Solid-phase Clean-up Research Articles

Large scale screening and quantification of micropollutants in fish from the coastal waters of Cochin, India: Analytical method development and health risk assessment

Urban estuarine and coastal water receive several micropollutants through industrial and agricultural influxes. The bioaccumulation of these micropollutants in fish and their entry into the coastal population's food chain raises significant food safety concerns. Hence, a comprehensive analytical method was developed for ultra-trace level quantification of 345 micropollutants in fish. The optimized sample preparation method could extract compounds suitable for both GC–MS/MS and LC-MS/MS analysis simultaneously. The target list of contaminants included 278 agricultural pesticides and also 102 endocrine disruptors covering polyaromatic hydrocarbons, polychlorinated biphenyls, organochlorines, and endocrine-disrupting pesticides. The GC–MS/MS with large volume injection (LVI) technique, and LC-MS/MS operating in MRM mode, achieved an LOQ of <2.00 ng/g for most of the analytes. The extraction strategy involved tri-phase partitioning between water, acidified acetonitrile, and hexane, followed by salting out. Dispersive solid phase cleanup (dSPE) with C18, Z-Sep+, CaCl2, and MgSO4 was able to reduce the matrix influence, and the method achieved satisfactory recovery in the range of 70.0–120.0 % for all the target analytes. The repeatability and reproducibility relative standard deviation values of the measured analytes were <20.0 %, and the Horwitz ratio values were well below 2. The method was used to accurately measure the target micropollutants in fish from the Cochin estuary, the highly urbanized portion of the Vembanad Lake, and an important Ramsar site. At least one or more of the 41 different micropollutants were identified and quantified in about 90.7 % of the 108 samples analyzed. The importance of large-scale screening and trace-level quantification methods in environmental monitoring and risk assessment is underscored by the results. The risk assessment showed a moderate risk of exposure to the nearby coastal population through the food chain.

Saliva identification in forensic samples by automated microextraction and intact mass analysis of statherin.

The enzyme α-amylase has long been a commonly targeted protein in serological tests for saliva. While being especially abundant in saliva, α-amylase is detectable in vaginal secretions, sweat, fecal matter, breast milk and other matrices. As a result, assays for α-amylase only provide a presumptive indication of saliva. The availability of mass spectrometry-based tools for the detection of less abundant, but more specific, protein targets (e.g., human statherin) has enabled the development of high confidence assays for human saliva. Sample throughput, however, has traditionally been low due to multi-step workflows for protein extraction, quantitation, enzymatic digestion, solid phase cleanup, and nano-/capillary-based chromatography. Here, we present two novel "direct" single-stage extraction strategies for sample preparation. These feature immunoaffinity purification and reversed-phase solid-phase microextraction in conjunction with intact mass analysis of human statherin for saliva identification. Mass analysis was performed on the Thermo Scientific Q-Exactive™ Orbitrap mass spectrometer with a 10-min analytical run time. Data analysis was performed using Byos® from Protein Metrics. Two sample sets were analyzed with a population of 20 individuals to evaluate detection reliability. A series of casework-type samples were then assayed to evaluate performance in an authentic forensic context. Statherin was confidently identified in 92% and 71% of samples extracted using the immunoaffinity purification and solid phase microextraction approaches, respectively. Overall, immunoaffinity purification outperformed the solid phase microextraction, especially with complex mixtures. In toto, robotic extraction and intact mass spectrometry enable the reliable identification of trace human saliva in a variety of sample types.

Validation, dissipation kinetics and monitoring of flonicamid and dinotefuran residues in paddy grain, straw, its processed produces and bran oil using LC-MS/MS

Flonicamid and dinotefuran are highly effective insecticides in paddy but residue persistence in crop and transmission into food and feed is unknown. This study aimed to examine initial deposits and dissipation kinetics of flonicamid and dinotefuran in paddy matrices and processed products including bran oil. The method was validated following acetonitrile extraction, dispersive solid phase clean-up and finally determination using liquid chromatography-mass spectrometry/mass spectrometry. Recoveries ranged from 76.6 to 109.7 percent for the paddy matrices tested. In a field experiment, flonicamid and dinotefuran were applied to paddy crops to study dissipation patterns. The half-lives of flonicamid and dinotefuran residues in paddy ranged from 2.0 to 3.0 days. However, at harvest time paddy grain and straw samples were found free from residues. Monitoring of residues in farm gate and market samples revealed that paddy products were not contaminated with flonicamid or dinotefuran residues.

Determination of triazines residues in fruits and vegetables: Methods comparison of ultrasonic solvent extraction with and without solid phase clean-up

ABSTRACT An ultrasonic solvent extraction (USE) method followed by liquid chromatography-photodiode array detector has been optimized and applied with and without solid-phase clean-up for analysis of triazines in fruits and vegetables. The correlation coefficient (r 2) > 0.999 was obtained for all the analytes at a linear range of 100–1000 µg/L. The recoveries obtained were 75–81% and 86–121% for USE with and without SPE clean-up, respectively, with relative standard deviation <20% implying good accuracy and precision. The detection limits ranged from 1.1–1.8 µg/kg to 0.6–1.0 µg/kg for USE with and without SPE clean-up, respectively. The quantification limits ranged from 3.4–5.2 µg/kg to 1.7–2.9 µg/kg for USE with and without SPE clean-up, respectively. The concentrations of triazines detected in fruits and vegetables ranged from 9 to 222 µg/kg. All the triazines were quantified at levels below the MRLs revealing no threat to human health. It can be concluded that the proposed inexpensive, environmentally friendly method can be effectively employed for regular monitoring of the concentration of the selected triazines fruits and vegetables. Moreover, it can be recommended that ultrasonic solvent extraction can be accurately applied without additional SPE clean-up.

Multi-residue determination of twenty aminoglycoside antibiotics in various food matrices by dispersive solid phase extraction and liquid chromatography-tandem mass spectrometry

An analytical method has been developed for the simultaneous determination of twenty aminoglycosides (AGs) in meat, milk, and egg using liquid chromatography-tandem mass spectrometry. The target analytes were separated on a reverse-phase C18 column and eluted with acetonitrile containing the ion-pairing reagent (heptafluorobutyric acid). For sample preparation, we used ammonium acetate buffer solution and dispersive solid-phase cleanup (C18). Linearity was obtained >0.98 (r2). The trueness (average recoveries) was between 70 and 118%. The precision (coefficient of variation) was in the range of 1–27%. The proposed method provides reliable screening, quantification, and identification of twenty AGs residues in various food matrices. The method was applied to analyze real samples collected from local market, demonstrating that method is robust and useful for determining AGs residues.

Determination of Emerging Contaminants in Cereals by Gas Chromatography-Tandem Mass Spectrometry.

Cereals are staple foods for human consumption in both developed and developing countries. In order to improve agricultural outputs, resources like reclaimed water for irrigation and biosolids and manure as fertilizers are frequently used, although they may increase the input of contaminants that can potentially be absorbed by crops and enter the food chain. Emerging contaminants (human and veterinary pharmaceuticals, personal care products, surfactants, plasticizers, and industrial additives, among others) are continuously introduced in the environment from a variety sources and these contaminants may enter the food chain through plant uptake. In this study, an analytical method, based on ultrasound-assisted extraction and dispersive solid-phase cleanup, was developed for the determination of emerging contaminants from different classes in four highly consumed cereal grains (wheat, oat, barley, and rice). These analytes were selected considering the results of our previous studies carried out in soil and vegetables and those frequently detected in real samples were chosen. The target compounds selected were bisphenol A (BPA), bisphenol F (BPF), methyl paraben, propyl paraben, linear chain nonylphenol in position 4 (4-n-NP), mixture of ring and chain isomers of NP and six pharmaceutical compounds (allopurinol, mefenamic acid, carbamazepine, paracetamol, diclofenac and ibuprofen). Recoveries ranging from 68 to 119% with relative standard deviations (RSD) <18% were obtained for all the compounds except for allopurinol, with recoveries that ranged from 30 to 66% with RSD ≤ 12% and the limits of detection achieved ranged from 0.03 to 4.9 ng/g. The method was applied to the analysis of 16 cereal samples, ten were purchased in local supermarkets and the rest were collected directly from agricultural fields, five of which were fertilized with organic amendments. Bisphenol A (BPA) was detected in all samples at levels that ranged from 1.6 to 1,742 ng/g. Bisphenol F, a substitute for BPA, was also found in six samples (up to 22 ng/g). Linear 4-n-NP was found in a reduced number of samples but the mixture of NP isomers was found in all the samples, being the mean concentrations in wheat, barley, oat and rice 49, 90, 142, and 184 ng/g, respectively.

Method optimization and validation for multi-class residue analysis in turmeric

Turmeric (Curcuma longa L.) is an economically important food and medicinal plant that grows in tropical and subtropical regions consumed worldwide. Turmeric is a difficult matrix for residue/contaminant analysis due to the high content of potentially interfering polyphenols (curcuminoids) and essential oils with physicochemical properties similar to target analytes. To solve this problem, a simple and straightforward sample preparation protocol based on ethyl acetate extraction and dispersive solid phase clean-up, followed by gas and liquid chromatography coupled to tandem mass spectrometry analysis, was optimized and validated, after selecting a representative blank material using gas chromatography coupled to ion mobility spectrometry and multivariate data analysis. Method validation was performed according to Codex guidelines for 67 pesticide residues, including 12 persistent organic pollutants, 4 aflatoxins and 3 dyes at 0.01, 0.02 and 0.05 mg kg−1level. Recoveries ranged between 60 and 120%, with relative standard deviations for repeatability and reproducibility below 20% and 32% respectively. Method performance was tested collaboratively between laboratories in Austria and Uruguay which helped proving the robustness of the methodology. The method was applied to the analysis of commercial samples and chlorpyrifos was detected in most of them.The novelty of the work relies in the optimization and validation of a multiclass method that allows analysis of four types of organic residues/contaminants, of paramount importance for food safety, using a single sample preparation step followed by gas and liquid chromatography coupled to tandem mass spectrometry determination.

Bioactive plant oxylipins-based lipidomics in eighty worldwide commercial dark chocolates: Effect of cocoa and fatty acid composition on their dietary burden

Phytoprostanes (PhytoPs) and phytofurans (PhytoFs) are plant oxylipins (isoprostane-prostaglandin-like compounds) formed by the free radical-catalyzed oxidation of α-linolenic acid (ALA, C18:3, n-3). These oxylipins have been previously described in an array of plant-based foods with similar concentrations as phenolics in some fruits and vegetables, but their occurrence in dark chocolate has not been addressed so far, neither their content nor the influence of cocoa percent and fatty acid composition on the generation of PhytoPs and PhytoFs, to establish new assays in order to boost the dietary burden of these new bioactive compounds, provided by natural plant-based foods intake. In this regard, 80 dark chocolate samples with cocoa (Theobroma cacao L.) content of up to 100% were assessed on their PhytoP and PhytoF profile. These target analytes were isolated using a dispersive liquid–liquid extraction followed by a solid-phase clean-up of the extracts, and quantified using a UHPLC coupled to a triple quadrupole-MS/MS detection system. The content of PhytoPs and PhytoFs in the array of chocolates analyzed oscillated from 2.45 to 1192.43 ng/g fw and from 144.57 to 840.19 ng/g fw, respectively. The profile of these metabolites was studied in conjunction with the fatty acid methyl esters (FAMEs) content and the percentage of cocoa; however, no relationship between PhytoPs and PhytoFs and FAMEs content nor the cocoa percentage was observed. The assessment of dark chocolates on the content of PhytoPs and PhytoFs is of great importance as there is increasing scientific evidence on their immunomodulatory and inflammatory activity, as well as their role as preventive agents against oxidative stress that could confer this food an additional interest to consumers.

Determination of booster biocides in sediments by focused ultrasound-assisted extraction and stir bar sorptive extraction–thermal desorption–gas chromatography–mass spectrometry

Booster biocides present in natural waters may be captured by the sediments. Highly sensitive, robust, selective and reliable analytical methods are required to evaluate their presence in the sediments. A focused ultrasound assisted extraction method for the simultaneous determination of five organic booster biocides (Chlorothalonil, Dichlofluanid, Sea-Nine 211, Irgarol 1051 and TCMTB) in marine sediments is proposed. The isolation of the target compounds from 0.5 g of sediment was efficient using 2.5 mL of methanol as solvent, an output amplitude of 50 W, 100% duty cycle and an extraction time of 300 s. The extraction procedure was followed by solid-phase clean-up on non-polar sorbents (Oasis HLB). The compounds were sampled using stir bars (20 mm length, 0.5 mm film thickness) coated with polydimethylsiloxane (PDMS). The stir bars were stirred at 900 rpm for 3 h at room temperature. Desorption was carried out by thermal desorption (TD), and the analytes were separated in the gas chromatography (GC). They were detected by triple quadrupole mass spectrometry (MS/MS) using the multiple reaction monitor (MRM) mode. The detection limits (DLs) of booster biocides were in the range of 0.02 to 2.2 ng g − 1 dry weight. The regression coefficients were higher than 0.999. The average recovery was higher than 86% (R.S.D.: 7–11%). The analytical procedure was applied to determination of the booster biocides in port sediment samples from the southwestern Spain. Sea-Nine 211 was found in one sediment at a level of 2.1 ng g−1. Irgarol was present in all the sediments at concentrations between 2 and 9 ng g−1.

Patulin in apple and apple juice: Method development, validation by liquid chromatography-tandem mass spectrometry and survey in Brazilian south supermarkets

In this work, a novel single method for patulin determination in apple and apple juice employing liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) is presented. Samples were extracted employing ethyl acetate acidified with acetic acid followed by sodium sulfate addition. The extracts were submitted to dispersive solid phase clean-up employing sodium sulfate and silica gel. The method was validated assessing linearity and linearity range, limits of detection and quantification, matrix effect, precision (RSD%) and accuracy (recovery from samples spiked at 25, 50 and 100 μg kg−1). The method showed to be suitable for patulin determination as the recovery ranged from 76 to 84% for apple and from 102 to 108% for apple juice, in both cases with RSD lower than 15%. Matrix effect was also evaluated and showed to be less intense for apple juice (−22%) than for apples (−42%). The validated method was applied to 62 samples (apple and apple juice) collected in supermarkets of southern Brazil, during the years 2016 and 2017. Apple samples showed contamination ranging from < LOQ to 757 μg kg−1 and apple juice from < LOQ to 1298 μg L−1.

Determination of melatonin content of different varieties of hemp (Cannabis sativa L.) by liquid chromatography tandem mass spectrometry

Melatonin (N-acetyl-5-methoxytryptamine), was first isolated in the bovine pineal gland, and then was discovered in bacteria, algae and higher plants. Melatonin concentrations in plants differ from species to species, among varieties within the same species and also within different organs or tissues of a given plant as roots, leaves, fruits, flowers, and seeds. Although the presence of melatonin in plants seems to be a universal trait, there is still lack of information on its occurrence in several plants, in particular in hemp (Cannabis sativa L.). The aim of this study was to develop a method to quantitate melatonin in the aerial parts of the plant, constituted of leaves and flower heads, and in the seeds, of four different hemp varieties using liquid chromatography–tandem mass spectrometry (LC–ESI/MS/MS). A sample preparation procedure with methanol extraction followed by solid-phase clean-up protocol was set up for melatonin extraction and a LC–ESI/MS/MS method in single reaction monitoring (SRM) was used for its determination. Chromatographic separation was achieved on a C18 column using a gradient elution with acetonitrile–buffer ammonium formate/formic acid system. The developed method, validated as per International Conference on Harmonization guidelines, was successfully applied to analyze hemp samples varieties belonging to fiber-type or drug-type chemotypes. The melatonin was found to accumulate highly in seeds in the range 13.43–30.40 ng g−1 while the content in the aerial parts was assessed in the range 1.16–4.85 ng g−1. No correlation was found between the melatonin levels detected in aerial parts and seeds in each hemp variety and the concentration of specific cannabinoids in the same variety.

Advantageous Extraction, Cleanup, and UHPLC-MS/MS Detection of Patulin Mycotoxin in Dietary Supplements and Herbal Blends Containing Hawberry from Crataegus spp.

Patulin (PAT) is a highly genotoxic mycotoxin still found as the common contaminant of various kinds of spoiled fruits and related commodities which are often endorsed as the health-enhancing products. Thus, a fast and convenient liquid-solid extraction followed by a solid-phase cleanup with the MycoSep®228 AflaPat multifunctional column was used for the highly efficient isolation of PAT with an average recovery of 112.7% from commercial dietary supplements and herbal blends formulated with dried hawberry. Analysis of the PAT content was carried out using gradient elution with a Synergi Polar C18 column (150 × 2 mm, 4 μm) and UHPLC system equipped with a mass spectrometer. PAT was detected in all (n=14) commercial single-component dietary supplements formulated with dried hawberry belonging to Crataegus monogyna and/or Crataegus laevigata. Similarly, PAT was detected in 67% of the studied multicomponent commercial herbal blends (n=6) that contained—in addition to hawberry—different amounts of apple, chokeberry, elderberry, hibiscus, or mallow. Moreover, the PAT content was determined in the hawberry collected from the mature wild hawthorn trees belonging to three botanical species, Crataegus monogyna Jacq., Crataegus laevigata (Poiret) DC, and Crataegus rhipidophylla Gand, growing in the recreational forest areas and in the law-protected state national forest park in Poland. In conclusion, to prevent PAT accumulation and reduce the health risk of consumers in globalizing markets, the implementation of improved cultivation/processing practices of hawthorn trees and hawberry as well as increased analytical control related to the presence of PAT in dietary supplements and herbal blends formulated with fresh, dried, or frozen hawberry should be urgently recommended.

Rapid and Effective Sample Cleanup based on Polyvinylpyrrolidone-Coated Magnetite Nanoparticles Coupled with New Pre-Column Derivatization for Determination of Aflatoxins B1, B2, G1 and G2 in Animal Feeds by High-Performance Liquid Chromatography with Fluorescence Detection

A novel method for the determination of aflatoxins B1, B2, G1, and G2 (AFB1, AFB2, AFG1, AFG2) in animal feed samples based on magnetic solid-phase cleanup and novel pre-column derivatization has been developed. In this work, synthesized polyvinylpyrrolidone-coated Fe3O4 magnetic nanoparticles were applied as adsorbents for rapid cleanup for extracts of animal feed samples. The purified extract was then derivatized with trifluoroacetic acid coupling ultraviolet irradiation which enabled the weakly fluorescent AFB1 and AFG1 transformed into their highly fluorescent hemiacetals derivatives. Afterward aflatoxins were separated and quantified by reverse phase liquid chromatography with fluorescence detection. The results indicated that four AFs presented excellent linear response with correlation coefficients > 0.996 and recoveries ranged from 86.7 to 108.9% with relative standard deviations (RSDs) from 3.6 to 6.4%. The limits of detection (LODs) were 0.0392, 0.2429, 0.0842, 0.4556 ng mL-1 for AFB1, AFB2, AFG1 and AFG2, respectively.

Determination of residual organophosphorus thioester pesticides in agricultural products by chemical isotope-labelling liquid chromatography-tandem mass spectrometry coupled with in-syringe dispersive solid phase clean-up and in situ cleavage

Chemical isotope labelling in combination with high-performance liquid chromatography-tandem mass spectrometry (CIL-HPLC-MS/MS) is a powerful method for quantitative profiling of targeted molecules. In the current work, we successfully developed a novel CIL-HPLC-MS/MS method for quantitative profiling of residual organophosphorus thioester pesticides (OPTPs) in agricultural products through the determination of the cleavage products of thiol (CP-thiol) compounds. In this method, we synthesized a novel pair of CIL reagents, i.e., N-(4-(carbazole-9-yl)-phenyl)-N-maleimide (NCPM-d0) and its deuterated analogue NCPM-d2, both of which contain a maleimide moiety as the reactive group and an isotope tag to sensitively label CP-thiol compounds. NCPM-d0 was used to label CP-thiol compounds cleaved from OPTPs in the investigated agricultural product samples, and NCPM-d2 was used to label CP-thiol compounds cleaved from OPTPs in the standard substance-spiked organic agricultural product samples. The heavily labelled derivatives were used as the internal standards (ISs) to compensate for the matrix effects during MS analysis. The NCPM-d0- and NCPM-d2-labelled derivatives generated two characteristic product ions (PIs) at m/z 372.5 and 374.5 under collision induced dissociation, respectively, which are used to establish the multiple reaction monitoring (MRM) mode-based detection. The precursor ions of NCPM-d0 and NCPM-d2 labelled derivatives of CP-thiol compounds were deduced according to the structures of the OPTPs. The peak pairs with a fixed mass difference and similar retention times were assigned as potential CP-thiol candidates for the identification of the corresponding OPTPs. Using the proposed method, we successfully determined seven residual OPTPs in agricultural product samples. Taken together, the presented method was demonstrated to be a promising new technique in the quantitation of OPTPs in agricultural product samples with high reliability.

Nano-titania-coated modified magnetic graphene oxide for pass-through cleanup of chloramphenicol, thiamphenicol, and florfenicol in human blood

To develop a rapid, effective, and accurate method for the simultaneous determination of chloramphenicol, thiamphenicol, and florfenicol in human blood by pass-through cleanup solid-phase extraction combined with liquid chromatography-tandem mass spectrometry (LC-MS/MS), novel nano-titania-coated modified magnetic graphene oxide (TiO2-Mag-GO) is used as the PRiME pass-through cleanup solid-phase extraction sorbent for the cleanup of blood phospholipids. The chromatographic separation was performed on an Eclipse Plus C18 column (100 mm×2.1 mm, 1.8 μm) using 0.08% (v/v) aqueous ammonia solution and acetonitrile having aqueous ammonia (0.08%, v/v) as mobile phases. The tandem mass spectrometer was operated using electrospray ion source (ESI) in the multiple reaction monitoring (MRM) mode. The results showed that the linearities were in the range of 0.1-10.0 μg/L with the determination coefficients (r2) greater than 0.9990 for chloramphenicol, thiamphenicol, and florfenicol. The limits of quantification (LOQs) (S/N>10) in the blood samples were between 0.056 and 0.082 μg/L and the recoveries ranged from 90.0% to 105% at three spiked levels. Precision values expressed as relative standard deviations (RSDs) were in the range of 1.2%-6.6%. The developed method can be used for routine analyses to determine chloramphenicol, thiamphenicol, and florfenicol in clinical studies.

An efficient cleanup method coupled with gas chromatography and mass spectrometry for multi-pesticides residue analysis in complex plant matrices.

We aimed to develop an efficient cleanup method for multi-pesticides residue analysis in complex plant matrices, shallot, ginger, garlic, onion, leek, and celery. Column chromatography was used as the cleanup method and fabricated with florisil and graphitized carbon black as the adsorbents. The amount of the graphitized carbon black adsorbent and the choice of the elution solvent were systematically investigated for exploring the best combination. The target pesticides covered organochlorine, pyrethroid, and organophosphorus pesticides, and were 38 in total. The method validation and comparison were performed to verify its feasibility and advantages in operation convenience and purification efficiency. The method limit of quantitation varied from 0.01 to 0.03mg/kg, which depends on the pesticides and the sample matrices. The recoveries of the pesticides ranged from 60.5 to 128% (RSD≤19.0%) at the spiked concentration level of 0.01 (or 0.03) mg/kg and 62.9 to 130% (RSD≤13.0%) at 0.1mg/kg. Compared with the commercial cleanup solid-phase extraction cartridges, the present adsorbent combination displayed better purification effect and shorter sample pretreatment time, demonstrating potential application prospect in the complex matrix sample analysis.

A Rapid Method for the Quantitative Determination of 34 Pesticides in Nonalcoholic Carbonated Beverages Using Liquid-Liquid Extraction Coupled to Dispersive Solid-Phase Cleanup Followed by Gas Chromatography with Tandem Mass Spectrometry.

An economical, rapid, and sensitive multiresidue method using liquid-liquid extraction (LLE) coupled with dispersive SPE (dSPE) cleanup was developed for the quantitative determination of 34 multiclass multiresidue (MCMR) pesticides (14 organochlorines, eight organophosphates, 10 synthetic pyrethroids, and two herbicides) in nonalcoholic carbonated beverages (cola, orange, lemon-lime, and citra) using GC with tandem MS. The procedure mainly involved LLE by dichloromethane and dSPE cleanup in the presence of magnesium sulfate, primary secondary amine, and C18. The RSD of the developed method was found to be less than 14%. The LOD and LOQ values for all the analyzed pesticides were found in the ranges of 0.001-0.027 μg/L and 0.004-0.088 μg/L, respectively. The LOQ levels of the pesticides analyzed were found to be well below the recommended limit by the European Union (0.1 μg/L in water). The mean recoveries of pesticides in different nonalcoholic carbonated beverages (cola, orange, lemon-lime, and citra) were found to be in the range of 79-111%, with RSDs less than 11%. The validation data prove that the method can be acceptable to regulatory agencies for the routine analysis of MCMR pesticides in nonalcoholic carbonated beverages.

Dilute, derivatise and shoot: Measurement of urinary free metanephrines and catecholamines as ethyl derivatives by LC-MSMS

BackgroundThe measurement of catecholamines and their metabolites in either urine or plasma is an important diagnostic test used to exclude the presence of neuroendocrine tumours. Because of weak chromatographic retention and potential ion-suppression, reverse-phase LC-MSMS is not ideal for analysis of these polar molecules. Here, we investigate derivatisation by ethylation as an alternative approach. MethodsA simple and rapid method involving acetaldehyde and a reducing agent was used to convert urine free metanephrines and catecholamines, and their deuterated analogues as internal standards, to mono-ethyl or diethyl- derivatives. Using an Agilent 6460 triple-quadrupole mass spectrometer, precursor and product ion mass spectra were recorded to allow comparison of multiple reaction monitoring methods for both derivatised and non-derivatised analytes under reverse-phase LC-MSMS conditions with positive electrospray ionization. ResultsConversion of biogenic amines to less polar ethyl derivatives increased their mass and enhanced the intensity of their molecular ions and fragments. Ethylation also improved the chromatographic properties of the amines, with greater retention and elution from reverse-phase HPLC columns with a methanol or acetonitrile gradient. The signal response of tandem mass spectrometric detection was increased up to 50-fold for ethyl metanephrines compared to non-derivatised compounds. This increase allowed for the omission of solid-phase extraction of urine as a clean-up step prior to analysis. The ‘dilute-derivatise-shoot’ method maintained analytical performance with respect to between-run imprecision (CV<6%) and accuracy in an external quality assurance program. Gender-related ranges for free metanephrines in early-morning spot urines, collected from adult patients, were similar using either derivatised or non-derivatised samples. ConclusionsThe LC-MSMS detection of free urine biogenic amines can be greatly enhanced by ethyl derivatisation, which is easy and rapid to perform. Advantages include improved chromatography and lower limits of quantitation, that negate the requirement for solid-phase clean-up of urine prior to analysis. A disadvantage is the potential toxicity of the derivatising agents used if they are not handled appropriately.

Clean-up and matrix effect in LC-MS/MS analysis of food of plant origin for high polar herbicides.

This study reports an innovative and sensitive procedure for analysis of difficult high polar herbicides (HPH) in diverse foods of plant origin. The QuPPe (Quick Polar Pesticides) method followed by determination by LC-MS/MS was modified. Chromatographic conditions, extraction, clean-up, and matrix effect were studied. Several liquid chromatography stationary and mobile phases were evaluated, and it was found that hydrophilic interaction chromatography (HILIC) gives good retention and sensitivity. An acidified methanol-water mixture was used as an effective extraction solvent of eleven HPH. Dispersive solid-phase clean-up sorbents (C18, GCB, Florisil, chitosan and graphene) were evaluated. The efficiency of the method was examined using data on recovery, precision and matrix effects. High extraction yields were achieved, and recoveries were within the 64-97% range with relative standard deviations <20% for all HPH in all commodities. Low matrix effects were observed when graphene was used during clean-up of onion extract and when chitosan was used for wheat, potato and pea extract.

Determination of Sulfonamides in Fish Using a Modified QuEChERS Extraction Coupled with Ultra-Performance Liquid Chromatography-Tandem Mass Spectrometry

In the present work, an improved QuEChERS (quick, easy, cheap, effective, rugged and safe) protocol coupled with ultra-performance liquid chromatography-tandem mass spectrometry analytical method was developed and validated for determination of trace sulfonamides residues in fish tissues. The QuEChERS protocol was modified in terms of extraction solvent, as well as a graphene-based dispersive solid-phase cleanup procedure. Some extraction conditions such as solvent, acidity, and the amount of graphene sorbent were evaluated. The matrix effect related to the QuEChERS extraction from fish tissues was studied and compared with conventional QuEChERS protocol. The target analytes were quantified by a triple-quadrupole linear ion-trap mass spectrometer in multiple-reaction monitoring mode. The matrix-matched calibration curves were performed at seven concentration levels and good linear relationship (R2 > 0.999) was observed within the range of 0.5–200 μg kg −1. Recoveries of the spiked samples ranged between 70.7 and 100.9 % with relative standard deviation lower than 9.2 %. The limits of quantification were between 2.62 and 9.03 μg kg−1. The method was successfully applied to the analysis of real samples.