Simultaneous determination of clenbuterol, salbutamol and ractopamine in milk by reversed-phase liquid chromatography tandem mass spectrometry with isotope dilution

Two-dimensional metal-organic framework nanosheets coated solid-phase microextraction Arrow coupled with UPLC-Q-ToF-MS for the determination of three veterinary residues in milk and pork

This study presents a method utilizing solid-phase microextraction Arrow (SPME Arrow) combined with ultra-performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF-MS) for the selective detection of three veterinary drugs-thiabendazole, sulfamethazine, and clenbuterol-in milk and pork. Two-dimensional metal-organic framework nanosheets (2D-MOFs) were employed as coating materials for the SPME Arrow. Three types of 2D-MOFs (Ni, Mn, and Co based) were synthesized and characterized using Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, and a physical adsorption analyzer. The 2D-MOF coatings were fabricated using the electrospinning technique, with polyacrylonitrile (PAN) serving as the binder. Comparative analysis of the three 2D-MOF coatings revealed that 2D-Ni-MOF was the optimal coating material for the SPME Arrow. Optimization of the coating preparation conditions and SPME procedures included determining the optimal mass ratio of 2D-Ni-MOF to PAN, electrospinning time, and extraction and desorption parameters. Equilibrium extraction was achieved within 60 min, and desorption was completed within 30 min. Subsequently, the 2D-Ni-MOF-SPME Arrow-UPLC-Q-TOF-MS method was established and validated under optimal conditions, demonstrating high precision with inter-day precision ranging from 3.8 % to 9.5 % and intra-day precision ranging from 5.1 % to 11.5 %. The reusability study indicated that the extraction performance of the new SPME Arrow remained consistent after 90 adsorption-desorption cycles. The method exhibited linearity in milk and pork over the ranges of 0.002-5 μg L-1 and 0.01-5 μg L-1, respectively. The detection limits in milk and pork were 0.001-0.004 μg L-1 and 0.003-0.007 μg L-1, respectively. This method demonstrated excellent applicability for determining residues of the three veterinary drugs in milk and pork.

Pesticide residue detection technology for herbal medicine: current status, challenges, and prospects

The domains of cancer therapy, disease prevention, and health care greatly benefit from the use of herbal medicine. Herbal medicine has become the mainstay of developing characteristic agriculture in the planting area increasing year by year. One of the most significant factors in affecting the quality of herbal medicines is the pesticide residue problem caused by pesticide abuse during the cultivation of herbal medicines. It is urgent to solve the problem of detecting pesticide residues in herbal medicines efficiently and rapidly. In this review, we provide a comprehensive description of the various methods used for pesticide residue testing, including optical detection, the enzyme inhibition rate method, molecular detection methods, enzyme immunoassays, lateral immunochromatographic, nanoparticle-based detection methods, colorimetric immunosensor, chemiluminescence immunosensor, smartphone-based immunosensor, etc. On this basis, we systematically analyze the mechanisms and some of the findings of the above detection strategies and discuss the challenges and prospects associated with the development of pesticide residue detection tools.

Occurrence, consumption level, fate and ecotoxicology risk of beta-agonist pharmaceuticals in a wastewater treatment plant in Eastern China

Beta-agonist pharmaceuticals are widely used in humans and livestock for disease treatment, legal or illegal growth promotion in food animals, bodybuilding, weight loss, and sports doping. The occurrence of beta-agonists in wastewater treatment plants and their subsequent environmental impacts require greater attention. This study determined the levels of 12 beta-agonists in a wastewater treatment plant and evaluated their ecotoxicological risks as well as consumption levels and risks to human health. Among the 12 selected beta-agonists, all were detected in wastewater and 11 in sludge. In most cases, the concentrations of beta-agonists were higher in spring than in summer. Their total average daily mass loads per capita in the influent and effluent were 1.35 μg/d/p and 2.11 μg/d/p, respectively. The overall removal efficiencies of individual beta-agonists ranged from -295.3 to 71.2%. Ecotoxicological risk assessment revealed a low risk to daphnid and green algae from the levels of fenoterol and the mixture of 12 selected beta-agonists in the effluent. The daily consumption levels of individual beta-agonists per capita were 0.028-1.200 μg/d/p. Regular monitoring of beta-agonists in municipal sewage systems and their risk assessment based on toxicological data are urgently required in the future.

Fully integrated colorimetric sensor based on transparency substrate for salbutamol determination

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Facile colorimetric method for the determination of salbutamol based on a simple redox reaction using permanganate as reagent was first investigated at the transparency-based analytical device (TAD).

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The colorimetric TAD sensor was in-lab constructed using a transparent PET-based substrate, showing good compatibility with the permanganate reagent which could result in a vivid color change, clearly observed by the naked eye.

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This proposed colorimetric TAD sensor was successfully applied for salbutamol determination in real drug samples with good accuracy and satisfactory recovery, highlighting the potential capability of this TAD-based colorimetric sensor in pharmaceutical application.

A facile colorimetric method based on a typical redox reaction was first developed for the determination of salbutamol (SAL) using a low-cost and portable transparency-based analytical device (TAD). The TAD was simply fabricated by wax-printing onto a transparent polymer-based substrate to create the hydrophobic barriers and the colorimetric reaction zones where the color changes could be easily observed with the naked eye. Potassium permanganate (KMnO₄), a common oxidizing agent, was deliberately used as a colorimetric reagent for SAL. Once SAL reacted with KMnO₄ in the acidified system, it could undergo oxidation and the color of KMnO₄ subsequently changed from light pink to orange. The color change corresponding to the SAL concentration could be clearly observed at the TAD sensor. In addition, the reaction color could be recorded using a digital camera and then analyzed by ImageJ for quantitative analysis. Under the optimized conditions, the developed method together with the TAD sensor exhibited high efficiency for SAL determination with linearity ranging from 0.5 to 40 mg·L⁻¹ and a limit of detection (LOD) of 0.05 mg·L⁻¹.

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This proposed TAD-based colorimetric method using permanganate as color reagent showed excellent performance in SAL detection with good accuracy and high precision.

Ractopamine at the Center of Decades-Long Scientific and Legal Disputes: A Lesson on Benefits, Safety Issues, and Conflicts

Ractopamine (RAC) is a synthetic phenethanolamine, β–adrenergic agonist used as a feed additive to develop leanness and increase feed conversion efficiency in different farm animals. While RAC has been authorized as a feed additive for pigs and cattle in a limited number of countries, a great majority of jurisdictions, including the European Union (EU), China, Russia, and Taiwan, have banned its use on safety grounds. RAC has been under long scientific and political discussion as a controversial antibiotic as a feed additive. Here, we will present significant information on RAC regarding its application, detection methods, conflicts, and legal divisions that play a major role in controversial deadlock and why this issue warrants the attention of scientists, agriculturists, environmentalists, and health advocates. In this review, we highlight the potential toxicities of RAC on aquatic animals to emphasize scientific evidence and reports on the potentially harmful effects of RAC on the aquatic environment and human health.

A Fast Method for the Simultaneous Analysis of 26 Beta-Agonists in Swine Muscle with a Multi-Functional Filter by Ultra-High Performance Liquid Chromatography-Tandem Mass Spectrometry

A rapid and simplified sample preparation method was developed for the simultaneous determination of 26 beta-agonists in swine muscle using a multi-functional filter (MFF) based on quick, easy, cheap, effective, rugged, and safe methods (QuEChERS). MFF integrated the cleanup and filter procedures, thereby significantly improving the efficiency of sample preparation compared with traditional solid-phase extraction. The sample was processed via enzymatic hydrolysis, purified with the optimized MFF containing 150 mg magnesium sulfate, 50 mg PSA, and 50 mg C18, and then analyzed using ultra-high performance liquid chromatography-tandem mass spectrometry. All procedures can be completed in 6.5 h. Good linearity (R2 > 0.99) was detected in all analytes. The recoveries ranged from 71.2% to 118.6%, with relative standard deviations (RSDs) of less than 18.37% in all spiked concentrations. The limits of detection (LOD) and the limits of quantitation (LOQ) were 0.01–0.10 and 0.10–0.50 μg/kg, respectively. The decision limit (CCα) and detection capacity (CCβ) values fluctuated in the range of 3.44–25.71 and 6.38–51.21 μg/kg, respectively. This method is a good alternative for detecting beta-agonist residues in swine muscle and can be successfully applied to the national risk monitoring of agro-product quality and safety in China.

Sensitive and Selective Detection of Clenbuterol in Meat Samples by a Graphene Quantum Dot Fluorescent Probe Based on Cationic-Etherified Starch

The use of clenbuterol (CLB) in large quantities in feedstuffs worldwide is illegal and potentially dangerous for human health. In this study, we directly prepared nitrogen-doped graphene quantum dots (N-GQDs) by a one-step method using cationic-etherified starch as raw material without pollution, which has the advantages of simple, green, and rapid synthesis of N-GQDs and high doping efficiency of nitrogen elements, compared with the traditional nitrogen doping method of reacting nitrogen source raw material with quantum dots. The N-GQDs synthesized by cationic etherification starch with different substitution degrees (DSs) exhibit good blue-green photoluminescence, good fluorescence stability, and water solubility. By comparing the fluorescence emission intensity of the two methods, the N-GQDs prepared by this method have higher fluorescence emission intensity and good fluorescence stability. Based on the static quenching mechanism between CLB and N-GQDs, a fluorescent probe was designed to detect CLB, which exhibited a wide linear range in the concentration range of 5 × 10⁻¹⁰~5 × 10⁻⁷ M (R² = 0.9879) with a limit of detection (LOD) of 2.083 × 10⁻¹³ M. More excitingly, the N-GQDs fluorescent probe exhibited a satisfactory high selectivity. Meanwhile, it can be used for the detection of CLB in chicken and beef, and good recoveries were obtained. In summary, the strategic approach in this paper has potential applications in the detection of risky substances in the field of food safety.

Cationic conjugated polymer-based FRET aptasensor for label-free and ultrasensitive ractopamine detection

A label-free fluorescence resonance energy transfer (FRET) platform based on cationic conjugated polymers and aptamers for ultrasensitive and specific ractopamine detection was constructed. This method exhibited a wide linear range from 0.05 to 500 μM and a low limit of detection of 47 nM, which make it an attractive assay platform for foodborne doping.

A label-free fluorescence resonance energy transfer (FRET) platform based on cationic conjugated polymers and aptamer has established for ultrasensitive and specific ractopamine (RAC) detection.

Tandem H/D Exchange-SET Reductive Deuteration Strategy for the Synthesis of α,β-Deuterated Amines Using D2O

α,β-Deuterated amines are crucial for the development of deuterated drugs. We intend to introduce the novel tandem H/D exchange-single electron transfer (SET) reductive deuteration strategy with high pot- and reagent-economy by the synthesis of α,β-deuterated amine using nitrile as the precursor. The H/D exchange of the -CH₂CN group was achieved by D₂O/Et₃N, which were also the required reagents in the tandem SmI₂-mediated SET reductive deuteration of the α-deuterated nitrile. The potential application of this method was further showcased by the synthesis of bevantolol-d₄.

Bismuth telluride decorated on graphitic carbon nitrides based binary nanosheets: Its application in electrochemical determination of salbutamol (feed additive) in meat samples

The design and fabrication of effective electrochemical sensor for ultrasensitive detection of feed additive and multidrug are highly significant in food analysis. In this work, we explored to develop the possibility for rapid detection of feed additive drug using bismuth telluride (Bi₂Te₃) decorated graphitic carbon nitrides (GCN) nanostructures as a modified electrode for electrochemical sensing. Herein, the modified electrode was focused on the development of electrocatalytic performances for the determination of salbutamol in food products. The electrochemical sensors are developed by bismuth telluride sheets interconnected with graphitic carbon nitrides sheets (Bi₂Te₃/GCN) on to a screen-printed carbon electrode. The binary nanosheets of Bi₂Te₃/GCN exhibited an enhanced electrocatalytic ability towards salbutamol detection owing to their selective adsorption, by the combination of electrostatic interaction of binary nanosheets and the formation of charge assisted interactions between salbutamol and Bi₂Te₃/GCN surfaces. A nanomolar limit of detection (1.36 nM) was calculated in 0.05 M phosphate buffer (PB) supporting electrolyte (pH 7.0) using differential pulse voltammetry. The linear dynamic ranges with respect to salbutamol concentration were 0.01-892.5 μM, and the sensitivity of the sensor was 36.277 μA μM^-1 cm^-2. The sensor stability and reproducibility performances were observed. However, the obtained results are highly satisfactory which suggest the application of binary nanosheets in real-time food analysis.

Meso-tetra(4-sulfonatophenyl)porphyrin silver/Ag nanoparticles/graphene-phase C3N4 with a sandwich-like structure and double-faced active centers via two-step room-temperature photocatalytic synthesis for ractopamine detection

Photochemical synthesis under visible light irradiation is a novel approach in the field of green chemistry, and composites with abundant active centers for electrochemical detection are highly attractive. Herein, a meso-tetra(4-sulfonatophenyl)porphyrin silver/Ag nanoparticles/graphene phase C₃N₄ nanosheets (Ag₂TPPS₄/AgNPs/ng-C₃N₄) material with a sandwich-like structure was synthesized using a two-step photocatalytic reaction at room temperature (25 °C). In the first visible light irradiation step and in the presence of a hole capture agent, Ag⁺ ions were photocatalytically reduced onto the surface of ng-C₃N₄ that was used as a photocatalyst. Then, the protons (H⁺) in the core of H₂TPPS₄ were substituted in situ by photo-oxidized Ag⁺ during the second visible light irradiation step and in the presence of an electron capture agent. The electrochemical response of Ag₂TPPS₄ and ng-C₃N₄ to ractopamine (RAC) results in the unique double-faced active centers of Ag₂TPPS₄/AgNPs/ng-C₃N₄, and the cores (AgNPs) are beneficial as bridges for the connection between Ag₂TPPS₄ and ng-C₃N₄ and for high-efficiency electron transfer. Hence, as-synthesized Ag₂TPPS₄/AgNPs/ng-C₃N₄ exhibits high sensitivity (a low detection limit of 5.1 × 10^-8 M, S/N = 3.0), a wide linear range (1 × 10^-7 to 1.2 × 10^-5 M), and long-term stability. Based on the experimental verification of the electrochemical dynamics and electrostatic attraction at the interface between the dual-active-center surface and RAC, the electrochemical mechanism has been clarified. Specifically, in the multi-cycle oxidation of RAC, the blue shift of specific UV-vis peaks also confirms the electrocatalytic oxidation of the two terminal hydroxyl groups of RAC. In brief, Ag₂TPPS₄/AgNPs/ng-C₃N₄ with a sandwich-like structure and double-faced active centers enhances the detection sensitivity and electrocatalytic efficiency towards RAC.

A highly selective and simple fluorescent probe for salbutamol detection based on thioglycolic acid-capped CdTe quantum dots

In this paper, a highly fluorescent water-soluble CdTe quantum dots (CdTe QDs) stabilized with thioglycolic acid (TGA) were synthesized for the quantitative and selective determination of salbutamol (SAL). When ten different of 2.09 × 10^-6 mol L^-1 alpha-2 adrenoceptor agonist were added to 4.38 × 10^-4 mol L^-1CdTe QDs solution, the fluorescence signal of the CdTe QDs quenched obviously by SAL with 57.32% and 0.815% - 7.00% for other nine kinds of veterinary medicine, such as tulobuterol, fenoterol, phenylethanamine A, simatero, penbutolol, clenbuterol, ractopamine, terbutaline and clorprenaline. The result shows that the CdTe QDs is highly sensitive sensor for SAL. The quenching mechanism has been investigated by absorption spectroscopy and K_SV at different temperatures, and shew a static quenching process than dynamic quenching. Under the optimal conditions, respectively the straight line equation (F₀/F = 0.1491 × 10⁶ C + 1.3078) was found between the relative fluorescence intensity and the concentration of SAL was in the range of 6.27 × 10^-8 to 2.09 × 10^-7 mol L^-1, and the limit of detection was 4.2 × 10^-8 mol L^-1. The proposed method has been applied to the determination of SAL in pig urine samples.

d-Penicillamine functionalized dendritic fibrous nanosilica (DFNS-DPA): synthesise and its application as an innovative advanced nanomaterial towards sensitive quantification of ractopamine

During the twentieth century, ractopamine (RAC) as one of the important and frequently used feed additives and doping agents has attracted considerable attention in the animal breeding industry and sports competitions.

A new potentiometric platform: Antibody cross-linked graphene oxide potentiometric immunosensor for clenbuterol determination

An immunosensor is based on the signal measurement obtained upon the reaction of an antibody antigen complex. It plays a significant role in various fields such as environmental analysis, production monitoring, drug detection or screening, veterinary medicine, and animal food. In this study, an antibody crosslinked graphen oxide (GO)-based potentiometric sensor has been developed for fast, simple, and economical detection of clenbuterol. In this context, the photosensitive amino acid bound GO platform is synthesized and used for the preparation of electrode material. Then, polymeric structure is characterized by infrared spectroscopy, and the performance of immunonano platform prepared by potentiometric sensor is evaluated. The effect of pH, response time, selectivity, and sensitivity is investigated. Under the optimized conditions, a simple and rapid method for the determination of clenbuterol from milk sample is established by immuno-potentiometric sensor. The detection limit has found to be 0.87 × 10^-9 mmol L^-1 for this immuno-potentiometric sensor. This immuno-potentiometric sensor has optimum pH at 7.0, a wide linear response (1.0 × 10^-2 to 1.0 × 10^-9 mmol L^-1 ), rapid response time (2 Min) and 36 weeks operational lifetime.

Sensitive detection of clenbuterol by hybrid iridium/silicon nanowire-enhanced laser desorption/ionization mass spectrometry

There is increasing demand for anti-doping drug monitoring in sports and food safety checks by developing sensitive and fast analytical methods. Here we report the development of hybrid Ir/SiNW as a new MALDI matrix for the detection of small molecules. This matrix is characterized by sufficient UV absorption, low-noise background, and high efficiency in ionization of small molecules. Sensitive detection of clenbuterol (LOD: 0.18 pmol) and a variety of other small molecules has been achieved using the Ir/SiNW matrix with a reproducible performance. Compared to the individual components separately, the matrix of hybrid Ir/SiNW synthesized via in situ growth can promote the MS signal intensity by up to 10 fold under identical experimental conditions. We provide a unique mechanism for the high performance of the hybrid Ir/SiNW matrix with the characteristic properties of hydrogen atom transfer and enhanced protonation at the interface of the hybrid nanostructures. Our approach of using a hybrid Ir/SiNW matrix enables detection of clenbuterol quantitatively in complicated biological samples and in vivo experiments, promising a useful tool for food security and anti-doping drug monitoring in sports.

The fabrication of a thiol-modified chitosan magnetic graphene oxide nanocomposite and its adsorption performance towards the illegal drug clenbuterol in pork samples

A novel thiol (provided by (3-mercaptopropyl) trimethoxysilane, MPTS)-modified chitosan magnetic graphene oxide nanocomposite (Fe₃O₄@SiO₂/GO/CS/MPTS) was synthesized and characterized for the first time as an efficient magnetic sorbent for the enrichment and extraction of trace levels of clenbuterol in pork samples (muscle, fat, heart and liver). Various greatly influential parameters were optimized using a Box-Behnken design (BBD) through the response surface methodology (RSM) to obtain more satisfactory recovery. Under optimum conditions, the method detection limits (MDLs) were in the range of 0.054-0.136 ng g^-1. The recoveries of three spiked levels ranged from 84.7% to 101.1%, and the relative standard deviations (RSDs) were lower than 9.3%. The results of the adsorption experiments showed that the maximum adsorption capacity of Fe₃O₄@SiO₂/GO/CS/MPTS for clenbuterol was 214.13 mg g^-1. The adsorption process was most consistent with pseudo second-order kinetics and Langmuir adsorption isotherm, indicating a homogeneous process with a chemisorptive nature. Also, the nanocomposite exhibited high adsorption capability for clenbuterol compared with Fe₃O₄@SiO₂/GO and Fe₃O₄@SiO₂/GO/CS. In addition, regeneration of the nanocomposite was effectively achieved, and it retained about 82% of its initial capacity after four cycles. All these results indicate that the synthetic nanocomposite is a promising efficient adsorbent for the adsorption of clenbuterol with high adsorption capacity and low cost.

Quantification of the β2-Adrenergic Feed Additives Ractopamine and Salbutamol by Reductive Amination-Assisted Modification

HIGHLIGHTS

A reductive amination-assisted method was used to synthesize standards and internal standards of ractopamine and salbutamol. Standard and internal standard analogs were fabricated by isotopic formaldehydes and sodium cyanoborohydride. A quantitative method of modified ractopamine and salbutamol was successfully validated. The reductive amination-assisted method enhances the signal for MS detection.

Development of Highly Sensitive Immunosensor for Clenbuterol Detection by Using Poly(3,4-ethylenedioxythiophene)/Graphene Oxide Modified Screen-Printed Carbon Electrode

Clenbuterol (CLB) is an antibiotic and illegal growth promoter drug that has a long half-life and easily remains as residue and contaminates the animal-based food product that leads to various health problems. In this work, electrochemical immunosensor based on poly(3,4-ethylenedioxythiophene)/graphene oxide (PEDOT/GO) modified screen-printed carbon electrode (SPCE) for CLB detection was developed for antibiotic monitoring in a food product. The modification of SPCE with PEDOT/GO as a sensor platform was performed through electropolymerization, while the electrochemical assay was accomplished while using direct competitive format in which the free CLB and clenbuterol-horseradish peroxidase (CLB-HRP) in the solution will compete to form binding with the polyclonal anti-clenbuterol antibody (Ab) immobilized onto the modified electrode surface. A linear standard CLB calibration curve with R² = 0.9619 and low limit of detection (0.196 ng mL-1) was reported. Analysis of milk samples indicated that this immunosensor was able to detect CLB in real samples and the results that were obtained were comparable with enzyme-linked immunosorbent assays (ELISA).

Application of Enzyme Digestion and Deconjugation Followed by Quick, Easy, Cheap, Effective, Rugged, Safe Extraction and Liquid Chromatography-Tandem Mass Spectrometry Methodology To Determine Ractopamine Residue in Pork

A new methodology is proposed for ractopamine residue analysis in pork. It consists of enzyme-mediated digestion and deconjugation steps; modified quick, easy, cheap, effective, rugged, and safe (QuEChERS) extraction; and liquid chromatography-tandem mass spectrometry (LC-MS/MS). In brief, the samples were digested with protease and then deconjugated with β-glucuronidase enzyme; they were then subjected to extraction and cleanup by QuEChERS and underwent sequential analysis by LC-MS/MS. The method performance was evaluated in accordance to the validation guidelines regulated by the Brazilian Ministry of Agriculture and Food Supply. The limit of detection was 0.15 μg/kg and limit of quantification was 0.5 μg/kg. When the method was applied to real samples, ractopamine residue was found in concentrations (up to 7.86 μg/kg) below international recommendation limits up to 10 μg/kg. The method is sensitive, accurate, quick, simple, and suitable for routine analysis; therefore, it is a monitoring tool that may be adopted by laboratories to achieve compliance levels.

An azo-coupling reaction-based surface enhanced resonance Raman scattering approach for ultrasensitive detection of salbutamol

To date, great achievements with GC-MS, HPLC-MS, and fluorescence biosensing techniques have been made to detect illegal additives of salbutamol (SAL) in swine meat. However, these methods are not suitable for rapid on-site screening due to either costly instruments or rather complicated and/or time consuming sample pretreatments. Herein, a simple, rapid and ultrasensitive approach based on an azo-coupling reaction and surface-enhanced resonance Raman scattering (SERRS) is presented. By combining with a magnetic SERS substrate, an indirect detection for SAL, with a LOD of 1.0 × 10-11 M (2.39 pg mL-1), was realized. Moreover, a colorimetric method for naked eye detection was successfully carried out for rapid screening of SAL in concentrations higher than 2.09 × 10-5 M (5 μg mL-1). In addition, the proposed method was successfully applied for the rapid determination of SAL in real swine meat. The entire process, including pretreatment, coupling reaction and SERRS detection, was performed within 7 min. Moreover, the SERRS fingerprint band being specific to corresponding functional group guarantees the selectivity for the target molecule. Therefore, the proposed strategy in the present study offers a new way to identify trace amounts of analytes, such as SAL as well as other illegal additives in health-related products and food.

Hollow Au-Ag Nanoparticles Labeled Immunochromatography Strip for Highly Sensitive Detection of Clenbuterol

The probe materials play a significant role in improving the detection efficiency and sensitivity of lateral-flow immunochromatographic test strip (ICTS). Unlike conventional ICTS assay usually uses single-component, solid gold nanoparticles as labeled probes, in our present study, a bimetallic, hollow Au-Ag nanoparticles (NPs) labeled ICTS was successfully developed for the detection of clenbuterol (CLE). The hollow Au-Ag NPs with different Au/Ag mole ratio and tunable size were synthesized by varying the volume ratio of [HAuCl4]:[Ag NPs] via the galvanic replacement reaction. The surface of hollow Ag-Au NPs was functionalized with 11-mercaptoundecanoic acid (MUA) for further covalently bonded with anti-CLE monoclonal antibody. Overall size of the Au-Ag NPs, size of the holes within individual NPs and also Au/Ag mole ratio have been systematically optimized to amplify both the visual inspection signals and the quantitative data. The sensitivity of optimized hollow Au-Ag NPs probes has been achieved even as low as 2 ppb in a short time (within 15 min), which is superior over the detection performance of conventional test strip using Au NPs. The optimized hollow Au-Ag NPs labeled test strip can be used as an ideal candidate for the rapid screening of CLE in food samples.

Novel ultrasensitive homogeneous electrochemical aptasensor based on dsDNA-templated copper nanoparticles for the detection of ractopamine

Herein, we describe a novel homogenous electrochemical aptasensor for the ultrasensitive detection of ractopamine (RAC) based on the signal amplification of a hairpin DNA cascade amplifier (HDCA) and electrocatalysis of dsDNA-templated copper nanoparticles.

Molecularly imprinted polymers as the extracted sorbents of clenbuterol ahead of liquid chromatographic determination

A pre-treatment methodology for clenbuterol hydrochloride (CLEN) isolation and enrichment in a complex matrix environment was developed through exploiting molecularly imprinted polymers (MIPs). CLEN-imprinted polymers were synthesized by the combined use of ally-β-cyclodextrin (ally-β-CD) and methacrylic acid (MAA), allyl-β-CD and acrylonitrile (AN), and allyl-β-CD and methyl methacrylate (MMA) as the binary functional monomers. MAA-linked allyl-β-CD MIPs (M-MAA) were characterized by Fourier transform-infrared (FT-IR) spectroscopy and a scanning electron microscope (SEM). Based upon the results, M-MAA polymers generally proved to be an excellent selective extraction compared to its references: AN-linked allyl-β-CD MIPs (M-AN) and MMA-linked allyl-β-CD MIPs (M-MMA). M-MAA polymers were eventually chosen to run through a molecularly imprinted solid-phase extraction (MISPE) micro-column to enrich CLEN residues spiked in pig livers. A high recovery was achieved, ranging from 91.03% to 96.76% with relative standard deviation (RSD) ≤4.45%.

A novel immunochromatographic assay based on a time-resolved chemiluminescence strategy for the multiplexed detection of ractopamine and clenbuterol

A novel multiplexed immunochromatographic assay (ICA) based on a time-resolved chemiluminescence (CL) strategy was developed for quantitative detection of β-agonists, by utilizing ractopamine (RAC) and clenbuterol (CLE) as the models. Different from conventional multiplexed ICA methods which usually require two or more test lines, this strategy was developed for detection of two β-agonists by using only one test line on the nitrocellulose membrane. In this study, horseradish peroxidase and alkaline phosphatase were used as the signal probes to label RAC antibody and CLE antibody, respectively. The two CL reactions with flash type and glow type kinetics characteristics were triggered simultaneously by injecting the coreactants, then the signals for RAC and CLE detections were recorded at 3 s and 300 s after coreactants injection, respectively. Owing to the utilization of CL detection, this protocol showed ideal sensitivity for quantitation. Under the optimal conditions, the detection limits for RAC and CLE were 0.17 ng mL(-1) and 0.067 ng mL(-1) (S/N = 3), respectively. The whole assay process can be accomplished within 20 min without complicated sample pretreatment. The proposed method was successfully applied for the detection of RAC and CLE in spiked swine urine. It opens up a new pathway for designing a low cost, time-efficiency and multiplexed strategy for rapid screening and field assay.

Early Life Exposure to Ractopamine Causes Endocrine-Disrupting Effects in Japanese Medaka (Oryzias latipes)

β-Agonists, which are used as human pharmaceuticals or feed additives, have been detected in aquatic environments. β-Agonists have also been proposed for use in aquaculture. However, there are limited data available regarding the adverse effects of β-agonists in aquatic organisms. In this study, ractopamine was selected as the representative β-agonist, and medaka embryos were exposed at concentrations ranging from 5 to 625 μg/L for 44 days. In contrast to what has been found in mammals, ractopamine caused no growth response in medaka. However, the transcriptional changes of genes related to the hypothalamic-pituitary-gonadal (HPG) axis, especially in females, suggested that β-agonists may have the potential to disrupt the endocrine system. Moreover, genes involved in anti-oxidative activity or detoxification were affected in a gender-specific manner. These findings, particularly the effects on the endocrine system of fish, will advance our understanding of the ecotoxicity of β-agonists.

New sulfonate composite functionalized with multiwalled carbon nanotubes with cryogel solid-phase extraction sorbent for the determination of β-agonists in animal feeds

A new mixed-mode cation-exchange sulfonate composite functionalized with multiwalled carbon nanotubes with polyvinyl alcohol cryogel was fabricated and used for the first time as a solid-phase extraction sorbent for the determination of β-agonists in animal feeds. Feed samples were extracted with 0.20 M phosphoric acid and methanol (1:4, v/v) using ultrasonication, cleaned-up using the developed sorbent to which the β-agonists bound then finally eluted with 5.0% ammonia in methanol and analyzed by high-performance liquid chromatography. Various parameters that affected the extraction efficiency were optimized. Under the optimal conditions, the developed sorbent strongly interacted with β-agonists by cationic exchange and hydrophobic and hydrophilic interactions, that provided a high extraction efficiency in the range of 92.8 ± 3.7-104.4 ± 2.3% over a range of 0.04-2.0 mg/kg for salbutamol and ractopamine, and 0.40-8.0 mg/kg for clenbuterol. The relative standard deviations were less than 6.0%. The developed method was successfully applied for the determination of β-agonists in various types of animal feed and effectively reduced any matrix interference.

Development and Application of a Method for Rapid and Simultaneous Determination of Three β-agonists (Clenbuterol, Ractopamine, and Zilpaterol) using Liquid Chromatography-tandem Mass Spectrometry

β-agonists are anabolic compounds that promote fat loss and muscle gain, and their administration to livestock may provide economic benefits by increasing growth rate and feed efficiency. For these reasons, β-agonists are also commonly added to livestock feed as growth promoters. This can introduce a significant risk of secondary human poisoning through intake of contaminated meat. A new method for the simultaneous determination of three β-agonists (clenbuterol, ractopamine, and zilpaterol) was developed in this study and applied to various meat samples. The limits of quantification, derived through a validation test following Codex guidelines, were 0.2 μg/kg for clenbuterol and zilpaterol, and 0.4 μg/kg for ractopamine. The average recoveries for clenbuterol, ractopamine, and zilpaterol ranged from 109.1% to 118.3%, 95.3% to 109.0%, and 94.1% to 120.0%, respectively. The recovery and coefficient of variation (CV) values fell within the acceptable range according to the Codex guidelines. This method reduced the analysis time without decreasing detection efficiency by modifying the pretreatment steps. This method could be utilized to manage the safety of imported meat products from countries where zilpaterol use is still permitted, thereby improving public health and preventing β-agonist poisoning due to secondary contamination.

Preparation of ractopamine-tetraphenylborate complexed nanoparticles used as sensors to rapidly determine ractopamine residues in pork

In this work, we reported a simple, fast, and sensitive determination of ractopamine (RAC) residues in pork by using novel ractopamine-tetraphenylborate complexed nanoparticles (RT NPs) as sensors. The prepared RT NPs exhibited a fast response time of 10 s, a wide linear range from 0.1 to 1.0 × 10(-7) mol/L, and a very low detection limit of 7.4 × 10(-8) mol/L. The prepared sensor also presents a high selectivity for ractopamine under different pH conditions ranged from 2.85 to 7.18. These results reveal that the fabricated RT NPs can be used as efficient electrochemical sensors to determine ractopamine in animal productions.

Highly selective and sensitive detection of β-agonists using a surface plasmon resonance sensor based on an alkanethiol monolayer functionalized on a Au surface

Immunosensor surfaces for surface plasmon resonance (SPR) have been constructed using a functionalized succinimidyl propanethiol monolayer as a linker to immobilize β-agonist protein conjugates on a Au surface. Because β-agonist is a small molecule, an indirect competitive inhibition immunoassay was used for detection. The lowest detection limits for ractopamine and salbutamol were 10 ppt (10 pg mL(-1)) and 5 ppt (5 pg mL(-1)), respectively. The fabricated immunosensor surface can be used again for detection after regeneration in 0.1 M sodium hydroxide. It was found that the same sensor surface could be reused for performing over 100 rapid immunoreactions. Moreover, one immunosensing-regeneration cycle requires only 600 s. The fabricated immunosensor surfaces were characterized using SPR and scanning tunneling microscopy observation. In the kinetic study of the indirect competitive immunosensing inhibition, the affinity constant (K1) of salbutamol antibody was smaller than the K1 of ractopamine antibody. Compared to a previous study of clenbuterol detection, it was concluded that the high K1 was coupled with low sensitivity. In the selectivity study, both immunosensor surfaces provided >90% of confidence level for the specific detection of β-agonist compounds. The fabrication of highly selective and sensitive sensor surfaces for detecting β-agonist compounds was confirmed.