Determination of the Nicotine Content in Solanaceae Vegetables by Solid-Phase Extraction Coupled with Ultra High-Performance Liquid Chromatography–Tandem Mass Spectrometry

A validated method based on solid-phase extraction and ultra high-performance liquid chromatography–triple quadrupole tandem mass spectrometry, with electrospray ionization operated in the positive ion mode and multiple reaction monitoring, was developed for the determination of nicotine in Solanaceae vegetables. Sample preparation involved liquid–solid extraction, centrifugation, filtration, and solid-phase extraction. Two kinds of solid-phase extraction adsorbents, based on different retention mechanisms, were investigated. Relatively higher recoveries were obtained with a hydrophilic–lipophilic-balanced cartridge. A deuterated internal standard was used for quantification. The limit of quantification (LOQ) of nicotine in different vegetables was found to be between 0.07 and 0.5 μg/kg. The nicotine levels in the vegetable samples were above the LOQs. The method described here is thus suitable for the analysis of large sample batches, because it provides accurate quantification, high sensitivity and rapid chromatographic separation with facile preparation. The solid-phase extraction cartridges and organic solvents used in this work are easy to obtain, enabling the application of this method in most analytical laboratories.     

Direct Chiral Determination of Acephate and Its Metabolite Methamidophos in Vegetables Using QuEChERS by Gas Chromatography–Tandem Mass Spectrometry

Currently, methamidophos, the main metabolite of acephate in the plants, has been paid particular attention in the risk evaluation of acephate because of its severely accurate toxicity, but the chirality of methamidophos and acephate has not been taken into account. In this study, a chiral separation and analysis method was developed to help evaluate the risks posing to the environment and human health. The efficiency of four commercial chiral capillary columns to accomplish enantioseparation of these two pesticides was firstly evaluated, and the chromatographic condition on the chose column BGB-176 SE was optimized. An analytical method for determination and confirmation of the enantiomers in vegetables by gas chromatography–tandem mass spectrometry was then developed with the column. QuEChERS was adopted to extract and clean the residues in vegetables. The mean recovery rates of quintuplicate results in cabbage and pakchoi ranged from 71.87 to 81.45 %; the relative standard deviation was less than 8.81 %. The limits of detection of enantiomers of acephate and methamidophos were 0.008 and 0.005 mg/kg, respectively. After the application of the method to vegetables from a market, it was proved that the metabolism of acephate and methamidophos in plants should be enantioselective.     

Determination of Botanical Insecticides Residues in Fish by Liquid Chromatography�CElectrospray Tandem Mass Spectrometry

A method for determining residues of four botanical insecticides oxymatrine, matrine, rotenone, and azadirachtin in fish by liquid chromatography–electrospray tandem mass spectrometry (LC–MS/MS) is described. The extraction was achieved using acetonitrile, with the addition of sodium chloride to induce a salting out effect before using n-hexane to defat. Chromatographic separation is achieved on Phenomenex Luna C18 column in the mobile phase composition of acetonitrile and 5 mmol/L ammonium acetate buffer consisting formic acid to provide protons for LC–MS/MS analysis. Accomplishing with the matrix matched calibration curves to compensate for the matrix effect, the quantitative data showed good linear response within the concentration ranges studied. Detection is carried out using positive-ion electrospray tandem mass spectrometry. Calibrations were linear over a working range of 0.5–50 μg/L for oxymatrine, matrine, rotenone, and 2–200 μg/L for azadirachtin. The average recoveries and the relative standard deviation ranged from 88.6–95.7% and 7.58–10.2%, respectively, in spiked fish samples at concentration levels ranging from 0.5 to 10 μg/kg for oxymatrine, matrine, and rotenone and from 2 to 50 μg/kg for azadirachtin. The limits of detection for oxymatrine, matrine, rotenone, and azadirachtin were 0.29, 0.37, 0.21, and 1.4 μg/kg, respectively. The method is accurate, specific, and sensitive for the analysis of the studied botanical insecticides residues in fish samples.     

Determination of 23 Dyes in Chili Powder and Paste by High-Performance Liquid Chromatography–Electrospray Ionization Tandem Mass Spectrometry

A sensitive and comprehensive method was developed to determine 23 prohibited dyes in chili powder and paste by high-performance liquid chromatography–electrospray ionization tandem mass spectrometry. Target compounds were simultaneously extracted from chili samples with acetonitrile and purified using freezing-lipid filtration. Chromatographic separation was achieved on a Waters UPLC BEH C18 column (100× 2.1 mm, 1.7 μm) with gradient elution. Detection and quantification were performed using mass spectrometry in multiple reaction monitoring mode. The method was validated for selectivity, linearity, recovery, precision, and limit of quantification (LOQ), using spiked chili powder and paste samples. The average recoveries of analytes were 58.6–122.1%, with relative standard deviations between 1.0% and 18.9%. The LOQs ranged from 0.2 to 50 μg/kg. This method was successfully applied to chili powder and paste obtained from local markets. Chrysoidine, Rhodamine B, Orange II, and Sudan I and IV were detected in several samples.     

Application of Fast Gas Chromatography–Mass Spectrometry in Combination with the QuEChERS Method for the Determination of Pesticide Residues in Fruits and Vegetables

A fast gas chromatography–mass spectrometry method has been developed for multiresidue determination of up to 56 pesticides in fruits and vegetables in a chromatographic run time of <10 min, using a single quadrupole mass spectrometer operating in selected ion monitoring mode. The well-known acetate-buffering version of the QuEChERS method has been used for sample preparation. Programmable temperature vaporizer injection of 3 μL allowed reaching limits of detection between 0.15 and 15 μg/kg for most compounds in the sample matrices tested. The applicability of the method has been evaluated in apple, orange, carrot, and tomato. Recoveries at three fortification levels (0.01, 0.1 and 0.5 mg/kg) ranged from 70 to 120 % for most compounds, with relative standard deviations below 20 % in all cases. The developed method has been applied to fruit and vegetable samples from different Spanish provinces.     

Determination of Amoxicillin Stability in Chicken Meat by Liquid Chromatography–Tandem Mass Spectrometry

An amoxicillin stability study was performed under different pH (1, 3 and 5) and temperature (4 °C, 22 °C, 37 °C and 55 °C) conditions and for incurred samples stored at −20 °C with the goals of better understanding amoxicillin degradation and characterising its main degradation products (amoxicilloic acid and amoxicillin diketopiperazine). The analytical methodology used consisted of a simple extraction using phosphate buffer (pH 8) with sodium chloride followed by a sample clean-up using OASIS? HLB cartridges and a liquid chromatography–tandem mass spectrometric analysis. Amoxicillin was found to be greatly unstable at temperatures above 22 °C for all pH values studied, so it was recommended that biological samples should be frozen at temperatures below −70 °C until analysis of the amoxicillin residues.     

Quantitative Determination and Confirmation of Five Synthetic Glucocorticoid Residues in Milk Powder by Gel Permeation Chromatography–Liquid Chromatography–Tandem Mass Spectrometry

A new method for multi-residue determination of five synthetic glucocorticoids (betamethasone, dexamethasone, prednisone, prednisolone, and hydrocortisone) in milk powder is developed. The glucocorticoids in the samples were extracted with tert-butyl methyl ether under ultrasonication incubation, and then cleaned up through gel permeation chromatography. After C18 LC gradient elution separation using acetonitrile with 0.1% formic acid as a mobile phase, the eluents were determined by liquid chromatography–tandem mass spectrometry with multiple reaction monitoring and positive ionization modes. The effective separation for the five glucocorticoids was achieved. The limit of quantification of the method for testing five glucocorticoids in milk powder was in the range from 0.2 to 0.5 μg kg⁻¹, which was lower than the maximum residue limits established by European Union for glucocorticoids in foods. Experiments on spiked samples of milk powder showed that the mean recoveries at addition level of 1.0, 3.0, and 5.0 μg kg⁻¹ were in the range of 71.2% and 103%, and the relative standard deviation ranged from 4.7% to 16.8%. The calibration curves for these drugs between 1.0 and 100 μg l⁻¹ showed good linearity, with correlation coefficient (r) more than 0.999. The real sample test showed that this method is sensitive and accurate. It can be used for qualitative and quantitative determination of studied glucocorticoid residues in milk powder samples.     

Determination of Pydiflumetofen Residues in Some Foods of Plant and Animal Origin by QuEChERS Extraction Combined with Ultra-Performance Liquid Chromatography–Tandem Mass

A rapid and effective analytical method for determination of pydiflumetofen residues in some foods of plant and animal origin (grapes, tomatoes, wheat, pork, milk, and eggs) was developed using a modified QuEChERS (quick, easy, cheap, effective, rugged, and safe) sample preparation procedure followed by ultra-performance liquid chromatography coupled with tandem mass spectrometry (UPLC–MS/MS). Acetonitrile was served as the extraction solvent, and an octadecylsilane-dispersive solid-phase extraction (C18-dSPE) was used to cleanup the analyte, and then detected by UPLC–MS/MS. Pydiflumetofen was eluted within 3.0 min from the HSS T3 chromatography column connected to an electrospray ionization source in positive mode. The linearity of the method was excellent (R²?≥?0.992) in the pydiflumetofen concentration range of 10–1000 μg kg^?1. The recoveries of spiked pydiflumetofen (10, 100, and 1000 μg kg^?1) from the matrices were satisfactory, being between 72.0 and 110.3%, and all with relative standard deviation values of <?15.1%. The limit of quantification for pydiflumetofen was 10 μg kg^?1. This study provides a method for the routine monitoring of pydiflumetofen.     

Determination of 103 Pesticides and Their Main Metabolites in Animal Origin Food by QuEChERS and Liquid Chromatography–Tandem Mass Spectrometry

A rapid and sensitive analytical multiresidue method has been developed for the simultaneous determination of 103 pesticides (herbicides, insecticides, and fungicides) and 18 metabolites in foods of animal origin using liquid chromatography-tandem with triple quadrupole in dynamic multiple reaction monitoring (DMRM) mode. A modified quick, easy, cheap, effective, rugged, and safe (QuEChERS) sample preparation technique was established, and the efficiency of the dispersive solid-phase extraction (d-SPE) cleanup step was evaluated by comparing the effects of different d-SPE sorbent combinations (primary secondary amine (PSA) + graphitized carbon black (GCB), PSA + C18, C18, and C18 + GCB). The limits of quantification (LOQs) ranged from 1 to 10 μg/kg, and the coefficient of determination (R ²) was ≥0.995 within the calibration linearity range of 0–250 μg/L for all pesticides. The combination of C18 + GCB was validated at two spiking levels (10 and 50 μg/kg) in chicken, fish, pork, and rabbit. Satisfactory recoveries (70–119%) and RSDs ≤17% were achieved for all analytes, except for naptalam (60–69%), pyrimethanil (40–49%), and thiabendazole (62–66%) at 10 μg/kg spiking level. The validated method was successfully applied to the analysis of real samples of food of animal origin.     

Determination of Triazoles in Tea Samples Using Dispersive Solid Phase Extraction Combined with Dispersive Liquid–Liquid Microextraction Followed by Liquid Chromatography–Tandem Mass Spectrometry

In this study, dispersive solid phase extraction (DSPE) combined with dispersive liquid–liquid microextraction (DLLME) method was developed for the determination of triazole fungicide residues in tea samples. DSPE with ODS C₁₈, primary secondary amine, and florisil as sorbents was applied to clean up and minimize matrix interference from tea samples; it was followed with the enrichment of target compounds in the DLLME procedure and detection with liquid chromatography–tandem mass spectrometry (LC-MS/MS). The effects of various experimental parameters on the DSPE and DLLME procedures were studied systematically, such as the kinds and volume of sorbents, extraction and dispersive solvents, and extraction time. Under optimum conditions, the method was validated in a tea matrix. The matrix-matched calibration curves of three triazoles had good linearity in the range of 0.0125–50 μg kg^?1, and the linear regression coefficients (r) ranged from 0.9998 to 0.9999. The limits of quantification (S/N?=?10) for penconazole, tebuconazole, and triadimenfon were 4.0, 7.8, and 31.6 ng kg^?1, respectively. The intra-day and inter-day relative standard deviations varied from 3.6 to 18.6 %. Recoveries in three concentration levels were between 91 and 118 %. The obtained results show that the proposed DSPE-DLLME-LC-MS method has the potential to analyze trace fungicides in a complex sample matrix.     

Simultaneous Determination of Three Tranquillizers in Lamb Liver by Ultra-Performance Liquid Chromatography–Tandem Mass Spectrometry

Food Analytical Methods - In animal husbandry, diazepam, chlorpromazine, and promethazine are illegally used to promote growth and increase weight, thus leading to food safety problems. Here, an...     

Simple Method for Determination of Fungicides in Citrus Fruits by Liquid Chromatography–Tandem Mass Spectrometry

A simple method for the determination of four fungicides (thiabendazole, imazalil, o-phenylphenol, and diphenyl) in citrus fruits has been developed. After spiking surrogates of these fungicides, the sample was extracted with acetonitrile, salted out, and the water was simultaneously removed using anhydrous magnesium sulfate and sodium chloride. The extract was first purified with a primary secondary amine and octadecylsilane, followed by the addition of dimethyl sulfoxide as a keeper solvent, and subsequently concentrated under a nitrogen stream. The compounds were analyzed by liquid chromatography–tandem mass spectrometry using the atmospheric pressure photoionization interface. The recoveries and relative standard deviations (RSDs) of the fungicides (1 mg kg^?1) were satisfactory (recovery 92–114 %; RSD <10 %). An evaluation with Shewhart QC plots revealed that all data points are within the controlled area, thus confirming the robustness of the method for analyzing the fungicide content of citrus fruits. The sample preparation time for ten samples was approximately 2 h, highlighting the time and labor efficiency of the method.     

Determination of Selected Polychlorinated Biphenyl Residues in Meat Products by QuEChERS Method Coupled with Gas Chromatography–Mass Spectrometry

Polychlorinated biphenyl (PCB) residues in food are an important food safety concern. Simple and sensitive analytical methods are needed to monitor PCB residues and ensure that food is safe for consumption. The aim of this study was to adapt a selective, sensitive, quick, and easy sample treatment for purification of animal fat matrices and to measure the level of PCB28, PCB52, PCB101, PCB118, PCB138, PCB153, and PCB180 in samples of meat products (salami, soudjouk, and sausage) produced in Turkey. The extraction and purification of meat products were performed via the modified quick, easy, cheap, effective, rugged, and safe (QuEChERS) method and PCB levels determined by gas chromatography–mass spectrometry. The linearity was satisfactory for all compounds studied, with correlation coefficients ≥0.99. The limits of determination and the limits of quantification were in the range of 0.144–0.382 and 0.479–1.274 ng g^?1, respectively. Recovery at 3 different spiking concentrations was 95.7–101 % and the relative standard deviations were <3.5 %. This validated method was observed to be more economic and eco-friendly, as it uses a smaller volume of extraction solvents that are also less toxic. The validated method was successfully applied to the analysis of selected PCBs in meat products with satisfactory results. The method’s results indicated the presence of PCBs in some of the meat product samples, although the levels were below the maximum residue limit for food products of animal origin in Turkey (40 ng g^?1 of fat), which is in accordance with EU and Turkish levels.     

Simultaneous Determination of 15 Plant Growth Regulators in Bean Sprout and Tomato with Liquid Chromatography–Triple Quadrupole Tandem Mass Spectrometry

The present paper describes the development and validation of a new reversed-phase liquid chromatography–electrospray ionization tandem mass spectrometric method for determination of 15 plant growth regulators in bean sprout and tomato. Plant growth regulators were extracted with mixed solvents methanol/acetonitrile/water/acetic acid (v/v/v/v, 40/40/20/1) from 10 g vegetable and analyzed directly without further cleanup. The identification of each analyte was established by chromatographic retention time, analyte-specific fragmentation patterns, and relative peak area ratios of precursor/product ion pairs. The recoveries of 15 plant growth regulators in bean sprout and tomato were 70.3–110.0 %. The repeatability of this method is excellent, and relative standard deviation value is less than 10 %.     

Simultaneous Determination of Triclabendazole and its Metabolites in Bovine and Goat Fat Tissues by Liquid Chromatography–Tandem Mass Spectrometry

A sensitive and reliable method for the simultaneous determination of triclabendazole, its main metabolites (triclabendazole sulfone and triclabendazole sulfoxide) and a marker residue (ketotriclabendazole) in edible ruminant fat tissues is developed and validated. Analytes are extracted from fat tissues with acetonitrile, and crude extracts are subjected to liquid?Cliquid extraction with n-hexane. Chromatographic separation is performed on a C₁₈ reversed-phase column with gradient elution. Analytes are detected by tandem quadrupole mass spectrometry after positive electrospray ionization by multiple reaction monitoring. Relative recoveries from spiked samples range from 86.1% to 114.3%, with relative standard deviations generally below 13.8%. Limits of detection and quantification for analytes are within 0.125?C1.25???g/kg and 0.5?C5???g/kg, respectively. The method proposed in this study was successfully applied to real sample testing.     

Liquid Chromatography–Tandem Mass Spectrometry Multiclass Method for 46 Antibiotics Residues in Milk and Meat: Development and Validation

A screening method for analysis of 46 antibiotics residues, belonging to different classes, such as tetracyclines, sulfonamides, fluoroquinolones, β-lactams, cephalosporins, macrolides and other minority groups was developed and validated for application in bovine milk and bovine, swine, poultry, equine, fish and shrimp meat samples. Sample preparation consists in solvent extraction followed by clean up with C18 bulk and low temperature purification. Instrumental analysis was performed using liquid chromatography coupled to tandem mass spectrometry system. Chromatographic separation was achieved using a C18 column. Mobile phase was composed by methanol and water. The method was validated according to Commission Decision 2002/657/EC criteria. Validation parameters such as specificity and detection capability (CCβ) were determined and considered suitable to the established criteria. Values of CCβ ranged from 1.0 to 50.0 μg L^?1 or μg Kg^?1, depending on the compound and the matrix. The proposed method has been applied into Brazilian National Residue Control Plan since 2013 for the determination of antibiotic residues. A total of 3833 samples were analyzed until the current date and 13 samples showed positive results with concentrations above the permitted. The method is fast, easy and adequate for high throughput analysis in routine laboratories.     

On-line Solid-Phase Extraction Coupled to Liquid Chromatography–Ion Trap Tandem Mass Spectrometry for Determination of Penicillins in Catfish

A highly selective method was developed for the simultaneous determination of eight penicillins in catfish using automated on-line solid-phase extraction coupled to liquid chromatography–tandem mass spectrometry (XLC–MS/MS). The type of cartridge, equilibration sample volume, volume of solvent to carry the sample into the cartridge, and elution times were studied in order to optimize the XLC operating conditions. MS/MS conditions were also adjusted for better peak resolution. The present method was validated in agreement with the criteria of Commission Decision 2002/657/EC, showing a linear range from 2 to 350 μg kg⁻¹ and regression coefficient higher than 0.995 for the studied penicillins. Decision limits, calculated in the case of substances with no permitted limit, were lower than 0.6 μg kg⁻¹, and detection capability values were lower than 2.0 μg kg⁻¹. Samples spiked at 2.0, 10.0, and 50.0 μg kg⁻¹ showed high recovery (72–92%) and precision values lower than 20% except for amoxicillin. The present method was also applied for the analysis of penicillins in 30 catfish samples bought in local markets.     

Simultaneous Determination of Trimethoprim and Diaveridine in Tissues of Chicken, Porcine, and Fish by Hydrophilic Interaction Liquid Chromatography–Tandem Mass Spectrometry

A sensitive liquid chromatography–tandem mass spectrometry method for simultaneous determination of trimethoprim and diaveridine in edible tissue samples (chicken and porcine muscle; liver, kidney, and fat tissues as well as fish muscle) was developed and validated in this study. Trimethoprim, diaveridine, and the internal standard trimethoprim-D₃ were extracted from samples using acetonitrile. The Oasis MCX Solid-Phase Extraction Cartridge was selected for cleaning up the extracts. Chromatographic separation was performed on a hydrophilic interaction liquid chromatography column with gradient elution. The analytes were determined using triple–quadrupole mass spectrometry in positive electrospray ionization and multiple reaction monitoring mode. The relative recoveries from spiked samples ranged from 82.5 to 117.2 %, with the relative standard deviations generally being below 15.4 %. Limits of detection and quantification for analytes were within 0.3–1 and 1–2 μg kg^?1, respectively. The proposed method was successfully applied to detect trimethoprim and diaveridine in real samples.     

Determination of Benzalkonium Homologues and Didecyldimethylammonium in Powdered and Liquid Milk for Infants by Hydrophilic Interaction Liquid Chromatography–Mass Spectrometry

In this study, a hydrophilic interaction liquid chromatography–mass spectrometry (HILIC-MS/MS) method for the determination of benzalkonium (BAC) homologues and didecyldimethylammonium (DDAC) was developed. A satisfactory chromatographic separation of BAC homologues and DDAC was achieved using, as mobile phase, acetonitrile–aqueous 50 mM ammonium formate (pH 3.2) (93?+?7 v/v) at 0.3 mL min^?1. The elution order of BAC homologues was from benzyldimethylhexadecylammonium chloride (C₁₆-BAC) to benzyldimethyldecylammonium chloride (C₁₀-BAC), the exact opposite with respect to separation using reversed liquid chromatography. The instrumental method was successfully applied to powdered and liquid milk for infants (about 50 samples). From powdered milk samples, BAC and DDAC were extracted using 5 % formic acid in methanol for 60 min at 60 °C in an ultrasonic bath; after dilution with water and 5 % NH₄OH solution, a purification step using a weak cationic exchange column was performed. Satisfactory limit of detections (LODs) were achieved, below 1.0 μg kg^?1 and 0.05 μg L^?1 for powdered and liquid milk for infants, respectively. No sample was free of BAC homologues and DDAC, and in one powdered milk sample, the contamination level exceeded 500 μg kg^?1, the maximum level recommended by the Standing Committee on the Food Chain and Animal Health for food and feed.