE provided excellent extraction recovery compared with individual extraction. The developed method was successfully applied to enrich and determine tetracycline residues in honey samples, with recoveries ranging from 80.0 to 121.5% and providing high enrichment factors ranging from 61 to 197. This alternative method is simple and rapid, with high extraction efficiency and a high enrichment factor and is also environmentally friendly for the analysis of tetracyclines.

A Highly Selective Electrochemical Sensor Based on Molecularly Imprinted Copolymer Functionalized with Arginine for the Detection of Chloramphenicol in Honey

Developing an efficient method for chloramphenicol (CAP) detection is of great significance for food safety. Arginine (Arg) was selected as a functional monomer. Benefiting from its excellent electrochemical performance, which is different from traditional functional monomers, it can be combined with CAP to form a highly selective molecularly imprinted polymer (MIP) material. It overcomes the shortcoming of poor MIP sensitivity faced by traditional functional monomers, and achieves high sensitivity detection without compounding other nanomaterials, greatly reducing the preparation difficulty and cost investment of the sensor. The possible binding sites between CAP and Arg molecules were calculated by molecular electrostatic potential (MEP). A low-cost, non-modified MIP electrochemical sensor was developed for the high-performance detection of CAP. The prepared sensor has a wide linear range from 1 × 10^-12 mol L^-1 to 5 × 10^-4 mol L^-1, achieves a very low concentration CAP detection, and the detection limit is 1.36 × 10^-13 mol L^-1. It also exhibits excellent selectivity, anti-interference, repeatability, and reproducibility. The detection of CAP in actual honey samples was achieved, which has important practical value in food safety.

Lab-made 3D-printed electrochemical sensors for tetracycline determination

Antibiotics such as tetracycline (TC) are widely prescribed to treat humans or dairy animals. Therefore, it is important to establish affordable devices in laboratories with minimal infrastructure. 3D printing has proven to be a powerful and cost-effective tool that revolutionizes many applications in electrochemical sensing. In this work, we employ a conductive filament based on graphite (Gr) and polylactic acid (PLA) (40:60; w/w; synthesized in our lab) to manufacture 3D-printed electrodes. This electrode was used "as printed" and coupled to batch injection analysis with amperometric detection (BIA-AD) for TC sensing. Preliminary studies by cyclic voltammetry and differential pulse voltammetry revealed a mass transport governed by adsorption of the species and consequent fouling of the redox products on the 3D printed surface. Thus, a simple strategy (solution stirring and application of successive potentials, +0.95 V followed by +1.2 V) was associated with the BIA-AD system to solve this effect. The proposed electrode showed analytical performance comparable to costly conventional electrodes with linear response ranging from 0.5 to 50 μmol L^-1 and a detection limit of 0.19 μmol L^-1. Additionally, the developed method was applied to pharmaceutical, tap water, and milk samples, which required minimal sample preparation (simple dilution). Recovery values of 92-117% were obtained for tap water and milk samples, while the content found of TC in the capsule was close to the value reported by the manufacturer. These results indicate the feasibility of the method for routine analysis involving environmental, pharmaceutical, and food samples.

Novel ZnFe2O4/BC/ZnO photocatalyst for high-efficiency degradation of tetracycline under visible light irradiation

Developing broad-spectrum light reactions, effective charge separation, and easily recoverable photocatalysts were considered cost-effective pollution remediation methods. The ZnFe₂O₄/BC/ZnO composite was prepared to achieve these objectives, where biochar (BC) was used as a conductive channel and ZnFe₂O₄ as a magnetic substance. Among them, the 0.6-ZBO composite performed the best, with photocatalytic removal of tetracycline (TC) reaching 85.6%. The photocatalytic degradation rated constant of 0.6-ZBO composite was 23.36 × 10^-3 min^-1, which was 7.6, 4.1, and 2.5 times higher than that of ZnFe₂O₄/BC, ZnO, and ZnFe₂O₄/ZnO samples, respectively. According to several characterization data, it was demonstrated that successful Z-scheme heterojunctions were constructed between ZnFe₂O₄ and ZnO. The 0.6-ZBO complex increased the range of light absorption and strengthened the separation of electron-hole pairs, thus improving the redox ability of the complex. In the different water matrices, the stability of 0.6-ZBO was excellent and its ability to remove TC decreased slightly to about 11% after 5 cycles. This work provided a valuable approach to design a novel and efficient system for degrading organic pollutants in wastewater using magnetic biochar.

Green synthetic nitrogen-doped graphene quantum dot fluorescent probe for the highly sensitive and selective detection of tetracycline in food samples

Tetracycline (TC) is a broad-spectrum antibiotic. When humans consume too much food containing tetracycline residues, it can be a serious health hazard. Therefore, it is essential to develop a strategy to detect TC. In this study, we prepared light blue-green luminescent nitrogen-doped graphene quantum dots (N-GQDs) by a hydrothermal method using the natural products potato straight-chain starch and urea as precursors; the fluorescence quantum yield of the prepared N-GQDs was 5.2%. We investigated the detection of tetracycline (TC) by this N-GQD fluorescent sensor based on the internal filtration effect (IFE) of TC on N-GQDs. The reaction is green, simple and no other contaminating products are present. A good linear relationship was established between the relative fluorescence intensity ratio of the system and the logarithm of the TC concentration of 2.5 × 10⁻¹⁰ to 5 × 10⁻⁶ M (R² = 0.9930), with a detection limit of 9.735 × 10⁻¹³ M. The method has been used to analyze TC in three real food samples (whole milk, skim milk, honey) with low detection limits (3.750 × 10⁻¹¹ to 2.075 × 10⁻⁹ M), wide linear range, and satisfactory recoveries of 93.80–109.20% were obtained. In conclusion, the proposed method is a green, rapid, highly sensitive and selective method for the detection of tetracycline in real food samples, demonstrating the potential application of N-GQDs in food detection.

Tetracycline (TC) is a broad-spectrum antibiotic.

Determination of Tetracycline Using Ultrasound-Assisted Dispersive Liquid-Liquid Microextraction Based on Solidification of Floating Organic Droplet Followed by HPLC-UV System

BACKGROUND

Tetracyclines (TCs) are a group of broad-spectrum antibiotics that may be used to control bacterial diseases in humans or are applied as feed additives to enhance growth in farm animals. TCs are released into the aquatic environment via different pathways. Many analytical methods combined with a preconcentration step have been introduced for the determination of TC in various environmental samples.

OBJECTIVE

The objective this paper is developing reliable analytical methods for determination of TC trace in various environmental samples.

METHOD

In the present work, combined ultrasound-assisted and dispersive liquid-liquid microextraction according to the solidification of floating organic drop as a sample preconcentration procedure for determining TC hydrochloride HPLC in water and serum samples was used.

RESULTS

A series of parameters, including the type and volume of disperser and extraction solvents, salt effect, extraction time, and pH of solution influencing the extraction efficiency of UA-DLLME-SFO was examined. Enrichment factors were in the range of 125-137 for TC hydrochloride under optimum conditions. The linear range was calculated from 0.005 to 3 mg/L and LOD at 0.002 mg/L. RSDs were in the range of 2.7 to 3.2 (n = 5). The UA-DLLME-SFO method used in water and serum samples revealed good extraction recoveries with RSD of 2.7-4.3%.

CONCLUSIONS

This method significantly decreased the organic solvent volume from 3 mL to 90 µL, also LOD and linear ranges were lower than or almost close to levels obtained in other research studies. In this procedure, an ultrasound bath enhanced the mixing and contact between the sample solution and the extraction solvent.

Flow Injection Techniques for Tetracycline Quantification: A Review

The multiple therapeutic potentials of tetracycline and its worldwide usage have encouraged researchers to develop various methods for its assay in various matrices and for different purposes. In this regard, different analytical techniques have been exploited. Among those techniques is flow injection (FI), which is an extended family of three generations and five versions. The current manuscript reviews the utilization of FI techniques for developing assay methods for tetracycline. The review covers more than forty methods, since the inception of FI techniques and up to date. The review highlights the advantages of the application of FI techniques for quantification of tetracycline in terms of reagent consumption, sample frequency, accuracy, and practitioner safety, besides instrumentation simplicity and cost-effectiveness. The review also addresses applications to several matrices ranging from simple matrices such as standard solutions and pharmaceutical formulations to complex matrices such as biological fluids and food. Prior to the review, a brief background on the principles and developments of FI techniques is illustrated.

Analytical Methods for the Quality Control of Veterinary Antimicrobials Medicines

Veterinary medicinal products (VMPs) are used for the prevention and treatment of diseases in animals. The safety and efficacy of these products must be proven by quality control tests. Special attention should be paid to veterinary antimicrobials medicines (VAMs), as changes in their potency can compromise pharmacotherapeutic treatment and contribute to microbial resistance. The aim of this work was to review the analytical methods available for assessing the quality of VAMs, to analyze regulatory issues and quality control programs. The review was performed on selected papers in the PubMed, ScienceDirect, Scopus and Virtual Health Library databases, between 2005 and 2020. After applying exclusion criteria, 19 studies were obtained. Of the analytical studies, the majority (61.54%) used the HPLC technique. In addition, methods by CE (15.39%) and by SPM, FIA and microbiological assay (7.69% each) were found. In studies of monitoring of VAMs available on the market, changes in tylosin, spiramycin, ampicillin, tetracyclines and penicillins were observed. This is worrying, as these quality deviations can contribute to the development of resistant microorganisms. Although international efforts have been implemented at the regulatory level to ensure the quality of VAMs, it was realized with this study that there is much to evolve in the development of new analytical methods and in monitoring the quality of VAMs. With this, it is expected that this study will instigate scientists in the analytical, regulatory, microbiological and veterinary fields to develop new research so that the demands necessary to guarantee the quality of VAMs are increasingly met.

Interest of flow injection spectrophotometry as an orthogonal method for analyzing biomolecule aggregates: Application to stressed monoclonal antibody study

This study aimed to explore the suitability of flow injection spectrophotometry (FIS) to analyze three degraded therapeutic monoclonal antibodies (bevacizumab, nivolumab, and rituximab). For this purpose, aggregates were generated with stirring, freeze-thaw, and heat stresses. The intact and stressed mab samples were filtered with 0.22 µm hydrophilic filters and analyzed by size exclusion chromatography (SEC), cation-exchange chromatography (CEX), and FIS. In terms of quantitative and qualitative analysis, protein loss and structural changes were assessed. Various aggregates profiles were obtained according to the mabs and the stresses. FIS allowed performing very satisfactory quantifications for each mab with intermediate precision RSD < 3.0 % and recovery between 97.9 and 102.0 %. From the protein loss measurements, it appears that SEC underestimates the mab aggregate proportions up to two times less as compared with FIS since the latter avoids any non-specific interactions (electrostatic or hydrophobic interactions). Using second derivative spectroscopy and multivariate data analysis, we noticed apparent structural differences, located in the regions 245-265 nm for rituximab and nivolumab and 280-300 nm for bevacizumab, depending on the stress. The FIS complementarity with the other techniques used in this study allowed us to demonstrate that the three mabs behave differently for a given stress condition. While extreme mechanical stress formed large aggregates irrespective of the mabs, rituximab showed to be less stable and more sensitive than the two other mabs under freeze-thaw and heat stresses, generating large aggregates (>200 nm) and partial unfolding. Nivolumab tends to form small aggregates less than 50 nm when heated and freeze-thawed. Moreover, freeze-thaw seems to generate native IgG-1 aggregates with rituximab. Similarly, bevacizumab showed to form these IgG-1 aggregates and was resistant to freeze-thaw, likely thanks to trehalose cryoprotectant from its formulation. Finally, FIS associated with multivariate analysis can provide rich information in one single run and appears to be a fast, simple, and reliable method to set complementary and orthogonal approaches for protein aggregates monitoring.

Ratiometric Fluorescent Probe Based on Diazotization-Coupling Reaction for Determination of Clenbuterol

In view of the potential harm caused by illegal feeding of clenbuterol (CLB) in the livestock industry, herein, a novel ratiometric fluorescent probe based on graphene quantum dots (GQDs)@[Ru(bpy)₃]²⁺ was elaborately constructed for CLB detection. In this probe, GQDs acted as response signals, and their fluorescence was remarkably quenched by CLB through the diazotization-coupling reaction. As for [Ru(bpy)₃]²⁺ as a reference signal, its fluorescence was hardly affected. The intensity ratio of two fluorophores showed good linearity with CLB concentration in the range of 0.05-40 μM, accompanied by visualization of fluorescence variation from yellow to red. The detection limit was as low as 0.029 μM. Particularly, the probe was successfully used to detect CLB in pork and beef samples with satisfactory recoveries. To our knowledge, this is the first report on a ratiometric fluorescent probe for the detection of CLB, which possesses broad application prospects in food safety risk monitoring.

A Critical Review of Biological Properties, Delivery Systems and Analytical/Bioanalytical Methods for Determination of Bevacizumab

Bevacizumab is a chimeric monoclonal human-murine antibody originated from murine monoclonal antibody (muMAb A4.6.1) with the human immunoglobulin IgG1. BVZ binds the extracellular portion of vascular endothelial growth factor receptors (VEGFR), which have tyrosine kinase activity. The mechanism of action of BVZ involves binding to VEGFR, Flt-1 (VEGFR-1) and KDR/Flk-1 (VEGFR-2), inducing homodimerization of two receptor subunits, and, consequently, autophosphorylation of their tyrosine kinase domains located inside the cytoplasm. With the advent of nanostructured systems it is increasingly necessary to look for safe analytical methods, ensuring the reliability of the results obtained by them, becoming essential to ensure the quality of medicines. In this work, the incorporation of bevacizumab in to different drug delivery systems was presented. Moreover, detailed investigation was performed about methods for qualitative and quantitative analyses of bevacizumab, including, biological fluids, and drug delivery systems, were investigated. Most recently high performance liquid chromatography coupled with various detectors, liquid chromatography, mass spectrometry and ELISA were used for this purpose. Thus, this review was performed to evaluate the benefits of bevacizumab carried by nanostructured systems and the analytical methods available for detection and quantification of these drugs.

Direct analysis of ascorbic acid in food beverage samples by flow injection analysis using reduced graphene oxide sensor

In this paper, a simple, sensitive and precise electroanalytical method was developed using flow injection analysis (FIA) with amperometric detection and reduced graphene oxide sensor for ascorbic acid determination in samples of multivitamin beverages, milk, fermented milk, and milk chocolate. The advantages of this sensor include a potential displacement of 450 mV and a 2-fold peak current increase for electrochemical oxidation of ascorbic acid, which resulted in a highly sensitive method. No interference of sample matrix was observed, avoiding solvent extraction procedures (samples were only diluted). The FIA allowed a high analytical frequency, approximately 96 injections per hour, together with adequate detection limit of 4.7 μmol L^-1. Good precision (RSD < 7%) and accuracy (recoveries between 91 and 108%) evidenced the robustness of the method. The method was compared with ultra-fast liquid chromatography (UFLC) obtaining statistically similar results (95% confidence level). The ascorbic acid content in samples varied from 0.065 to 2.53 mmol L^-1.

Solution growth of 1D zinc tungstate (ZnWO4) nanowires; design, morphology, and electrochemical sensor fabrication for selective detection of chloramphenicol

Development of 1D nanostructures with novel morphology is a recent scientific attraction, so to say yielding unusual materials for advanced applications. In this work, we have prepared solution grown, single-pot 1D ZnWO₄ nanowires (NWs) and the morphology is assessed for label-free but selective detection of chloramphenicol. This is the first report where, such structures are being investigated for this purpose. Transmission electron microscopy shows the presence of strands of ZnWO₄ of about 20 nm in diameter. The formed NWs were highly dispersed in nature with uniform size and shape. X-ray diffraction analysis confirmed high purity of the designed NWs despite solution synthesis. X-ray photoelectron spectroscopy confirmed surface valence state of ZnWO₄. Fourier transform infrared spectroscopy was employed for the ascription of functional groups, whereas, optical properties were investigated using photoluminescence. NWs were employed for the detection of a model antibiotic, chloramphenicol. The developed sensor exhibited excellent limit of detection, 0.32 μM and 100% specificity as compared to its structural and functional analogues such as thiamphenicol and clindamycin. This work can broaden new opportunities for the researchers to explore unconventional nanomaterials bearing unique morphologies and quantum phenomenon for the label-free detection of other bioanalytes.

New Poly(Ionic Liquid) Based Fiber for Determination of Oxytetracycline in Milk Samples by Application of SPME-CE Technique

In this work, a procedure using solid phase microextraction in combination with capillary electrophoresis was developed for the determination of oxytetracycline in milk samples. The method involves the synthesis of poly(1-allyl-3-methyl imidazolium) chloride film on a stainless-steel bar via electropolymerization and its use as an adsorbent for oxytetracycline (OT) by an ionic exchange mechanism. The coated fiber is then immersed in milk samples for retention of oxytetracycline residues, followed by elution, drying, and reconstitution before analysis with capillary electrophoresis. The proposed method achieves a limit of detection of 70 µg L^⁻¹ with adequate precision and uncertainty, making this methodology appropriate for the determination of OT in milk samples. The method was applied to the pre-concentration and quantification of oxytetracycline in ten commercial milk samples. Two tested samples were positive for the presence of oxytetracycline but the concentration was below the maximum residue limit according to the international normative standard. The proposed methodology was evaluated according to the Eco-Scale approach, and the total score of 51 indicated that the methodology proposed is both green and acceptable despite the multi-stage character. SPME-CE methodology allows us to perform the sample pre-treatment and determination of OT in an effective and greener way, decreasing the number of steps during the analysis and the generation of waste.

Triple-helix molecular switch-based aptasensors and DNA sensors

Utilization of traditional analytical techniques is limited because they are generally time-consuming and require high consumption of reagents, complicated sample preparation and expensive equipment. Therefore, it is of great interest to achieve sensitive, rapid and simple detection methods. It is believed that nucleic acids assays, especially aptamers, are very important in modern life sciences for target detection and biological analysis. Aptamers and DNA-based sensors have been widely used for the design of various sensors owing to their unique features. In recent years, triple-helix molecular switch (THMS)-based aptasensors and DNA sensors have been broadly utilized for the detection and analysis of different targets. The THMS relies on the formation of DNA triplex via Watson-Crick and Hoogsteen base pairings under optimal conditions. This review focuses on recent progresses in the development and applications of electrochemical, colorimetric, fluorescence and SERS aptasensors and DNA sensors, which are based on THMS. Also, the advantages and drawbacks of these methods are discussed.

Characteristics, Biological Properties and Analytical Methods of Ursolic Acid: A Review

Ursolic acid (UA) is a naturally occurring triterpenoid which is a promising candidate for the development of new therapeutic approaches and for the prevention and treatment of several diseases owing to its pharmacological importance. However, its low solubility in aqueous medium affects its therapeutic application. Several strategies have been used to overcome this obstacle. In this study, the incorporation of UA in to different drug delivery systems was found to be highly efficient. In addition, important investigations were performed about methods for qualitative and quantitative analyses of UA in various raw materials, including plants, biological fluids, and drug delivery systems, were investigated. Most recently high performance liquid chromatography coupled with various detectors, gas chromatography-mass spectrometry and capillary electrophoresis were used for this purpose. Thus, this review was performed to evaluate the biological effects of UA demonstrated thus far as well as the currently used, delivery systems and analytical methods.

A Critical Review of Properties and Analytical Methods for the Determination of Oxytetracyline in Biological and Pharmaceutical Matrices

Antibiotics have an unquestionable importance in the treatment of many infections. Oxytetracycline is an antibiotic belonging to the class of tetracyclines, available for use in human and veterinary medicine. Development of analytical methods that prove the quality and efficacy of these drugs is fundamentally important to the pharmaceutical industry. In this context, the research presents an overview of the analytical profile of oxytetracycline, describing its chemical and pharmacological properties, and analytical methods for quantification of this drug in biological samples and pharmaceutical products. Oxytetracycline can be analyzed in these matrices by many types of methodologies. However, high-performance liquid chromatography is the most widely used, being recommended by official compendia. This kind of study can be useful to support the development of new efficient and sustainable analytical methods that may be utilized in the quality control routine of oxytetracycline in pharmaceutical products and pharmacokinetic monitoring in biological samples.