Determination of nitroxynil in cow milk by reversed-phase high-performance liquid chromatography with dual-electrode coulometric detection

Fast and sensitive detection of nitroxynil using a chalcone-based supramolecular fluorescent sensor

Nitroxynil as a veterinary drug has been widely used for treatment of parasitic worms in food-producing sheep and cattle. However, the residual nitroxynil in edible animal products can lead to severe adverse effects on human health. Thus, development of an effective analytical tool for nitroxynil is of great significance. In the present study, we designed and synthesized a novel albumin-based fluorescent sensor, which was capable of detecting nitroxynil with the fast response (<10 s), high sensitivity (limit of detection ∼8.7 ppb), high selectivity, and excellent anti-interference property. The sensing mechanism was clarified by using the molecular docking technique and mass spectra. Moreover, this sensor showed the detection accuracy comparable to standard HPLC method, and meanwhile exhibited much shorter response time and higher sensitivity. All the results demonstrated that this novel fluorescent senor could serve as a practical analytical tool for determination of nitroxynil in real food samples.

Voltammetric estimation of residual nitroxynil in food products using carbon paste electrode

A simple and sensitive voltammetric method was developed and validated for the recognition of the veterinary drug nitroxynil (NTX). The method is based on studying its voltammetric behavior at a carbon paste electrode. Square wave voltammetry (SWV) was successfully applied in this study. The anodic peak current obtained was a linear function of NTX concentration in Britton Robinson buffer of pH 3 over the range of 3.9 × 10^–6–1.0 × 10⁻⁴ M with lower detection and quantitation limits of 3.1 × 10^–7 and 9.4 × 10^–7 M, respectively. The proposed method was first applied to the assessment of the drug in commercial vials. The method was further used to monitor the residual amounts of the drug in bovine meat, kidney, fat, and milk samples. The results obtained were favourably compared with those given by reference method. The interference likely to be introduced by co-administered drugs was evaluated. The electrode reaction was elucidated, and electron transfer kinetics were studied.

Spectrofluorometric determination of residual amounts of nitroxynil in food samples

Because of the frequent treatment of dairy cows with nitroxynil (NTX), the presence of the later residues in animal tissues and milk has a significant concern. The quantum yield of the reaction product was calculated. A highly sensitive and rapid spectrofluorometric method for determining the anthelmintic drug (NTX) residual amounts is developed. The proposed approach is based on using Zn/HCl to reduce NTX nitro group to an amino group, resulting in a highly fluorescent derivative that was detected at each of λ_em 302 nm and 364 nm after excitation at λ_ex = 277 nm. The experimental conditions were carefully studied and optimized. The proposed approach showed good linearity (r² ≥ 0.9998) with linearity range of 10.0-100.0 ng/mL with a detection limit of 1.89 ng/mL, 1.27 ng/mL and quantification limit of 5.73 ng/mL, 3.86 ng/mL at λ_em 302 nm and 364 nm, respectively; that is far below the Minimum Regulatory Limits (MRLs) of NTX in animal tissues and milk. The proposed approach was successfully applied for the analysis of the drug in its veterinary formulations, and the obtained results agreed well with those of the official British Pharmacopeia method. Moreover, the proposed method's application was extended to efficiently determine the residues of nitroxynil in meat, liver, kidney and milk samples.

Review of the Analytical Methods Based on HPLC-Electrochemical Detection Coupling for the Evaluation of Organic Compounds of Nutritional and Environmental Interest

This review would like to show the state of the art regarding the coupling of High-Performance Liquid Chromatography (HPLC) with Electrochemical Detection (ED). Since a universal detector for HPLC is not available, the electrochemical detection methods, thanks to their versatility and specificity, are competitive with respect to the detectors currently used. The papers present in literature on HPLC-ED technique are analyzed and discussed: for example, they regard the development of analytical determinations of resveratrol, rosmarinic acid, aromatic heterocyclic amines and glyphosate in food matrices such as meat, aromatic plants, vegetables, fruit and tomato juices. These papers show that electrochemical sensors used as detectors for HPLC can offer better sensitivity values than other detectors. Furthermore, the use of specific working potentials allows avoid matrix interferences to be avoided by almost exclusively determining the analytes of interest. It should be underlined that HPLC-ED methods have a selectivity that allows for limitation of the sample preparation and clean-up procedures to a minimum, making them quick and easy to apply. In addition, these methods offer advantages such as the possibility of direct analysis, that derivatization is often not necessary, the cost-effectiveness of the instrumentation and the possibility of regenerating the electrodes which allows numerous analyses in succession.

A rapid colloidal gold-based immunochromatographic strip assay for monitoring nitroxynil in milk

BACKGROUND

Nitroxynil (NIT) is a veterinary drug against hepatic fluke disease for food-producing cattle and sheep. NIT has a long half-life time in animals since it is highly bound to plasma protein. Therefore NIT possibly remains in animal edible tissues or milk due to drug abuse. In this study, a specific murine monoclonal antibody (mAb) against NIT was prepared and an immunochromatographic strip assay based on the mAb was developed for screening NIT in milk.

RESULTS

The affinity constant of the anti-NIT mAb was 2.93 × 10¹⁰ and the anti-NIT mAb had almost no cross-reactivity with other analogs, so that it showed good specificity. The cutoff value of this test strip was considered to be 50 ng mL^-1 by the naked eye. When detected by the strip reader, the half maximum inhibition concentration (IC₅₀ ) of the immunoassay strip was calculated to be 5.716 ng mL^-1 and the limit of detection (LOD) was 1.146 ng mL^-1 . Intra-assay recoveries from 88.80 to 97.13% were obtained, with the highest coefficient of variation (CV) at 9.01%; inter-assay recoveries ranged from 84.60 to 106.87%, with the highest CV at 9.93%.

CONCLUSION

The operative procedure of the proposed method can be completed within 10 min. The strip developed in this study was a practical tool for rapid semiquantitative and quantitative detection of NIT in milk. This study suggested great potential for analytically monitoring NIT in other food samples. © 2019 Society of Chemical Industry.

Analysis of Food by High Performance Liquid Chromatography Coupled with Coulometric Detection and Related Techniques: A Review

The development of single coulometric cells in combination with high performance liquid chromatography to dual cells and to the coulometric electrode array detector is described. An overview is given about the application of these methods in food chemistry. Easily oxidizable compounds, such as phenolic substances, pesticides, or vitamins, can be determined, as well as substances with high oxidation potentials or electroinactive compounds. Substances exhibiting poor electrochemical activity can be transformed to electroactive compounds by precolumn derivatization, postcolumn photochemical reactions, postcolumn enzyme reactors, or by using the oxidative/reductive mode for coulometric electrode array detection. Furthermore, it is shown that the interesting combination of high performance liquid chromatography with electrochemistry and mass spectrometry has opened further possibilities with respect to interpretation of redox reactions, drug metabolism studies, metabolomics, and electrochemical derivatization.

Voltammetric assay of the anthelmintic veterinary drug nitroxynil in bulk form and formulation at a mercury electrode

The electrochemical behavior of the anthelmintic veterinary drug nitroxynil at the mercury electrode was studied in a series of Britton-Robinson universal buffer of pH 1.9-11 containing 20% (v/v) ethanol using dc-polarography cyclic voltammetry and controlled-potential coulometry. The voltammograms exhibited two irreversible cathodic steps over the pH range 1.9-10.2; the height of the first step is double that of the second one. Controlled-potential coulometry in the B-R universal buffer of pH 1.9-10 at a mercury pool working electrode revealed the consumption of four and two electrons via the first and second reduction steps, respectively, which attributed to reduction of the NO2 group to the hydroxylamine stage (first step), and then to the amine stage (second step). Three voltammetric analytical procedures including dc-polarography, differential-pulse adsorptive stripping voltammetry and square-wave adsorptive stripping voltammetry were optimized for the direct determination of bulk nitroxynil. The three proposed procedures were applied for analysis of bulk nitroxynil with limits of detection of 3 x 10(-5), 1.31 x 10(-8) and 8.4 x 10(-10)M and limits of quantification of 1 x 10(-5), 4.36 x 10(-8) and 2.80 x 10(-9)M, respectively. The three procedures were successfully applied to the determination of nitroxynil in formulation (Dovenix, 25% nitroxynil injection solution) without the necessity for sample pretreatment and/or time-consuming extraction steps prior to the analysis.

Concentration in Plasma and Excretion in Milk of Lactating Cows after Oral Administration of Tribromsalan, Oxyclozanide and Bromofenofos

The fasciolicides tribromsalan (TBS), oxyclozanide (OCZ) and bromofenofos (BFF) were orally administered to three lactating cows. The concentrations of TBS, OCZ and the BFF metabolite dephosphate bromofenofos (DBFF) in plasma, and the excretion of these compounds in milk were determined by high-performance liquid chromatography. In plasma, the concentrations of TBS, OCZ and DBFF reached maximum at about 1.0 day and the compounds remained detectable until 5.7, 7.4 and 15.1 days after administration, respectively. The detection limits of these compounds in plasma were 10, 2 and 2 ppb, respectively. In milk, the concentrations of TBS, OCZ and DBFF reached maximum at about 24 hours and the compounds remained detectable until 30-47, 30-47 and 78-119 hours after administration, respectively. The detection limits of these compounds in milk were 5.1 and 1 ppb, respectively. The residence times of TBS and BFF were very close to the withdrawal times of the fasciolicides.

Analytical considerations for trace determinations of drugs in breast milk

Recent scientific and regulatory interest in lacteal excretion of drugs has prompted this review of bioanalytical sample preparation techniques for milk. The composition and properties of milk are reviewed, with emphasis on how the sample preparation is affected. The most important principals of mammary gland pharmacology, including protein binding, ion trapping and liquid solubility, are described. Because adequate milk volume is difficult to obtain from some smaller rodent species, special arrangements for sample collection, control preparation and assay standardization often need to be made. Several commonly-used sample preparation approaches for drugs in milk, including direct injection, dialysis and ultrafiltration, protein precipitation, liquid-liquid extraction, solid-phase extraction and immunoaffinity extraction. Have been reported with varying degrees of success. The advantages and disadvantages of each of these approaches is discussed.

High-performance liquid chromatographic method for the determination of the anthelmintic nitroxynil in cattle muscle tissue with on-line anion-exchange clean-up

A high-performance liquid chromatographic method for the determination of the anthelmintic nitroxynil has been developed. The drug was extracted from cattle muscle tissue with 1% triethylamine in acetonitrile. The extract was evaporated to dryness and taken up in 0.1 M ammonium acetate-acetonitrile (50:50, v/v). The extract was then injected onto a polymeric anion-exchange precolumn. After clean-up with 0.1 M ammonium acetate-acetonitrile (50:50, v/v) for 5 min, the precolumn was eluted with 1% aqueous trifluoroacetic acid-acetonitrile (50:50, v/v) onto a PLRP-S polymer column and chromatographed with a mobile phase of 0.01 M phosphate pH 7-acetonitrile (80:20, v/v). Detection was by ultraviolet at 273 nm. Average recoveries at four levels from 0.005 to 1.000 mg kg-1 were > 88%. The limit of determination was 0.005 mg kg-1.