Determination of Dimetridazole, Metronidazole and Ronidazole in Salmon and Honey by Liquid Chromatography Coupled with Tandem Mass Spectrometry

Modern Methods for Assessing the Quality of Bee Honey and Botanical Origin Identification

This paper is a summary of the latest literature on methods for assessing quality of natural bee honey. The publication briefly characterizes methods recommended by the International Honey Commission, published in 2009, as well as newer methods published in the last 10 years. Modern methods of assessing honey quality focus mainly on analyzing markers of individual varieties and classifying them into varieties, using, among others, near infrared spectroscopy techniques (NIR), potentiometric tongue, electronic nose, nuclear magnetic resonance (NMR), zymography, polymerase chain reaction (PCR), DNA metabarcoding, and chemometric techniques including partial least squares (PLS), principal component analysis (PCA) and artificial neural networks (ANN). At the same time, effective techniques for analyzing adulteration, sugar, and water content, hydroxymethylfurfural (HMF), polyphenol content, and diastase activity are being sought. Modern techniques enable the results of honey quality testing to be obtained in a shorter time, using the principles of green chemistry, allowing, at the same time, for high precision and accuracy of determinations. These methods are constantly modified, so that the honey that is on sale is a product of high quality. Prospects for devising methods of honey quality assessment include the development of a fast and accurate alternative to the melissopalynological method as well as quick tests to detect adulteration.

A voltammetric screening method to determine ronidazole in bovine meat

An original voltammetric screening method, employing glassy carbon electrode (GCE) with the differential-pulse voltammetry technique (DPV), has been developed to determine residues of the anti-parasitic agent Ronidazole (RNZ) in bovine meat. By using cyclic voltammetry (CV), it has been demonstrated that an irreversible cathodic process occurs at approximately -0.740 V (vs. Ag|AgCl, KCl 3 mol L^-1) in a 0.100 mol L^-1 phosphate buffer at pH 6.5 as supporting electrolyte. Furthermore, the behavior of RNZ in CV indicates the occurrence of a diffusion mass transfer process to the working electrode surface. The RNZ reduction mechanism was proposed as a 6-electron transfer, similar to Metronidazole under the same pH range. Quantification of RNZ and method validation were then carried out by DPV. The relative standard deviation (RSD) were 3.21% for intraday precision of 10 consecutive repetitions and 6.78% for interday precision after five analysis. Limits of detection and quantification were also obtained, and the values were 0.107 and 0.358 mg kg^-1, respectively. The recovery percentage for three different concentrations of RNZ in the bovine meat matrix ranged between 98.1% and 100.3%. The method proved to be efficient for screening RNZ in bovine meat.

Removal of metronidazole from aqueous media by C. vulgaris

This current study investigated the removal of metronidazole from aqueous media by C. vulgaris. Two different initial sizes of inoculum (0.05 and 0.5 g L^-1) were tested for a wide concentration range of metronidazole (1-50 μM). The effect of metronidazole concentrations on biomass production was studied for 20 days. The exopolymeric substances (EPS) were quantified and correlated with the removal of antibiotics from aqueous media. Specifically, MDZ stimulated the production of EPS in C. vulgaris, which played the major role in the adsorption of this antibiotic. Also, metronidazole significantly influenced the zeta potential of C. vulgaris in the test cultures, indicating a change in surface characteristics. This decrease in surface negative charge caused auto-flocculation phenomena at a stationary phase. Chronic and acute toxicity experiments showed that metronidazole was harmful to C. vulgaris at stationary phase. Results from this study would advance our knowledge on the treatment of metronidazole-contaminated waters with C. vulgaris as a green technology-oriented process.

Hierarchical multi-layered molybdenum carbide encapsulated oxidized carbon nanofiber for selective electrochemical detection of antimicrobial agents: inter-connected path in multi-layered structure for efficient electron transfer

The schematic illustration for electrochemical sensing of MTZ at Mo₂/C/f-CNF modified GCE.

Development and validation of a liquid chromatography tandem mass spectrometry assay for the measurement of faecal metronidazole

BACKGROUND

Metronidazole is an oral antibiotic which is widely used in the treatment of patients with Clostridium difficile associated disease.

METHODS

This article describes the validation of a LC-MS/MS assay for the measurement of metronidazole in human faecal samples.

RESULTS

Matrix matched and aqueous standards showed no significant difference in performance for the routine calibration of the assay. D⁴ deuterated metronidazole internal standard eluted with a different retention time to the undeuterated metronidazole on chromatography, hence zidovudine was used as an internal standard. Ion suppression was noted for both metronidazole and zidovudine due to unidentified compounds present in the faecal matrix and this was improved by extracting a smaller quantity of faeces and diluting the extract prior to analysis. Measurement uncertainty was 13% at 28,400ng/ml, 7.2% at 3300ng/ml, 3.9% at 320ng/ml, 13.6% at 109ng/ml and 30.9% at 20ng/ml. The assay was shown to be linear on dilution and the sensitivity of the assay was superior to HPLC assays using UV detection. The limit of detection was 5ng/ml, the limit of quantitation was 66ng/ml and the upper limit of the working range was 30,000ng/ml. Patient samples were stable at -20°C for 12months and extracted faecal samples were stable on storage for 1week at 4°C. There were no specific requirements for patient preparation or time of sample collection relative to taking metronidazole.

CONCLUSIONS

Metronidazole can be quantified in faecal samples using LC-MS/MS which opens up opportunities for further research in this area.

Toxic concentrations of metronidazole to Microcystis protocystis

Antimicrobials are among the most commonly used drugs and have become a class of contaminants with great environmental importance. Metronidazole is an antimicrobial used for the therapeutic management of several human diseases. The toxicity of antimicrobials on aquatic species may affect sensitive microorganisms and reduce metabolic processes. Cyanobacteria is a group of organisms that are of great ecological importance in aquatic environments. Studies indicate that cyanobacteria are very sensitive to some antimicrobials. Therefore, it is necessary to evaluate the effects of metronidazole contamination on phytoplankton. The aim of this study was to investigate the effects of metronidazole on the growth of the cyanobacterium Microcystis protocystis and to evaluate the stability of this antimicrobial agent in the culture medium over a period of 96 hours. M. protocystis was resistant to growth inhibition by metronidazole. The EC50 of this antimicrobial for M. protocystis was 117.3 mg L–1. Under the growth inhibition test conditions, neither a significant change in the MNZ concentration nor the presence of drug metabolites or degradation products was observed. These results indicate low cellular uptake of the antimicrobial agent and its persistence in the culture medium.