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.

Determination of nitroxynil residues in tissues and bovine milk by immunobiosensor.

Nitroxynil is an anthelmintic drug mainly used for the control of liver fluke in sheep and cattle. The European Commission has established maximum residue limits in bovine and ovine muscle (400 µg kg(-1)), fat (200 µg kg(-1)), liver (20 µg kg(-1)) and kidney (400 µg kg(-1)), and more recently in bovine and ovine milk (20 µg kg(-1)). To ensure that these limits are not exceeded through incorrect use of the drug, it is necessary to monitor samples using robust and reliable methods capable of low-level detection. An inexpensive and rapid immunobiosensor-based screening procedure, capable of high sample throughput, was developed that is capable of detecting nitroxynil at <10 µg kg(-1) in bovine milk, at <10 µg kg(-1) in bovine liver, and at <200 µg kg(-1) in bovine and ovine muscle. The methods were fully validated and the milk assay was utilised in a comparison study of nitroxynil-incurred samples.

Determination of bithionol, bromophen, nitroxynil, oxyclozanide, and tribromsalan in milk with liquid chromatography coupled with tandem mass spectrometry.

LC/MS/MS was developed to determine the residues of bithionol (BTN), bromofen (BMF), nitroxynil (NTX), oxyclozanide (OCZ), and tribromsalan (TBS) in milk. Samples were extracted with ethyl acetate and cleaned up by liquid-liquid separation with acetonitrile and n-hexane. The compounds were determined by RP-LC using a C18 column with 0.1% formic acid-methanol. Mass spectral acquisition was performed in the negative mode by applying selected-reaction monitoring. The method was validated in milk spiked with these compounds at 5-600 microg/kg; average recoveries were in the range 83.8-97.1%, with RSD values of 1.4-8.0%. The interassay RSDs were less than 11%. The LODs of these compounds in milk were 0.1 microg/kg. The method was applied to 24 raw milk samples. The concentration of these compounds in all samples was lower than the Japanese maximum residue limits. The method is rapid, sensitive, and specific for monitoring residues of BTN, BMF, NTX, OCZ, and TBS in milk.

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.

Spectrophotometric multicomponent resolution of a veterinary formulation containing oxfendazole and oxyclozanide by multivariate calibration-prediction techniques.

Four multivariate calibration-prediction techniques, classical least-squares, inverse least-squares, principal component regression and partial least-squares regression were applied to the spectrophotometric multicomponent analysis of a veterinary formulation containing oxfendazole (OXF) and oxyclozanide (OXC) without any separation step. The multivariate calibrations were constructed by measuring the absorbance values at 14 points in the 285-350 nm wavelength range and by using the training set of standard mixtures containing OXF and OXC in the different compositions. The validity of building multivariate calibrations was checked by using the synthetic mixtures of both drugs. The multivariate calibration models were successfully applied to the spectrophotometric determination of OXF and OXC in laboratory prepared mixtures and a veterinary formulation. The results obtained were statistically compared with each other.

Voltammetric determination of praziquantel in tablets and biological fluids.

A simple method is described for the determination of praziquantel (CAS 55268-74-1) in its pure form, tablet formulations and biological fluids. The proposed method depends upon the polarographic activity of praziquantel at the dropping mercury electrode (DME) in Britton Robinson buffers, whereby a well-defined catholic wave is produced over the pH range 7-12. The wave was characterized as being irreversible diffusion-controlled with limited adsorption properties. The diffusion current constant (Id) was 0.56 +/- 0.004 (n = 11). The current-concentration relationship was found to be rectilinear over the range 8-48, 3.2-38.4 and 0.48-20 micrograms.ml-1 using direct current (DCt), differential pulse polarographic (DPP) and alternating current (ACt) odes, respectively, with minimum detection limit (S/N = 2) of 0.32 microgram.ml-1 (1.02 x 10(-6) mol/l and 0.02 microgram.ml-1 (6.4 x 10(-8) mol/l) for DPP and ACt modes respectively. The average percent recovery was favourably compared to a reference method with a satisfactory standard deviation. The proposed method was applied to spiked human urine and plasma. The percentage recoveries were 99.33 +/- 0.79 and 98.23 +/- 0.53, respectively.

Vilsmeier formylation of praziquantel: synthesis and application for polarographic assay.

A simple and sensitive method for the polarographic determination of praziquantel (1) after derivatization using Vilsmeier formylation is described. The polarographically active compound obtained by this procedure has been separated, identified and prepared using N,N-dimethylformamide and phosphorus oxychloride.

LC assay method for oxfendazole and oxyclozanide in pharmaceutical preparation.

A method has been developed for the simultaneous determination of oxfendazole and oxyclozanide in a pharmaceutical preparation. The method involves reversed phase chromatography with isocratic elution of the mobile phase and detection at 300 nm. The range of quantification for oxfendazole and oxyclozanide was found to be 2-7 microg ml(-1) and 3-10 microg ml(-1), respectively. The validity of the method was evaluated in terms of linear regression analysis, precision, specificity and accuracy.