Determination of selected pesticides in fruit juices by matrix solid-phase dispersion and liquid chromatography–tandem mass spectrometry

A rapid and sensitive liquid chromatography–tandem mass spectrometry method has been developed for the analysis of acephate, monocrotophos, carbendazim, acetamiprid, dimethoate, simazine, carbofuran, atrazine, diuron, DNOC (4,6-dinitro-o-cresol), malathion and tebufenozide in fruit juices. Extracts were obtained by matrix solid-phase dispersion using diatomaceous earth as dispersant and dichloromethane as eluent. Significant matrix effects observed for most of the pesticides tested were eliminated using matrix-matched standards. The quantification of the analytes was carried out using the most sensitive transition. The confirmation of residues detected in real samples was performed by repeated injection and acquiring additional transitions to that used for quantification. Recoveries were in the range 71–118%. Repeatability of the method, expressed as the relative standard deviation, was in general between 5–15%. Low limits of detection (0.01–0.94 ng ml⁻¹) and quantification (0.03–3.12 ng ml⁻¹) were readily achieved with this method for all tested pesticides.     

Confirmatory analysis of steroids in muscle using liquid chromatography–tandem mass spectrometry

A method is described for screening and confirmation of synthetic and endogenous steroids in muscle tissue. The method is sensitive, selective, and rapid and the consumption of organic solvents is low, compared to previously published methods. The procedure involves hydrolysis, defattening with heptane and final clean up with SPE using C₁₈ cartridge. After filtration, the analytes are analysed by LC/MS/MS and quantification is performed using deuterated internal standards. Decision limits (CCα) varied from 0.02 to 0.33?µg?kg^?1 and the detection capabilities (CCβ) were <0.50?µg?kg^?1. The mean within-laboratory reproducibility ranged 5–22% (%RSD_IR). Endogenous steroids (e.g. testosterone, epitestosterone and androstenedione) have been included in the method, to provide an insight into their levels, as the presence of these steroids was detected several times during analysis of imported meat.     

Rapid determination of lycopene and β-carotene in tomato by liquid chromatography/electrospray tandem mass spectrometry

BACKGROUND: The tomato fruit is a dietary source of carotenoids, bioactive antioxidant compounds that play an important role in the prevention of degenerative diseases. Several extraction and detection techniques regarding carotenoids in tomatoes can be found in the literature, mainly based on high‐performance liquid chromatography separation and ultraviolet‐visible detection. RESULTS: The best extraction conditions and tandem mass spectrometry (MS) analysis were evaluated: lycopene and β‐carotene were extracted in a cyclohexane/ethyl acetate mixture without the addition of antioxidants, next separated by liquid chromatography on a C₁₈ column and then determined through electrospray tandem MS. Ionic suppression by the matrix in negative ionisation mode did not allow the analysis of extracts, hence the positive ionisation mode was chosen. Validation parameters demonstrated the suitability for purpose of the analytical method: accuracy, precision, linearity and detection limits were adequate. The method was finally applied to different tomato samples, and differences could be easily highlighted. CONCLUSION: The method was simple, fast and appropriate for the purpose of analysing lycopene and β‐carotene in tomatoes. Copyright © 2011 Society of Chemical Industry     

Development and validation of multi-residue and multi-class method for antibacterial substances analysis in non-target feed by liquid chromatography – tandem mass spectrometry

A confirmatory HPLC-MS/MS method for the determination of residues of 11 antibacterial substances from different therapeutic class (β-lactams, lincosamides, fluoroquinolones, macrolides, pleuromutilins and sulfonamides) in animal feeds has been developed. The sample preparation is based on extraction with 0.1% formic acid in acetonitrile. Separation of the analytes was performed on biphenyl column with a gradient of 0.1% formic acid in acetonitrile and 0.1% formic acid in Milli-Q water. The developed method was validated following the guidelines included in the European Union Commission Decision 2002/657/EC. Limits of detection ranging from 79.22 to 193.60 µg/kg; instrumental and analytical linearity coefficients were above 0.99 for matrix-match calibration; and relative recoveries ranging from 76.04% to 117.39%. Repeatability of the method was in the range of 2.41–19.76% (CV, %), whereas reproducibility ranged from 6.52 to 28.40% (CV %). The method shown to be efficient and precise for quantification of the 11 antibacterial substances in animal feed. The results demonstrate the feasibility of the method for routine use to monitor these substances in feed. The validated method was successfully applied to eight suspect feed samples collected from the Association of American Feed Control Officials (AFFCO) and feed manufactures from Galicia (Spain) in June and July 2017. Of these 8 non-target feeds, 5 were positive for the presence of tiamulin, tylosin and sulfadiazine.     

Determination of trichothecenes in cereals and cereal-based products by liquid chromatography–tandem mass spectrometry

A sensitive, accurate and precise method for the simultaneous determination of nivalenol (NIV), deoxynivalenol (DON), T-2 toxin (T-2) and HT-2 toxin (HT-2) in different food matrices, including wheat, maize, barley, cereal-based infant foods, snacks, biscuits and wafers, has been developed. The method, using liquid chromatography coupled with atmospheric pressure chemical ionization triple quadrupole mass spectrometry (LC–APCI–MS/MS), allowed unambiguous identification of the selected trichothecenes at low µg per kg levels in such complex food matrices. A clean-up procedure, based on reversed phase SPE Oasis® HLB columns, was used, allowing good recoveries for all studied trichothecenes. In particular, NIV recoveries significantly improved compared to those obtained by using Mycosep® #227 columns for clean-up of the extracts. Limits of detection in the various investigated matrices ranged 2.5–4.0 µg kg^?1 for NIV, 2.8–5.3 µg kg^?1 for DON, 0.4–1.7 µg kg^?1 for HT-2 and 0.4–1.0 µg kg^?1 for T-2. Mean recovery values, obtained from cereals and cereal products spiked with NIV, DON, HT-2 and T-2 toxins at levels from 10 to 1000 µg kg^?1, ranged from 72 to 110% with mean relative standard deviation lower than 10%. A systematic investigation of matrix effects in different cereals and cereal products was also carried out by statistically comparing the slopes of standard calibration curve with matrix-matched calibration curve for each of the four toxins and the eight matrices tested. For seven of the eight matrices tested, statistically significant matrix effects were observed, indicating that, for accurate quantitative analysis, matrix-matched calibration was necessary. The method was applied to the analysis of 57 samples of ground wheat originated from South Italy and nine cereal food samples collected from retail markets.     

Simultaneous determination of 15 components in Radix Glehniae by high performance liquid chromatography–electrospray ionization tandem mass spectrometry

A novel qualitative and quantitative method using high performance liquid chromatography coupled with tandem mass spectrometry was developed for simultaneous analysis of 15 components including 10 coumarins, four phenolic acids and adenosine in Radix Glehniae, an important traditional Chinese medicine. The separation was performed on a C₁₈ column with isocratic elution consisted of 0.1% formic acid and methanol (30:70, v/v). The identification and quantification of the analytes were achieved on a hybrid quadrupole linear ion trap mass spectrometer. Multiple-reaction monitoring (MRM) scanning was employed for quantification with switching electrospray ion source polarity between positive and negative modes in a single run. Full validation of the method was carried out (linearity, precision, accuracy, limit of detection and limit of quantification). The results indicated that the method was simple, rapid, specific and reliable. And we successfully applied it to analyze 20 Radix Glehniae samples from different sources.     

Assessment of liquid chromatography–tandem mass spectrometry approaches for the analysis of ceftiofur metabolites in poultry muscle

The use of cephalosporin antibiotics in veterinary practice is likely to play an important role in the development of β-lactam-resistant bacteria. To detect off-label cephalosporin antibiotic usage, an analytical method is needed that, besides the native compound, also detects their active metabolites. In this paper, the applicability of three approaches for the quantitative analysis of ceftiofur using LC–MS/MS is assessed, viz. (A) analysis of ceftiofur, desfuroylceftiofur and/or desfuroylceftiofur cystein disulfide, (B) derivatisation of ceftiofur metabolites to desfuroylceftiofur acetamide and (C) chemical hydrolysis using ammonia, to produce a marker compound for ceftiofur. We found that approach A was not suited for quantitative analysis of total ceftiofur concentration or for effectively detecting off-label use of ceftiofur. Approach B resulted in adequate quantitative results, but was considered a single compound method because it depends on cleavage of a thioester group, which is present in only a limited number of cephalosporin antibiotics. Approach C showed adequate quantitative results but, in contrast to approach B, it is applicable to a range of cephalosporin antibiotics. Therefore, it is applicable as a broad quantitative screening of cephalosporin compounds in poultry tissue samples to indicate off-label use of cephalosporins in poultry breeding. Based on this study, it was concluded that approach C is the most suitable to detect off-label use of a range of cephalosporin antibiotics.     

Improved method for the determination of 12 non-nutritive sweeteners and monitoring in various foods using liquid chromatography–tandem mass spectrometry

An improved and highly sensitive method was developed and validated for the determination of 12 (7 permitted and 5 non-permitted in Korea) non-nutritive sweeteners in various foods using liquid chromatography-electrospray ionisation-tandem mass spectrometry. The chromatographic separation was performed on an Xbridge BEH C18 column (3 mm × 100 mm, 2.5 μm) with gradient elution using 10 mM ammonium acetate in water and 10 mM ammonium acetate in methanol. Sample preparation consisted of simple dilution, homogenisation, centrifugation and purification with a C18 cartridge prior to analysis. The relative matrix effect (%ME) was within ±20% for all sweeteners. The method also showed good linearity (R² > 0.99). The limit of detection and limit of quantification values in sample were in the range of 0.02–2.66 and 0.06–8.05 mg kg^?1, respectively. The recoveries at three concentration levels ranged between 80% and 119%, with relative standard deviation values below 10%. In addition, the expanded uncertainties determined for 12 sweeteners in 5 different food matrices were confirmed to be <14%. Finally, the method was successfully applied to the analysis of sweeteners in 681 food samples purchased in Korea, Australia and Turkey. These results demonstrate that the method is suitable for the simultaneous determination of multiple-sweeteners in a variety of foods.     

Determination of tetracyclines in multi-specie animal tissues by pressurized liquid extraction and liquid chromatography–tandem mass spectrometry

A specific, sensitive and robust pressurized liquid extraction (PLE) and liquid chromatography tandem mass spectrometry (LC–MS/MS) method for determining tetracycline, chlortetracycline, oxytetracycline and doxycycline in bovine, swine, poultry and lamb muscle tissues is presented. PLE was performed using an ASE^® 200 from Dionex and water as extractant, followed by solid-phase extraction (SPE) using an Oasis HLB cartridge. The method was validated for beef, chicken, pork and lamb meat in compliance with the requirements set by Commission Decision, 2002/657/EC [Commission Decision 2002/657/EC (2002). Implementing Council Directive 96/23/EC concerning the performance of analytical methods and interpretation of results. Official Journal of European Communities, L239, 66–98. (Available at: <http://europe.eu.int>)]. The average recoveries of the different meat samples, spiked with the four tetracyclines at three levels (1, 100 and 200 μg kg⁻¹ of each tetracycline), were always higher than 89% with intraday and interday precision lower than 15% and 17%, respectively. A good linearity was established for the four tetracyclines in the range from 5 to 10,000 μg kg⁻¹ with r > 0.995. The limits of quantification (LOQs) were between 0.5 and 1 μg kg⁻¹, which are well below the tolerance levels set by the European Union. The decision limit (CCα) and the decision capability (CCβ) were in the range 101–116 and 112–130 μg kg⁻¹, respectively. Compared with previous methods, sample preparation time required for the analysis and LOQs, are reduced. The method demonstrated its successful application for the analysis of 100 meat samples. Two samples of beef and one sample of chicken out of 25 of each type tested positive while none of 25 samples of either, lamb or pork, tested positive.     

Optimization of a solid phase extraction and hydrophilic interaction liquid chromatography–tandem mass spectrometry method for the determination of metformin in dietary supplements and herbal medicines

Metformin is one of the most common adulterants found in anti-diabetic dietary supplements and herbal medicines. An analytical method based on hydrophilic interaction chromatography (HILIC)/tandem mass spectrometry was developed and validated for the determination of metformin in dietary supplements and herbal medicines. Sample preparation involved solid phase extraction of the analyte using Plexa PCX cartridges, and cleanup by a primary–secondary amine (PSA) adsorbent for minimization of the matrix effect. Chromatographic separation was performed on a HILIC column using a mixture of 0.025 mol/L ammonium formate (pH 3) and acetonitrile (18:82, v/v) as the mobile phase at flow rate of 0.25 mL/min. The method was validated in four matrices (capsules, honeyed pills, tablets and oral solutions). The method had a good linear range (5–500 ng/mL), and the overall precision and accuracy ranged from 2.2% to 9.9% and 4.6% to 11.3%, respectively.     

Naturally-occurring folates in foods: Method development and analysis using liquid chromatography–tandem mass spectrometry (LC–MS/MS)

An accurate method for detecting and quantifying both synthetic (folic acid) and naturally-occurring folates in foods is described. A system capable of analysing the five most commonly occurring folates (pteroylglutamic acid, 5-methyltetrahydrofolate, tetrahydrofolate, 10-formylfolate and 5-formyltetrahydrofolate) in 20 min using liquid chromatography–tandem mass spectrometry (LC–MS/MS) was developed. Quantification of folates was performed using ¹³C labelled internal standards. This paper outlines the development of a comparatively fast LC–MS/MS method, method validation using commercially available folate standards and establishment of the method’s suitability for quantification using selected reaction monitoring (SRM) mass spectrometry. The application of the system was verified by analysing several certified reference materials and comparing results with certified values as determined by microbiological assay. LC–MS/MS promises to be an ideal tool for the quantitative analysis of folates in food.     

Analysis of pesticide residues in seaweeds using matrix solid-phase dispersion and gas chromatography–mass spectrometry detection

Products containing organophosphates, carbamates and pyrethroids pesticides, employed as chemotherapeutants in aquaculture, can remain as residues in the marine environment. Matrix solid-phase dispersion (MSPD) was developed to extract seventeen pesticides from seaweed samples using Florisil and graphitized carbon black as clean-up adsorbents prior to gas chromatography–mass spectrometry (GC–MS) determination. The extraction has been optimised by a Box–Behnken design. The optimal conditions were 1 g of seaweed sample, 4 g of anhydrous sodium sulphate as dispersant, 3.6 g of Florisil and 0.4 g of GCB and an elution volume of 14 mL of a hexane:ethyl acetate mixture containing 40% ethyl acetate. The recoveries ranged from 81.6% to 113.2% with relative standard deviations (RSDs) ranging from 1.6% to 13.2%. The limits of detection (LOD) ranged from 0.5 to 2.9 ngg⁻¹. Internal quality control was successfully carried out to verify the quality of the data obtained in the analysis of these pesticides in seaweed samples.     

Assessment of strobilurin fungicides’ content in soya-based drinks by liquid micro-extraction and liquid chromatography with tandem mass spectrometry

Seven strobilurin fungicides were pre-concentrated from soya-based drinks using dispersive liquid–liquid micro-extraction (DLLME) with a prior protein precipitation step in acid medium. The enriched phase was analysed by liquid chromatography (LC) with dual detection, using diode array detection (DAD) and electrospray-ion trap tandem mass spectrometry (ESI-IT-MS/MS). After selecting 1-undecanol and methanol as the extractant and disperser solvents, respectively, for DLLME, the Taguchi experimental method, an orthogonal array design, was applied to select the optimal solvent volumes and salt concentration in the aqueous phase. The matrix effect was evaluated and quantification was carried out using external aqueous calibration for DAD and matrix-matched calibration method for MS/MS. Detection limits in the 4–130 and 0.8–4.5 ng g^?1 ranges were obtained for DAD and MS/MS, respectively. The DLLME-LC-DAD-MS method was applied to the analysis of 10 different samples, none of which was found to contain residues of the studied fungicides.     

Multiclass method for fast determination of veterinary drug residues in baby food by ultra-high-performance liquid chromatography–tandem mass spectrometry

A simple and rapid multiresidue method for the determination of different veterinary drug residues in meat-based baby food (MBF) and powdered milk-based infant formulae (PMIF) has been developed. The method involves an extraction procedure based on buffered QuEChERS (quick, easy, cheap, effective, rugged and safe) methodology, without any further clean-up step, followed by ultra-high performance liquid chromatography coupled to tandem mass spectrometry (UHPLC-MS/MS). The method has been validated in two baby food matrices (MBF and PMIF) at three different concentration levels, obtaining suitable recoveries and precision (inter and intra-day precision) values. Quantification was carried out using matrix-matched standard calibration. Furthermore, the decision limit (CCα) and the decision capability (CCβ) were evaluated, ranging from 0.5 to 16.2 μg/kg and from 1.2 to 22.4 μg/kg, respectively. Finally, the method was applied to the analysis of several kinds of baby food samples and traces of some veterinary drugs were detected.     

Identification of the antidiarrhoeal components in official rhubarb using liquid chromatography–tandem mass spectrometry

Though the purgative components in official rhubarb are well documented as anthraquinone glycosides and sennosides, the antidiarrhoeal effect and its chemical basis have not been reported before. In this study, liquid chromatography coupled with electrospray ionisation tandem mass spectrometry was used to investigate the main chemicals in the antidiarrhoeal fraction previously isolated from Rheum palmatum L. In total 10 compounds were identified in the fraction as follows: gallic acid, galloyl glucose, di-O-galloyl-glucose, glucopyranosyl-galloyl-glucose, coumaroyl-O-galloyl-glucose, trimer of catechin, catechin gallate, catechin-glucopyranoside, carboxyl-chrysophanol-O-glucose and emodin-O-glucose. The predominant components identified in the fraction were rhubarb tannins, except for two anthraquinone glycosides of low contents. The polyphenolic analysis also showed the occurrence of abundant tannins. So, the antidiarrhoeal basis of rhubarb was primarily proposed as tannin-related compounds.     

Multi-residual analysis of 16 β-agonists in pig liver,kidney and muscle by ultra performance liquid chromatography tandem mass spectrometry

A delicate method was developed for simultaneous analysis of 16 illegal residual β-agonists in pork tissues including liver, kidney and meat. The samples were subjected to enzymatic hydrolysis, extracted with perchloric acid, and then dual Oasis HLB and MCX solid phase extraction (SPE) cartridges were used for cleanup. The analytes were quantified by ultra performance liquid chromatography coupled with electrospray ionisation tandem mass spectrometry (UPLC–ESI–MS/MS) operating in positive multiple-reaction mode (MRM). Matrix-fortified calibration curves were performed to compensate for the matrix effect and loss in sample preparation. CCα and CCβ of the analytes upon the method ranged from 0.02 to 0.79 μg/kg and from 0.04 to 1.62 μg/kg, respectively.     

Quantitative analysis of glycoconjugate precursors of guaiacol in smoke-affected grapes using liquid chromatography–tandem mass spectrometry based stable isotope dilution analysis

Guaiacol has been shown to accumulate in glycoconjugate forms in the fruit and leaves of grapevines following vineyard exposure to bushfire smoke. To investigate the glycosylation of guaiacol in smoke-affected grapes, a quantitative stable isotope dilution analysis method using liquid chromatography-tandem mass spectrometry was developed and validated, using the [²H₄]-labelled analogue of guaiacol β-d-glucopyranoside as internal standard. The method was subsequently applied to the analysis of grapes sampled from grapevines exposed to either bushfire or experimental smoke, enabling compositional comparisons of guaiacol glycoconjugates in smoke-affected grapes from different varieties to be determined, for the first time.     

Determination of Gibberellin A3 residue in fruit samples by liquid chromatography–tandem mass spectrometry

A fast, simple, low cost, and high throughput method has been developed for the determination of Gibberellin A3 residue in fruit samples (apple, orange, peach, pear and grape). Analysis is performed by LC–MS/MS operated in the multiple reaction monitoring (MRM) mode, acquiring two specific precursor-product ion transitions per target compound. The method has been validated showing good linearity and selectivity. Limits of quantification (LOQs) were 10 μg kg⁻¹ for apple, orange, peach, pear and grape samples. The average recoveries, measured at three concentration levels (10, 20 and 200 μg kg⁻¹) were in the range 77.8–96.2% for the compound tested with relative standard deviations below 13.7%. The proposed method is rapid, simple and could be utilised for the routine analysis of Gibberellin A3 in fruit samples.     

Interference-free determination of illegal dyes in sauces and condiments by matrix solid phase dispersion (MSPD) and liquid chromatography (HPLC–DAD)

A fast, simple and effective extraction method based on matrix solid phase dispersion (MSPD) was developed and validated for the simultaneous cleaning-up and quantitative extraction of illegal dyes (sudan I, sudan II, sudan III and sudan IV) from different sauces and condiments. Several parameters as sorbent, cleaning procedure to eliminate carothenoids and other interferences, and solvents for elution were evaluated to find the optimal MSPD conditions. The best results were obtained using a system containing washed sea sand and Florisil as sorbents and sodium sulphate as desiccant; hexane was used as defatted agent and acetonitrile as elution solvent. Quantitative analyses were performed by liquid chromatography (LC) with diode array detection (DAD). The chromatographic separation was performed on a Phenomenex Synergy Polar RP column with isocratic elution using methanol/acetonitrile/water 65/20/15, v/v/v, as the mobile phase at a flow rate of 1.0 mL min⁻¹ and 30 °C of temperature. Under these conditions sudan I–IV recoveries were between 60% and 99% and relative standard deviations ranging from 2.0% to 10.0%. Limits of detection resulted five times lower than the values required by European regulations and were ranged between 0.05 and 0.09 μg g⁻¹. The applicability of this MSPD–DAD method to determine illegal sudan dyes in sauce and condiment samples was demonstrated. This method has potential to be applied using a simple instrumentation present in most analytical laboratories.