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.     

Determination of nonylphenol ethoxylate metabolites in vegetables and crops by high performance liquid chromatography-tandem mass spectrometry

A method has been developed for the simultaneous determination of the concentration of nonylphenol (4-NP), nonylphenol monoethoxylates (NP₁EO) and nonylphenol diethoxylates (NP₂EO) in vegetables and crops by liquid chromatography-tandem quadrupole mass spectrometry (HPLC-MS/MS). These target compounds were extracted from vegetable and crop samples with acetonitrile, and then the extracts were cleaned using solid phase extraction with graphitised carbon black tandem primary secondary amine (PSA) cartridges. The MS method enabled highly reliable identification by monitoring the corresponding ammonium adduct [M+NH₄]⁺ in the positive mode for NP₁EO and NP₂EO, and the deprotonated molecule [M−H]⁻ in the negative mode for 4-NP. Recoveries for the spiked samples ranged from 65% to 118%. The limit of detection (LOD) of 4-NP, NP₁EO and NP₂EO was 3, 5 and 0.1 μg kg⁻¹, respectively. This method would be useful for the quick and routine detection of the residues of 4-NP, NP₁EO and NP₂EO in vegetables and crops.     

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%).     

Fast determination of myo-inositol in milk powder by ultra high performance liquid chromatography coupled to tandem mass spectrometry

A simple and fast method has been developed and validated for the determination of myo  -inositol in milk powder samples, using solid–liquid extraction with water (0.01% formic acid, v/v):methanol (1:1, v/v). The determination was carried out by ultra-high-performance liquid chromatography coupled to tandem mass spectrometry (UHPLC−MS/MS) using an electrospray ionisation source (ESI) in positive mode. Chromatographic separation was carried out using as mobile phase water (0.01% formic acid, v/v) and methanol in gradient mode. Data acquisition under MS/MS was achieved by applying selected reaction monitoring, using 181.0→$\to$109.0 and 181.0→$\to$81.0 for quantification and confirmation purposes, respectively. The technique provides a sensitive and selective determination of myo-inositol in the analysed samples, with a run time of 4 min. The limit of detection and quantification were 0.2 and 0.5 mg kg⁻¹, respectively. The method was applied to six fortified commercial milk powder samples containing myo-inositol amounts ranging from 290 to 2200 mg kg⁻¹.     

Optimization of gas chromatography–single quadrupole mass spectrometry conditions for multiresidue analysis of pesticides in grapes in compliance to EU-MRLs

A single quadrupole GC–MS method was optimized for multiresidue determination of 47 pesticides in grapes with limit of quantifications of each compound in compliance with the EU-MRL requirements. Sample preparation involved extraction of 10 g sample with 10 ml ethyl acetate (+10 g sodium sulphate) by homogenization at 15,000 rpm followed by centrifugation at 3000 rpm. The supernatant was cleaned by dispersive solid phase extraction with primary secondary amine and acidified with 0.1% formic acid. Residues were estimated in selected ion monitoring mode with programmable temperature vaporizer-large volume injection (8 μl). All the GC and MS parameters were thoroughly optimized to achieve satisfactory linearity (R² > 0.99) within 0.01–0.25 mg kg⁻¹ with minimum matrix interferences. Recoveries at 0.01 and 0.02 mg kg⁻¹ were within 67–120% with associated precision RSD below 19%. The method was successfully applied for analysis of the real world samples for incurred residues.     

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.     

Analyses of selected non-authorized insecticides in peppers by gas chromatography/mass spectrometry and gas chromatography/tandem mass spectrometry

Two methods based on gas chromatography coupled with mass spectrometry and tandem mass spectrometry analyzers are described for the identification, confirmation and quantitation of two EU-banned insecticides: isocarbophos and isofenphos-methyl, detected in recent monitoring programmes in pepper samples. The proposed methodologies involved a liquid–liquid extraction with acetonitrile followed by a cleanup step by dispersive solid-phase extraction using primary–secondary amine as sorbent material. Recovery studies performed on peppers spiked at different fortification levels (10 and 50 μg kg⁻¹) yielded average recoveries in the range 85–98% with RSD values below 8%. Identification, confirmation and quantitation were carried out by gas chromatography/mass spectrometry (GC–MS) in selected ion monitoring mode and gas chromatography/tandem mass spectrometry (GC–MS/MS) using an ion trap operating in the multiple reaction monitoring (MRM) mode. The obtained limits of detection (LODs) were in the range 0.1–0.3 μg kg⁻¹, depending on the technique. The proposed methods were successfully applied to the analysis of suspected pepper samples.     

Rapid and selective determination of hydrogen peroxide residues in milk by batch injection analysis with amperometric detection

We report a highly rapid, precise, selective and sensitive analytical method for the determination of hydrogen peroxide in milk using a batch-injection analysis (BIA) with amperometric detection at a Prussian-blue bulk modified graphite-composite electrode. An electronic micropipette injected 100 μL aliquots of 10-fold diluted samples (high and low-fat milk) directly onto the modified electrode immersed in the BIA cell. The analytical features of our proposed method includes low RSD between injections (0.76%, n = 9), low detection limit (10 μmol L⁻¹), elevated analytical frequency (up to 80 h⁻¹) and satisfactory recovery values for spiked samples. A fresh and highly reproductive electrode surface can be easily obtained by simple mechanical polishing (RSD = 1.6%, n = 5). The storage stability of the PB-modified graphite-composite surpassed 1 year keeping equivalent performance as initially presented. The association of BIA with an improved amperometric detector provides great promise for routine monitoring of hydrogen peroxide in milk and other beverages.     

Analysis of multi-pesticide residues in the foods of animal origin by GC–MS coupled with accelerated solvent extraction and gel permeation chromatography cleanup

A new analytical method was developed to simultaneously determine residues of 109 pesticides (including isomers) in the foods of animal origin. Acetonitrile was selected for accelerated solvent extraction (ASE) for effectively extracting the pesticides from the fatty samples. The cleanup was performed with an automated gel permeation chromatography (GPC) cleanup system. The prepared samples were analysed with GC–MS in the selected ion monitoring mode (SIM) using one target and two qualitative ions for each analyte. Chlorpyrifos-d₁₀ was used as an internal standard. The lowest limit of detection was 0.3 μg kg⁻¹ for some pesticides. The recoveries and relative standard deviations (RSDs) were checked by spiking untreated samples with pesticides at 0.05, 0.1 and 0.2 mg kg⁻¹. The average recoveries of most pesticides were from 62.6% to 107.8%. The precision values expressed as RSD were all ?20.5% (n = 6). Good linearity (r ? 0.99) was observed between 0.05 and 1.5 μg mL⁻¹.     

Quantitative analysis of lincomycin and narasin in poultry, milk and eggs by liquid chromatography-tandem mass spectrometry

This study presents the simultaneous extraction and determination of lincomycin (LCM) and narasin (NAR) by using liquid chromatography-electrospray ionisation tandem mass spectrometry (LC-MS/MS) on samples from poultry, milk and eggs (n = 196). The homogenised samples are extracted with acetonitrile and the extract is further cleaned using C₁₈ solid-phase extraction cartridges. The recoveries of the analytes in different matrices were found ranging from 90% to 101% and 85% to 95% for LCM and NAR, respectively. The corresponding limits of detection were 0.6 and 1.5 ng g⁻¹ for LCM and NAR, respectively. As a result of monitoring, NAR was not detected in any samples and LCM was detected in one egg with a concentration of 25 ng g⁻¹. The method was relatively simple to perform and therefore could be used for food safety surveillance activities.     

Microwave-assisted extraction and determination of cyanuric acid residue in infant formula samples by liquid chromatography–tandem mass spectrometry

In the present work, microwave-assisted extraction method in combining with liquid chromatography–tandem mass spectrometry (LC–MS/MS) was proposed for the determination of cyanuric acid (CYA) in infant formula samples. The separation was performed on a MERCK ZIC HILIC column (150 × 2.1 mm i.d., 5 μm) with gradient elution of 20 mM ammonium acetate solution – acetonitrile. The method could respond linearly with cyanuric acid at concentrations from 1.0 to 50 ng mL⁻¹ with a quantification limit of 0.25 mg kg⁻¹. The intra- and inter-day precision was less than 4% and the recovery of the assay was in the range of 86.7–93.1%. In the analysis of practical spiked infant formula samples, the new method yielded satisfactory results. Due to its simplicity and accuracy the straightforward method is particularly suitable for routine cyanuric acid detection.     

Development and application of a method for the analysis of two trichothecenes: deoxynivalenol and T-2 toxin in meat in China by HPLC-MS/MS

A reliable and sensitive method was developed and successfully applied for the determination of deoxynivalenol and T-2 toxin simultaneously in pig dorsal muscle, pig back fat and chicken muscle by high performance liquid chromatography coupled with tandem mass spectrometry (HPLC-MS/MS) analysis. Limit of detection of deoxynivalenol and T-2 was 0.02 μg/kg and 0.007 μg/kg, and limit of quantification of deoxynivalenol and T-2 was 0.07 μg/kg and 0.02 μg/kg, respectively. Sixty-six meat samples were analyzed and deoxynivalenol was detected in the samples of pig back fat, with concentrations lower than 0.5 μg/kg, and T-2 toxin was detected in the samples of pig dorsal muscle, pig back fat and chicken muscle, with concentrations lower than 0.5 μg/kg. The results of sample analysis show that only trace residues of deoxynivalenol and T-2 toxin were detected in the samples analyzed.     

A validated matrix solid-phase dispersion method for the extraction of organophosphorus pesticides from bovine samples

A method based on matrix solid-phase dispersion (MSPD) was developed for the quantitative extraction of five organophosphorus (OPPs) pesticides from bovine samples. The determination was carried out by high performance liquid chromatography (HPLC) with diode array spectrophotometric UV detection. The MSPD extraction with octadecylsilyl (C18) sorbent combined with a silica gel clean-up and acetonitrile elution was optimised for chlorpyrifos, chlorfenvinphos, diazinon, fenitrothion, and parathion-methyl. The method was validated, yielding recovery values higher than 94%, except for chlorfenvinphos in liver (55%), and precision values, expressed as relative standard deviations (RSDs), which were less than or equal to 15% in liver and 11.5% in muscle at spiking levels of 0.25, 2.5 and 5 μg g⁻¹. Linearity was studied from 0.5 to 15 μg g⁻¹, and the limits of detection (LODs) were found to be lower than 0.1 μg g⁻¹_. This method was applied to the analysis of real samples with confirmative analyses performed using gas chromatography–mass spectrometry (GC–MS) in selected ion monitoring mode (SIM).     

Quantitative analysis of volatiles in transesterified coconut oil by headspace-solid-phase microextraction-gas chromatography–mass spectrometry

A simple and fast headspace-solid-phase microextraction (HS-SPME) method coupled with gas chromatography–mass spectrometry (GC–MS) was developed for the analysis of volatile compounds in transesterified coconut oil by applying solvent dilution. Solvent dilution conditions (solvent type and solvent amount) and HS-SPME sampling parameters (adsorption temperature and time) were optimised through monitoring the adsorption result of the selected volatiles (octanoic acid esters) in transesterified coconut oil samples. The incubation of methanol (800 μl)-diluted oil (200 μl) sample at 60 °C for 30 min led to the best result. The method was further validated by determining the calibration linear range, correlation coefficient (R²), accuracy, precision, limit of detection and limit of quantification through spiking standards into the blank matrix consisting of coconut oil and methanol. This method may also be applicable for detection and determination of volatile compounds in other transesterified oil samples.     

A multi-residue method for fast determination of pesticides in tea by ultra performance liquid chromatography–electrospray tandem mass spectrometry combined with modified QuEChERS sample preparation procedure

A multi-residue method was developed for rapid determination of pesticide residues in tea by ultra performance liquid chromatography–electrospray tandem mass spectrometry (UPLC/MS/MS). The QuEChERS method was used for sample preparation. In order to minimise the matrix effects from tea, a solid phase extraction (SPE) cartridge layered with graphite carbon/aminopropylsilanized silica gel was applied as complementary to QuEChERS method. For accurate quantification, representative matrix-matched calibration curves were applied to compensate matrix effects. Limits of quantification varied with different pesticides but all can be measured at 0.01 mg kg⁻¹ level in a 5 g tea sample except dichlorvos (0.02 mg kg⁻¹). Recoveries ranged from 70% to 120% and relative standard deviation (RSD) met the European United Quality Control guideline. Efficiency and reliability of this method were investigated by the analysis of both fermented and unfermented Chinese tea samples.     

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.     

Determination of falcarinol in carrot (Daucus carota L.) genotypes using liquid chromatography/mass spectrometry

A new analytical method for the determination of falcarinol [(Z)-heptadeca-1,9-diene-4,6-diyn-3-ol] in carrot root samples has been developed and validated. The method consists of accelerated solvent extraction (ASE) of lyophilised carrot root samples with ethyl acetate and LC–MS analysis of the extracts. Falcarinol was determined by extracting the main ion species generated in the ESI positive mode, m/z 268 [M+H–H₂O+MeCN]⁺, from the full MS chromatogram. Quantitation was performed using a falcarinol calibration curve (correlation coefficient 0.9975) as an external standard and pelargonic acid vanillylamide as an internal standard. The method showed good precision with interday and intraday variation of less than 4% and high recovery (average recovery rate 97.9%). LOD (S/N = 3) and LOQ (S/N = 10) were 2.5 and 7 ng, respectively. Using this method, 27 different carrot genotypes grown and harvested under the same conditions were analyzed, and falcarinol contents ranging from 0.70 to 4.06 mg/100 g fresh weight were determined.     

Determination of acrylamide in roasted chestnuts and chestnut-based foods by isotope dilution HPLC-MS/MS

A collaboratively trial tested isotope dilution liquid chromatographic method with positive electrospray ionisation tandem mass spectrometry for the analysis of acrylamide in bakery ware and potato products has been extended to the determination of acrylamide in roasted chestnuts and chestnut-based foods. As chestnuts have a similar composition to potatoes, considerable amounts of acrylamide can be expected, especially in roasted chestnut products. This paper presents the concentrations of acrylamide in 31 different chestnut samples (fresh, roasted, flour, cooked, glazed) that were collected in nine European countries during 2005/2006. The influence of the roasting time on the acrylamide content was also experimentally investigated. A test portion was extracted after homogenisation with water and isotopically labelled acrylamide was added. The extract was centrifuged and the supernatant was cleaned-up in two consecutive solid phase extraction steps. The final extract was analysed by high performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS). An HPLC column based on graphitised carbon was applied for chromatographic separation. Acrylamide concentrations in purchased roasted chestnuts were in the range of <8–1278 μg/kg whereas only low amounts (<4–159 μg/kg) were found in chestnut products. However, the median acrylamide content of the commercial roasted chestnut samples was 90 μg/kg. The influence of the roasting time on the acrylamide content in roasted chestnuts was evaluated too. As with roasted and fried potato products, the roasting time has a significant influence on the acrylamide formation. Therefore, the consumers might be exposed to significant amounts of acrylamide by eating roasted chestnuts, especially when a batch remains in the roasting vessel for too long time.     

Interference-free determination of acrylamide in potato and cereal-based foods by a laboratory validated liquid chromatography–mass spectrometry method

A simple and rapid method was developed and validated for the determination of acrylamide in potato and cereal-based foods by using a single quadrupole liquid chromatography–mass spectrometry (LC–MS) interfaced with positive atmospheric pressure chemical ionization (APCI+). Acrylamide was simply extracted with 0.01 mM acetic acid in a vortex mixer prior to LC–MS analysis. The applicability of validated method was shown for a wide range of processed foods including chips, fries, crisps, breads, biscuits and cookies. The mean recovery was found to be 99.7 with a repeatability of 1.8% in the range 100–1000 ng/g. During LC–MS analyses, the major interfering co-extractive was identified as valine which yields characteristic [M + H]⁺ and compound specific product ions having m/z of 118 and 72, respectively. Valine increased the baseline signal preventing accurate and precise quantitation, and resulted in poorer sensitivity in selected ion monitoring mode. The adverse effect of valine could be limited by instrumentally adjusted delay time or by solid-phase extraction with strong cation-exchanger sorbent.     

LC–MS/MS analysis of phenols for classification of red wine according to geographic origin,grape variety and vintage

A rapid LC–MS/MS method for quantification of phenols and polyphenols in authentic wine samples with unrivalled sensitivity was developed. Excellent limits of detection in the low μg L⁻¹ range were achieved. Reversed phase HPLC employing sub-2 μm particles as stationary phase allowed high-throughput analysis with analysis times of 10 min for 11 compounds. The phenolic pattern was assessed in 97 authentic wine samples (stored under identical conditions without further treatment or modification) comprising eleven geographical Austrian regions, six grape varieties and five vintages. Canonical discriminant analysis was applied to the data set showing the suitability of the (poly)phenolic spectrum for classification of the wine samples. The method allowed a geographic discrimination of several grape varieties and a grape variety based discrimination of four regions. As a novel finding excellent (poly)phenol-based differentiation of the five investigated vintages (2003–2007) was achieved.