Development of multiple monolithic fiber solid‐phase microextraction and liquid chromatography–tandem mass spectrometry method for the sensitive monitoring of aminoglycosides in honey and milk samples

A simple and sensitive method for the simultaneous extraction and determination of six aminoglycosides in honey and milk samples was developed using multiple monolithic fiber solid‐phase microextraction and liquid chromatography with tandem mass spectrometry. The multiple monolithic fibers based on poly(methacrylic acid‐co‐ethylenedimethacrylate) monolith as the extraction medium was used to concentrate target analytes. Because there were abundant carboxyl groups in the monolith, the monolithic fibers could extract aminoglycosides effectively through cation‐exchange and hydrophobic interactions. To obtain optimum extraction performance, several extraction parameters including desorption solvent, adsorption and desorption time, pH value and ionic strength in sample matrix, were investigated in detail. Under the optimized extraction conditions, the limits of detection of the proposed method were 0.10–0.30 and 0.23–0.59 μg/kg for honey and milk samples, respectively. Satisfactory linearity was achieved for analytes with the coefficients of determination above 0.99. At the same time, the developed method showed acceptable method repeatability and reproducibility. Finally, the proposed method was successfully applied to the determination of aminoglycosides in real honey and milk samples. Recoveries obtained for the determination of six target analytes in spiking samples ranged from 67.9 to 110%, and the relative standard deviations were in the range of 1.2–11%.     

Method validation,residue analysis and dietary risk assessment of trifloxystrobin and trifloxystrobin acid in milk,eggs and pork

Trifloxystrobin (TFS) is a widely used strobilurin fungicide and its residues accumulating in animal-derived food could result in potential harm to consumers. By optimization of extraction solvents and cleanup sorbents, a residue analysis method for TFS and its metabolite trifloxystrobin acid (TFSA) was established in milk, eggs and pork based on QuEChERS sample preparation and LC–MS/MS. The calibration curves exhibited good linearity with determination coefficients (R²) >0.9930 over the range of 0.5–250 ng/ml for both TFS and TFSA. The recoveries of the two analytes were 81–100% with RSD 3–10% and 76–96% with RSD 2–13%, respectively. The limit of quantification (LOQ) was 1 ng/g for both analytes. The milk, egg and pork samples, 30 each, were collected from the 30 main producing regions in China, and residues of TFS and TFSA were analyzed. The concentrations of both analytes were lower than the corresponding LOQs and maximum residue limits. Long-term dietary risk assessment showed that the hazard quotients were 0.001–0.003%, indicating an absence of unacceptable risks in milk, eggs and pork to the health of common consumers in China.     

β‐Cyclodextrin polymer@Fe3O4 based magnetic solid‐phase extraction coupled with HPLC for the determination of benzoylurea insecticides from honey,tomato, and environmental water samples

In this work, a magnetic β‐cyclodextrin polymer was successfully prepared and used as an adsorbent for the magnetic solid‐phase extraction of six benzoylurea insecticides (diflubenzuron, triflumuron, hexaflumuron, teflubenzuron, flufenoxuron, and chlorfluazuron) from honey, tomato, and environmental water samples. The influence of the main experimental conditions on the extraction was studied. Under the optimized conditions, the β‐cyclodextrin polymer@Fe₃O₄ showed an excellent extraction performance for the benzoylurea insecticides. A good linearity was obtained for the analytes in the range of 3.0–800 ng/g for honey samples, 0.3–160 ng/g for tomato samples, and 0.1–80.0 ng/mL for water samples, with the correlation coefficients above 0.9998. Satisfactory repeatabilities were achieved, with the relative standard deviations less than 5.7%. The limits of detection (S/N = 3) of the method for the benzoylurea insecticides were 0.2–0.8 ng/g for honey samples, 0.04–0.10 ng/g for tomato samples, and 0.02–0.05 ng /mL for water samples. The method was successfully used for the determination of the six benzoylurea insecticides residues in honey, tomato, and environmental water samples with a satisfactory result.     

Dissipation and residue determination of penicillin G and its two metabolites in citrus under field conditions by DSPE/UPLC–MS/MS

A rapid determination method of residual penicillin G and its two metabolites in citrus was developed and validated by dispersive solid-phase extraction and ultra-high performance liquid chromatography–tandem mass spectrometry (DSPE/UPLC–MS/MS). The samples were extracted with 80% acetonitrile and purified with octadecylsilane. High linearity was obtained with correlation coefficients (r²) >0.9981. The limits of quantification were 0.005–0.01 mg/kg. The recoveries of penicillin G and its metabolites spiked in blank citrus were within 76.7–107%, with relative standard deviations of 1.3–9.6%. The dissipation dynamics and distribution of penicillin G in citrus followed first-order kinetics, with half-life of 1.7–2.7 days. Penicillin G degraded easily in citrus and the metabolite was mainly penilloic acid, which can exist stably for long time. The terminal residues of penicillin G in pulp, whole citrus and peels were 0.015–0.701, 0.047–7.653 and 0.162–13.376 mg/kg, respectively. The hazard indexes for risk assessment of citrus were significantly <1, suggesting that the health risks to humans after consumption of citrus were insignificant and negligible. These results could provide necessary data for evaluating the safe and proper use of penicillin G in citrus.     

Application of dispersive liquid–liquid microextraction followed by gas chromatography/mass spectrometry as effective tool for trace analysis of organochlorine pesticide residues in honey samples

A dispersive liquid–liquid microextraction (DLLME) method followed by gas chromatography/mass spectrometry (GC/MS) was applied for the trace determination of organochlorine pesticides in honey samples. The type and volume of organic extraction and disperser solvents, pH, effect of added salt content and centrifuging time and speed were optimized to find the appropriate extraction conditions. In DLLME, 30 µL of 1,2-dibromomethane (serving as extractant) and 1.5 mL of acetonitrile (serving as disperser) were applied. The limit of detection (3 s) and limit of quantification (10 s) for all the analytes of interest (organochlorine pesticides) varied from 0.004 to 0.07 and from 0.02 to 0.3 ng g^?1, respectively. The extraction recovery ranged from 91 to 100 %, and the enrichment factors ranged from 171 to 199. The relative standard deviation was <6 % for intraday (n = 6) and <8 % interday (n = 4) measurements. The proposed DLLME–GC/MS method was confirmed to be fast, simple to perform, friendly to environment and suitable for analysis of organochlorine pesticide residues at trace levels in honey samples.     

An efficient and fast microwave-assisted extraction method developed for the simultaneous determination of 18 organochlorine pesticides in sediment

An efficient and fast microwave-assisted extraction (MAE) method followed by gas chromatographic separation with mass spectrometric detection (GC–MS) was developed for the extraction of 18 organochlorine pesticides (OCPs) from sediment. Parameters affecting the MAE procedure such as the type and volume of the extraction solvent, irradiation power, temperature and irradiation time were successfully optimised. Under the optimal conditions, extraction efficiencies in the range of 73.4–119% were obtained with THF–HEX (9:1, v/v) for all OCPs studied. The method was linear over the range of 2.9–5000 ng g^?1 with determination coefficients (r²) higher than 0.992 for all analytes. The limits of detection, LODs (S/N = 3), obtained varied from 1.0 to 2.2 ng g^?1 and limits of quantification, LOQs (S/N = 10) were between 2.9 and 6.8 ng g^?1. The proposed method was successfully applied to the analysis of real sediment samples and acceptable recoveries from 70.1 to 124% with RSDs ≤14.8% were obtained. 10 OCPs were determined below their LOQ and 8 OCPs in the range of 124–2830 ng g^?1. The MAE method was compared with Soxhlet, shake flask and ultrasonic solvent extraction techniques. Thus, the MAE–GC–MS method could efficiently be used for selective extraction and quantification of the target analytes from the complex sediment matrices.     

Use of solid phase extraction and liquid chromatography-tandem mass spectrometry for simultaneous determination of various pharmaceuticals in surface water

This article presents the development, validation and application of a new multi-residue method for simultaneous determination of 36 pharmaceuticals (histamine receptor antagonists, psychoactive stimulant, antiepileptics, antihypertensive, non-steroidal anti-inflammatory, analgesic and antipyretic, lipid regulator, antibiotics, antibacterial, skin care ingredient and metabolites of nicotine and lipid regulators) in surface water using solid phase extraction (Strata-X at pH 5) and liquid chromatography-tandem mass spectrometry (LC–MS/MS). Recoveries were greater than 70% with less than 20% SD for the majority of analytes. The instrumental quantification limit was between 2 and 181 pg, and method quantification limit varied from 0.5 to 98 ng L^?1 in spiked stream water. The pH and sorbent dependence of matrix effects is discussed. The optimised method was used to determine the occurrence of target analytes in surface water from the coastal Lake Erie in Oregon, northwest Ohio. Seventeen analytes were detected with concentrations up to hundreds of nanogram per litre in stream and lake water samples.     

Determination of metoserpate,buquinolate, and diclofenac in pork,eggs, and milk using liquid chromatography–tandem mass spectrometry

In this work, a method was developed for the simultaneous determination of residual metoserpate, buquinolate and diclofenac in pork, milk, and eggs. Samples were extracted with 0.1% formic acid in acetonitrile, defatted with n‐hexane, and filtered prior to analysis using liquid chromatography–tandem mass spectrometry. The analytes were separated on a C₁₈ column using 0.1% acetic acid and methanol as the mobile phase. The matrix‐matched calibration curves showed good linearity over a concentration range of 5–50 ng/g with coefficients of determination (R²) ≥0.991. The intra‐ and inter‐day accuracies (expressed as recovery percentage values) calculated using three spiking levels (5, 10, and 20 μg/kg) were 80–108.65 and 74.06–107.15%, respectively, and the precisions (expressed as relative standard deviation) were 2.86–13.67 and 0.05–11.74%, respectively, for the tested drugs determined in various matrices. The limits of quantification (1 and 2 μg/kg) were below the uniform residual level (0.01 mg/kg) set for compounds that have no specific maximum residue limit (MRL). The developed method was tested using market samples and none of the target analytes was detected in any of the samples. The validated method proved to be practicable for detection of the tested analytes in pork, milk, and eggs.     

Pesticide residues analysis in honey using ethyl acetate extraction method: validation and pilot survey in real samples

This paper presents a cost-effective and validated multi residue confirmatory method for the determination of 167 chemically different pesticides and a survey study on Cyprus honey samples. This method uses ethyl acetate for the extraction of pesticides from honey and the determination is performed with liquid chromatography (LC) coupled to mass spectrometry (MS) operating in tandem mode (MS/MS) and with GC–ECD (gas chromatography with electron capture detector) analysis. The LC-MS/MS analytical system is especially important in the analysis of polar and non-volatile pesticides. For the validation of the method, blank honey samples were spiked with 146 pesticides (organophosphorous, carbamates, triazoles, amides, neonicodinoids, strobilurines, phenylureas, bendimidazoles and others) for the LC-MS/MS analysis at three levels: 0.01, 0.05 and 0.1 mg kg^?1 and with 21 pesticides for the GC-ECD analysis at two levels: 0.01 and 0.05 mg kg^?1for organochlorines and 0.05 and 0.2 mg kg^?1for the pyrethroids. As blank sample, a sample of honey which did not contain detectable levels of the analytes sought was used. The validation study was in accordance to the DG SANCO guidelines. The scope of validation included recovery, linearity, limits of quantification and precision. Linearity is demonstrated all along the range of concentration that was investigated with correlation coefficients ≥0.98. Recoveries of the majority of compounds were in the 70%–120% range and were characterised by precision lower or equal to 20%. The validated method was used for a survey of 36 samples of honey produced in different areas of Cyprus and this is the first work on Cypriot honey samples investigating a broad range of pesticides. Only coumaphos was detected at concentrations higher than 0.01 mg kg^?1 in the 58.6% of the honey samples analysed for Coumaphos. The results were evaluated in accordance to the provisions of the Commission Regulation (EU) No 37/2010 on pharmacologically active substances and their classification regarding maximum residue limits (MRLs) in foodstuffs of animal origin. The concentrations of coumaphos in all positive samples were at levels much lower than the MRL.     

Determination of lincomycin and tylosin residues in honey by liquid chromatography/tandem mass spectrometry

A simple and rapid analytical method was developed for the determination of lincomycin and tylosin residues in honey as part of field studies examining the efficacy and target animal safety of these antibiotics to control American foulbrood disease in honey bees. Residues of the antibiotics were determined using liquid chromatography/electrospray ionization tandem mass spectrometry (LC/ESI-MS/MS). Honey samples were diluted and injected directly into the LC/MS/MS system without additional cleanup by solid-phase extraction or liquid-liquid partitioning. A six-port valve system was utilized to selectively route eluant from the LC column into the mass spectrometer only during a relatively short portion of the chromatographic run corresponding to the elution of the analytes of interest. Minimal contamination of the MS source chamber was observed despite the analysis of large numbers of samples. Using internal standard quantitation, excellent accuracy and precision were obtained with no apparent matrix-to-matrix variation. Based on the analysis of fortified replicates, the mean percent deviation from the theoretical concentration and the percent relative standard deviation were both less than 10% for tylosin over an analytical range of 10-1000 microg/kg. Slightly higher mean percent deviations and relative standard deviations were observed for the analysis of lincomycin in fortified replicate samples. The method detection limits were determined to be 5 and 2 microg/kg for lincomycin and tylosin, respectively.     

Simultaneous Determination of Fluoxetine,Estrone, Pesticides,and Endocrine Disruptors in Wastewater by Gas Chromatography–Mass Spectrometry (GC–MS) Following Switchable Solvent–Liquid Phase Microextraction (SS–LPME)

A simple and sensitive analytical method for the determination of fluoxetine, estrone and selected pesticides and endocrine disruptors has been proposed for wastewater analysis by gas chromatography–mass spectrometry (GC–MS). A switchable solvent was produced with N,N-dimethylbenzylamine by changing its hydrophobic properties by the addition of CO₂ for protonation. Sodium hydroxide was added to switch the solubility of the extraction solvent and to allow phase separation in the sample/standard medium. Analytical parameters affecting the extraction outputs such as volume of switchable solvent, concentration and volume of sodium hydroxide, mixing type and period were investigated to improve the extraction recovery of the selected analytes. Under the optimum conditions, limits of detection and limits of quantification for the analytes were calculated in the ranges of 0.16–8.6?ng mL^?1 and 0.54–29?ng mL^?1, respectively. The developed method was successfully applied to synthetic wastewater and two municipal wastewater samples. None of the selected analytes were detected in the samples. High recovery values demonstrated that the proposed method was reliable and applicable to complex matrices.     

Development of a rapid and sensitive method for the simultaneous determination of 1,2-dibromoethane, 1,4-dichlorobenzene and naphthalene residues in honey using HS-SPME coupled with GC-MS

A new method for the simultaneous determination of 1,4-dichlorobenzene (p-DCB), naphthalene and 1,2-dibromoethane (1,2-DBE) residues in honey has been developed. Analysis is carried out using gas chromatography-mass spectrometry (GC/MS) in selected ion monitoring mode (SIM), after extraction and preconcentration of target analytes by headspace solid-phase microextraction (HS-SPME), with a 100 microm film thickness polydimethylsiloxane (PDMS) fiber. Several parameters affecting the extension of the adsorption process (i.e., addition of salt, extraction time, extraction temperature) were studied. The optimal conditions for the determination of these analytes were established. The proposed HS-SPME method showed good sensitivity, without carryover between the samples. Linearity was studied from 5 to 2500 microg kg(-1) for p-DCB, 0.5 to 500 microg kg(-1) for naphthalene and 5 to 500 microg kg(-1) honey for 1,2-DBE with correlation coefficients (r(2)) ranging from 0.9901 to 0.9999. Precision was assessed and both intra and inter-day R.S.D.s (%) were below 6.3%. The detection limits were found to be 1, 0.1 and 2 microg kg(-1) honey for p-DCB, naphthalene and 1,2-DBE, respectively. The percentage recoveries that were evaluated with the proposed HS-SPME method and the standard addition calibration technique gave values among 72.8 and 104.3% for measurements in samples spiked with one target analyte or mixtures of the three. This method has been applied for the analysis of unknown honey samples. The results showed an excellent applicability of the proposed method for the determination of the target compounds in honey samples.     

Simultaneous determination of l‐tetrahydropalmatine and its active metabolites in rat plasma by a sensitive ultra‐high‐performance liquid chromatography with tandem mass spectrometry method and its application in a pharmacokinetic study

A sensitive and reliable ultra‐high‐performance liquid chromatography with tandem mass spectrometry (UHPLC–MS/MS) method was developed and validated for simultaneous determination of l ‐tetrahydropalmatine (l ‐THP) and its active metabolites l ‐isocorypalmine (l ‐ICP) and L ‐corydalmine (l ‐CD) in rat plasma. The analytes were extracted by liquid–liquid extraction and separated on a Bonshell ASB C₁₈ column (2.1 × 100 mm; 2.7 μm; Agela) using acetonitrile–formic acid aqueous as mobile phase at a flow rate of 0.2 mL/min in gradient mode. The method was validated over the concentration range of 4.00–2500 ng/mL for l ‐THP, 0.400–250 ng/mL for l ‐ICP and 1.00–625 ng/mL for l ‐CD. Intra‐ and inter‐day accuracy and precision were within the acceptable limits of <15% at all concentrations. Correlation coefficients (r ) for the calibration curves were >0.99 for all analytes. The quantitative method was successfully applied for simultaneous determination of l ‐THP and its active metabolites in a pharmacokinetic study after oral administration with l ‐THP at a dose of 15 mg/kg to rats.     

Development of a liquid chromatography–tandem mass spectrometry method for the determination of Grayanotoxins in rat blood and its application to toxicokinetic study

A sensitive and specific high‐performance liquid chromatography–tandem mass spectrometry (LC‐MS/MS) method was developed for the determination of Grayanotoxin I (GTX I) and Grayanotoxin III (GTX III) in rat whole blood. Grayanotoxins (GTXs) and clindamycin as internal standard (IS) were extracted from rat blood via solid‐phase extraction using PEP solid‐phase extraction cartridges. Chromatographic separation of the analytes was achieved on a Kinetex C₁₈ (100 × 2.1 mm, 2.6 µm) reversed‐phase column using a gradient elution with the mobile phase of 1% acetic acid in water and methanol at a flow rate of 0.2 mL/min. Electrospray ionization mass spectrometry was operated in the positive ion mode with multiple reaction monitoring. The calibration curves obtained were linear over the concentration range of 1–100 ng/mL with a lower limit of quantification of 1 ng/mL for GTXs. The relative standard deviation of intra‐day and inter‐day precision was below 6.8% and accuracy ranged from 94.8 to 106.6%. The analytes were stable in the stability studies. The validated method was successfully applied to the quantification and toxicokinetic study of GTXs in rats for the first time after oral administration of 11.52 mg/kg mad honey and 0.35 mg/kg GTX III, respectively. Copyright © 2014 John Wiley & Sons, Ltd.     

Simultaneous determination of simazine,cyanazine, and atrazine in honey samples by dispersive liquid–liquid microextraction combined with high‐performance liquid chromatography

A rapid and simple sample preparation method was developed for simultaneous determination of three triazine herbicides in honey samples. The selected herbicides were extracted from honey samples by ionic liquid dispersive liquid–liquid microextraction, separated on a C₁₈ column (250 mm × 4.6 mm id, 5 μm) using acetonitrile and H₂O as the mobile phase with gradient elution, and then detected by high‐performance liquid chromatography. The parameters, such as the type and volume of the extraction and disperser solvent, ion strength, pH, extraction time, and centrifuge time were optimized in order to provide the excellent extraction performance. Good linearity was showed for all the target herbicides over the tested concentration range with correlation coefficient higher than 0.994. Three spiked levels (0.005, 0.05, 0.10 mg/kg) were applied for determination of the recoveries of the targets in honey samples in the range of 80–103% with relative standard deviations not larger than 10.6%. The limits of quantification for the analytes ranged between 1.5 and 4.0 μg/kg. The developed method was applied for determination of the target compounds residues in real samples.     

Simultaneous detection of bacitracin and polymyxin B in livestock products using liquid chromatography with tandem mass spectrometry

With the overarching aim to develop a simple and reliable method for the quantitative analysis of polypeptide antibiotics in various livestock products, the content of bacitracin, and polymyxin B in pork, beef, chicken, milk, and eggs was analyzed using colistin sulfate as an internal standard. The extracted samples were eluted via solid‐phase extraction using 2% formic acid in acetonitrile/methanol (1:1, v/v). The two polypeptides were identified and quantified based on the intensities of mass fragments from the respective triply charged precursor ions (bacitracin: 474.97 amu and polymyxin B: 402 amu) at the defined retention time windows using liquid chromatography with electrospray ionization tandem mass spectrometry in time‐scheduled multiple reaction monitoring mode. The calibration curves showed good linearity over the concentration range 50–2500 ng/mL with determination coefficients ≥ 0.991. The mean recoveries were in the range 80.3–88.8% with relative standard deviations <13% for all samples. The limits of quantitation ranged from 30–250 ng/g. The developed method was applied to market samples, but the target analytes were not detected in any of the samples. The developed method is reliable for the simultaneous detection of bacitracin and polymyxin B in pork, beef, chicken, milk, and eggs.     

Simultaneous determination of seven multiclass veterinary antibiotics in surface water samples in the Republic of Korea using liquid chromatography with tandem mass spectrometry

A simultaneous determination method using solid‐phase extraction and liquid chromatography with tandem mass spectrometry was developed to detect and quantify the presence of seven multiclass veterinary antibiotics (13 compounds in total) in surface water samples, which included the effluents of livestock wastewater and sewage treatment plants, as well as the reservoir drainage areas from dense animal farms. The pH of all water samples was adjusted to 2 or 6 before solid‐phase extraction using Oasis HLB cartridges. The developed method was fully validated in terms of linearity, method detection limit, method quantitation limit, accuracy, and precision. The linearity of all tested drugs was good, with R² determination coefficients ≥ 0.9931. The method detection limits and method quantitation limits were 0.1–74.3 and 0.5–236.6 ng/L, respectively. Accuracy and precision values were 71–120 and 1–17%, respectively. The determination method was successfully applied for monitoring water samples obtained from the Yeongsan River in 2015. The most frequently detected antibiotics were lincomycin (96%), sulfamethazine (90%), sulfamethoxazole (88%), and sulfathiazole (50%); the maximum concentrations of which were 398.9, 1151.3, 533.1, and 307.4 ng/L, respectively. Overall, the greatest numbers and concentrations of detected antibiotics were found in samples from the effluents of livestock wastewater, sewage treatment plants, and reservoir drainage areas. Diverse veterinary antibiotics were present, and their presence was dependent upon the commercial sales and environmental properties of the analytes, the geographical positions of the sampling points, and the origin of the water.     

Quantitative determination of metformin,glyburide and its metabolites in plasma and urine of pregnant patients by LC‐MS/MS

This report describes the development and validation of an LC‐MS/MS method for the quantitative determination of glyburide (GLB), its five metabolites (M1, M2a, M2b, M3 and M4) and metformin (MET) in plasma and urine of pregnant patients under treatment with a combination of the two medications. The extraction recovery of the analytes from plasma samples was 87–99%, and that from urine samples was 85–95%. The differences in retention times among the analytes and the wide range of the concentrations of the medications and their metabolites in plasma and urine patient samples required the development of three LC methods. The lower limit of quantitation (LLOQ) of the analytes in plasma samples was as follows: GLB, 1.02 ng/mL; its five metabolites, 0.100–0.113 ng/mL; and MET, 4.95 ng/mL. The LLOQ in urine samples was 0.0594 ng/mL for GLB, 0.984–1.02 ng/mL for its five metabolites and 30.0 µg/mL for MET. The relative deviation of this method was <14% for intra‐day and inter‐day assays in plasma and urine samples, and the accuracy was 86–114% in plasma, and 94–105% in urine. The method described in this report was successfully utilized for determining the concentrations of the two medications in patient plasma and urine. Copyright © 2014 John Wiley & Sons, Ltd.     

LC–MS–MS Simultaneous Determination of Paracetamol, Pseudoephedrine and Chlorpheniramine in Human Plasma: Application to a Pharmacokinetic Study

A liquid chromatography–tandem mass spectrometry (LC–MS–MS) method was developed for the simultaneous determination of paracetamol, pseudoephedrine and chlorpheniramine in human plasma. Diphenhydramine was used as the internal standard. Analytes were extracted from alkalized human plasma by liquid–liquid extraction (LLE) using ethyl acetate. After electrospray ionization positive ion fragments were detected in the selected reaction monitoring (SRM) mode with a triple quadrupole tandem mass spectrometer. The method was linear in the concentration range of 20.0–10000.0 ng mL^?1 for paracetamol, 1.0–500.0 ng mL^?1 for pseudoephedrine and 0.1–50.0 ng mL^?1 for chlorpheniramine. The intra- and inter-day precisions were below 14.5% and the bias was between ?7.3 and +2.8% for all analytes. The validated LC–MS–MS method was applied to a pharmacokinetic study in which each healthy Chinese volunteer received a tablet containing 300 mg benorylate, 30 mg pseudoephedrine hydrochloride and 2 mg chlorpheniramine maleate. This is the first assay method described for the simultaneous determination of paracetamol, pseudoephedrine and chlorpheniramine in human plasma samples.     

Core-shell magnetic porous organic polymer for magnetic solid-phase extraction of fluoroquinolone antibiotics in honey samples followed by high-performance liquid chromatography with fluorescence detection

By monomer-mediated in-situ growth synthesis strategy, with hydroquinone and 1,3,5-tris(4-aminophenyl)benzene as monomers, a core-shell magnetic porous organic polymer was synthesized through a simple azo reaction. Based on this, a magnetic solid-phase extraction–high-performance liquid chromatography–fluorescence detection method was proposed for the analysis of fluoroquinolones in a honey sample. With ofloxacin, ciprofloxacin, enrofloxacin, lomefloxacin, and difloxacin as target analytes, factors affecting the extraction efficiency had been optimized. The LODs were 1.5–5.4 ng/L (corresponding to 0.23–0.81 μg/kg in honey). The linear range was 0.005–20 μg/L for difloxacin, 0.01–20 μg/L for ofloxacin, ciprofloxacin and lomefloxacin, and 0.02–20 μg/L for enrofloxacin. The enrichment factor was 84.4–91.7-fold with a high extraction efficiency of 84.4–91.7%. The method was assessed by the analysis of target fluoroquinolones in honey samples, and the recoveries for the spiked samples were 79.3–95.8%. The results indicated that the established magnetic solid-phase extraction–high-performance liquid chromatography–fluorescence detection method is efficient for the analysis of trace fluoroquinolones in honey.