Synergistically Enhanced Electrochemical Sensing of Food Adulterant in Milk Sample at Erbium Vanadate/Graphitic Carbon Nitride Composite.

Dimetridazole (DMZ), a nitroimidazole derivative, is a notable antibiotic that has garnered growing interest in the medical community owing to its noteworthy pharmacological and toxicological properties. Increasing interest is being directed toward developing high-performance sensors for continuous monitoring of DMZ in food samples. This research investigated an electrochemical sensor-based nano-sized ErVO4 attached to a sheet-like g-CN-coated glassy carbon electrode to determine dimetridazole (DMZ). The chemical structure and morphological characterization of synthesized ErVO4@g-CN were analyzed with XRD, FTIR, TEM, and EDS. Irregular shapes of ErVO4 nanoparticles are approximately 15 nm. Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were followed to examine the electrochemical performance in pH 7 phosphate buffer solution for higher performance. This electrochemical sensor showed a low detection limit (LOD) of 1 nM over a wide linear range of 0.5 to 863.5 µM. Also, selectivity, stability, repeatability, and reproducibility studies were investigated. Furthermore, this electrochemical sensor was applied to real-time milk sample analysis for the detection of analytes.

Defective metal-organic framework derived from the waste plastic bottles for rapid and efficient nitroimidazole antibiotics removal.

In order to alleviate the pressure on the ecological environment and human health caused by wastewater of nitroimidazole antibiotics and poly(ethylene terephthalate) (PET) plastic waste, we propose a strategy of using defective MIL-68(Al) (d-MIL-68(Al)) derived from waste PET plastic for dimetridazole (DMZ) capture. The resulting d-MIL-68(Al) exhibits an excellent adsorption capacity of 555.6 mg g-1, which is three times of pristine MIL-68(Al) (181.8 mg g-1), demonstrating that the defective structures in d-MIL-68(Al) play a crucial role in the adsorption process. Remarkably, d-MIL-68(Al) can remove nearly 97% of DMZ in the first 10 s, and the removal efficiency reached 99% after adsorption equilibrium, affording a record kinetic rate constant k2 (2.84 g mg-1 min-1). In short, d-MIL-68(Al) possesses both an ultrafast adsorption rate and outstanding adsorption capacity toward DMZ compared with reported adsorbents. Mechanism analysis reveals that the excellent DMZ adsorption performances can be ascribed to the abundant active sites caused by defective structures, as well as the π-π stacking and hydrogen bonding interactions between MOF and DMZ. Hence, d-MIL-68(Al) derived from waste PET plastic is an efficient porous adsorbent for rapid DMZ removal, which not only possesses great potential for wastewater treatment, but also reduces the harmful PET plastic waste, reflecting the concept of sustainable development.

[Simultaneous determination of 40 plant growth regulators, fungicides, insecticides, and antibiotics in bean sprouts by QuEChERS-high performance liquid chromatography-tandem mass spectrometry].

Chromatography combined with mass spectrometry is the most commonly used detection technology, and it offers the advantages of high sensitivity and high selectivity. The quick, easy, inexpensive, effective, rugged, and safe (QuEChERS) method is low-cost, effective, and time efficient. The application of the QuEChERS has now been extended to the analysis of contaminants in food samples. The aim of the study was to identify different concentration levels of multiple harmful drug residues in bean sprouts. In this study, QuEChERS coupled with high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) was established for the simultaneous determination of 40 plant growth regulators, fungicides, insecticides, and antibiotics in bean sprouts. In the HPLC-MS/MS experiment, gibberellic acid, 4-fluorophenoxyacetic acid, chloramphenicol, N6-(δ2-isopentenyl)-adenine, 6-benzylaminopurine, 4-chlorophenoxyacetic acid, and 2,4-dichlorophenoxyacetic acid (2,4-D) were analyzed by MS/MS with negative electrospray ionization (ESI-). The other 33 target analytes (chlormequat, ronidazole, metronidazole, pymetrozine, dimetridazole, methomyl, carbendazim, enoxacin, levofloxacin, pefloxacin mesylate, norfloxacin, ciprofloxacin, enrofloxacin, thiabendazole, lomefloxacin, chlorpyrifos, sarafloxacin, imidacloprid, etc.) were analyzed by MS/MS with positive electrospray ionization (ESI+). Sensitive MS conditions were realized by optimizing the instrumental parameters such as the desolvent temperature, collision energy, spraying needle position, precursor ions, and product ions. Then, the optimal pretreatment method was determined by comparing the recovery rates of the 40 drugs obtained with different extraction solvents (methanol, acetonitrile, acetonitrile containing 0.1% ammonia, acetonitrile with 1% acetic acid), different extraction methods (ultrasonic extraction, shaking extraction), and purification with primary secondary amine (PSA) and C18. In this study, the bean sprouts samples were extracted twice by 10 mL acetonitrile with 1% acetic acid, and extracted under ultrasonic conditions. Then, the extracting solution was only cleaned with 100 mg C18. The chromatographic separation of the 40 compounds was accomplished on a Waters ACQUITY UPLC BEH C18 column (100 mm×2.1 mm, 1.7 µm) with gradient elution. Methanol and 0.01% formic acid aqueous solution were used as the mobile phases. The 40 compounds were analyzed in the multiple reaction monitoring (MRM) mode. The matrix matching external standard method was used for quantitative determination. The results showed that the 40 compounds could be analyzed within 15 min. Under the optimized conditions, the calibration curves showed good linearities for the 40 compounds, and the coefficients of determination (r2) were greater than 0.99 in the range of 2-200 µg/L. The limits of detection (LODs) and limits of quantification (LOQs) were in the range of 0.1-3 µg/kg and 0.3-9 µg/kg, respectively. Using negative bean sprouts as the substrates, the recovery tests were carried out at three spiked levels of 5, 10, and 50 µg/kg. The average recoveries of the 40 drugs were 78.5% to 115.3%, and the corresponding relative standard deviations (RSDs) were 1.3% to 9.7% (n=6). This method was successfully applied to the analysis of the 40 drug residues in 21 batches of local bean sprouts in Handan city. The results revealed the presence of extensive drug residues in the bean sprouts. The 26 batches were detected to varying degrees, among which 4-chlorophenoxyacetic acid, carbendazim, 6-benzyladenine, 2,4-D, enrofloxacin, and metronidazole were detected at high rates. The detection rates of 4-chlorophenoxyacetic acid, 6-benzyladenine, carbendazim, 2,4-D, gibberellic acid, and enrofloxacin were 28.6%, 19.0%, 9.5%, 9.5%, 4.8%, and 4.8%, respectively. The contents ranged from 37.5-352.4, 32.4-273.1, 28.8-38.7, 316.1-20.2, 19.9 and 13.6 µg/kg, respectively. Given its advantages of simplicity, rapidness, and high sensitivity, the developed method can be used for the rapid and accurate determination of trace levels of the 40 drug residues in large quantities of bean sprouts.

New theoretical investigation of mechanism, kinetics, and toxicity in the degradation of dimetridazole and ornidazole by hydroxyl radicals in aqueous phase.

Dimetridazole (DMZ) and ornidazole (ONZ) have been widely used to treat anaerobic and protozoal infections. The residues of DMZ/ONZ persist in the water environment. The mechanisms and kinetics of hydroxyl-initiated oxidation, the primary DMZ/ONZ degradation method, were evaluated by quantum chemical methods.·OH-induced degradation of DMZ and ONZ shared many mechanistic and kinetic characteristics. The most feasible degradation pathway involved forming OH-imidazole adducts and NO2. The OH-imidazole adducts were subsequently degraded into double·OH imidazole intermediates. The rate coefficients for·OH degradation of DMZ and ONZ were 4.32 × 109 M-1 s-1 and 4.42 × 109 M-1 s-1 at 298 K, respectively. The lifetimes of DMZ and ONZ treated with·OH at concentrations of 10-9-10-18 mol L-1 at 298 K were τDMZ = 0.231-2.31 × 108 s and τONZ = 0.226-2.26 × 108 s, respectively. Toxicity assessment showed that the first degradation products of DMZ and ONZ exhibited enhanced aquatic toxicity, whereas most of the secondary degradation products were not harmful to aquatic organisms. Some of transformation products were still developmental toxicant or mutagenicity positive.

A dye encapsulated zinc-based metal-organic framework as a dual-emission sensor for highly sensitive detection of antibiotics.

Self-assembly of two Zn-MOFs, [Zn2L(DMF)3]·H2O·5DMF (1) and [Zn2L(H2O)2]·4H2O·3DMF (2), was achieved with an amide-functionalized tetracarboxylate ligand under similar conditions. Incorporated amide groups make the tetratopic linkers exhibit different configurations, tetrahedron and square, and subsequently combine tetrahedral [Zn2(CO2)4] clusters or square paddle-well [Zn2(CO2)4] clusters to afford a lon net for 1 and a nbo net for 2. Remarkably, 2 demonstrated high porosity and amide group decorated cages, and thereby proved to be a good capturing agent for a fluorescent dye molecule (DMASM). Consequently, a dual-emitting DMASM@2 sensor was successfully fabricated based on effective energy transfer from the host framework to DMASM with the variable luminescent color being visible to the naked eye. DMASM@2 could be used for the detection of metronidazole (MDZ) and dimetridazole (DTZ) with high sensitivity and remarkable recyclability.

Facile synthesis of neodymium stannate nanoparticles an effective electrocatalyst for the selective detection of dimetridazole in biological samples.

In this work, pyrochlore neodymium stannate nanoparticles (Nd2Sn2O7 NP) have been synthesized by a facile co-precipitation technique and employed as an electrode material on GCE for the determination of dimetridazole (DM) drug. The physical properties and texture of the Nd2Sn2O7 NP were characterized by PXRD, Raman spectroscopy, FE-SEM, EDX mapping, XPS, and HR-TEM analytical studies. The electrocatalytic investigation of Nd2Sn2O7 NP/GCE was carried out by CV, and DPV techniques. The fabricated Nd2Sn2O7 NP/GCE shows a lower LOD of 6 nm towards the determination of DM and the calculated sensitivity is 0.61 µA µM-1 cm-2. In addition to that, the constructed sensor delivers notable repeatability, reproducibility, and superior selectivity with the existence of metal ions, biological molecules, and nitro compounds, enabling the electrochemical detection of DM. Furthermore, Nd2Sn2O7 NP/GCE sensor displays acceptable recovery results in the real sample analysis in biological fluids such as human blood serum and human urine.

A highly sensitive poly-arginine based MIP as an electrochemical sensor for selective detection of dimetridazole.

In this experiment, a highly effective electrochemical sensor based on a molecularly imprinted polymer has been developed for ultrasensitive detection of dimetridazole. The sensor was made by incorporating of dimetridazole as a template molecule during the electropolymerization of poly-arginine on a glassy carbon electrode. The modified electrode GCE/P-Arg@MIP was characterized by voltammetric and microscopic techniques. Differential pulse voltammetry method was used to detect target analyte under the optimum condition. The DPV response to dimetridazole was linear at 0.1 × 10-9 to 10 × 10-6 mol L-1 (R2 = 0.996), with a method detection limit (S/N = 3) of 0.1 × 10-9 mol L-1. Moreover, the proposed sensor shows satisfactory recovery ranges for the determination dimetridazole in commercially available egg, milk and honey samples.

Adsorption capacity of different types of carbon nanotubes towards metronidazole and dimetridazole antibiotics from aqueous solutions: effect of morphology and surface chemistry.

The effect of surface chemistry and morphology of carbon nanotubes (CNTs) on their adsorption capacity towards dimetridazole (DTZ) and metronidazole (MNZ) antibiotics from water solutions was investigated in this work. The CNTs studied were single-walled carbon nanotubes (SWCNTs), CNTs doped with nitrogen (N-CNTs), multiwalled CNTs (MWCNTs), and MWCNTs functionalized with carboxylic groups (MWCNT-COOH). The experimental adsorption equilibrium data were best interpreted with the Redlich-Peterson (R-P) isotherm model. At T of 25 °C and pH of 7, the capacities of adsorption decreased as follows: SWCNT > MWCNT > N-CNT ≈ MWCNT-COOH, and the maximum capacities of SWCNT towards MNZ and DTZ were 101 mg/g and 84 mg/g, correspondingly. The SWCNT had the highest adsorption capacity because SWCNT presented the largest surface area, and was the only nanomaterial with a basic surface. The adsorption of both antibiotics on the CNTs was predominantly ascribed to the π-π stacking. The basic groups promoted the π-π stacking interactions and favored the adsorption capacity towards MNZ and DTZ. The capacity of SWCNT for adsorbing MNZ was lessening substantially by reducing the pH from 11 to 2, and the electrostatic interactions caused this trend. The Sheindorf-Rebuhn-Sheintuch adsorption model interpreted the data for the competitive adsorption of DTZ and MNZ on SWCNT adequately.

A QuEChERS-Based Sample Preparation Method for the Analysis of 5-Nitroimidazoles in Bovine Milk by HPLC-DAD.

In this study, a simple, cost-effective, and sensitive HPLC diode-array detection method was developed for the simultaneous determination of six different 5-nitroimidazoles [metronidazole, 2-hydroxymethyl-1-methyl-5-nitro-1H-imidazole, dimetridazole (DMZ), ronidazole, ornidazole, and ipronidazole] in bovine milk samples. A QuEChERS-based sample preparation procedure was optimized by evaluating different cleanup sorbents, including zirconium-based sorbents (Z-Sep and Z-Sep+), C18, and primary-secondary amine (PSA), as well as EMR-Lipid cleanup solution. Acceptable analytical performance for all analytes was observed with recoveries in the range of 45-93% and RSDs of less than 15%. Negligible matrix interference was observed for most of the analytes due to application of PSA sorbent in a dispersive solid-phase extraction cleanup step. Method LOQs (mLOQs) for five of the six investigated analytes were set at a satisfactory low food product value of 2.5 ng/mL. For DMZ only, the mLOQ was set at 10 ng/mL. The procedure was evaluated through the analysis of 10 different natural samples.

Direct and indirect electrochemical reduction prior to a biological treatment for dimetridazole removal.

Two different electrochemical reduction processes for the removal of dimetridazole, a nitroimidazole-based antibiotic, were examined in this work. A direct electrochemical reduction was first carried out in a home-made flow cell in acidic medium at potentials chosen to minimize the formation of amino derivatives and then the formation of azo dimer. Analysis of the electrolyzed solution showed a total degradation of dimetridazole and the BOD5/COD ratio increased from 0.13 to 0.24. An indirect electrochemical reduction in the presence of titanocene dichloride ((C5H5)2TiCl2), which is used to reduce selectively nitro compounds, was then investigated to favour the formation of amino compounds over hydroxylamines and then to prevent the formation of azo and azoxy dimers. UPLC-MS/MS analyses showed a higher selectivity towards the formation of the amino compound for indirect electrolyses performed at pH 2. To confirm the effectiveness of the electrochemical reduction, a biological treatment involving activated sludge was then carried out after direct and indirect electrolyses at different pH. The enhancement of the biodegradability was clearly shown since mineralization yields of all electrolyzed solutions increased significantly.

Transfer of nitroimidazoles from contaminated beeswax to honey.

Nitroimidazoles are not authorised for the treatment of honey bees in the European Union. However, they can be found in honey largely because they are illegally used in apiculture for the treatment of Nosema. The aim of the study was to examine the possible transfer of nitroimidazoles (metronidazole, ronidazole, dimetridazole and ipronidazole) from contaminated beeswax to honey. The wax foundations fortified with a mixture of four nitroimidazoles at three concentration levels (1000, 10,000 and 100,000 µg kg-1) were placed in beehives to let the honeybees (Apis mellifera L.) draw out the contaminated wax foundations to honeycombs. At 1 month from the start, the frames filled with capped honey were removed from the hives for a first sampling of honey. Next, the honeycombs were further incubated for 5 months in the laboratory at 35°C and sampled monthly. In the sampled honey, the concentrations of nitroimidazoles and their main metabolites (hydroxymetronidazole, 2-hydroxymethyl-1-methyl-5-nitroimidazole, hydroxyipronidazole) were determined by LC-MS/MS and compared with those determined in the nitroimidazole-containing wax foundations. Each of the tested nitroimidazoles could migrate from beeswax to honey kept in the contaminated combs at each tested concentration level. Higher maximum concentrations of residues in honey sampled from contaminated combs at 1000, 10,000 and 100,000 µg kg-1 were observed for metronidazole (28.9, 368.5 and 2589.4 µg kg-1 respectively) and ronidazole (27.4, 232.9 and 2351.2 µg kg-1 respectively), while lower maximum concentrations were measured for dimetridazole (0.98, 8.4 and 67.7 µg kg-1) and ipronidazole (0.9, 7.9 and 35.7 µg kg-1 respectively). When we took into account that a frame completely filled with honey on both sides of the comb contained 110 g of beeswax and 2488 g of honey, and that this ratio was constant, then maximum amounts of initial metronidazole, ronidazole, dimetridazole and ipronidazole that migrated from contaminated wax foundations to honey could be calculated: 65-89%, 55-63%, 1.7-2.7% and 1.4-2.3%, respectively.

Multi-class method for the determination of nitroimidazoles, nitrofurans, and chloramphenicol in chicken muscle and egg by dispersive-solid phase extraction and ultra-high performance liquid chromatography-tandem mass spectrometry.

This study describes the development of a multiresidue method for the efficient identification and quantification of nitroimidazoles, nitrofurans, and chloramphenicol in chicken and egg. After derivatization of nitrofuran metabolites, dispersive-solid phase extraction was used for the extraction of target analytes. An optimization strategy involved the selection of sorbents and extraction solutions for dispersive-solid phase extraction in order to achieve acceptably high recoveries and reduce co-extractives in the final extracts. Analytes were determined by ultra-high performance liquid chromatography-tandem mass spectrometry, in one single injection with a chromatographic run time of 7.5min. Mean recoveries ranged from 86.4% to 116.7% and interday precision was lower than 18%. The limits of quantification were between 0.1 and 0.5µg/kg, which were satisfactory to support surveillance monitoring. Finally, the method was applied to real samples, and metabolite of furazolidone, metronidazole and its metabolite, dimetridazole and its metabolite were detected in both chicken and egg samples.

Overall adsorption rate of metronidazole, dimetridazole and diatrizoate on activated carbons prepared from coffee residues and almond shells.

This study analyzed the overall adsorption rate of metronidazole, dimetridazole, and diatrizoate on activated carbons prepared from coffee residues and almond shells. It was also elucidated whether the overall adsorption rate was controlled by reaction on the adsorbent surface or by intraparticle diffusion. Experimental data of the pollutant concentration decay curves as a function of contact time were interpreted by kinetics (first- and second-order) and diffusion models, considering external mass transfer, surface and/or pore volume diffusion, and adsorption on an active site. The experimental data were better interpreted by a first-order than second-order kinetic model, and the first-order adsorption rate constant varied linearly with respect to the surface area and total pore volume of the adsorbents. According to the diffusion model, the overall adsorption rate is governed by intraparticle diffusion, and surface diffusion is the main mechanism controlling the intraparticle diffusion, representing >90% of total intraparticle diffusion.

Determination of the persistence of dimetridazole, metronidazole and ronidazole residues in black tiger shrimp (Penaeus monodon) tissue and their stability during cooking.

The depletion of three banned nitroimidazole drugs - dimetridazole (DMZ), metronidazole (MNZ) and ronidazole (RNZ) - was investigated in black tiger shrimp (Penaeus monodon) following in-water medication. The highest concentrations of residues were measured immediately after the 24-h immersion (d0). At this time, MNZ and MNZ-OH residues were measured in shrimp tissue samples at concentrations ranging from 361 to 4189 and from 0.28 to 6.6 µg kg(-1), respectively. DMZ and its metabolites HMMNI ranged in concentration between 31,509 and 37,780 and between 15.0 and 31.9 µg kg(-1), respectively. RNZ and HMMNI concentrations ranged from 14,530 to 24,206 and from 25.0 to 55 µg kg(-1), respectively. MNZ, DMZ and RNZ were the more persistent marker residues and can be detected for at least 8 days post-treatment. MNZ-OH was only detectable on d0 following treatment with MNZ. HMMNI residues were only detectable up to d1 (0.97-3.2 µg kg(-1)) or d2 (1.2-4.5 µg kg(-1)) following DMZ and RNZ treatment, respectively. The parent drugs MNZ, DMZ and RNZ were still measureable on d8 at 0.12-1.0, 40.5-55 and 8.8-18.7 µg kg(-1), respectively. The study also investigated the stability of nitroimidazole residues under various cooking procedures (frying, grilling, boiling, and boiling followed by microwaving). The experiments were carried out in shrimp muscle tissue containing both high and low concentrations of these residues. Different cooking procedures showed the impact on nitroimidazole residue concentration in shrimp tissue. Residue concentration depleted significantly, but partially, by boiling and/or microwaving, but the compounds were largely resistant to conventional grilling or frying. Cooking cannot therefore be considered as a safeguard against harmful nitroimidazole residues in shrimp.

[Kinetics and Reactive Species Analysis of Dimetridazole Degradation by TiO2].

Dimetridazole is considered as an emerging pollutant in waterbodies, which can potentially impact ecosystem and human health. Heterogeneous photocatalytic decomposition of dimetridazole by TiO2 was investigated under 365 nm UV light and effects of initial pH, TiO2 content and dimetridazole concentration on photocatalytic process were discussed. The results indicated that the optimized experiment condition is that the TiO2 content of 1 g x L(-1), dimetridazole concentration of 40 mg x L (-1), pH of 11, dimetridazole can be removed 90%. The photocatalytic degradation kinetics of dimetridazole could be fitted to the quasi-first-order equation. Photocatalytic degradation of dimetridazole can take place via two pathways: oxidation by *OH and reduction by e -.

A sequential procedure for rapid and accurate identification of putative trichomonacidal agents.

In the current report, a sequential step-wise methodology based on in silico, in vitro and in vivo experimental procedures for the prompt detection of potential trichomonacidal drugs is proposed. A combinatorial of 12 QSAR (Quantitative Structure-Activity Relationship) models based on Linear Discrimination Analysis (LDA) are suggested for the rational identification of new trichomonacidal drugs from virtual screening of in house chemical libraries and drug databases. Subsequently, compounds selected as potential anti-trichomonas are screened in vitro against Trichomonas vaginalis. Finally, molecules with specific trichomonacidal activity are evaluated in vivo. Herein, different molecules were exposed to the proposed methodology. Firstly, the agents were virtually screened and two of the eight molecules (G-1 and dimetridazole) were classified as trichomonacidals by the 12 models. Subsequently both drugs were proved in vitro and in vivo following the workflow procedure. Although a remarkable in vitro activity was observed in both cases, dimetridazole achieved higher MIC100 activity than metronidazole against the resistant isolate. Furthermore, the in vivo models showed a remarkable reduction of lesions of more than 55% in both compounds. These observations support the current flowchart screening and suggest the use of dimetridazole as a promising drug-like scaffold for novel therapeutic alternatives against T. vaginalis resistant infections.

A novel core-shell magnetic nano-sorbent with surface molecularly imprinted polymer coating for the selective solid phase extraction of dimetridazole.

A novel core-shell magnetic nano-sorbent with surface molecularly-imprinted polymer coating was prepared via a sol-gel process. Methyltrimethoxysilane and 3-aminopropyltriethoxysilane were used as functional monomers, tetraethyl orthosilicate as cross-linker, and Al(3+) as dopant to generate Lewis acid sites in the silica matrix for the metal coordinate interactions with the template dimetridazole (DMZ). The ratios of the monomers, the dopant, and the cross-linker, were optimised by a OA9 (3(4)) orthogonal array design. The resultant sorbent was characterised by scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, powder X-ray diffraction, and magnetometry. The binding performances of the sorbent were evaluated by static, kinetic and selective adsorption experiments. The nano-sorbent was successfully applied to solid phase extraction followed by spectrophotometric determination of DMZ in real samples. Spiked recoveries ranged from 90.33% to 106.20% for egg, milk powder, and pig feed samples, with relative standard deviations of less than 4.54%.

Development of a rapid method for the determination and confirmation of nitroimidazoles in six matrices by fast liquid chromatography-tandem mass spectrometry.

A rapid liquid chromatography-tandem mass spectrometric (LC-MS/MS) method was developed to identify and to quantify nitroimidazoles, metronidazole (MNZ), ronidazole (RNZ) and dimetridazole (DMZ) and their corresponding hydroxy metabolites, MNZ-OH and 2-hydroxymethyl-1-methyl-5-nitroimidazole (HMNNI) in plasma, milk, muscle, egg, honey and feed samples. The same sample clean-up procedure including a novel solid-phase extraction (SPE) on polymeric Strata-SDB cartridges was used for each matrix. The analytes were separated on Kinetex XB C-18 core-shell type HPLC column using isocratic elution mode with a mobile phase containing 0.1% formic acid in water/methanol (88/12, v/v, pH 2.6) at a flow rate of 0.7 ml/min. The main advantage of the developed method is that the analysis time of only 3 min, which is about three to ten times shorter than in other reported HPLC methods. The developed method was validated using a matrix-comprehensive in-house validation strategy. The matrix effect of LC-MS/MS analysis was also investigated. Results are presented from the successful application of the developed method to an incurred pork meat certified reference material and to incur porcine plasmas in a proficiency test in year 2011.

Determination of dimetridazole, metronidazole and ronidazole in salmon and honey by liquid chromatography coupled with tandem mass spectrometry.

A liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) method was developed to determine the residues of dimetridazole (DMZ), metronidazole (MNZ) and ronidazole (RNZ) in salmon and honey. These compounds were extracted with ethyl acetate from samples and cleaned up using a silica solid phase extraction (SPE) cartridge. These compounds were determined by reversed-phase LC using a C18 column with distilled water-methanol as the mobile phase, and MS detection in the positive mode by applying selected reaction monitoring (SRM). DMZ-d(3), MNZ-(13)C(2),(15)N(2) and RNZ-d(3) were used as internal standards. The method was validated in salmon and honey spiked with these compounds at 0.4-2 µg/kg, and average recoveries were in the range of 91.2-107.0%. Repeatability was 1.7-17.1% and intermediate precision was less than 20%. The detection limits of DMZ, MNZ and RNZ in salmon and honey were 0.05-0.2 µg/kg. The method was applied to 3 salmon and 20 honey samples. The concentrations of these compounds in all samples were lower than the detection limits established by the Ministry of Health, Labour and Welfare in Japan.

Genetically different clonal isolates of Trichomonas gallinae, obtained from the same bird, can vary in their drug susceptibility, an in vitro evidence.

Trichomonas gallinae is a flagellated protozoon which parasitizes in the upper digestive tract of different birds, especially columbiformes (doves and pigeons) and falconiformes. The parasite is also a common inhabitant of the crop of psittacine birds and is frequently detected in budgerigars. The lesions associated with T. gallinae infection of the upper digestive tract range from mild inflammation of the mucosa to large caseous lesions that block the lumen of the oesophagus. Nitroimidazoles are considered to be the drugs of choice for the treatment of trichomonosis. However, only a few studies report the existence of resistant strains of T. gallinae to these drugs. Thus, in the present investigation cloned cultures of T. gallinae obtained from budgerigars and pigeons were analysed for the first time for their in vitro susceptibilities against four 5´-nitroimidazole derivates, including metronidazole, dimetridazole, ronidazole and ornidazole. Significantly different minimal lethal concentrations (MLCs) were observed for them against all four drugs. The lowest MLCs revealed the Trichomonas isolates obtained from two budgerigars, ranging from 2.0 ± 0.3 to 3.0 ± 0.7 µg/ml for metronidazole and dimetridazole, and from 2.0 ± 0.6 to 6.7 ± 1.7 µg/ml for ornidazole and ronidazole. Contrary to this, the highest MLCs were recorded for one Trichomonas isolate obtained from a pigeon, ranging from 83.3 ± 6.7 (for dimetridazole and ronidazole) to 103.3 ± 3.3 µg/ml (for metronidazole and ornidazole). The data obtained for the resistance testing were further compared with already available genetic data of the small subunit rRNA gene sequences and ITS-1, 5.8S rRNA and ITS-2 sequences, indicating a certain correlation between in vitro results and strain relationships.