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.     

Simultaneous determination of bisphenol A,octylphenol, and nonylphenol by pressurised liquid extraction and liquid chromatography–tandem mass spectrometry in powdered milk and infant formulas

A new analytical method, using pressurised liquid extraction (PLE) and liquid chromatography–tandem mass spectrometry (LC–MS/MS), was developed for the simultaneous determination of bisphenol A (BPA), octylphenol (OP) and nonylphenol (NP) in powdered infant formulas (IF) and powdered skimmed milk (PM). The analytes were extracted by PLE, using this optimised conditions: ethyl acetate as solvent, 70 °C of temperature, reversed-phase silica C₁₈ as dispersing agent and three cycles of extraction. The extracts were then injected in LC–MS/MS using a Gemini C₁₈ column and a mixture of 5% water and 95% methanol/acetonitrile, both with 0.1% ammonia, as a mobile phase. Recoveries at different fortification levels (0.5 and 0.05 mg kg⁻¹), were between 89% and 92% for BPA, 84 and 98% for OP, and 93% and 101% for NP. The method was applied to the analysis of samples of PM and IF, bought in Italian and Spanish markets. In positive samples, phenols concentration ranged from 0.07 to 1.29 mg kg⁻¹ for BPA, from 0.028 to 1.55 mg kg⁻¹ for OP and from 0.026 to 1.47 mg kg⁻¹ for NP.     

Simultaneous determination of kasugamycin and validamycin-A residues in cereals by consecutive solid-phase extraction combined with liquid chromatography–tandem mass spectrometry

Two polar aminoglycosides, kasugamycin and validamycin-A, were determined in cereals (brown rice, wheat and corn) by high-performance liquid chromatography–tandem mass spectrometry. The analytes were extracted from samples using methanol and water (70:30, v/v) at pH 5.5, purified using both a hydrophilic–hydrophobic-balanced cartridge and a strong cation-exchange cartridge, and then analysed using multiple reaction monitoring in positive electrospray ionisation mode with a special ReproSil 100 C₁₈ high-performance liquid chromatography column. This newly proposed method yielded good sensitivity and excellent chromatographic performance. The limits of quantification for kasugamycin and validamycin-A were 4.1 µg/kg and 1.0 µg/kg, respectively. The recoveries for both compounds at three fortification levels (4, 100 and 500 µg/kg for kasugamycin; 1, 10 and 100 µg/kg for validamycin-A) ranged from 75% to 110%, and the relative standard deviations were below 15%.     

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.     

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     

Automated on-line solid-phase extraction coupled to liquid chromatography–tandem mass spectrometry for determination of lipophilic marine toxins in shellfish

Automated on-line solid-phase extraction (SPE) coupled to liquid chromatography–tandem mass spectrometry (LC–MS/MS) has been developed for fast determination of lipophilic marine toxins in shellfish samples. The direct coupling of an on-line SPE column to LC–MS/MS was accomplished using column switching techniques. Suitable chromatographic separation was performed on a reversed-phase C18 column under alkaline conditions (pH 11).     

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.     

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.     

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.     

Simultaneous quantitative determination of Sudan dyes using liquid chromatography–atmospheric pressure photoionization–tandem mass spectrometry

Atmospheric pressure photoionization–tandem mass spectrometry (APPI–MS/MS) method has been developed for quantitative determination of Sudan I to IV dyes. This study demonstrates the applicability of a simple isocratic normal phase HPLC method using isopropanol (0.3%) in n-hexane as the mobile phase for the separation of these dyes. A simple extraction procedure using n-hexane has been applied for the extraction of these dyes from spiked samples of chilli powder and tomato sauce. The quantitative determination of Sudan I to IV is obtained from the spiked tomato sauce and chilli powder samples by external standard method under single reaction monitoring (SRM) mode. The study includes a detailed investigation on LOD, LOQ, linearity and recovery of Sudan I to IV dyes. The LOD ranged from 5–18 μg/l and LOQ ranged from 10–24 μg/l. The present method can be a powerful analytical tool for the simultaneous quantitative determination of Sudan dyes present in food products.     

Liquid chromatography–tandem mass spectrometry for the determination of chrysoidine in yellow-fin tuna

A high performance liquid chromatography (HPLC) coupled to electrospray ionisation tandem mass spectrometry (MS/MS) method was described for the residue detection of chrysoidine in yellow-fin tuna in the present study. Samples were cleaned up with solid phase extraction (SPE) cartridge, and then injected into HPLC for separation. Multiple-reaction monitoring (MRM) was applied for quantitative determination. Results showed that the low limit of detection (LOD) of the method was 1.25 × 10⁻¹² g, and the low limit of quantification (LOQ) was 0.42 μg/L. The standard calibration curve was y = 2333.9x −845 (r² > 0.99) with the linear range of 0.63–100 μg/L. The average recoveries of chrysoidine ranged from 86.0% to 108.0% when the spiked concentration was from 0.5 μg/kg to 20 μg/kg. And the developed method also showed the good test precisions (RSD%: 4.38–14.27%).     

Determination of sulbactam in raw bovine milk by isotope dilution–ultra-high-performance liquid chromatography–tandem mass spectrometry

We developed a sensitive and selective isotope dilution ultra-high-performance liquid chromatography–tandem mass spectrometry (UPLC-MS/MS) method for the determination of sulbactam residue in raw bovine milk. Sulbactam and internal standard, sulbactam-d₅, were extracted from raw bovine milk via liquid-liquid extraction and enriched with strong anion exchange solid-phase extraction cartridges and finally analyzed by using UPLC-MS/MS with multiple reaction monitoring mode. The method was validated according to European regulations. The calibration curve showed good linearity, with a correlation coefficient of 0.9998. Decision limit and detection capability of sulbactam were determined by matrix calibration curve and were 0.0445 and 0.0517 μg/L, respectively. The recoveries of sulbactam in fortified raw bovine milk ranged from 72.1 to 91.5%, with the intra- and interday relative standard deviations ranging from 3.0 to 18.9%. Furthermore, the developed method was applied to analyzing real raw bovine milk samples collected from dairy farms in Beijing, China. Sulbactam was not determined in all samples. The proposed method could ultimately serve as a methodological foundation for the determination of sulbactam in different types of raw milk and dairy products.     

Analysis of isothiazolinone biocides in paper for food packaging by ultra-high-performance liquid chromatography–tandem mass spectrometry

A novel and simple method to detect isothiazolinone-type biocides (2-methyl-3-isothiazolinone (MI), 5-chloro-2-methyl-3-isothiazolinone (CMI), 1,2-benzisothiazolinone (BIT) and 2-octyl-3-isothiazolinone (OIT)) in paper used for food packaging by ultrasonic extraction coupled with UPLC-MS/MS was developed. Parameters affecting process efficiency such as extraction solvents, UPLC mobile phase, gradient elution procedure and MS/MS conditions were studied to optimise the operating conditions. Using the optimised gradient elution procedure, the retention time was less than 6?min. The limits of detection (LODs) were found to be between 0.001 and 0.010?mg?kg^?1, which was validated using actual concentrations. After diluting the standard solution with a blank matrix, the linear calibration curve ranges were 0.002–1.000?mg?kg^?1 for BIT and OIT, 0.005–1.000?mg?kg^?1 for MI, and 0.020–1.000?mg?kg^?1 for CMI, with correlation coefficients higher than 0.9985 (n?=?6). A good level of precision with a mean recovery greater than 81.3% and a relative standard deviation (RSD) less than 6.2% were also obtained. A methodology has been proposed for the analysis of isothiazolinones in paper.     

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.     

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.     

A simple,rapid and novel method based on salting-out assisted liquid–liquid extraction for ochratoxin A determination in beer samples prior to ultra-high-performance liquid chromatography coupled to tandem mass spectrometry

A novel, simple, easy and cheap sample treatment strategy based on salting-out assisted liquid-liquid extraction for ochratoxin A (OTA) ultra-trace analysis in beer samples using ultra-high-performance liquid chromatography-tandem mass spectrometry determination was developed. The factors involved in the efficiency of pre-treatment were studied employing factorial design in the screening phase and the optimal conditions of the significant variables on the analytical response were evaluated using a central composite face-centred design. Consequently, the amount of salt ((NH₄)₂SO₄), together with the volumes of sample, hydrophilic (acetone) and nonpolar (toluene) solvents, and times of vortexing and centrifugation were optimised. Under optimised conditions, the limits of detection and quantification were 0.02 µg l^?1 and 0.08 µg l^?1 respectively. OTA extraction recovery by SALLE was approximately 90% (0.2 µg l^?1). Furthermore, the methodology was in agreement with EU Directive requirements and was successfully applied for analysis of beer samples.     

Application of dispersive liquid–liquid microextraction for the determination of selected organochlorine pesticides in honey by gas chromatography–mass spectrometry

Dispersive liquid–liquid microextraction (DLLME) is a rapid and easy technique that consumes minute amounts of organic solvents. In this work, we present chemometric study on optimization of DLLME parameters for the extraction of aldrin, endrin, lindane, α-endosulfan, 4,4′-DDT and its metabolites from honey matrix. Method quantification limits (MQLs) vary between 0.3 ng/g for 2,4′-DDE and 4,4′-DDE to 13.2 ng/g for α-endosulfan and enable determination at levels below EU-established Maximum Residue Limits. The developed method is linear (R ² > 0.994) in the investigated range (MQL—100 ng/g), with preconcentration factors of 13.2–30.5 and good repeatability (CV ≤ 17%). A comparison with other available methods reported in the last decade is provided. The method has been applied to 19 real samples from Poland, and the results show that organochlorine pesticides (OCPs) are present in analysed honeys at levels not posing threat to human health (below 14 ng/g for sum of 4,4′-DDT and metabolites and below 5 ng/g for aldrin, endrin and lindane). To the best of our knowledge, this is the first reported application of DLLME for the determination of OCPs in honey.     

Confirmatory method for the determination of various acetylgestagens in animal kidney fat using liquid chromatography–tandem mass spectrometry

A confirmatory method has been developed and validated that allows for the simultaneous detection of medroxyprogesterone acetate (MPA), megestrol acetate (MGA), melengestrol acetate (MLA), chlormadinone acetate (CMA) and delmadinone acetate (DMA) in animal kidney fat using liquid chromatography–tandem mass spectrometry (LC–MS/MS). The compounds were extracted from kidney fat using acetonitrile, defatted using a hexane wash and subsequent saponification. Extracts were then purified on Isolute? CN solid-phase extraction cartridges and analysed by LC–MS/MS. The method was validated in animal kidney fat in accordance with the criteria defined in Commission Decision 2002/657/EC. The decision limit (CCα) was calculated to be 0.12, 0.48, 0.40, 0.63 and 0.54 µg kg^–1, respectively, for MPA, MGA, MLA, DMA and CMA, with respective detection capability (CCβ) values of 0.20, 0.81, 0.68, 1.07 and 0.92 µg kg^–1. The measurement uncertainty of the method was estimated at 16, 16, 19, 27 and 26% for MPA, MGA, MLA, DMA and CMA, respectively. Fortifying kidney fat samples (n = 18) in three separate assays showed the accuracy of the method to be between 98 and 100%. The precision of the method, expressed as % RSD, for within-laboratory reproducibility at three levels of fortification (1, 1.5 and 2 µg kg^–1 for MPA, 5, 7.5 and 10 µg kg^–1 for MGA, MLA, DMA and CMA) was less than 5% for all analytes.     

Determination of aflatoxins in edible oil from markets in Hebei Province of China by liquid chromatography–tandem mass spectrometry

Analysis of aflatoxin B₁ (AFB₁), B₂ (AFB₂), G₁ (AFG₁) and G₂ (AFG₂) in 76 edible oil samples (peanut oil, soybean oil, corn embryo oil and blended oil) was performed by liquid chromatography–tandem mass spectrometry (LC–MS/MS). The oils were sampled from three areas (Shijiazhuang, Baoding and Tangshan) of Hebei Province of China. AFB₁ was detected in 22 samples representing 28.9%, followed by AFB₂ (7.89%) and AFG₁ (3.95%), while no AFG₂ contamination was detected in any samples. AFB₁ levels in oil samples ranged 0.14–2.72?µg?kg^?1 and AFB₂ ranged 0.15–0.36?µg?kg^?1, while lower levels of 0.01–0.02?µg?kg^?1 for AFG₁ were recorded. The paper is part of an on-going investigation of aflatoxin contamination in Chinese edible oils.