Novel magnetic porous organic polymer containing amino and triazine bifunctional groups for efficient adsorption of nitroimidazoles.

In this paper, a novel magnetic hyper-crosslinked polymer with amino and triazine bifunctional groups (M-NH2-THCP) was developed. M-NH2-THCP has strong nitroimidazoles (NDZs) enrichment effect, and therefore it was used as an adsorbent to extract five NDZs from lake water, catfish and shrimp meat prior to HPLC. Polar interaction, π-π stacking interaction, hydrogen bond and Lewis acid-base interaction were attested to be the major adsorption mechanism. The method has a good linearity in the range of 0.1-100 ng mL-1 for lake water, 10-400 ng g-1 for catfish and shrimp muscle with R2 > 0.9964. The limits of detection of NDZs were 0.03-0.04 ng mL-1 for lake water, 1.0-2.0 ng g-1 for catfish and 2.0-2.5 ng g-1 for shrimp, which is superior to most reported method. The method recoveries were 87.6-119 %, and relative standard deviations were less than 8.7 %. M-NH2-THCP holds great application potential in pollutants enrichment, separation and removal.

Green synthesis of azo-linked porous organic polymer for enrichment of nitroimidazoles from water, shrimp and Basa fish.

Reliable monitoring of nitroimidazoles (NDZs) is of great significance to public health. Herein, an azo-linked porous organic polymer (Res-POPs) was prepared by green synthesis method using natural resveratrol as monomer for the first time. Using Res-POPs as sorbent, a facile method coupling solid-phase extraction with high performance liquid chromatography-diode array detection was developed for effective detecting NDZs. The method achieved good linearities (0.06 âˆ¼ 100 ng mL-1 for water, 1.8 âˆ¼ 200 ng g-1 for shrimp, and 1.5 âˆ¼ 200 ng g-1 for Basa fish) with determination coefficients above 0.995, low detection limits (0.02 âˆ¼ 0.05 ng mL-1, 0.60 âˆ¼ 1.00 ng g-1 and 0.50 âˆ¼ 0.90 ng g-1 for water, shrimp and Basa fish), high method recovery (85 %∼114 %) and relative standard deviations below 8.2 %. The results demonstrated the superiority and the promising potential of the established method for detection of NDZs compared with the reported method.

Biochar/sodium alginate mixed matrix membrane as adsorbent for in-syringe solid-phase extraction towards trace nitroimidazoles in water samples prior to ultra-high-performance liquid chromatography-tandem mass spectrometry analysis.

In the present work, the herb (Poria cocos (Schw.) Wolf) residue, as an environmentally friendly and renewable biomass source, was converted into novel biochar. Biochar/sodium alginate mixed matrix membrane was fabricated. On this basis, a biochar/sodium alginate mixed matrix membrane-based in-syringe solid-phase extraction was developed combined with ultra-high performance liquid chromatography-tandem mass spectrometry to determine nitroimidazoles in water samples. The factors including times of exaction, type, and volume of elution solvent, and sample solution pH were thoroughly optimized. Then the correlation coefficient was 0.9995-0.9997. The limit of detection of four analytes was between 0.006 and 0.014 ng/mL, and the recovery was between 79.02% and 99.1%. Consequently, the established method would provide a new perspective on monitoring nitroimidazoles in water samples.

Porphyrin-based hypercrosslinked polymers as sorbents for efficient extraction of nitroimidazoles from water, honey and chicken breast.

In this work, a series of 5,10,15,20-tetraphenylporphyrin (TPP)-based hyper crosslinked polymers were prepared by Friedel-Crafts reaction. Among them, the HCP-TPP-BCMBP, which was prepared by using TPP as the monomer and with 4,4'-Bis(chloromethyl)-1,1'-biphenyl (BCMBP) as the cross-linking agent, had the best adsorption capability for the enrichment of the nitroimidazoles of dimetridazole, ronidazole, secnidazole, metronidazole, and ornidazole. Then, a solid-phase extraction (SPE) method with the HCP-TPP-BCMBP as adsorbent coupled with HPLC-UV detection for the determination of nitroimidazole residues in honey, environmental water, and chicken breast samples was established. The influence of the main factors that affect the SPE, i.e., sample solution volume, sample loading rate, sample pH, and eluent and its volume, were studied. Under the optimal conditions, the limits of detection (S/N = 3) for the nitroimidazoles were measured to be in the range of 0.02-0.04 ng mL-1, 0.4-1.0 ng g-1 and 0.5-0.7 ng g-1 for environmental water, honey, and chicken breast samples, with the determination coefficients being in the range of 0.9933-0.9998. The analytes recoveries by the method in fortified samples fell in the range from 91.1% to 102.7% for environmental water, from 83.2% to 105.0% for honey, and from 85.9% to 103.0% for chicken breast samples, and the relative standard deviations for the determination were less than 10%. It shows that the HCP-TPP-BCMBP has a strong adsorption capability for some polar compounds.

Determination of nitroimidazole antibiotics based on dispersive solid-phase extraction combined with capillary electrophoresis.

For a long time, the detection of nitroimidazole antibiotics (NIABs) has been a research focus in environmental analytical chemistry. In this work, a novel technique for the analysis of nitroimidazoles was established based on capillary electrophoresis (CE). UiO-66, synthesized using a solvothermal method, was utilized as an adsorbent in the dispersive solid-phase extraction (DSPE) of five different NIABs. The separation and detection of NIABs in environmental water samples were accomplished using the CE diode array detection method. The optimal extraction conditions were obtained after systematically studying the effects of adsorption time, the amount of extractant, and elution solvent on extraction efficiency. According to the results of the study, the limit of detections of the five NIABs were between 16 and 97 ng/mL, the relative standard deviations were between 0.32% and 0.55%, and the spike recoveries were between 87.43% and 104.8%. This study presents a novel technique for measuring NIABs in complex water samples.

Facile synthesis of hypercrosslinked polymer as high-efficiency adsorbent for the enrichment of nitroimidazoles from water, honey and chicken meat.

Design and fabrication of functionalized hypercrosslinked polymers (HCPs) for enhancing their performance by using green renewable monomers has attracted considerable research interest. In this study, hydroxyl­functional HCP (labeled as OHHCP) was prepared via the knitting method by applying natural naringenin as a monomer for the first time. Due to the good hydrophilicity and strong H-bonding ability, the OHHCP showed high extraction capacity for nitroimidazoles. Thus, it was successfully applied as a potent adsorbent for solid phase extraction of five nitroimidazoles in water, honey and chicken meat, followed by high-performance liquid chromatography-diode array detector analysis. At the optimized conditions, the limit of detections (S/N = 3) of the proposed method for water, honey and chicken samples were 0.02 - 0.06 ng mL-1, 0.5 - 1.0 ng g-1 and 0.8 - 1.0 ng g-1, respectively. The recoveries were 80.0 - 110%, and the relative standard deviations were below 10.0%. The OHHCP also displayed good application prospects for other organic compounds with H-bonding capability. This study highlights the facile preparation of OH-functionalized HCPs from renewable and natural resources as potent adsorbents for polar compounds.

Exploration of an imine-based covalent organic framework for the solid phase extraction of nitroimidazoles in milk and meat samples.

TAPT-AN-COF, an imine-based covalent organic framework, was synthesized by a solvothermal method of 2,4,6-trihydroxy-benzene-1,3,5-tricarbaldehyde (TP) and 4,4',4″-(1,3,5-Triazine-2,4,6-triyl)trianiline (TAPT). The structure was characterized and tested by several techniques, revealing that the material had good stability and high specific surface area. The adsorption experiment demonstrates that the adsorption isotherm of TAPT-AN-COF followed the Freundlich isothermal equation, while its adsorption kinetics conformed to the pseudo second-order kinetic model. After characterization, the prepared TAPT-AN-COF was used to separate and enrich nitroimidazoles (NDZs) in milk and meat as the solid-phase extraction (SPE) adsorbent. The effects of adsorbent dosage, pH value, washing solvent, elution solvent type and volume on recoveries were studied. Under the optimal conditions, a method for the determination of NDZs in milk and meat samples was established based on high performance liquid chromatography-ultraviolet detection(HPLC-UVD).The result showed that NDZs had good linearity in the concentration range of 25-500 µg·kg-1, and the determination coefficients (r2) were all above 0.99. When spiked at 25, 50 and 125 µg·kg-1, the recoveries of three kinds of food samples ranged from 64.5% to 85.3%, the limits of detection (LODs) were between 2 and 10 µg·kg-1, and the relative standard deviations were all below 15.9%. In addition, the recoveries of NDZs didn't decrease significantly after being reused for 6 times, showing that TAPT-AN-COF has excellent reusability. Compared with HLB and MCX sorbents, TAPT-AN-COF had better extraction efficiency and qualified purification efficiency. The established method had a satisfying performance on the determination of NDZs in food samples.

Amino-functionalized hypercrosslinked polymer as sorbent for effective extraction of nitroimidazoles from water, drink and honey samples.

The three hypercrosslinked polymers (HCP) materials, designated as OPD-HCP, MPD-HCP and PPD-HCP, were synthesized by using o-phenylenediamine (OPD), m-phenylenediamine (MPD) and p-phenylenediamine (PPD) as monomers. They were characterized by infrared spectroscopy, powder X-ray diffraction, nitrogen sorption isotherms, and scanning electron microscopy. Then, the HCPs were explored as solid-phase extraction (SPE) adsorbent for the extraction of five nitroimidazoles (NDZs) (metronidazole, ronidazole, secnidazole, dimetridazole and ornidazole). Among the three HCPs, the MPD-HCP has the best adsorption performance for the NDZs. With the help of high-performance liquid chromatography with ultraviolet detection (HPLC-UV), good linear response range (0.07-40.0 ng mL-1), high method recovery (86.8%-113.3%), low limits of detection (0.02-0.15 ng mL-1) and good precision with the relative standard deviations of less than 8.1% were achieved for the determination of the NDZs in water samples. The effective determination of the NDZs in peach juice, honey tea, and honey samples were also realized by the developed method with satisfactory results. Based on both the experimental results and density functional theory calculation, the adsorption mechanism can be attributed to multiple interactions between the MPD-HCP and the NDZs, including hydrogen bonding, hydrophilic, and electrostatic interactions. The method provides a new alternative of choice for the determination of some NDZs in real samples.

Facile fabrication of tyrosine-functionalized hypercrosslinked polymer for sensitive determination of nitroimidazole antibiotics in honey and chicken muscle.

The preparation of tyrosine-functional novel hypercrosslinked polymer (HCP@Tyr) was achieved by knitting 1,3,5-triphenylbenzene with l-tyrosine via simple Friedel-Crafts reaction. The HCP@Tyr displayed large surface area (1220 m2 g-1) and high adsorption capacity (30 mg g-1) for nitroimidazoles (NDZs). With HCP@Tyr as potent sorbent, an efficient extraction method was developed to simultaneously extract five NDZs from honey and chicken muscle samples before high performance liquid chromatography-diode array detection. Under optimized conditions, the proposed method provided a good linearity in the range of 0.75-200.0 ng g-1 for honey and 1.5-100.0 ng g-1 for chicken muscle sample. Low detection limits (S/N = 3) were obtained to be 0.10-0.24 ng g-1 for honey and 0.15-0.30 ng g-1 for chicken muscle. The method recovery was 80.7-120% with relative standard deviations below 9.2%. The HCP@Tyr based method can serve as a reliable and sensitive tool for detection of NDZs in honey and chicken muscle samples.

Three-dimensional acanthosphere-like hierarchical Co@graphitic carbon for dispersive magnetic solid-phase extraction of nitroimidazole.

Herein, a magnetic three-dimensional acanthosphere-like hierarchical Co@graphitic carbon (3D Co@GC) is introduced as an efficient adsorbent for extraction of three nitroimidazoles (NMZs: metronidazole (MNZ), ornidazole (ONZ) and tinidazole (TNZ)) from environmental water and food samples. The proposed 3D Co@GC was synthesized by a simple template-free method, which consisted of plentiful freely arranged one-dimensional nanowires. The adsorption properties of 3D Co@GC for three NMZs were investigated systematically by adsorption kinetic and isotherm studies. 3D Co@GC exhibits good adsorption capacity and fast adsorption kinetics toward three NMZs by virtue of its unique hierarchical structure. In addition, it was also found that a bit of methanol can effectively elute the adsorbed NMZs, eliminating the need for other dangerous strong acid or base solutions. Thus, 3D Co@GC as adsorbent to extraction three trace NMZs followed by direct quantification detection of targets with high-performance liquid chromatography with ultraviolet-visible detector (HPLC-UV) was developed. The parameters of dispersed magnetic solid-phase extraction (d-MSPE) were optimized by univariate and multivariate methods (Box-Behnken design). This established method revealed wide linear range and low limits of detection. Furthermore, the satisfactory recoveries of NMZs (86.7-106.7%) were acquired in spiked river water, honey, milk, and muscle samples. This study might provide a potential strategy for the efficient extraction and sensitive analysis of trace NMZs in river water, honey, milk, and muscle samples.

Multi-class, multi-residue determination of 132 veterinary drugs in milk by magnetic solid-phase extraction based on magnetic hypercrosslinked polystyrene prior to their determination by high-performance liquid chromatography-tandem mass spectrometry.

A quantitative multi-class multi-residue analytical method was developed for the determination of veterinary drugs in milk by high-performance liquid chromatography - tandem mass spectrometry (HPLC-MS/MS). A total of 132 veterinary drugs investigated belonged to almost 15 classes including sulfonamides, ß-lactams, tetracyclines, quinolones, macrolides, nitrofurans, nitroimidazoles, phenicols, lincosamides, pleuromutilins, macrocyclic lactones, quinoxaline antibiotics, benzimidazoles, anthelmintics, coccidiostats and some others. A magnetic solid-phase extraction procedure was developed using magnetic hypercrosslinked polystyrene (HCP/Fe3O4) for the sample preparation prior to HPLC-MS/MS without deproteinization step. The results indicated recoveries of 85-107% for 14 sulfonamides, 85-120% for 13 ß-lactams, 89-115% for 4 tetracyclines, 82-119% for 14 quinolones, 82-115% for 8 macrolides, 97-109% for 4 nitrofurans, 84-115% for 10 nitroimidazoles, 89-114% for 3 phenicols, 86-111% for 3 lincosamides, 97-102% for 2 pleuromutilins, 72-88% for 4 macrocyclic lactones, 87-104% for 4 quinoxaline antibiotics, 76-119% for 21 benzimidazoles, 79-115% for 12 anthelmintics, 81-118% for 12 coccidiostats and 75-119 % for 5 unclassified drugs, with relative standard deviations (RSDs) of less than 20%, and the LOQs ranged from 0.05 to 1 µg kg-1. This methodology was then applied to field-collected real milk samples and trace levels of some veterinary drugs were detected.

A magnetic solid phase extraction based on UiO-67@GO@Fe3O4 coupled with UPLC-MS/MS for the determination of nitroimidazoles and benzimidazoles in honey.

A novel composite material consisting of zirconiumbiphenyldicarboxylate metal-organic framework, graphite oxide and ferroferric oxide was fabricated by a facile one-step method and served as a magnetic solid phase extraction sorbent for the simultaneous determination of nitroimidazoles and benzimidazoles in honey. The amount of graphite oxide for the synthesis of composite material and analysis parameters were optimized. The optimum parameters were: dipotassium hydrogen phosphate buffer solution (pH 6) as diluent solvent, adsorption time 10 min, desorption time 5 min, methanol/acetonitrile (1:1, V/V) as desorption solvent. The targets were detected by ultra-high performance liquid chromatography tandem mass spectrometry. The recoveries of twelve analytes ranged in 70.5%-103.4% with relative standard deviations lower than 12.9% (n = 3). The quantification limits were 0.2-0.6 µg/kg. Using the composite material as sorbent, a simple, rapid and environmental-friendly method based on magnetic solid phase extraction was successfully developed for determination of seven nitroimidazoles and five benzimidazoles in honey.

Magnetic mesoporous carbon nanosheets derived from two-dimensional bimetallic metal-organic frameworks for magnetic solid-phase extraction of nitroimidazole antibiotics.

We prepared two-dimensional (2D) bimetallic metal-organic frameworks (Ni-ZIF-8) nanosheets by a simple solvent-free method at room temperature. The morphology and composition of Ni-ZIF-8 can be controlled through adding different amounts of Ni. And then, the 2D magnetic mesoporous nanosheets (Ni/ZnO@C) were synthesized by directly pyrolyzing Ni-ZIF-8 under argon atmosphere and explored as magnetic solid phase extraction (MSPE) adsorbents for the determination of nitroimidazole antibiotics (NIABs). Magnetic Ni nanoparticles embedded in carbon nanosheets uniformly resulted in high magnetization saturation of Ni/ZnO@C for easy separation. The Ni/ZnO@C can form hydrogen bond and π-π interaction with three NIABs resulting from their rich N-H containing imidazole, π-electron. Due to the high specific surface area and high mass transfer rate of 2D Ni/ZnO@C, the materials showed satisfactory adsorption capacity and rapid adsorption kinetics for NIABs. A rapid and effective method of Ni/ZnO@C-MSPE combined with high-performance liquid chromatography was proposed for the determination of NIABs. Several main parameters affecting MSPE were investigated. Under the optimal conditions, wide linear was achieved ranging from 0.1 to 500 µg⋅L-1 with a low detection limit of 0.025-0.05 µg⋅L-1. The established method has been successfully applied to analyze NIABs from environmental water samples with satisfactory recovery from 74.33 to 105.71%.

Development and validation of a liquid chromatography-tandem mass spectrometry method for quantifying delamanid and its metabolite in small hair samples.

New all-oral regimens for rifampin-resistant tuberculosis (RR-TB) are being scaled up globally. Measurement of drug concentrations in hair assesses long-term drug exposure. Delamanid (DLM) is likely to be a key component of future RR-TB treatment regimens, but a method to describe its quantification in hair via liquid chromatography-tandem mass spectrometry (LC-MS/MS) has not previously been described. We developed and validated a simple, fast, sensitive, and accurate LC-MS/MS method for quantifying DLM and its metabolite DM-6705 in small hair samples. We pulverized and extracted two milligrams of hair in methanol at 37 °C for two hours, and diluted 1:1 with water. A gradient elution method eluted DLM, DM-6705, and the internal standard OPC 14714 within 3 min, bringing overall analysis time to 5.5 min. The method has limits of detection (LOD) of 0.0003 ng/mg for DLM and 0.003 ng/mg for DM-6705. The established linear dynamic ranges are 0.003-2.1 ng/mg and 0.03-21 ng/mg for DLM and DM-6705, respectively. Eleven of 12 participant hair samples had concentrations within DLM's linear dynamic range, while all 12 samples had concentrations within the quantifiable range for DM-6705. The ranges of concentrations observed in these clinical samples for DLM and DM-6705 were 0.004-0.264 ng/mg hair and 0.412-12.041 ng/mg hair respectively. We demonstrate that while DLM was detected in hair at very low levels, its primary metabolite DM-6705 had levels approximately 100 times higher. Measuring DM-6705 in hair may accurately reflect long-term adherence to DLM-containing regimens for drug-resistant TB.

Fabrication of magnetic porous organic framework for effective enrichment and assay of nitroimidazoles in chicken meat.

A magnetic porous organic framework (M-POF) was rationally designed and served as a sorbent for magnetic solid-phase extraction of six nitroimidazoles from chicken meat prior to their assay by high-performance liquid chromatography with diode array detection. The M-POF exhibited good magnetic responsiveness and outstanding affinity to nitroimidazoles with large adsorption capacity up to 36 mg g-1. Under optimal conditions, the developed method offered good linearity (r greater than 0.992) in the range of 1.5-100.0 ng g-1, low limits of detection (S/N = 3) of 0.5-0.8 ng g-1, low limits of quantification of 1.5-2.5 ng g-1 and high enrichment factors of 80-175 for the nitroimidazoles. The method was successfully applied to analyze nitroimidazoles in chicken meat. The recoveries were 80.2-118% with relative standard deviations lower than 12%. The adsorption mechanism was further explored and the results showed that the M-POF exhibited adsorption potential for compounds with strong polar interactions.

Development of a multi-class method to determine nitroimidazoles, nitrofurans, pharmacologically active dyes and chloramphenicol in aquaculture products by liquid chromatography-tandem mass spectrometry.

LC-MS/MS method was developed for the efficient identification and quantification of 21 banned substances including various nitroimidazoles, nitrofurans, pharmacologically-active dyes and chloramphenicol, respectively in aquaculture products. The sample preparation was started by acid-treatment with 2-nitrobenzaldehyde (NBA) to liberate matrix-bound residues of nitrofurans. A modified QuEChERS method was optimized for the extraction and clean-up of the target analytes. The metabolites of the four conventional nitrofurans (nitrofurantoin, furazolidone, nitrofurazone and furaltadone) and of three other nitrofurans (nifursol, nifuroxazide, and nitrovin), and an underivatizable nitrofuran (nifurpirinol) were simultaneously detected. Furthermore, 21 banned substances were quantified by LC-MS/MS with ESI using one single injection. To evaluate and validate the performance of the method, the criteria of the Decision (EC) no 2002/657 were applied. Decision limit (CCα) of target analytes ranged 0.067-1.655 µg/kg in aquaculture products. The recovery ranged 77.2%-125.6%, and the relative standard deviations of inter-day analyses (RSD) were less than 25%.

Residue study of nitroimidazoles depletion in chicken feathers in comparison with some other selected matrixes.

This paper presents the results from a residue study conducted on a statistically representative number of chicken broilers that were individually orally treated with the selected nitroimidazoles (metronidazole, ornidazole and ipronidazole) in an appropriate amount close to the theoretical therapeutic dose. A mutual persistence comparison of the monitored analytes in feathers, serum, muscle and shanks was performed and attention was also paid to selected metabolites (hydroxymetronidazole and hydroxyipronidazole). An analytical LC/MS/MS method using SupelMIP SPE nitroimidazoles cartridges was developed for the determination of nitroimidazoles residues in poultry feathers, serum, muscle and shanks and the method was validated according to Commission Decision 2002/657/EC. High concentrations of nitroimidazoles residues in feathers were observed 19 days after the broilers' treatment unlike the muscle and serum samples, where nitroimidazoles depletion was significantly faster (residue concentrations were below detection limits in 5 days in muscle and in 12 days in serum). Shanks (chicken claws) also proved to be a very useful matrix for the detection of nitroimidazoles drugs misuse due to the longer persistence of these drugs residues and their metabolites in this matrix (determinable concentrations were observed 19 days after the broilers' last treatment). Feathers and shanks appear to be suitable matrixes for the screening of various nitroimidazoles in poultry because long-term persistence of residues enables reliable detection of the illegal use of nitroimidazoles compounds in official checks.

Adsorption of nitroimidazole antibiotics from aqueous solutions on self-shaping porous biomass carbon foam pellets derived from Vallisneria natans waste as a new adsorbent.

Powdered biomass adsorbents can potentially remove antibiotics from wastewater. However, recovering or separating the adsorbents after use is difficult. The preparation of mold-assisted shaping of biomass carbon foam pellets (BCFPs) without compaction and addition of binder instead of powdered adsorbent, is rarely reported. Therefore, the study explored the formation mechanism of BCFPs by using Vallisneria natans (V. natans) waste as precursor and investigated the adsorption performance and mechanisms of metronidazole (MNZ) and dimetridazole (DMZ) onto BCFPs. The optimal preparation conditions were V. natans-and-ZnCl2 mass ratio of 1:2.4, carbonization temperature of 600 °C, and time of 90 min. BCFPs exhibited uniform size, excellent floatability, and abundant micropores. The Brunauer-Emmett-Teller specific surface area, total pore volume, and micropore volume of BCFPs were 922.56 m2 g-1, 0.421 cm3 g-1, and 0.386 cm3 g-1, respectively. The adsorption process of MNZ and DMZ was both described well by pseudo-first-order kinetic model. However, the isotherm data fitted well with Langmuir for MNZ and Dubinin-Radushkevic model for DMZ, with a maximum monolayer adsorption capacity of 64.23 and 82.58 mg g-1, respectively. The nature of the adsorption process is endothermic and spontaneous. The adsorption mechanisms of MNZ and DMZ onto BCFPs were mainly hydrogen bonding, π-π interactions, and micropore filling. Preparation of BCFPs with high mechanical strength and excellent adsorption capacity from V. natans waste without compaction and any binder is feasible. Furthermore, BCFPs are easily separated and recyclable adsorbents, and their average recovery rate was 99.6%.

Confirmatory Analysis of Nitroimidazoles and Hydroxy Metabolites in Honey by Dispersive-Solid Phase Extraction and Ultra-High Performance Liquid Chromatography-Tandem Mass Spectrometry.

An ultra-high performance liquid chromatography-tandem quadrupole mass spectrometry (UHPLC-MS/MS) method was developed and validated for confirmatory analysis of four nitroimidazoles and three hydroxy metabolites in honey. Honey samples were dissolved in 2% formic acid solution and nitroimidazoles and metabolites were isolated and enriched by dispersive-solid phase extraction using mixed-mode strong cation-exchange sorbent. The determination involves separation of analytes on an UHPLC C18 column and detection by multiple reaction monitoring in positive ionization mode. The recovery of the method was ranged from 90.2 to 105.6% with inter-day relative standard deviations of less than 11.2%. The limits of detection and limits of quantification were in the ranges of 0.02⁻0.07 µg/kg and 0.05⁻0.2 µg/kg, respectively. Honey samples from the market were analyzed to demonstrate the applicability of the proposed method.

[Determination of nitroimidazoles and their metabolites in animal-derived foods by liquid chromatography-tandem mass spectrometry coupled with dispersive solid phase extraction].

A method for the quantitative analysis of nitroimidazoles and their metabolites in four kinds of animal-derived foods by liquid chromatography-tandem mass spectrometry (LC-MS/MS) coupled with dispersive solid phase extraction (dSPE) was established. The samples (2.0 g) were extracted with ethyl acetate. The extracts were degreased with hexane and purified with 50 mg primary-secondary amine (PSA), and then filtered through a hydrophilic polytetrafluoroethylene (PTFE) membrane. The analytes were separated on a C18 column, and detected in selected reaction monitoring (SRM) mode via positive electrospray ionization. The matrix matching and internal standard method was used. The nitroimidazoles and their metabolites showed good linearity in the range of 0.5-20.0 µg/L with correlation coefficients greater than 0.99. The limits of detection of the nitroimidazoles and their metabolites in animal-derived foods were between 0.1 and 0.5 µg/kg. The recoveries varied between 84.2% and 120.8%, with relative standard deviations (n=6) ranging from 2.0% to 16.2% at spiked levels of 1.0, 3.0, and 10.0 µg/kg. The proposed method is accurate, fast, cheap, easy, and can satisfy the requirements of monitoring nitroimidazoles and their metabolites in animal-derived foods.