Determination of Trichothecenes in Cereal Matrices Using Subcritical Water Extraction Followed by Solid-Phase Extraction and Liquid Chromatography-Tandem Mass Spectrometry

Subcritical water extraction followed by solid-phase extraction and ultra-high performance liquid chromatography coupled with tandem mass spectrometry detection is reported for the first time for the determination of 6 trichothecenes (deoxynivalenol, deoxynivalenol-3-glucoside, 3-acetyl-deoxynivalenol, 15-acetyl-deoxynivalenol, HT-2 toxin, and T-2 toxin) from different cereals. Water with 1% formic acid was used as the extraction solvent followed by a solid-phase extraction clean-up, achieving good performance with acceptable extraction recoveries, method detection limits between 0.05 μg kg^?1 and 4.0 μg kg^?1, and method quantification limits between 0.4 μg kg^?1 and 20 μg kg^?1. The use of water as the extraction solvent allowed a selective extraction affording low matrix effect levels and the detection and quantification of natural target trichothecenes at very low concentration levels. This extraction method was applied to different cereals, a pseudocereal and an oilseed sample, of which maize, millet, and oat were contaminated by at least one trichothecene.     

Simultaneous Determination of Eight Tranquilizers in Pork by Ultra-Performance Liquid Chromatography Coupled with Electrospray Tandem Mass Spectrometry

An ultra-performance liquid chromatography/electrospray ionization tandem mass spectrometry (UPLC-ESI-MS/MS) method was developed and validated for quantification of eight tranquillizers (chlorpromazine, imipramine hydrochloride, diazepam, nitrazepam, nordazepam, oxazepam, flurazepam, and haloperidol) in pork. Sample pretreatment consisted of extraction by acetonitrile, defatted by n-hexane, and further solid phase extraction by hydrophilic-lipophilic balance (HLB) extraction cartridges. The triple quadrupole mass spectrometer was operated in positive ion mode, and multiple reaction monitoring was used for drug quantification. The method was validated over the concentration ranges of 1.0 ～ 250 μg kg^?1 for the eight tranquillizers. The calibrations were performed in sample matrices, and the interference effect of sample matrices on the ionization was effectively eliminated. Good linear relationship (R ² > 0.99) was observed within the concentration range of 1.0–250 μg kg^?1. The average recoveries of the eight tranquillizers spiked at three levels ranged from 63.7 to103.2 % with the relative standard deviation below 11.8 %. The limits of detection were between 0.06 and 0.30 μg kg^?1, and the limits of quantification were between 0.2 and1.0 μg kg^?1 for all analytes in pork. This validated method has been successfully used to quantify the concentration of the eight tranquillizers in pork samples.     

Simultaneous Determination of Multiclass Pesticides and Antibiotics in Honey Samples Based on Ultra-High Performance Liquid Chromatography-Tandem Mass Spectrometry

A simple, fast, and efficient method was developed for simultaneous determination of 79 pesticides and 13 antibiotics compounds of different chemical classes of pesticides and antibiotics in honey samples by ultra-high performance liquid chromatography with tandem mass spectrometry (UHPLC-MS/MS). The sample preparation procedure includes homogenization with McIlvaine buffer 0.1 mol L^?1 (pH 4), followed by extraction with acetonitrile and cleanup with florisil, using dispersive solid phase extraction (d-SPE). The proposed method was validated with good results, such as linearity (r ²?>?0.9901), normality, and independence of the evaluated data, as well as recoveries between 70 and 120 % with relative standard deviation (RSD) <20 % for most of the compounds spiked from 0.1 to 200 μg kg^?1. The experimental method limits of detection and quantification were from 0.03 to 1.51 μg kg^?1 and from 0.1 to 5 μg kg^?1, respectively, for the pesticides. For the antibiotics, the decision limits (0.1 to 2 μg g^?1) and the detection capacity (0.12 to 2.81 μg g^?1) were below the maximum residue limits (MRLs) established for honey by the Brazilian and European legislation. The method was successfully applied to real samples from different botanical and geographic origins. From them, 44 % presented residues from 0.12 to 10 μg kg^?1 of one or more analytes. The proposed method combines the advantages of a quick sample preparation step with the selectivity and sensitivity of the UHPLC-MS/MS and proved to be suitable for routine analyses.     

Reproducible Molecularly Imprinted QCM Sensor for Accurate,Stable, and Sensitive Detection of Enrofloxacin Residue in Animal-Derived Foods

This study describes the development of a novel reproducible molecularly imprinted quartz crystal microbalance (QCM) sensor for the accurate and sensitive analysis of the residue of enrofloxacin (ENRO) in animal-derived foods. This proposed sensor was easily fabricated by directly immobilizing molecularly imprinted polymer (MIP) of ENRO on the surface of a QCM Au chip, which combined the advantages of selective recognition from the MIP with the high sensitivity and portability of a QCM sensor. The parameters in the fabrication and measurement process were optimized and discussed in detail. It was verified that the MIP-modified QCM Au chip performed favorably for the detection of ENRO residue in common animal-derived food products and demonstrated acceptable accuracy (recovery: pure milk 77.2–84.2%, egg 77.3–85.6%, chicken muscle 73.5–89.1%, pork 74.7–85.8%), precision (relative standard deviation (RSD, n = 3), pure milk 2.9–8.0%, egg 2.9–6.4%, chicken muscle 3.4–6.8%, pork 2.2–4.7%), and sensitivity (limit of detection, pure milk 0.31 μg L^?1, egg 0.44 μg kg^?1, chicken muscle 0.54 μg kg^?1, pork 0.57 μg kg^?1). The MIP-modified QCM Au chip for sensing ENRO was portable, could be stored for an extended period of time, and reused for more than 30 analysis cycles with a response attenuation of 7.8%. These results have demonstrated that the proposed MIP QCM sensor presents an accurate, sensitive, rapid, and low-cost methodology for ENRO residue detection in animal foods. This research is very promising for the development of novel effective devices applied to the detection of various contaminants in the field of food safety.     

Determination of Pesticide Residues in Golden Berry (<Emphasis Type="Italic">Physalis peruviana</Emphasis> L<Emphasis Type="Italic">.</Emphasis>) by Modified QuEChERS Method and Ultra-High Performance Liquid Chromatography-Tandem Quadrupole Mass Spectrometry

A fast and effective multiresidue method for the determination of 42 pesticides in golden berry was developed and validated. A modified QuEChERS method was established for sample preparation followed by ultra-high performance liquid chromatographic-tandem mass spectrometry (UHPLC-MS/MS) determination with electrospray ionization in a triple quadrupole system. Validation results were satisfactory, since the method presented recoveries between 70 and 114 % with relative standard deviations (RSD) <20 % for blank samples spiked from 5 to 25 μg kg^?1. The method limit of detection and limit of quantification were 1.5 and 5 μg kg^?1 _, respectively. Matrix effect ranged from ?32 to 218 % and was compensated using matrix-matched calibration. Method linearity was established from 2.5 to 100 μg kg^?1 with r ² ≥ 0.99. The proposed method combines the advantages of a simple and fast sample preparation step by a modified QuEChERS method with the high selectivity and sensitivity of the UHPLC-MS/MS system using selected reaction monitoring. The method was successfully applied to commercial samples, proving to be an efficient alternative for routine analysis. From the 16 analyzed samples, 13 presented residues of one or more pesticides (carbendazim, chlorpyrifos ethyl, dimethoate, propamocarb, and tebuconazole) in the concentration range of 2.0 to 55.6 μg kg^?1.     

Analytical Method Validation and Rapid Determination of Polycyclic Aromatic Hydrocarbons (PAHs) in Cocoa Butter Using HPLC-FLD

A simple, fast and ecological analytical method using a semi-automatic fat extractor and HPLC-FLD (fluorescence detection) for determination of polycyclic aromatic hydrocarbon markers i.e. benzo(a)anthracene (BaA), chrysene (Chr), benzo(a)pyrene (BaP) and benzo(b)fluoranthene (BbF) in cocoa butter has been validated. Validation’s procedure performed out in concordance with French standard NF V03-110 (2010) was based on existing polycyclic aromatic hydrocarbon (PAH) determination methods in various smoked foodstuffs and edible vegetable oils. Determination of correlation coefficients for specific PAHs ranged from 0.9992 to 0.9998. Respective values of limits of detection were 0.010, 0.011, 0.033 and 0.029 μg kg^?1 and those of quantification were 0.035, 0.038, 0.111 and 0.098 μg kg^?1 for BaA, Chr, BbF and BaP. Both values of repeatability and intermediary precision tests coefficients of variation were less than 5%. Recovery scores of four PAH markers matched EU standard 836/2011 recommendations. Sum of four PAH markers (BaA, Chr, BbF, BaP) contents varied from 5.42?±?0.58 to 11.37?±?0.01 μg kg^?1 whereas those of BaP was comprised between 0.26?±?0.00 and 1.75?±?0.13 μg kg^?1 in 20 cocoa butter samples extracted from raw cocoa bean stored at Ivorian cocoa farmer levels.     

Determination of benzo[α]pyrene in edible oil using tetraoxocalix[2]arene[2]triazine bonded silica SPE sorbent

Benzo[α]pyrene (BaP) is a well-known carcinogen in edible oil. In this study, a method combined solid-phase extraction (SPE) with fluorescent detection was developed using tetraoxocalix[2]arene[2]triazine sorbent (SiO₂-OCA) for the clean-up and enrichment of BaP. The interaction between SiO₂-OCA and BaP involves a donor–acceptor complex mechanism. The experimental procedure was as follows: BaP was extracted from edible oil with DMF/H₂O (9:1, v/v). Then, the ratio of DMF/H₂O was adjusted to 1:2 prior to SPE. The final concentrate was analysed using a fluorescence detector at excitation and emission wavelengths of 255 and 420 nm. The method was fully validated. The linearity was in the range of 0.1–100 μg kg^?1 with a coefficient of 0.999. The limits of detection and quantification were 0.03 and 0.1 μg kg^?1, respectively. The average recoveries were in the range of 88.0 ? 122.3%. The intraday and interday precisions were 6.8% and 9.2%, respectively. Compared with other methods, the method reported in this article shows a good detection limit, high reproducibility and recovery and linearity over a broad concentration range. This established method was also applied to evaluate real samples. The concentration of six tested samples was below 5 μg kg^?1.     

Analysis of Multiple β-Agonist and β-Blocker Residues in Porcine Muscle Using Improved QuEChERS Method and UHPLC-LTQ Orbitrap Mass Spectrometry

The objective of the present study is to develop and optimize a simple, high-throughput method for determining 14 β-agonists (i.e., banbuterol, brombuterol, cimaterol, cimbuterol, clenbuterol, clenpeterol, clorpenaline, isoxsuprine, mabuterol, mapenterol, ractopamine, salbutamol, terbutaline, and tulobuterol) and two β-blockers (propranolol and penbutolol) in porcine muscle. The samples were pretreated by a modified quick, easy, cheap, efficient, rugged, and safe (QuEChERS) method, and analysis was carried out in a reversed phase HSS T3 C18 column using gradients of acetonitrile and 5 mmol L^?1 ammonium acetate (0.1 % formic acid) solution for elution. Ultra-high performance liquid chromatography coupled with high-resolution mass spectrometry (UHPLC-LTQ Orbitrap MS, resolution 60,000) was used for qualification and quantification of the 16 target compounds. Under optimized conditions, the limits of detection and quantification obtained ranged from 0.17 to 1.67 μg kg^?1 and from 0.56 to 5.00 μg kg^?1, respectively. Recoveries for spiking levels of 5.0, 10.0, and 20.0 μg kg^?1 ranged from 62.4 to 121.9 %, from 60.4 to 104.3 %, and from 66.5 to 121.3 %, respectively. The relative standard deviations obtained were lower than 20 % for all spiking levels assayed. The proposed method was applied successfully in sample analysis, and satisfactory results were obtained.     

Determination and surveillance of hydrocortisone and progesterone in livestock products by liquid chromatography-tandem mass spectrometry

A simple analytical method for the determination of hydrocortisone and progesterone in bovine, swine, and chicken muscle and eggs was developed. Hydrocortisone and progesterone were extracted with acetonitrile and subsequently cleaned-up using an Oasis^® HLB mini-cartridge. The method was validated in accordance with Japanese guidelines and exhibited trueness from 86.6% to 104.3% and precision (relative standard deviations (RSDs) of repeatability and within reproducibility were under 8.7% and 11.7%, respectively). The method was applied to 103 bovine muscle, 137 swine muscle, 69 chicken muscle and 52 egg samples that were commercially available in Tokyo, Japan. The hydrocortisone concentration was 0.9–41.2 µg kg^?1 in all bovine muscle samples, with an average of 7.7 µg kg^?1 and a median of 6.2 µg kg^?1. The progesterone concentration in 50 samples exceeded the limit of quantification (LOQ) and reached a maximum of 95.4 µg kg^?1. Hydrocortisone was also detected in all swine muscle samples at concentrations of 2.0–56.0 µg kg^?1. Its average and median concentrations amounted to 13.1 and 11.3 µg kg^?1, respectively. Twenty-three samples contained progesterone levels surpassing the LOQ, with a maximum concentration of 107.0 µg kg^?1. No chicken muscle samples contained any of the analytes. The progesterone concentration was 15.5–200.0 µg kg^?1 in all egg samples, with an average of 95.4 µg kg^?1 and a median of 90.5 µg kg^?1.     

Simultaneous determination of chloramphenicol,florfenicol and florfenicol amine in ham sausage with a hybrid chemiluminescent immunoassay

A novel chemiluminescent immunoassay utilising two types of primary antibodies (murine monoclonal antibody and rabbit polyclonal antibody) and two types of horseradish peroxidase–labelled secondary antibodies was established for simultaneously detecting multiple amphenicol residues in ham sausage. After combining the extract procedure of the target amphenicol into one simplified method, this hybrid chemiluminescent immunoassay could screen chloramphenicol (CAP), florfenicol (FF) and its metabolite florfenicol amine (FFA) at the same time by adding the corresponding secondary antibody. Ham sausage samples were analysed by using this hybrid immunoassay, with LODs of CAP being 0.01 μg kg^?1, of FF being 2.8 μg kg^?1 and of FFA being 3.0 μg kg^?1. The applicability of the proposed method has been validated by determining CAP, FF and FFA in ham sausage samples with satisfactory results. Good recoveries and high correlation with traditional enzyme-linked immunosorbent assay and LC-MS/MS results illustrated that the developed hybrid chemiluminescent immunoassay could screen high-throughput ultra-trace amphenicol residues effectively at one time.     

Magnetic solid-phase extraction coupled with HPLC for the determination of Allura Red in food and beverage samples

A magnetic solid-phase extraction (MSPE) protocol prior to HPLC was developed for the extraction and determination of Allura Red in food samples. Magnetic nanoparticles were coated with tetraethylorthosilicate and 3-aminopropyltriethoxysilane and modified by graphene. Scanning electron microscopy, transmission electron microscopy and Fourier-transform infrared spectrometry were used to characterise the graphene-functionalised sorbents; and the main parameters affecting the extraction such as sample volume, temperature, pH and time were investigated and established. Under optimised conditions, the pre-concentration factor of Allura Red was 200, and the calibration curve was linear at a concentration range of 5–1500 μg kg^?1. The LOD was 2 μg kg^?1, the limit of quantification was 7 μg kg^?1, and the relative standard deviation was 3.3%. The prepared MSPE procedure was simple and fast, and it was successfully applied for the determination of Allura Red in beverages, candy and jelly.     

Optimization of QuEChERS Procedure Coupled to GC-ECD for Organochlorine Pesticide Determination in Carrot Samples

An optimised version of the Quick, Easy, Cheap, Effective, Rugged and Safe (QuEChERS) method for simultaneous determination of 14 organochlorine pesticides in carrots was developed using gas chromatography coupled with electron-capture detector (GC-ECD) and confirmation by gas chromatography tandem mass spectrometry (GC-MS/MS). A citrate-buffered version of QuEChERS was applied for the extraction of the organochlorine pesticides, and for the extract clean-up, primary secondary amine, octadecyl-bonded silica (C18), magnesium sulphate (MgSO₄) and graphitized carbon black were used as sorbents. The GC-ECD determination of the target compounds was achieved in less than 20 min. The limits of detection were below the EU maximum residue limits (MRLs) for carrots, 10–50 μg kg^?1, while the limit of quantification did exceed 10 μg kg^?1 for hexachlorobenzene (HCB). The introduction of a sonication step was shown to improve the recoveries. The overall average recoveries in carrots, at the four tested levels (60, 80, 100 and 140 μg kg^?1), ranged from 66 to 111 % with relative standard deviations in the range of 2–15 % (n?=?3) for all analytes, with the exception of HCB. The method has been applied to the analysis of 21 carrot samples from different Portuguese regions, and β-HCH was the pesticide most frequently found, with concentrations oscillating between less than the limit of quantification to 14.6 μg kg^?1. Only one sample had a pesticide residue (β-HCH) above the MRL, 14.6 μg kg^?1. This methodology combines the advantages of both QuEChERS and GC-ECD, producing a very rapid, sensitive and reliable procedure which can be applied in routine analytical laboratories.     

Determination of acrylamide in food using a UPLC–MS/MS method: results of the official control and dietary exposure assessment in Cyprus

ABSTRACT

The determination of acrylamide in potato products, bakery products and coffee, and the human dietary exposure is reported. The method reported is based on a single extraction step with water, followed by the clean-up of the extract using solid phase extraction columns and finally, the determination of acrylamide using UPLC–MS/MS. The MS/MS detection was carried out using an ESI interface in positive ion mode. Internal calibration was used for the quantification of acrylamide, because of the suppression/enhancement matrix effects due to the complex nature of the samples. The method performance characteristics were determined after spiking blank samples. The mean recoveries in spiked coffee samples, potato chips, breakfast cereals and crispbread ranged from 93% to 99%, with RSDs lower than 5% for both repeatability and reproducibility conditions. The estimated limits of detection and quantification of the method were 10 and 32 μg kg^?1, respectively. The method was used for monitoring acrylamide in 406 samples. Acrylamide amounts ranged from <32 to 2450 μg kg^?1. A total of 360 samples (89%) were contaminated with acrylamide, but only 14% of the samples exceeded the benchmark levels of the EU legislation. Foods with the highest mean acrylamide amounts were potato crisps (642 μg kg^?1), French fries (383 μg kg^?1) and biscuits (353 μg kg^?1). The mean and 95th percentile acrylamide exposures of adolescents in Cyprus were 0.8 and 1.8 μg kg^?1 body weight per day, respectively. The estimated levels of dietary exposure to acrylamide are not of concern with respect to neurotoxicity. However, the margins of exposure (MOEs) indicate a concern for carcinogenicity. Potato fried products (45%), fine bakery ware (21%) and potato chips (14%) contributed the most to overall acrylamide exposure.     

Multi-residual Pesticide Monitoring in Commercial Chinese Herbal Medicines by Gas Chromatography–Triple Quadrupole Tandem Mass Spectrometry

To investigate multi-residual pesticide monitoring data in commercial Chinese herbal medicines on major markets, an easy, rapid, and selective gas chromatography with mass spectrometry (GC/MS/MS) method was established for simultaneously determining multi-residual pesticides including organochlorine, pyrethroid, carbamate, and organophosphorus pesticides in Chinese herbal medicines. The analytical method was based on an efficient extraction procedure and further cleanup steps by solid-phase extraction columns, yielding recovery rates in the range of 70.0–120.0 % for the majority of pesticides, except for hexachlorobenze, diazinon, β-HCH, δ-HCH, and omethoate, with precision values expressed as relative standard deviation of 0.1–14.7 %. The limits of detection of the established GC/MS/MS method for all investigated pesticides ranged from 0.01 to 3.6 μg kg^?1 and limits of quantification from 0.03 to 11.88 μg kg^?1. With this validated method, multi-residual pesticides of 132 Chinese herbal medicine samples were analyzed. The monitoring results indicated that pesticide residue was found in 74 samples. In total, 51 pesticides were found with detection rate ranging from 0.76 to 18.94 %. An 82.3 % of positive pesticides were found in less than 6 % of samples. Hexachlorobenzene was found in 25 samples, quintozene in 15 samples, and acephate and simazine in 13 samples. Concentrations of pesticide residue from monitoring data obtained ranged from 0.5 to 203.5 μg kg^?1. The simple and rapid method can be used as routine analysis method in multi-residual pesticide monitoring of Chinese herbal medicines.     

Determination of glyphosate,AMPA, and glufosinate in honey by online solid-phase extraction-liquid chromatography-tandem mass spectrometry

A simple method was developed for the simultaneous determination of glyphosate, its main degradation product (aminomethylphosphonic acid), and glufosinate in honey. Aqueous honey solutions were derivatised offline prior to direct analysis of the target analytes using online solid-phase extraction coupled to liquid chromatography-tandem mass spectrometry. Using the developed procedure, accuracies ranging from 95.2% to 105.3% were observed for all analytes at fortification levels of 5, 50, and 150 μg kg^?1 with intra-day precisions ranging from 1.6% to 7.2%. The limit of quantitation (LOQ) was 1 μg kg^?1 for each analyte. Two hundred honey samples were analysed for the three analytes with AMPA and glyphosate being most frequently detected (99.0% and 98.5% of samples tested, respectively). The concentrations of glyphosate were found to range from <1 to 49.8 μg kg^?1 while those of its degradation product ranged from <1 to 50.1 μg kg^?1. The ratio of glyphosate to AMPA was found to vary significantly amongst the samples where both analytes were present above the LOQ. Glufosinate was detected in 125 of 200 samples up to a maximum concentration of 33.0 μg kg^?1.     

Optimization and Validation of a Method Without Alkaline Clean-Up for Patulin Analysis on Apple Puree Agar Medium (APAM) and Apple Products

A sensitive high-performance liquid chromatography-UV (HPLC-UV) method, based on the Association of Analytical Communities (AOAC) Official method 2000.02, was developed and validated for the high-throughput analysis of patulin in in vitro experiments on apple puree agar medium (APAM). The importance of repeating the ethyl acetate extraction step at liquid-liquid extraction (LLE) was examined, as well as the extent of patulin degradation during the sodium carbonate clean-up. In addition to this alkaline clean-up, the efficiency of using an Oasis HLB or C₁₈ cartridge as solid-phase extraction (SPE) clean-up was compared. This resulted in a two-step ethyl acetate LLE, followed by an Oasis HLB SPE clean-up, without alkaline clean-up conditions. The method was fully validated for APAM, cloudy apple juice, and apple puree. Average patulin recoveries at levels of 100, 500, and 1000 μg kg^?1 of APAM varied between 95 and 113 % over 3 independent days, with an interday precision (RSD_R) of 5 to 10 %. Recovery experiments carried out with the spiked apple juice (at 50 μg kg^?1) and apple puree (10 μg kg^?1) showed average recovery rates laying between 80–101 % (RSD_R?=?12 %) and 77–100 % (RSD_R?=?9 %), respectively. This method offered a detection limit of 3–4 μg kg^?1 and a quantification limit of 5–8 μg kg^?1 for APAM, apple juice, and puree.     

Simultaneous Determination of Nine Quinolones in Food by Liquid Chromatography with Fluorescence Detection

A confirmatory analytical method for simultaneous determination of nine regulated quinolones (Council Regulation 2377/90/ECC) in six matrices of animal origin is proposed. The sample pretreatment involves double step liquid extraction with acetonitrile and purification by solid-phase extraction on Oasis HLB cartridges. The quinolones were separated by liquid chromatography on C18 Zorbax column with gradient elution program. Aqueous formic acid, methanol, and acetonitrile were used as a mobile phase. A multi-wavelength excitation/emission program was used for sensitive fluorescence detection of quinolones. The proposed sample pretreatment protocol was applied to each of the six studied matrices without any modification. The method was validated according to Commission Decision 2002/657 EC. Residues were quantified down to 15 μg kg^?1 with limits of detection and quantification ranging from 3 to 50 μg kg^?1 and from 7.5 to 100 μg kg^?1, respectively. The recoveries at the maximum residual limits (MRLs) were between 77 and 120 % with RSD values lower than 30 %. For quinolones without established MRL or maximum required performance limit, the accuracy and precision of the method were estimated at concentration levels corresponding to the lowest linear calibration point and recoveries between 70 and 130 % were achieved. Decision limits, detection capability, and linear range in eggs, milk, fish, ovine muscle, chicken muscle, and porcine kidney are also reported.     

Simple and fast spectrophotometric determination of low levels of thiabendazole residues in fruit and vegetables after pre-concentration with ionic liquid phase microextraction

There is a great importance of monitoring thiabendazole (TBZ) residues in fruits and vegetables to ensure food safety. Therefore, a new ionic liquid (IL) phase microextraction method using IL, 1-butyl-3-methylimidazoliumhexafluorophosphate [C₄mim][PF₆], as extracting solvent is proposed for simple and fast determination of low levels of TBZ in fruits and vegetables by spectrophotometry. The method is based on selective complex formation of TBZ with Cu(II) ions in presence of PF₆^– as counter ion at pH 5.5, and then microextraction of the complex into the fine micro-drops of IL phase. After optimisation of variables affecting microextraction efficiency, the analytical parameters of the method were determined by calibration curves. The method exhibits a linear relationship (0.3–280 μg L^?1), low detection limit (0.1 μg L^?1), good intra- and inter-day precision (2.4–4.5% as RSD_r%, 2.1–5.6% as RSD_R%), good recovery (≥95.1–98.2%) and high sensitivity enhancement factor (150) by solvent-based calibration curve. It allows a detection limit of 0.24 μg L^?1 and a range of 0.8–250 μg L^?1 by the matrix-matched calibration curve. After validation, the method was successfully applied to the determination of TBZ residues with method quantification limits in fruit and vegetables of 2.0 and 2.5 µg kg^?1 with and without adding polyvinylpyrrolidone (PVP-15) solution. Recoveries range from 85.5% to 98.2% after spiking (10, 50 and 100 µg kg^?1, n: 3).     

Development and Validation of a Sensitive Indirect Competitive Enzyme-Linked Immunosorbent Assay for the Screening of Florfenicol and Thiamphenicol in Edible Animal Tissue and Feed

To monitor the illegal use of florfenicol (FF) and thiamphenicol (TAP) in edible animal tissue and feed, a sensitive monoclonal antibody-based indirect competitive enzyme-linked immunosorbent assay (ic-ELISA) has been developed with simple sample preparation and cleanup. The obtained monoclonal antibody (5F4) that has isotype IgG1 showed an IC₅₀ value of 0.21 μg L^?1 for FF and 0.35 μg L^?1 for TAP, respectively. It did not exhibit measurable cross-reactivity with other antibiotics. The limits of detection (LODs) for FF and TAP in a muscle matrix ranged from 0.07 to 0.14 μg kg^?1 and in a feed matrix ranged from 2.9 to 5.2 μg kg^?1. The recoveries were 72.8 to 113.4 % with a coefficient of variation of less than 15 %. Good correlation between the ELISA and HPLC-MS/MS results in the tissues tested demonstrated the reliability of our ic-ELISA. This ELISA is a useful tool for screening FF and TAP in edible animal tissue and feed.     

Gas Purge Microsyringe Extraction Coupled with Dispersive Liquid-Liquid Microextraction for the Determination of Acidic Compounds in Food Packaging Materials

A green, simple and sensitive method was developed for the analysis of volatile carboxylic acids (VFAs) and perfluorocarboxylic acids (PFCAs) in food packaging materials. The acidic compounds in food packaging materials were first extracted by gas purge microsyringe extraction (GP–MSE) with 1.0 mL 0.1 mol·L^?1 NaOH solution, then the analytes were dispersive liquid-liquid microextracted (DLLME) by 50 μL chloroform as extraction solvent and 200 μL acetonitrile as dispersive solvent. The 2-(5-Benzoacridine) ethyl-p-toluenesulfonate (BAETS) with excellent fluorescence property was applied to enhance the high performance liquid chromatography (HPLC) sensitivity. The obtained recoveries for the VFAs ranged from 92.0 to 101 %. The method LODs calculated at a signal-to-noise ratio (S/N) of 3 were in the range of 0.80–3.40 μg·kg^?1, while the LOQs calculated at S/N of 10 were in the range of 2.5–10.2 μg·kg^?1. All compounds were in good linearity with concentration coefficients of higher than 0.997. Perfluorooctanoic acid (PFOA) was found in all of the 15 kinds of samples analyzed with concentrations ranging from 4.86–7.56 μg·kg^?1. Acetic acid, butyric acid, and caprylic acid were found in half of the samples analyzed. The other analytes were also found in more than 30 % samples with concentrations varied between 3.96 and 293 μg·kg^?1.