Multiresidue determination of fluoroquinolones in poultry muscle and kidney according to the regulation 2002/657/EC. A systematic comparison of two different approaches: Liquid chromatography coupled to high-resolution mass spectrometry or tandem mass spectrometry

Quantitative monitoring ofloxacin in beef by TLC-SERS combined with machine learning analysis

Ofloxacin is one kind of quinolone antibiotic drugs, the abuse of ofloxacin in livestock and aquaculture may bring bacterial resistance and healthy problem of people. The illegally feeding cattle with ofloxacin will help it keep health, but the sedimentation of ofloxacin could bring problem in food safety. The accurate, simple and instant monitoring ofloxacin from beef by portable sensor was of vital issue in food quality. A simple and reliable method was proposed for instant and quantitative detecting ofloxacin in beef, in which the thin-layer chromatography (TLC) -surface-enhanced Raman scattering (SERS) spectroscopy was in tandem with machine learning analysis base one principal component analysis-back propagation neural network (PCA-BPNN). The TLC plate was composed with diatomite, that was function as the stationary phase to separate ofloxacin from beef. The real beef juice was directly casted onto the diatomite plate for separating and detecting. The directly monitor ofloxacin from beef was achieved and the sensitivity down to 0.01 ppm. The PCA-BPNN was used as reliable model for quantitative predict the concentration of ofloxacin, that shown superior accuracy compared with the traditional model. The results verify that the diatomite plate TLC-SERS combined with machine-learning analysis is an effective, simple and accurate technique for detecting and quantifying antibiotic drug in meat stuff to improve the food safety.

Simultaneous Determination of Multiple Contaminants in Chicken Liver Using Dispersive Liquid-Liquid Microextraction (DLLME) Detected by LC-HRMS/MS

Simultaneous determination of a mixture of food contaminants, including pesticides, sulphonamides, fluoroquinolones, anthelmintics, and aflatoxin B1, in solid biological samples (chicken liver) by dispersive liquid-liquid microextraction/liquid chromatography-high resolution mass spectrometry (DLLME/LC-HRMS) is presented. Previous work focused on the application of DLLME to single-class contaminants. In this work, the DLLME extraction method has been extended to complex multiresidues in the biological matrix. The first part of this study was the selection of an appropriate solvent that enabled the dissolution of analytes from the chicken livers. The matrix-matched calibration curves showed good linearity in the range 0.5-50.0 µg kg^-1 for aflatoxin B1 and 50-500 µg kg^-1 for pesticides, fluoroquinolones, sulphonamides, and anthelmintics, with a coefficient of determination (R²) values of 0.9916-0.9967. The mean recoveries were in the range of 80.4-96.3%, and the relative standard deviation (RSD) values were in the range of 1.53-8.98%. The limit of detection (LOD) and the limit of quantification (LOQ) values were 0.03 µg kg^-1 and 0.09 µg kg^-1, respectively, for aflatoxin B1, and for pesticides, fluoroquinolones, sulphonamides, and anthelmintics, they were in the range of 0.011-1.197 µg kg^-1 and 0.150-2.579 µg kg^-1, respectively. The developed method was compared with the standard solid phase extraction (SPE) method, and there was no significant difference between the two methods.

Development and Validation of a Method for Determination of 43 Antimicrobial Drugs in Western-Style Pork Products by UPLC-MS/MS with the Aid of Experimental Design

Western-style pork products have attracted many modern urban consumers, and these products have rapidly entered the Chinese market. The current hazard analysis of processed meat products mainly focuses on processing hazards (PAHs, microorganisms, and food additives), with less attention to veterinary drug residues. According to the survey results, the residues of antimicrobial drugs (sulfonamides and quinolones) in pork and its products in China are a severe problem, which may cause metabolic reactions, toxic effects, or enhance drug resistance. This study applied a modified QuEChERS method combined with ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MSMS) to develop a rapid and sensitive method for determining antimicrobial drugs in bacon and ham was successfully evaluated methodologically by EU 2002/657/EC. This study used a three-level, three-factor Box-Behnken design (BBD) to optimize the QuEChERS method by response surface methodology. The excellent linearity of the calibration curve was shown in the corresponding concentration range with a coefficient of determination greater than 0.99. The values of decision limit (CCα) and detection capability (CCβ) were in the range of 10.9-31.3 μg/kg and 11.8-52.5 μg/kg, respectively. The method successfully detected two trace levels of antimicrobial drugs in commercially available samples, including sulfadiazine and moxifloxacin.

Detection and Degradation Characterization of 16 Quinolones in Soybean Sprouts by Ultra-High Performance Liquid Chromatography-Tandem Mass Spectrometry

Recently, there have been increasing safety concerns about the illegal abuse of quinolone in soybean sprouts. This study aimed to establish an ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method for the simultaneous detection of 16 quinolones (QNs) in soybean sprouts, and then reveal their degradation characteristics. The samples were extracted with acetonitrile (with 1% formic acid), purified by a C18 adsorbent, and separated by an ACQUITY UPLC BEH C18 (1.7 μm, 2.1 mm × 100 mm) column. The internal standard method was applied for quantitative determination. The results demonstrated that the quantification linear range for 16 QNs was between 2.0 ng/mL and 50.0 ng/mL. The detection limits were between 0.5 μg/kg and 4.0 μg/kg, and the quantification limits were between 2.0 μg/kg and 20.0 μg/kg. This method was used to screen for quinolones in 50 batches of market soybean sprouts; the obtained results showed good agreement with those of the standard method. It was found that QNs possessed longer degradation half-life (T_1/2) in the storage stage of soybean sprouts, while they degraded to some extent during the germination stage via active enzyme action. In particular, ciprofloxacin was the most stable QNs with a T_1/2 of 70.71 d during the storage stage of soybean sprouts. This work not only offers an accurate and efficient QNs residual analysis strategy but also provides a reference for the supervision and management of QNs in foods.

Pretreatment Methods for the Determination of Antibiotics Residues in Food Samples and Detected by Liquid Chromatography Coupled with Mass Spectrometry Detectors: A Review

With the increasing use of antibiotics worldwide, antibiotic monitoring has become a topic of concern. After metabolizing of antibiotics in animals, the metabolites enter the environment through excreta or ingested by the human body via food chain that may exacerbate the emergence of antibiotic resistance and then threaten human's life. This article summarized several analytical methods used for the determination of antibiotics in recent 10 years. Due to the complex matrices and low concentration level of antibiotics in the food samples, a reliable analysis method is required to maximize the recovery rate. Several techniques like solid phase extraction (SPE), dispersive liquid-liquid microextraction (DLLME) and QuEChERS have been frequently used in the pretreatment process for analytes extraction and concentration. After the pretreatment, ultra-high performance liquid chromatography combined with mass spectrometry has been a reliable method for quantitative analysis and is able to determine multiple antibiotics simultaneously. This review also gives an overview about analytical conditions for antibiotics residues in different food samples and their method validation parameters.

A sensitive aptasensor based on rolling circle amplification and G-rich ssDNA/terbium (III) luminescence enhancement for ofloxacin detection in food

As the light-harvesting "antenna", G-rich oligonucleotides (such as the G-quadruplex) can interact with lanthanide (III) to bring a luminescent enhancement response. In this study, phenomenon of luminescent enhancement of G-triplex/terbium (III) (G3/Tb³⁺) and interaction between G3 and Tb³⁺ were first reported and characterized. Based on G3/Tb³⁺ luminescence, a label-free aptasensor for the detection of ofloxacin (OFL) residues in the food was developed. The OFL triggered the action of rolling circle amplification (RCA) allowed for the amplification product of G3-forming sequences in the single-stranded DNA, which promoted the conformational transition of the G3/Tb³⁺ complexes once the addition of Tb³⁺. Under the optimal conditions, the logarithmic correlation between the G3/Tb³⁺ luminescence intensity and the concentration of OFL was found to be linear in the range of 5-1000 pmol L^-1 (R² = 0.9949). The limit of detection was 0.18 pmol L^-1 (3σ/slope). Additionally, the good recoveries of 90.19-108.89 % and the relative standard deviations values of 0.59-5.87 % were obtained in the application of the aptasensor detecting OFL in the practical samples. These results confirmed that the present aptasensor has a good analytical performance and bright prospect for detecting ofloxacin residues in food.

Multi-templates surface molecularly imprinted polymer for simultaneous and rapid determination of sulfonamides and quinolones in water: effect of carbon-carbon double bond

In this work, the effect of a carrier modified with a carbon-carbon double bond (C=C) on preparing multi-templates surface molecularly imprinted polymer MIP (C=C@MIP) for simultaneous detection of sulfonamides and quinolones was investigated. The results showed that the adsorption capacities of the C=C@MIP were obviously higher than those of MIP, which is the carrier without modified C=C, suggesting that C=C played a key role in preparing MIP with higher adsorption capacities. Then, C=C@MIP was used as adsorbents for solid-phase extraction (SPE) and coupled with high-performance liquid chromatography (HPLC) for the simultaneous determination of sulfonamides and quinolones in water. The method showed excellent applicability, with the adsorption capacities of 19.92, 16.38, 12.92, 18.37, 14.49, 12.01, 16.98, 23.33, and 14.29 mg/g for SDZ, STZ, SMZ, SMX, SDM, ENRO, OFL, LOME, and GATI, respectively. The spiked recoveries and relative standard deviations (RSDs) of sulfonamides and quinolones using C=C@MIP were 81.59-100.7 % and 3.75-7.37 %, respectively. The limits of detection (LODs) for SDZ, STZ, SMZ, SMX, SDM, ENRO, OFL, LOME, and GATI were 0.013, 0.012, 0.012, 0.013, 0.014, 0.012, 0.013, 0.015, and 0.015 μg/L, respectively.

Trace Analysis of Multiclass Antibiotics in Food Products by Liquid Chromatography-Tandem Mass Spectrometry: Method Development

It is commonly known that the widespread use of antibiotics has led to their existence in food products as residues and ingestion of these food products may create a selection pressure on bacteria inhabiting the human body. In this study, an optimized method for the analysis of antibiotic residues in different food groups, including cereals, meat, eggs, milk, vegetables, and fruits, was developed using solvent extraction, solid-phase extraction cleanup, and liquid chromatography-mass spectrometry (LC-MS/MS). The limits of detection (LODs) were achieved as 0.007-1.1, 0.008-0.46, 0.002-0.67, 0.007-0.63, 0.001-0.098, and 0.005-0.26 ng/g in ng/g in cereals, meat, eggs, milk, vegetables, and fruits, respectively. The overall average recoveries at three spiking levels of the 81 antibiotics (5, 25, and 50 ng/g dry weight) were 82 ± 26, 77 ± 26, 70 ± 34, 69 ± 31, 73 ± 29, and 62 ± 37% in cereals, meat, eggs, milk, vegetables, and fruits, respectively. The method was then applied to the analysis of the targets in the collected wheat flour, mutton, chicken egg, boxed milk, cabbage, and banana samples, with the total concentration of the antibiotics detected being 4.4, 2.3, 36, 5.5, 2.7, and 14 ng/g, respectively. This work suggests that the developed method provides a time- and cost-effective method to identify and quantify antibiotic residues in common food products.

High-resolution mass spectrometry for bioanalytical applications: Is this the new gold standard?

Liquid chromatography coupled to quadrupole-based tandem mass spectrometry (QqQ) is termed the "gold standard" for bioanalytical applications because of its unpreceded selectivity, sensitivity, and the ruggedness of the technology. More recently, however, high-resolution mass spectrometry (HRMS) has become increasingly popular for bioanalytical applications. Nonetheless, this technique is still viewed, either as a screening technology or as a research tool. Although HRMS is actively discussed during scientific conferences, it is yet to be widely utilised in routine laboratory settings and there remains a reluctance to use HRMS for quantitative measurements in regulated environments. This paper does not aim to comprehensively describe the potential of the latest HRMS technology, but rather, it focuses on what results can be obtained and outlines the author's experiences over a period of many years of the routine application of various forms of HRMS instrumentation. Fifteen years ago, some nine different QqQ methods were used in the author's laboratory to analyse a variety of different veterinary drug resides. Today, many more analytes are quantified by seven HRMS methods and just three QqQ methods remain in use for the analysis of a small set of compounds yet to be upgraded to HRMS analysis. This continual upgrading and migration of analytical methods were accompanied by regularly participating in laboratory proficiency tests (PTs). The PT reports (covering a range of analytes and analytical methods) were used to compare the accuracy of HRMS- versus QqQ-based measurements. In the second part of this paper, the particular strengths and limitations of HRMS for both method development and routine measurements are critically discussed. This also includes some anecdotal experiences encountered when replacing QqQ assays with HRMS methods.

Multi-templates surface molecularly imprinted polymer for rapid separation and analysis of quinolones in water

Rapid separation and analysis of trace quinolones (fleroxacin (FLRX), enoxacin (EN), norfloxacin (NOR), ciprofloxacin (CIP), enrofloxacin (ENRO), and lomefloxacin hydrochloride (LOME)) in real water samples were achieved by using a multi-templates molecularly imprinted polymer (MIP) based solid phase extraction (SPE) coupled with dispersive liquid-liquid microextraction (DLLME) followed by high performance liquid chromatography (HPLC). The MIP was prepared via surface molecular imprinting, using the selected quinolones as the templates and mesoporous silica modified magnetic graphene oxide as the carrier. The preparation and adsorption conditions were optimized. The MIP presented high adsorption capacity and wonderful selective recognition for the quinolones, with the adsorption capacities of 20.15, 20.88, 18.01, 20.01, 16.98, and 17.09 mg/g for FLRX, EN, NOR, CIP, ENRO, and LOME, respectively. Meanwhile, a SPE-DLLME-HPLC method for trace detection of FLRX, EN, NOR, CIP, ENRO, and LOME in real water samples was developed and showed outstanding applicability. The spiked recoveries and relative standard deviations (RSDs) were 89.67-100.5%, and 3.59-7.12%, respectively.

Laser irradiation desorption of microcystins from protein complex in fish tissue and liquid chromatography-tandem mass spectrometry analysis

Microcystins are a group of cyanotoxins which interact with the C-terminal region of PP1 and PP2A proteins, so denaturation and inactivation are necessary for breaking covalent binding to release microcystins. In this study, a novel extraction method was developed by laser irradiation desorption of microcystins from fish protein. The sample was mixed with aqueous methanol and irradiated by a 450 nm laser, with an optimized value of laser power density at 8 W and exposure time at 5 min. ThenLC-MS/MS was applied for the determination of microcystins in fish extracts. The ionization behaviors of microcystins were investigated firstly, and doubly charged microcystins were selected as precursor ions in multiple reaction monitoring scan for quantification. This proposed quantitative method was well validated in terms of selectivity, linearity, sensitivity, accuracy, recovery, and stability. The successful application of this LC-MS/MS method showed its ability for the analysis of microcystins in low concentration, and it would be of significant interest for environmental and food safety applications to ensure the safety of fish and related products.

Bright Yellow Fluorescent Carbon Dots as a Multifunctional Sensing Platform for the Label-Free Detection of Fluoroquinolones and Histidine

Owing to their diverse properties, fluorescent carbon dots (CDs) have attracted more attention and present enormous potential in development of sensors, bioimaging, drug delivery, microfluidics, photodynamic therapy, light emitting diode, and so forth. Herein, a multifunctional sensing platform based on bright yellow fluorescent CDs (Y-CDs) was designed for the label-free detection of fluoroquinolones (FQs) and histidine (His). The Y-CDs with superior optical and biological merits including high chemical stability, good biocompatibility, and low cytotoxicity were simply synthesized via one-step hydrothermal treatment of o-phenylenediamine ( o-PD) and 4-aminobutyric acid (GABA). The Y-CDs can be utilized to directly monitor the amount of FQs based on fluorescence static quenching owing to the specific interaction between FQs and Y-CDs. Then, the fluorescence of this system can be effectively recovered upon addition of His. The multifunctional sensing platform exhibited high sensitivity and selectivity toward three kinds of FQs and His with low detection limits of 17-67 and 35 nM, respectively. Benefiting from these outstanding characters, the Y-CDs were successfully employed for trace detection of FQs in real samples such as antibiotic tablets and milk products. Furthermore, the probe was also extended to cellular imaging. All of the above prove that this multifunctional sensing platform presents great prospect in multiple applications such as biosensing, biomedicine, disease diagnosis, and environmental monitoring.

Freeze-thaw approach: A practical sample preparation strategy for residue analysis of multi-class veterinary drugs in chicken muscle

Seven drugs from different classes, namely, fluoroquinolones (enrofloxacin, ciprofloxacin, sarafloxacin), sulfonamides (sulfadimidine, sulfamonomethoxine), and macrolides (tilmicosin, tylosin), were used as test compounds in chickens by oral administration, a simple extraction step after cryogenic freezing might allow the effective extraction of multi-class veterinary drug residues from minced chicken muscles by mix vortexing. On basis of the optimized freeze-thaw approach, a convenient, selective, and reproducible liquid chromatography with tandem mass spectrometry method was developed. At three spiking levels in blank chicken and medicated chicken muscles, average recoveries of the analytes were in the range of 71-106 and 63-119%, respectively. All the relative standard deviations were <20%. The limits of quantification of analytes were 0.2-5.0 ng/g. Regardless of the chicken levels, there were no significant differences (P > 0.05) in the average contents of almost any of the analytes in medicated chickens between this method and specific methods in the literature for the determination of specific analytes. Finally, the developed method was successfully extended to the monitoring of residues of 55 common veterinary drugs in food animal muscles.

Characterization of chiral amino acids from different milk origins using ultra-performance liquid chromatography coupled to ion-mobility mass spectrometry

Milk contains free amino acids (AAs) that play essential roles in maintaining the growth and health of infants, and D-AA isomers are increasingly being recognized as important signalling molecules. However, there are no studies of the different characteristics of chiral AA (C-AA) from different milk origins. Here, UPLC coupled to ion-mobility high-resolution MS (IM-HRMS) was employed to characterize 18 pairs of C-AAs in human, cow, yak, buffalo, goat, and camel milk. The results proved that milk origins can be differentiated based on the D- to L- AA ratio-based projection scores by principal component analysis. The present study gives a deeper understanding of the D- to L- AA ratio underlying the biological functions of different animal milks, and provide a new strategy for the study of AA metabolic pathways.

Validation approach for a fast and simple targeted screening method for 75 antibiotics in meat and aquaculture products using LC-MS/MS

An approach is described to validate a fast and simple targeted screening method for antibiotic analysis in meat and aquaculture products by LC-MS/MS. The strategy of validation was applied for a panel of 75 antibiotics belonging to different families, i.e., penicillins, cephalosporins, sulfonamides, macrolides, quinolones and phenicols. The samples were extracted once with acetonitrile, concentrated by evaporation and injected into the LC-MS/MS system. The approach chosen for the validation was based on the Community Reference Laboratory (CRL) guidelines for the validation of screening qualitative methods. The aim of the validation was to prove sufficient sensitivity of the method to detect all the targeted antibiotics at the level of interest, generally the maximum residue limit (MRL). A robustness study was also performed to test the influence of different factors. The validation showed that the method is valid to detect and identify 73 antibiotics of the 75 antibiotics studied in meat and aquaculture products at the validation levels.

Optimizing Mass Spectrometry Analyses: A Tailored Review on the Utility of Design of Experiments

Mass spectrometry (MS) has emerged as a tool that can analyze nearly all classes of molecules, with its scope rapidly expanding in the areas of post-translational modifications, MS instrumentation, and many others. Yet integration of novel analyte preparatory and purification methods with existing or novel mass spectrometers can introduce new challenges for MS sensitivity. The mechanisms that govern detection by MS are particularly complex and interdependent, including ionization efficiency, ion suppression, and transmission. Performance of both off-line and MS methods can be optimized separately or, when appropriate, simultaneously through statistical designs, broadly referred to as "design of experiments" (DOE). The following review provides a tutorial-like guide into the selection of DOE for MS experiments, the practices for modeling and optimization of response variables, and the available software tools that support DOE implementation in any laboratory. This review comes 3 years after the latest DOE review (Hibbert DB, 2012), which provided a comprehensive overview on the types of designs available and their statistical construction. Since that time, new classes of DOE, such as the definitive screening design, have emerged and new calls have been made for mass spectrometrists to adopt the practice. Rather than exhaustively cover all possible designs, we have highlighted the three most practical DOE classes available to mass spectrometrists. This review further differentiates itself by providing expert recommendations for experimental setup and defining DOE entirely in the context of three case-studies that highlight the utility of different designs to achieve different goals. A step-by-step tutorial is also provided.

Quantitative performance of online SPE-LC coupled to Q-Exactive for the analysis of sofosbuvir in human plasma

A quantitative strategy towards the detection of sofosbuvir in human plasma was developed with online-SPE-LC-HRMS using t-MS², t-SIM and F-SIM modes.