Ultra-high Liquid Chromatography-tandem Mass Research Articles

Rapid Determination of 53 Stimulants Residues in Animal Food by Ultra-high Liquid Chromatography Tandem Mass Spectrometry

Rapid Determination of 53 Stimulants Residues in Animal Food by Ultra-high Liquid Chromatography Tandem Mass Spectrometry

Metabolite Profiling of External and Internal Petals in Three Different Colors of Tea Flowers (Camellia sinensis) Using Widely Targeted Metabolomics.

The flower is the reproductive organ of the tea plant, while it is also processed into different kinds of products and thus of great significance to be utilized. In this study, the non-volatile secondary metabolites in the internal and external petals of white, white and pink, and pink tea flowers were studied using a widely targeted metabolomics method with ultra-high liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). A total of 429 metabolites were identified, including 195 flavonoids, 121 phenolic acids, 40 alkaloids, 29 lignans and coumarins, 19 tannins, 17 terpenoids, and 8 other metabolites. The metabolites in the internal and external petals of different colored flowers showed great changes in flavonoids. Most flavonoids and all tannins in the internal petals were higher compared with the external petals. Some phenolic acids were more accumulated in the external petals, while others showed opposite trends. The pink tea flower contained more flavonoids, alkaloids, lignans, coumarins, terpenoids, and tannins compared with white tea flowers. In addition, cyanidin-3-O-glucoside was more accumulated in the external petals of the pink flower, indicating that anthocyanin may be the main reason for the color difference between the pink and white tea flower. The enriched metabolic pathways of different colored flowers were involved in flavonoid biosynthesis, glycine, serine and threonine metabolism, glycerophospholipid metabolism, and phenylpropanoid biosynthesis. The findings of this study broaden the current understanding of non-volatile compound changes in tea plants. It is also helpful to lay a theoretical foundation for integrated applications of tea flowers.

Evaluation of dried blood spots as an alternative sampling strategy for 5-fluorouracil monitoring: From method development to clinical application

Therapeutic drug monitoring (TDM) of 5-Fluorouracil (5-FU) is strongly recommended because of its large inter-individual pharmacokinetic variability, narrow therapeutic window, and incidence of toxicity. However, there are several factors that limit the application of TDM in clinical settings. Considering the intrinsic advantages of dried microsamples, such as minimally invasive sampling, analyte stability, and cost-effective logistics, this study aimed to develop a method for the determination of 5-FU in dried blood spots (DBS) using ultra-high liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) and to evaluate its clinical application. Sample preparation was based on an aqueous extraction followed by protein precipitation. Separation was performed in an Acquity UPLC® HSS C18 (150 ×2.1 mm, 1.8 µm), and the mobile phases were water and acetonitrile with 0.5% acetic acid. The total run time was 5.5 min. The method was linear from 100 to 2000 ng/mL, precise (maximum CV% of 7.5%), and accurate (98.3–115.4%). The average recovery was 70%. Blood hematocrit had a minimal impact on the assay. DBS samples were stable for 21 days at 4, 25, and 45 °C. A total of 40 paired samples of plasma, capillary DBS, and venous DBS were analyzed. Median 5-FU concentrations were 444.7, 637.0, and 499.7 ng/mL for plasma, capillary DBS, and venous DBS, respectively. Capillary and plasma concentrations were significantly correlated (r > 0.90), but there was a lack of agreement between the methods, as capillary DBS levels were on average 146% of plasma. Venous DBS corresponded to 110% of the measured plasma concentrations, with a strong correlation (r > 0.97) and agreement between the methods. Our study is the first to report the use of DBS samples to quantify 5-FU. Further studies are needed to establish whether capillary samples can replace plasma.

Biomarkers identification in follicular fluid of women with OHSS by using UPLC-MS method.

To figure out the differentially changed metabolites and disturbed pathways in follicular fluid (FF) of patients with OHSS in comparison to the control group undergoing in vitro fertilization (IVF), we conducted this metabolomic analysis between two groups, the OHSS group included 30 patients treated with oocyte retrieval and developed OHSS in the next 7-14 days, while another 30 patients without OHSS tendency were selected as the control group. The FF samples were obtained during the process of oocyte retrieval. FF samples were analyzed using ultra-high liquid chromatography-tandem mass spectrometry (UPLC-MS). The results identified a total of 59 differentially changed metabolites, including 33 decreased metabolites (P < 0.01) and 26 increased metabolites (P < 0.01) in FF of OHSS compared with the control group. 12 metabolites could be the most valuable biomarkers for OHSS based on ROC results. Our correlation analyses showed that deoxyinosine levels were found positively correlated with serum estradiol (E2) levels in OHSS patients, while L-isoleucine, pyruvic acid, maleamate, and arachidonic acid were found to be positively correlated with the number of retrieved oocytes. Furthermore, 4-hydroxyphenylacetaldehyde, deoxycorticosterone, creatinine, and creatine were found to be negatively associated with serum E2 levels, while 4-hydroxyphenylacetaldehyde, L-carnitine, isovaleric acid and L-2-hydroxyglutaric acid were negatively related with the number of oocytes retrieved in OHSS patients. Taken together, our study provides better identification of OHSS FF metabolic dynamics, suggesting the metabolic compounds can be used as valuable predictors or treatment targets of OHSS.

Association of maternal perfluoroalkyl substance exposure with postpartum haemorrhage in Guangxi, China

Postpartum haemorrhage (PPH) is the leading cause of maternal death worldwide, and it may be caused by environmental endocrine disruptors. Prenatal exposure to perfluoroalkyl substances (PFASs) in women has been linked to pregnancy disorders and adverse birth outcomes, but no data are available on the relationship between PFAS exposure during pregnancy and postpartum haemorrhage. This study aimed to explore the associations of maternal PFAS exposure with the postpartum haemorrhage risk and total blood loss. A total of 1496 mother-infant pairs in the Guangxi Zhuang birth cohort were included between June 2015 and May 2018. The concentration of PFASs in serum was detected using ultrahigh liquid chromatography-tandem mass spectrometry. Multiple binomial regression and linear regression models were used to analyse individual PFAS exposures. The mixture of PFASs was analysed using Bayesian Kernel Machine Regression (BKMR). In single substance exposure models, exposure to perfluorohexanesulfonic acid (PFHxS) increased the risk of postpartum haemorrhage (OR: 3.42, 95 % CI: 1.45, 8.07), while exposure to perfluorododecanoic acid (PFDoA) was inversely associated with the risk of postpartum haemorrhage (OR: 0.42, 95 % CI: 0.22, 0.80). The concentrations of perfluoroundecanoic acid (PFUnA) (β: 0.06, 95 % CI: 12.32, 108.82) and perfluorononanoic acid (PFNA) (β: 0.05, 95 % CI: 0.40, 88.95) exposure were positively correlated with the amount of postpartum haemorrhage; this result occurred only in the absence of covariate adjustment. In BKMR models, the risk of postpartum haemorrhage increased with increasing exposure to a PFAS mixture. In conclusion, our study suggested that maternal serum PFAS exposure during pregnancy was associated with the risk of postpartum haemorrhage.

Development and validation of a multianalyte method for quantification of aflatoxins and bongkrekic acid in rice and noodle products using PRiME-UHPLC-MS/MS method

An analytical method based on PRiME (process, robustness, improvements, matrix effects, ease of use) HLB purification followed by the ultra-high liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) detection has been developed for the determination aflatoxin B1, B2, G1 and G2 and bongkrekic acid in rice and noodle products. Five toxins were separated on a Waters BEH C18 column by gradient elution, scanned by ESI+ and ESI− dynamic switching and detected with MRM mode. LOD, LOQ, matrix effects, accuracy and precision of the developed method were investigated. Under the optimal sample pretreatment conditions, high sensitivity (LOQs: 0.20–0.40 μg/kg), good recoveries (80.5%-106.6%) and acceptable precision (2.4%-7.2%) were obtained for the analysis of the four aflatoxins and bongkrekic acid. This method was successfully applied to the analysis of rice and noodle products, demonstrating its applicability and suitability for the routine analysis of aflatoxins and bongkrekic acid in rice and noodle products.

Comparative N-glycoproteomic analysis of Tibetan and lowland chicken fertilized eggs: Implications on proteins biofunction and species evolution.

The characterization and functionality of protein glycosylation among different related species are of common interest. Herein, non-standard quantification and N-glycosylation enrichment technology combined with ultra-high liquid chromatography-tandem mass spectrometry were used to establish detailed N-glycoproteomics of fertilized eggs, and quantitatively compared between Tibetan and lowland chicken. A total of 396N-glycosites from 143 glycoproteins were found. Specifically, compared with lowland chicken egg white, 32N-glycosites of 22 glycoproteins were up-regulated and 57N-glycosites of 25 glycoproteins were down-regulated in Tibetan chicken egg white. Also, 137N-glycosites in 72 glycoproteins showed much higher-degree glycosylation and 36N-glycosites in 15 glycoproteins displayed lower-degree glycosylation in Tibetan chicken egg yolk than those in lowland chicken egg yolk. Through bioinformatic analysis, these varied glycoproteins werehighlyassociated with antifreeze activity, hypoxia adaptation, coagulation cascade, and binding/immunity activities, which may be related to plateau hypoxia and cold stress. PRACTICAL APPLICATIONS: These findings provide a new insight on the role of biological egg N-glycoproteins related to environmental adaptation and evolution, which may be further applied in improving egg processing and human health, by developing biomolecules for food and medical industry.

Phosphoproteomic analysis of duck egg yolk provides novel insights into its characteristics and biofunctions.

Although the importance of phosphorylation in the function of proteins is known, investigation of the protein phosphorylation of duck egg yolk (DEY) is still very limited. This study aimed to conduct a detailed phosphoproteomic study of DEY using immobilized metal affinity chromatography and ultra-high liquid chromatography tandem mass spectrometry. A total of 253 phosphorylation sites assigned to 66 phosphoproteins were identified in DEY, of which VTG-1, VTG-2, and fibrinogen alpha chain were found to be the highly phosphorylated proteins in DEY. The biological functions of the identified phosphoproteins were illuminated through gene ontology analysis, which showed that they were mainly involved in binding, catalytic, immune response, and metabolic activity. S-X-E and S-X-S were found to be the most conserved serine motifs of phosphorylation in DEY. The comparison of DEY phosphoproteins with those of chicken egg yolk (CEY) revealed that differences mostly involved molecular functions and biological processes. The comparison also revealed a higher phosphorylation level in DEY proteins. The higher phosphorylation level in DEY proteins than that in CEY proteins are supposed to help enhance duck growth performance and biological activities (e.g. antibacterial and antioxidant ability) for better adapting the humid environment the duck lived. © 2021 Society of Chemical Industry.

Determination of Three Types of New Psychoactive Tryptamines in Blood by QuEChERS Combined with UPLC-MS/MS

Objective To establish a method combining QuEChERS and ultra-high liquid chromatography-tandem mass spectrometry （UPLC-MS/MS） for rapid screening and testing of three types of new psychoactive tryptamines in human blood： 5-MeO-DALT, 5-MeO-MiPT and 5-MeO-DiPT. Methods The effects of the type of extractant, the type and dosage of salting-out agent, and the dosage of adsorbent on the test results of the three tryptamines were investigated. Blood samples were processed by QuEChERS method and then determined by UPLC-MS/MS. Results The linear relationships of 5-MeO-DALT, 5-MeO-MiPT and 5-MeO-DiPT in human blood were good in the range of 0.5-100, 0.5-100 and 0.2-100 ng/mL, respectively, with their coefficients higher than 0.99. The limits of detection （LODs） were 0.1-0.2 ng/mg. The recoveries ranged from 84.86% to 94.57%. Intra-day and inter-day precisions were good. Conclusion The method is simple, rapid, easy to operate and has a high recovery. It is suitable for the qualitative and quantitative study of tryptamines in blood and can provide the reference for public security organs to deal with related cases.

Multianalyte method for the determination of regulated, emerging and modified mycotoxins in milk: QuEChERS extraction followed by UHPLC–MS/MS analysis

A simple method for the quantification of 40 mycotoxins in milk was developed. This method is based on a QuEChERS extraction followed by the ultra-high liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) detection, and allows the simultaneous analysis of regulated, emerging, and modified mycotoxins. A sample treatment procedure was optimized to include a concentration step for the analysis of some compounds such as aflatoxin M1. The method was in-house validated in terms of limits of detection (LODs), limits of quantification (LOQs), linearity, recoveries, and precision. LOQs lower than 10 ng/mL were obtained, and recoveries ranged from 61% to 120% with a precision, expressed as the relative standard deviation, lower than 15%. Therefore, acceptable performance characteristics were obtained fulfilling European regulations. The method was successfully applied for the quantification of mycotoxins in raw milk. It can be highlighted high occurrence of beauvericin and enniatins were found in low amounts.

Multi-detection method for mycotoxins with a modified QuEChERS extraction in feed and development of a simple detoxification procedure

A new multi-mycotoxin analysis method was developed to identify and quantify 22 mycotoxins in multiple feed matrices. This method is based on a QuEChERS (quick, easy, cheap, effective, rugged and safe) extraction procedure followed by the ultra-high liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) detection. The QuEChERS extraction procedure was optimized for minimizing the matrix effect of maize. Obtained recoveries ranged from 67 % to 94 % and low LOQs (from 0.22 to 32.64 μg/kg) for regulated and emerging mycotoxins were obtained. Then, the method was expanded to seven raw materials and eight feedstuffs. In these matrices, the recovery for most mycotoxins was also high enough to fulfill the current legislation. The developed method was used for the analysis of 75 samples obtained from a nearby feed factory. Maize and maize-based products showed the highest occurrence of mycotoxins, although always below the legal limit. In addition, the ability of spheres of different composition and size to eliminate mycotoxins from raw materials and feedstuffs was tested. Up to 28 % of the mycotoxin content can be removed from matrices by using glass spheres of 2 mm of diameter. Therefore, a new process for the physical removal of mycotoxins was developed.

One-step icELISA developed with novel antibody for rapid and specific detection of diclazuril residue in animal-origin foods

ABSTRACT Diclazuril, a broad-spectrum anticoccidial drug, may be accumulated in edible tissues of animals through illegal use, which poses potential threats to human health through the food chain. In this study, an innovative hapten was designed and an immunogen of diclazuril was successfully synthesised with keyhole limpet haemocyanin as carrier protein; then a monoclonal antibody with high specificity was obtained. Furthermore, based on the novel antibody, a one-step indirect competitive enzyme-linked immunosorbent assay (icELISA) was established for rapid and specific detection of diclazuril residues. Compared with the traditional icELISA method, this method saves at least 0.5 hours and one washing step. Under the optimal conditions, the one-step icELISA for diclazuril exhibited good performance with a 50% inhibition concentration (IC50) value of 0.952 μg/kg. The average recoveries of the icELISA ranged from 73.1% to 115.5% with the coefficient of variation lower than 12.7%, which was evaluated by detecting spiked animal-origin food samples. Finally, the one-step icELISA shows a good correlation with an ultra-high liquid chromatography-tandem mass spectrometry method. Those results demonstrate that the one-step icELISA developed for diclazuril detection is time-saving, low-cost, specific, sensitive, and reliable. It shows good potential for social, environmental, and economic benefits in future use.

Restricted access carbon nanotube for microextraction by packed sorbent to determine antipsychotics in plasma samples by high-performance liquid chromatography-tandem mass spectrometry

This manuscript describes the development of the restricted access carbon nanotube (RACNT) as a selective stationary phase for microextraction by packed sorbent (MEPS) to determine antipsychotics (chlorpromazine, clozapine, olanzapine, and quetiapine) in untreated plasma samples from schizophrenic patients by ultra-high liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). The synthesis was achieved by chemically covering commercial multi-walled carbon nanotubes with bovine serum albumin (BSA) to subsequently pack the material in a polyethylene conical tube (1000μL). The RACNTs' sorbents were able to exclude about 97% of the plasma proteins, maintaining the same performance for about 100 assays. The MEPS variables (sample pH, draw-eject cycles, desorption and phase cleanup) were evaluated to improve sensibility and selectivity. The MEPS/UHPLC-MS/MS method was linear at concentrations ranging from the lower limit of quantification (10.0ngmL-1) to the upper limit of quantification (200-700ngmL-1) with coefficients of determinations higher than 0.99. The precision assays presented relative standard deviation (RSD) values lower than 13%, and the accuracy assays presented relative error (RE) values that ranged from - 8.01 to 11.53%. Neither significant matrix effects nor carryover was observed. The developed method was successfully applied to determine antipsychotics drugs for therapeutic drug monitoring of schizophrenic patients.

Quantitative phosphoproteomic analysis of fertilized egg derived from Tibetan and lowland chickens

In this study, immobilized metal affinity chromatography and ultra-high liquid chromatography tandem mass spectrometry were used to establish detailed phosphoproteomes of fertilized egg, and further quantitative compared those from Tibetan chicken and lowland chicken. A total of 138 phosphosites from 42 phosphoproteins were identified. Specifically, 103 phosphosites representing 41 phosphoproteins were detected in Tibetan chicken egg, and 125 sites in 40 phosphoproteins were found in lowland chicken egg; 47 phosphosites in 26 phosphoproteins were found in fertilized egg white, while 109 phosphosites in 24 phosphoproteins were identified in fertilized egg yolk. Thirty-one phosphoproteins carrying 83 phosphosites (12 phosphosites from 10 phosphoproteins in egg white and 52 sites from 17 proteins in egg yolk) showed significantly different phosphorylation between Tibetan and lowland chicken eggs, which were mainly involved in binding, catalysis, allergenic and cryoprotectant activities. Besides, several amino acid polymorphisms in ovalbumin and vittelligion-2 were detected, which might alter 3D structures and biofunctions. Our data recorded the egg phosphoprotein abundances and biological activities of two chicken species. These results provide a solid foundation to better understand the egg phosphoprotein characteristics, especially to explore the impacts of cross-species alteration of phosphorylation status on the structure, function and nutritional properties.

QiDiTangShen Granules Activate Renal Nutrient-Sensing Associated Autophagy in db/db Mice.

QiDiTangShen granules (QDTS) have been proven to reduce the proteinuria in patients with diabetic nephropathy (DN) effectively. The present study was aimed to investigate the mechanism underlying QDTS’s renoprotection. The main components of QDTS were identified by ultra-high liquid chromatography-tandem mass spectrometry and pharmacological databases, among which active components were screened by oral bioavailability and drug-likeness. Their regulation on autophagy-related nutrient-sensing signal molecules (AMPK, SIRT1, and mTOR) was retrieved and analyzed through the Pubmed database. Then, db/db mice were randomly divided into three groups (model control, valsartan and QDTS), and given intragastric administration for 12 weeks, separately. Fasting and random blood glucose, body weight, urinary albumin excretion (UAE) and injury markers of liver and kidney were investigated to evaluate the effects and safety. Renal histological lesions were assessed, and the expressions of proteins related to nutrient-sensing signals and autophagy were investigated. Thirteen active components were screened from 78 components identified. Over half the components had already been reported to improve nutrient-sensing signals. QDTS significantly reduced UAE, ameliorated mesangial matrix deposition, alleviate the expression of protein and mRNA of TGF-β, α-SMA, and Col I, as well as improved the quality of mitochondria and the number of autophagic vesicles of renal tubular cells although the blood glucose was not decreased in db/db mice. Compared to the db/db group, the expression of the autophagy-inducible protein (Atg14 and Beclin1) and microtubule-associated protein 1 light chain 3-II (LC3-II) were up-regulated, autophagic substrate transporter p62 was down-regulated in QDTS group. It was also found that the expression of SIRT1 and the proportion of p-AMPK (thr172)/AMPK were increased, while the p-mTOR (ser2448)/mTOR ratio was decreased after QDTS treatment in db/db mice, which was consistent with the effect of its active ingredients on the nutrient-sensing signal pathway as reported previously. Therefore, QDTS may prevent the progression of DN by offering the anti-fibrotic effect. The renoprotection is probably attributable to the regulation of nutrient-sensing signal pathways, which activates autophagy.

A QuEChERS based extraction procedure coupled to UPLC-MS/MS detection for mycotoxins analysis in beer

A new method based on a QuEChERS extraction followed by the ultra-high liquid chromatography tandem mass spectrometry (UPLC-MS/MS) detection has been developed for the analysis of mycotoxin in beer. The method allows the identification and quantification of 23 mycotoxins with different chemical characteristic including regulated, emerging and masked compounds. A sample treatment procedure involving a QuEChERS extraction and dispersive solid-phase clean-up steps was applied. This protocol involves a new approach based on a sample concentration before the extraction. The method was in-house validated in terms of limits of detection (LODs), limits of quantification (LOQs), linearity, repeatability and recoveries. For most compounds, recoveries ranged from 70% to 110% with LOQs (from 0.038 to 30.43 µg/L) lower than the maximum residue levels established in European regulations. In general, acceptable performance characteristics were obtained fulfilling the current legislation. Therefore, the proposed method is appropriate for routine analysis of beer.

A UPLC-MS/MS method for simultaneous determination of five flavonoids from Stellera chamaejasme L. in rat plasma and its application to a pharmacokinetic study.

Stellera chamaejasme L. has been used as a traditional Chinese medicine for the treatment of scabies, tinea, stubborn skin ulcers, chronic tracheitis, cancer and tuberculosis. A sensitive and selective ultra-high liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method was developed and validated for the simultaneous determination of five flavonoids (stelleranol, chamaechromone, neochamaejasmin A, chamaejasmine and isochamaejasmin) of S. chamaejasme L. in rat plasma. Chromatographic separation was accomplished on an Agilent Poroshell 120 EC-C18 column (2.1 × 100 mm, 2.7 μm) with gradient elution at a flow rate of 0.4 mL/min and the total analysis time was 7 min. The analytes were detected using multiple reaction monitoring in positive ionization mode. The samples were prepared by liquid-liquid extraction with ethyl acetate. The UPLC-MS/MS method was validated for specificity, linearity, sensitivity, accuracy and precision, recovery, matrix effect and stability. The validated method exhibited good linearity (r ≥ 0.9956), and the lower limits of quantification ranged from 0.51 to 0.64 ng/mL for five flavonoids. The intra- and inter-day precision were both <10.2%, and the accuracy ranged from -11.79 to 9.21%. This method was successfully applied to a pharmacokinetic study of five flavonoids in rats after oral administration of ethyl acetate extract of S. chamaejasme L.

Simultaneous determination of 14 antiviral drugs and relevant metabolites in chicken muscle by UPLC-MS/MS after QuEChERS preparation.

A fast method for the simultaneous determination of 14 antiviral drugs and relevant metabolites in chicken muscle by ultra-high liquid chromatography tandem mass spectrometry (UPLC-MS/MS) was developed. The analytes included anti-influenza drugs (amantadine, rimantadine, oseltamivir, oseltamivir carboxylate, memantine, arbidol, and moroxydine), anti-herpes drugs (acyclovir, ganciclovir, famciclovir, penciclovir, ribavirin and its main metabolite TCONH2), and an immunomodulator (imiquimod). The samples were pretreated using a modified QuEChERS (Quick, Easy, Cheap, Effective, Rugged and Safe) method. The determination of the target compounds was conducted in less than 11.0min, and specificity was ensured by the use of multiple reaction monitoring (MRM) acquisition mode. Good linearities (R(2)>0.9928) were obtained in the range of 0.1-100μg/L, and the recovery rates were 56.2-113.4% with RSDs of 1.7-10.3% for intra-day precision and 2.4-8.8% for inter-day precision. The LODs and LOQs of all analytes were in the ranges of 0.02-1.0 and 0.05-2.5μg/kg, respectively. An analysis of real samples suggested that this method is simple, sensitive, reliable and practical for the detection of antiviral drugs in animal tissue.

Determination of phenolic compounds by ultra high liquid chromatography-tandem mass spectrometry: Applications in nuts

A new method for qualitative and quantitative analysis of fourteen common polyphenolic compounds (gallic acid, 3,4-dihydroxybenzoic or proto-catechuic acid, chlorogenic acid, caffeic acid, syringic acid, 2-hydroxycinnamic or o-coumaric acid, p-coumaric acid, ferulic acid, rutin, rosmarinic acid, catechin, epicatechin, kaempferol and trans-cinnamic acid) was developed using ultra high liquid chromatography (UHPLC) coupled with tandem mass spectrometry (MS/MS). Selected phenolic compounds were detected in multiple reaction monitoring (MRM) mode and determined simultaneously in a 13-min analysis time and a number of validation parameters (calibration range, limit of detection, limit of quantification, repeatability, precision, and recovery) were studied. To show the usefulness of the method, phenolic compounds were studied in nuts such as hazelnut (Corylus avellana L.), pistachio (Pistaciae vera L.) and almond (Prunus amygdaleus L.).

Simultaneous determination of amantadine, rimantadine and memantine in chicken muscle using multi-walled carbon nanotubes as a reversed-dispersive solid phase extraction sorbent.

A modified quick, easy, cheap, effective, rugged, and safe (QuEChERS) method using multi-walled carbon nanotubes (MWCNTs) as a reversed-dispersive solid phase extraction (r-dSPE) material combined with ultra-high liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) was developed for the simultaneous determination of amantadine, rimantadine and memantine in chicken muscle. The satisfactory separation of isomers (rimantadine and memantine) was obtained on an Acquity BEH C18 column (2.1 mm × 100 mm, 1.7 μm) after optimization of mobile phase composition, column temperature and flow rate. The method involved an acetonitrile-based sample preparation and a dSPE clean-up procedure with MWCNTs material. Variations in the type and amount of MWCNTs, the pH value of the extract, the extraction time for MWCNTs, and the type of eluent were used to determine the optimal parameters for increasing the sample throughput and the sensitivity. The samples were quantified using amantadine-D15, rimantadine-D4 and memantine-D6 as the internal standards. Under the optimized conditions, recoveries of 96.8-104.6% and the values of coefficient of variation (CV) of 3.8-6.4% were obtained for the three drugs in chicken muscle at three spiked levels (0.5, 1.0 and 1.5 μg/kg), and the decision limits (CCα) and detection capabilities (CCβ) were 0.15-0.20 μg/kg and 0.20-0.25 μg/kg, respectively. Positive results were obtained from local supermarket using this method, and the concentrations obtained from the newly developed method compared well to the previously reported method.