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1.
J Chromatogr A ; 1636: 461794, 2021 Jan 11.
Artigo em Inglês | MEDLINE | ID: mdl-33341433

RESUMO

A rapid, simple, and generic analytical method for the simultaneous determination of 140 undesirable low-weight pesticides and mycotoxins from different chemical classes in black tea was developed. The method involved swelling the sample in ammonium acetate buffer, extraction with acetonitrile-dimethyl sulfoxide, cleanup by dual dispersive solid-phase extraction (D-SPE) with the assistance of low-temperature centrifugation, and analysis by ultraperformance liquid chromatography coupled with electrospray ionization tandem mass spectrometry using multiple reaction monitoring mode. The interferences in the extract were eliminated by the combination of dual d-SPE using only C18 sorbent and anhydrous magnesium sulfate, which maintained the chromatographic column under the ideal condition for a long time and enabled satisfactory recoveries of hydrophobic and hydrophilic analytes simultaneously. Matrix-matched calibration curves were obtained for most target compounds with linear regression coefficients above 0.9900. The limits of quantification (LOQs) ranged within 0.5-10.0 µg/kg, which were usually sufficient to verify the compliance of products with legal tolerances. Satisfactory recoveries of 64.5%-138.1% were obtained in black ta samples with the relative standard deviation (RSD) values between 1.8 and 25.9%. The inter-day precision ranged within 2.2%-24.9%. For over 90% of the analytes, the recoveries were between 70% and 120%, with RSD values below 15.0%. The application of this method in routine monitoring programs can drastically reduce effort and time.


Assuntos
Cromatografia Líquida de Alta Pressão/métodos , Micotoxinas/análise , Praguicidas/análise , Espectrometria de Massas em Tandem/métodos , Chá/química , Acetonitrilos/química , Tampões (Química) , Dimetil Sulfóxido/química , Reprodutibilidade dos Testes , Extração em Fase Sólida , Espectrometria de Massas por Ionização por Electrospray
2.
J Chromatogr A ; 1633: 461605, 2020 Dec 06.
Artigo em Inglês | MEDLINE | ID: mdl-33128973

RESUMO

The drift and noise of acetonitrile-water gradient baselines (5-95%, v/v, 5 min linear gradient) in reversed phase liquid chromatography (RPLC) are recorded at a wavelength of 215 nm using 0.1% trifluoroacetic acid (TFA) as the mobile phase additive, a 4.6 mm  ×  150 mm 5 µm Symmetry-C18 RPLC column, and an Arc system (low-pressure gradient proportioning valve or GPV, pump with a stroke volume of either 66 or 132 µL, no mixer) as the LC instrument. These observations are predicted from solid-liquid adsorption thermodynamics which requires the measurement of the excess adsorption isotherm of acetonitrile from water onto the RPLC column and of the variation of the Henry's constant of TFA as a function of the volume fraction of acetonitrile in the bulk mobile phase. The incomplete mixing of the acetonitrile and water packets delivered by the low-pressure GPV is represented by a sinusoidal perturbation of the programmed volume fraction of acetonitrile during the entire gradient. The variation of the TFA absorbance at 215 nm with increasing acetonitrile concentration is measured in order to transform TFA concentration into the observable absorbance unit. The drift and noise of the gradient baseline are calculated by solving numerically (Rouchon method) the equilibrium-dispersive (ED) mass balance equations of acetonitrile and TFA. The agreement between the calculated and observed gradient baselines is very good as the proposed model of chromatography accurately accounts for the displacement of TFA between stationary and mobile phases (early excess and late deficit of TFA concentration relative to 0.1%) and for the frequency (equal to the ratio of the applied flow rate to the stroke volume) and the amplitude of the periodic noise recorded during the gradient. From a practical viewpoint, the drift of the gradient baseline can be minimized by maximizing the ratio of the gradient volume to the hold-up volume ( > 10) and/or by minimizing the retention factor of the mobile phase additive in the water-rich eluent (k < 0.2). The reduction of the noise amplitude below 0.1 mAU as requested by the pharmaceutical industry imposes the ratio of the flow rate to the stroke volume of the pump to be larger than 1 Hz. This opens avenues towards the development of new GPV, pump, and mixers in order to mix efficiently the solvent packets delivered by conventional LC instrument.


Assuntos
Cromatografia de Fase Reversa/métodos , Termodinâmica , Acetonitrilos/química , Adsorção , Solventes/química , Ácido Trifluoracético/química , Água/química
3.
J Chromatogr A ; 1628: 461436, 2020 Sep 27.
Artigo em Inglês | MEDLINE | ID: mdl-32822976

RESUMO

In recent years, mussel-inspired polydopamine (PDA) based materials have been widely used as stationary phases for open-tubular capillary electrochromatography (OT-CEC) because of their various excellent properties. Nevertheless, the traditional synthesis routes of functionalized PDA-based capillary columns usually are time-consuming and limited in aqueous solutions. Herein, we report a facile and rapid route to prepare octadecylamine (ODA) functionalized PDA coated OT-CEC columns in organic solvents via a novel one-step in situ solvothermal-assisted coating strategy. Through this developed solvothermal-assisted approach, the growth rate of ODA/PDA coating was significantly speeded up and their hybrid coating process on the capillary inner surface could be rapidly completed in 60 min. The successful preparation of the solvothermal-assisted ODA/PDA hybrid coating were systematically characterized and confirmed by several methods. The influence of the preparation parameters on the formation of hybrid coating and the separation ability of the ODA/PDA modified columns were systematically explored. Consequently, the high-efficiency baseline separation of four kinds of neutral, acidic and basic analytes were achieved based on the ODA/PDA modified columns. The repeatability of the solvothermal-assisted ODA/PDA coated column was also studied, and the relative standard deviations for intra-day, inter-day and column-to-column were all less than 5%. Additionally, the solvothermal-assisted ODA/PDA modified column exhibited good stability and long lifetime.


Assuntos
Aminas/química , Eletrocromatografia Capilar/métodos , Indóis/química , Polímeros/química , Solventes/química , Temperatura , Acetonitrilos/química , Tampões (Química) , Eletro-Osmose , Halogenação , Concentração de Íons de Hidrogênio , Espectroscopia de Infravermelho com Transformada de Fourier , Fatores de Tempo
4.
J Chromatogr A ; 1626: 461365, 2020 Aug 30.
Artigo em Inglês | MEDLINE | ID: mdl-32797844

RESUMO

Sequential injection chromatography (SIC) is an alternative for fast chromatographic separations with low consumption of organic solvents. However, its separation capacity is restricted by the use of short chromatographic columns and the limitations for gradient elution. The present work aimed to expand the analytical capacity of SIC by exploiting a multidimensional approach with two chromatographic columns, different in their separation mechanisms, which increased the selectivity and peak resolution. The viability of the proposal was demonstrated by separation of aromatic biogenic amines (histamine, tyramine, phenylethylamine, and tryptamine), whose unidimensional separation was not achieved either by using cyanopropyl or C18 chromatographic columns. In the two-dimensional approach, the fraction of the eluate unresolved in the first dimension (containing tyramine and phenylethylamine) was collected in a sampling loop and, subsequently, inserted in the second chromatographic dimension (heart-cutting mode). Under the optimized conditions, the first chromatographic dimension was based on a cyanopropyl monolithic column and an aqueous mobile phase composed of phosphoric acid solution, pH 2.5, while the second dimension employed a C18 superficially porous particle column and a mobile phase composed of acetonitrile and phosphoric acid aqueous solution, pH 2.5 (7:93, v/v). The total analysis time was 8 min, and a resolution of 1.72 was achieved between the nearest peaks (tyramine and phenylethylamine). Linear responses were obtained within 10 and 50 mg L-1 (r > 0.997), with detection limits estimated at 2.7, 7.7, 1.9, and 0.3 mg L-1, for histamine, tyramine, phenylethylamine, and tryptamine, respectively, and a coefficient of variation of 3.0% (n = 12).


Assuntos
Cromatografia/métodos , Acetonitrilos/química , Aminas Biogênicas/isolamento & purificação , Ácidos Fosfóricos/química , Solventes/química
5.
J Chromatogr A ; 1626: 461373, 2020 Aug 30.
Artigo em Inglês | MEDLINE | ID: mdl-32797851

RESUMO

Simulation software for liquid chromatography can accelerate method development capabilities. In two-dimensional chromatography this is particularly attractive because there are more method variables to consider, provided simulations can account for the effects of injecting effluent from the first dimension separation into the second dimension column. In this paper we describe the adaptation of a previously described model (the Forssén model) to enable prediction of the profile of an injection pulse as it exits an Active Solvent Modulation (ASM) valve and enters the second dimension column under a variety of flow rate and sample loop size conditions (a global model). Experimentally measured injection profiles were used to train empirical models capable of generating injection profiles as a function of sample loop volume and flow rate. The resulting parameters were then used to generate an injection profile for a loop volume not used in the training set. The resulting profile agreed well with the experimentally obtained profile for this sample loop. Finally, chromatograms were simulated using previously developed simulation software incorporating the injection profile models developed in this work. Chromatographic peaks were simulated for valerophenone on an Agilent Zorbax Stablebond C18 stationary phase with an acetonitrile/water mobile phase gradient. Results of simulations based on experimental injection profiles, profiles predicted using the Forssén or global models, and rectangular injection profiles were compared. Comparison of the resulting chromatographic peaks revealed good agreement between those produced using experimental profiles or the Forssén or global models, with less than ± 0.3% deviations for retention times and less than ± 10% deviations for the peak widths (expressed as σ).


Assuntos
Cromatografia Líquida/métodos , Solventes/química , Acetonitrilos/química , Água/química
6.
J Chromatogr A ; 1627: 461421, 2020 Sep 13.
Artigo em Inglês | MEDLINE | ID: mdl-32823116

RESUMO

Herein we present an efficient, column-switching method that relies on a custom-made T-union passive diffusion micromixer to assist water dilution and promote trap solute focusing of a high sample volume dissolved in pure organic solvent using a 0.075 mm i.d. nano-LC column. This method allows injecting 20 µL (or higher) of sample volume, speeding up the analysis time, with a 400-fold increase of the limits of quantitation for selected compounds. Five pesticides in different media were used as model compounds, and the analyses were carried out with a triple quadrupole mass spectrometer equipped with a Liquid Electron Ionization (LEI) LC-MS interface working in multiple reaction monitoring (MRM) mode. The system microfluidics were investigated using COMSOL modeling software. Robustness of the entire system was evaluated using a post-extraction addition soil extracts with limits of detection values spanning from 0.10 to 0.45 µg/L. Reproducible results in terms of peak area, peak shape, and retention times were achieved in soil matrix. Repeatability test on peak area variations were lower than 10%.


Assuntos
Cromatografia de Fase Reversa/métodos , Elétrons , Microfluídica/métodos , Nanopartículas/química , Espectrometria de Massas em Tandem/métodos , Água/química , Acetonitrilos/química , Difusão , Limite de Detecção , Praguicidas/análise , Reprodutibilidade dos Testes , Solventes/química
7.
J Chromatogr A ; 1627: 461430, 2020 Sep 13.
Artigo em Inglês | MEDLINE | ID: mdl-32823119

RESUMO

There is a huge, still increasing market for synthetic and therapeutic peptides. Their quality control is commonly based on a generic reversed-phase liquid chromatography (RPLC) method with C18 stationary phase and acetonitrile gradient with 0.1% trifluoroacetic acid in the mobile phase. It performs exceptionally well for a wide variety of impurities, yet structurally closely related impurities with similar sequences, not resolved in preparative RPLC, may easily coelute in the corresponding QC run as well. To address this problem an advanced generic 2D-LC impurity profiling method was developed in this work. It employs a selective comprehensive (high resolution sampling) RP×RP 2D-LC separation using a 100×2.1 mm ID column with the common acidic generic gradient in the first dimension, while RPLC under basic pH on a short 30×3 mm ID column is used in the second dimension. Recording data with a UV detector at 215 nm after 1D separation provides the common generic 1D chromatogram. However, after the 2D separation a flow splitter enabled recording of the signals of complementary detectors comprising a diode array detector (DAD) in-line with a charged aerosol detector (CAD) and a quadrupole-time-of-flight (QTOF) mass spectrometer (MS) with an electrospray ionization (ESI) source. Generic conditions of this 2D-LC method have been established through optimization of 2D stationary and mobile phase considering different pH values and buffer concentrations. The orthogonal separation principle has been documented by a number of therapeutic peptides including Exenatide, Octreotide, Cyclosporine A and Oxytocin as well as some other proprietary synthetic peptides. The information density can be further enhanced by using the QTOF-MS detector by data independent acquisition with SWATH. Through this sequential window acquisition of all theoretical fragment ion mass spectra it became possible to collect MS/MS data comprehensively in the high-resolution sampling window, thus enabling the extraction of 2D-EICs from fragment ions and the generation of 2D-contour plots of all product ions. Using Oxytocin as an example for an important therapeutic peptide, the ability of this advanced generic sRP-UV×RP-DAD-CAD-ESI-QTOF-MS/MS method with SWATH for peptide quality control is discussed.


Assuntos
Cromatografia Líquida de Alta Pressão/métodos , Cromatografia de Fase Reversa/métodos , Peptídeos/análise , Acetonitrilos/química , Tampões (Química) , Concentração de Íons de Hidrogênio , Ocitocina/análise , Controle de Qualidade , Solventes/química , Espectrometria de Massas em Tandem
8.
J Chromatogr A ; 1627: 461390, 2020 Sep 13.
Artigo em Inglês | MEDLINE | ID: mdl-32823096

RESUMO

A dispersive solid phase extraction method was combined with deep eutectic solvent-based solidification of floating organic drop-dispersive liquid-liquid microextraction and used for the extraction/preconcentration of some organophosphorus pesticides residues from edible oil samples. The extracted analytes were quantified with gas chromatography-nitrogen phosphorous detector. In this procedure, the sample lipids are saponified with a sodium hydroxide solution and then the analytes are adsorbed onto a primary secondary amine sorbent. After that the analytes are desorbed with acetone as an elution/dispersive solvent and mixed with choline chloride: 3,3-dimethyl butyric acid deep eutectic solvent and the mixture is rapidly dispersed into deionized water. Then, the obtained cloudy solution is centrifuged and placed into an ice bath. The extraction solvent is solidified on the top of the solution. Finally, it is removed and dissolved in acetonitrile, and 1 µL of the solution is injected into the separation system. Validation of the method showed that limits of detection and quantification were in the ranges of 0.06-0.24 and 0.20-0.56 ng mL-1, respectively. Enrichment factors and extraction recoveries of the analytes ranged from 170-192 and 68-77%, respectively. The method had an acceptable precision with relative standard deviations less than ≤9.2% for intra- (n=6) and inter-day (n=6) precisions at four concentrations (3, 10, 50, and 250 ng mL-1, each analyte). Finally the method was used for determination of the analytes in five edible oil samples.


Assuntos
Microextração em Fase Líquida/métodos , Compostos Organofosforados/análise , Praguicidas/análise , Óleos Vegetais/química , Extração em Fase Sólida/métodos , Solventes/química , Acetonitrilos/química , Reprodutibilidade dos Testes , Hidróxido de Sódio/química , Soluções , Sonicação , Fatores de Tempo
9.
J Biosci Bioeng ; 130(4): 437-442, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32616382

RESUMO

Fast enantiomeric separation of amino acids was studied by liquid chromatography/mass spectrometry (LC/MS) on a chiral crown ether stationary phase. A chiral crown ether bonded silica column (3 mm internal diameter (i.d.), 5 cm long) packed with 3 µm particles was employed instead of a 15 cm column packed with 5 µm particles used in our previous study. In addition, the extra-column variance, becoming more serious for smaller columns, was reduced by replacing 0.127 mm i.d. post-column tubes with shorter, smaller-diameter (0.0635 mm i.d.) tubes. The results demonstrated the benefits of using shorter columns packed with smaller particles and the reduction of the extra-column band broadening for fast enantiomeric separation. Finally, the enantiomeric separation of 18 pairs of proteinogenic amino acids was achieved within 2 min with a resolution (Rs) > 1.5 for each pair using an isocratic mobile phase of acetonitrile/water/trifluoroacetic acid (ACN/W/TFA) = 96/4/0.5, and a flow rate 1.2 mL/min at 30°C. This is the highest throughput method for simultaneous chiral separation of all proteinogenic amino acids except proline to date.


Assuntos
Aminoácidos/química , Aminoácidos/isolamento & purificação , Cromatografia Líquida/métodos , Éteres de Coroa/química , Espectrometria de Massas , Acetonitrilos/química , Aminas/química , Dióxido de Silício/química , Estereoisomerismo , Fatores de Tempo , Ácido Trifluoracético/química , Água/química
10.
J Chromatogr A ; 1625: 461334, 2020 Aug 16.
Artigo em Inglês | MEDLINE | ID: mdl-32709359

RESUMO

A comprehensive study on the chiral separation of bupivacaine, mepivacaine, prilocaine and propanocaine with eight commercial polysaccharide-based chiral stationary phases (CSPs) in reversed phase conditions compatible with MS detection is performed. Methanol and acetonitrile are used as organic modifiers. Retention and resolution values obtained for each compound in the different CSPs and mobile phases are compared. The polysaccharide-based CSPs tested present different enantioselectivity towards the analytes. From the results, the experimental conditions for determining the enantiomers of bupivacaine, mepivacaine, prilocaine and propanocaine in saline aqueous samples using MS detection are used, for the first time, to perform an enantioselective biodegradability study.


Assuntos
Anestésicos Locais/isolamento & purificação , Cromatografia de Fase Reversa/métodos , Polissacarídeos/química , Acetonitrilos/química , Biodegradação Ambiental , Cromatografia Líquida de Alta Pressão , Metanol/química , Peso Molecular , Estereoisomerismo , Água/química
11.
J Chromatogr A ; 1624: 461218, 2020 Aug 02.
Artigo em Inglês | MEDLINE | ID: mdl-32540066

RESUMO

In this study, amylose- and cellulose-phenylcarbamate-based chiral columns with different chiral-selector (CS) chemistries were compared to each other for the separation of enantiomers of basic chiral analytes in acetonitrile and aqueous-acetonitrile mobile phases in HPLC. For two chemistries the amylose-based columns with coated and immobilized CSs were also compared. The comparison of CSs containing only electron-donating or electron-withdrawing substituents with those containing both electron-donating and electron-withdrawing substituents showed opposite results for the studied set of chiral analytes in the case of amylose and cellulose derivatives. Along with the chemistry of CS the focus was on the behavior of polysaccharide phenylcarbamates in acetonitrile versus aqueous acetonitrile as eluents. In agreement with earlier results, it was found that in contrast to the commonly accepted view, polysaccharide phenylcarbamates do not behave as typical reversed-phase materials for basic analytes either. In the range of water content in the mobile phase of up to 20-30% v/v the behavior of these CSs is similar to hydrophilic interaction liquid chromatography (HILIC)-type adsorbents. This means that with increasing water content in the mobile phase up to 20-30% v/v, the retention of analytes mostly decreases. The important finding of this study is that the separation efficiency improves for most analytes when switching from pure acetonitrile to aqueous acetonitrile. Therefore, in spite of reduced retention, the separation of enantiomers improves and thus, the HILIC-range of mobile phase composition, offering shorter analysis time and better peak resolution, is advantageous over pure polar-organic solvent mode. Interesting examples of enantiomer elution order (EEO) reversal were observed for some analytes based on the content of water in the mobile phase on Lux Cellulose-1 and Lux Amylose-2 columns.


Assuntos
Amilose/química , Celulose/química , Cromatografia Líquida de Alta Pressão/métodos , Preparações Farmacêuticas/isolamento & purificação , Fenilcarbamatos/química , Acetonitrilos/química , Elétrons , Etanolaminas/análise , Etanolaminas/isolamento & purificação , Preparações Farmacêuticas/análise , Propanolaminas/análise , Propanolaminas/isolamento & purificação , Propranolol/análise , Propranolol/isolamento & purificação , Estereoisomerismo , Água/química
12.
J Chromatogr A ; 1624: 461234, 2020 Aug 02.
Artigo em Inglês | MEDLINE | ID: mdl-32540074

RESUMO

Atmospheric amines contribute to the nucleation and initial growth of new particles as well as secondary organic aerosol formation, influencing the radiative balance of the Earth's atmosphere. In this study, we develop an ion chromatography (IC) method for separating and quantifying the nine most abundant amines (methylaminium (MMAH+), dimethylaminium (DMAH+), trimethylaminium (TMAH+), ethylaminium (MEAH+), diethylaminium (DEAH+), propylaminium (MPAH+), butylaminium (MBAH+), ethanolaminium (MEOH+), and triethanolaminium (TEOH+)) from six common inorganic species in atmospheric aerosols. The retention times of the amines were altered by the addition of acetonitrile to the eluent because acetonitrile can reduce the adsorption of hydrophobic amines on the stationary phase. The developed method achieved the successful separation of DEAH+ and TMAH+ from inorganic cations, which often coelute with each other in established IC methods. The interference of K+ on the determination of MEAH+ was eliminated by the complexation of K+ with 18-crown-6, which prolonged the retention time of K+. Finally, 9 target amines and 6 common inorganic cations were separated, with a resolution Rs ≥ 1.2 for DEAH+ and MPAH+ and Rs > 1.5 for other species. The detection limits varied in the range of 0.34-1.48 ng for the 9 amines and 0.19-0.56 ng for the inorganic cations. The developed method was successfully applied for the determination of low molecular weight amines and inorganic cations in PM2.5 collected from an urban site in Shanghai and an isolated coast of Chongming Island. Eight amines were detected in the urban samples, in which MMAH+ and DMAH+ dominated. The average amine concentration in the urban aerosols was 76.3 ± 38.4 ng m-3, which is approximately 4-fold higher than those in the marine samples collected from the coast.


Assuntos
Acetonitrilos/química , Aminas/análise , Atmosfera/química , Cromatografia por Troca Iônica/métodos , Éteres de Coroa/química , Compostos Inorgânicos/análise , Aerossóis/análise , Cátions , China , Limite de Detecção , Padrões de Referência
13.
Chemosphere ; 258: 127278, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32554006

RESUMO

Syringe filters are widely used for sample pretreatments in laboratories. This study found that, surprisingly, these filters can leak dissolved organic carbon (DOC) that can potentially serve as precursors of disinfection by-products (DBPs). Nine common types of syringe filters were assessed. The results showed that the DOC of ultrapure water increased after syringe filtration. The DOC shed from filter membranes was characterized, whose spectra showed that the main compounds exhibited a low apparent molecular weight. Five classes of DBPs were investigated including trihalomethanes, haloacetaldehydes, haloacetonitriles, haloacetamides and halonitromethanes, among which trichloromethane (TCM), dichloroacetaldehyde (DCAL), trichloroacetaldehyde (TCAL), dichloroacetonitrile (DCAN), and trichloronitromethane (TCNM) were principally detected. The DBP formation was affected by chlorination time and membrane types. In general, the use of the poly vinylidene fluoride membrane resulted in the highest formation of TCM and TCAL, whereas nylon and mixed cellulose esters membranes contributed significantly to the formation of DCAN and TCNM, respectively. The shedding DOC and the formation of TCM, DCAL and TCAL from filter membranes were mitigated effectively by pre-washing; however, the contribution of membrane leakage to DCAN and TCNM formation was still notable, even with a pre-wash volume of 50 mL. When unwashed syringe filters were used for a real water sample, the DBP formation increased by up to 73.2% compared to the pre-washed ones; particularly for TCNM it was always over 15%. Therefore, for better quality control in laboratories, more attention should be paid to the syringe filters during sample pre-treatments, particularly when DBP formation is being investigated.


Assuntos
Desinfetantes/análise , Desinfetantes/química , Desinfecção/métodos , Membranas Artificiais , Acetonitrilos/análise , Acetonitrilos/química , Clorofórmio/análise , Clorofórmio/química , Cromatografia em Gel , Filtração/instrumentação , Filtração/métodos , Halogenação , Hidrocarbonetos Clorados/análise , Hidrocarbonetos Clorados/química , Peso Molecular , Trialometanos/análise , Trialometanos/química , Poluentes Químicos da Água/análise , Poluentes Químicos da Água/química , Purificação da Água/métodos
14.
Food Chem ; 331: 127190, 2020 Nov 30.
Artigo em Inglês | MEDLINE | ID: mdl-32562982

RESUMO

Monitoring neonicotinoid residues in grains is of significant interest for the proper assessment of pesticide exposure to human. The quick, easy, cheap, effective, rugged, and safe extraction method combined with dispersive liquid-liquid micro-extraction (QuEChERS-DLLME) was developed for extracting, purifying, and concentrating seven common neonicotinoid pesticides from the grains (rice, millet, and maize). Water and acetonitrile were used in tandem as extractants in QuEChERS, while water, acetonitrile, and trichloromethane in DLLME acted as the external phase, dispersant, and extractant, respectively. Comprehensive consideration of the single factor test and response surface method to optimize parameters including type and volume of extractants and dispersant. The evaluation showed that the QuEChERS-DLLME method held excellent linearity (R2 > 0.99). The limits of quantitation ranged from 0.003 to 0.08 µg kg-1 for the seven insecticides. The recoveries were in the range of 62-118%, and good reproducibility was obtained with a relative standard deviation below 15%.


Assuntos
Grão Comestível/química , Contaminação de Alimentos/análise , Microextração em Fase Líquida/métodos , Neonicotinoides/análise , Resíduos de Praguicidas/análise , Espectrometria de Massas em Tandem/métodos , Acetonitrilos/química , Cromatografia Líquida/métodos , Inseticidas/análise , Limite de Detecção , Oryza/química , Reprodutibilidade dos Testes , Zea mays/química
15.
Food Chem ; 327: 127015, 2020 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-32434124

RESUMO

A simple and reliable analytical method was established for the simultaneous determination of tiafenacil and its six metabolites in fruits. The method involves three steps: extraction using acidified acetonitrile, clean-up by octadecylsilane(C18) and graphitized carbon black (GCB), and detection using liquid chromatography coupled with tandem mass spectrometry (UHPLC-MS/MS). The method was validated on seven matrices spiked at 10, 100 and 1000 µg kg-1. Average recoveries ranged from 73% to 105% with intra-day RSDr (n = 5) of 1.0%-13.0% and inter-day RSDR (n = 15) of 1.1%-14.6%. Good linearities (R2 > 0.9911) were obtained for seven analytes in all matrices. The limit of quantification (LOQs) for tiafenacil and its six metabolites were 10 µg kg-1 in all matrices. This analytical method provides a basis for the establishment of maximum residue limits (MRL) and for the monitoring of tiafenacil residues in fruits.


Assuntos
Cromatografia Líquida de Alta Pressão/métodos , Contaminação de Alimentos/análise , Frutas/química , Herbicidas/análise , Pirimidinas/análise , Espectrometria de Massas em Tandem/métodos , Acetonitrilos/química , Fracionamento Químico , Análise de Alimentos/métodos , Herbicidas/metabolismo , Limite de Detecção , Reprodutibilidade dos Testes
16.
Artigo em Inglês | MEDLINE | ID: mdl-32361630

RESUMO

Ibotenic acid (IBA) is an amino acid and muscimol (MUS) is the decarboxyl derivative of IBA. They are mushroom neurotoxins with high polarity and low molecular weight. Only one transition (159->113 for IBA and 115->98 for MUS) can be found when directly measured by high performance liquid chromatography-triple quadrupole mass spectrometry (LC-MS/MS). Therefore, the identification and quantification of trace amount of the toxins in biomaterial are difficult. A highly sensitive and accurate analytical method for IBA and MUS in plasma was developed by LC-MS/MS with the application of bimolecular dansylation and internal standard calibration. Acetonitrile was used for protein precipitation and for toxin extraction from plasma. The toxins and internal standards (L-tyrosine-13C9,15N for IBA and tyramine-d4 for MUS) were derivatized with dansyl chloride (DNSCl). The reaction conditions of the bimolecular dansylation were optimized and the fragmentation pathways of the derivatives in MS/MS were studied. Method validation was carried out according to the Bioanalytical Method Validation Guidance for Industry (FDA, USA, 2018). The limits of detection for IBA and MUS in plasma were 0.3 ng mL-1 and 0.1 ng mL-1, respectively. The linear ranges in plasma were 1-500 ng mL-1 and 1-200 ng mL-1 with the correlation coefficients of 0.998 and 0.999 for IBA and MUS, respectively. The recoveries at three spiked levels were 90.7-111.4% with relative standard deviations (RSDs) of 6.4-10.3% for IBA and the results were 85.1-94.2% with RSDs of 5.0-8.9% for MUS. The toxin levels in patients' plasma samples under different poisoning degree were presented.


Assuntos
Agaricales/química , Ácido Ibotênico/sangue , Muscimol/sangue , Neurotoxinas/sangue , Espectrometria de Massas em Tandem/métodos , Acetonitrilos/química , Cromatografia Líquida de Alta Pressão , Compostos de Dansil/química , Humanos , Limite de Detecção , Padrões de Referência , Reprodutibilidade dos Testes
17.
Food Chem ; 328: 127134, 2020 Oct 30.
Artigo em Inglês | MEDLINE | ID: mdl-32473493

RESUMO

An efficient single quadrupole gas chromatography with mass spectrometry method was developed and validated for the determination of indoxacarb residues in tomato and soil. Residues were extracted from the samples using acetonitrile as extracting solvent and the extracts were purified through primary secondary amine and graphitized carbon black. Recoveries were obtained in the range of 92.12-110.51% with the relative standard deviation of 1.32-4.32%. Indoxacarb dissipated with half-life of 3.12-3.21 and 1.24-1.35d for tomato and soil, respectively following doses of indoxacarb 14.5% SC at 60, 90 and 120 g.a.i./ha. Safe waiting periods were found to be 1-3d. The residues were removed from tomato fruit was in the range of 16.73 to 54.32% using simple decontamination approaches. The present study suggest that the use of indoxacarb in tomato at recommended dose, does not seem to pose any dietary risk to the consumers. The soil RQ values indicated low level of risk to earthworms and arthropods.


Assuntos
Contaminação de Alimentos/análise , Lycopersicon esculentum/química , Oxazinas/análise , Resíduos de Praguicidas/análise , Poluentes do Solo/análise , Acetonitrilos/química , Exposição Dietética , Análise de Alimentos/métodos , Cromatografia Gasosa-Espectrometria de Massas , Meia-Vida , Humanos , Índia , Oxazinas/metabolismo , Medição de Risco , Poluentes do Solo/metabolismo , Solventes/química , Fatores de Tempo
18.
J Chromatogr A ; 1622: 461152, 2020 Jul 05.
Artigo em Inglês | MEDLINE | ID: mdl-32376024

RESUMO

The chiral separations of small peptides is an important challenge in the biological and medical sciences, because different stereoisomers of chiral drugs can often possess different pharmacological, pharmacokinetic, and/or toxicological activities. Commercially available crown ether chiral stationary phases based on S-(3,3'-diphenyl-1,1'-binaphthyl)-20-crown-6 (CROWNPAK CR-I (+)) and (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid (ChiroSil RCA (+)) have been successfully used for separating enantiomers of various racemic compounds containing primary amino groups. In this investigation, enantioresolution of more complex model analyte - tetrapeptide Tyr-Arg-Phe-Lys-NH2, has been reported on crown ether chiral stationary phases. Organic and acidic modifier content in aqueous mobile phase was tested. All Tyr-Arg-Phe-Lys-NH2 stereoisomers showed U-shaped retention plots, based on ACN content in mobile phase. Increased retention of tetrapeptide stereoisomers was observed at low (<35%) and at high (>70%) acetonitrile content in the mobile phase, indicating that different separation mechanisms are most likely involved. As a result, baseline separation of all eight tetrapeptide enantiomer pairs was achieved under isocratic elution mode on both chiral columns.


Assuntos
Éteres de Coroa/química , Peptídeos/química , Peptídeos/isolamento & purificação , Acetonitrilos/química , Padrões de Referência , Estereoisomerismo , Fatores de Tempo
19.
J Chromatogr A ; 1621: 461050, 2020 Jun 21.
Artigo em Inglês | MEDLINE | ID: mdl-32265050

RESUMO

Consumption of ciguatoxin-contaminated seafood can lead to ciguatera poisoning (CP). The diagnosis of CP in humans is based on the clinical symptoms after eating the fish from tropical or subtropical areas because no confirmatory clinical tests are available. One of the challenges for ciguatoxin analysis is their extremely low but toxicologically relevant concentration in biological samples. We previously reported a method using acetonitrile to precipitate proteins and extract the ciguatoxins simultaneously in whole blood samples from animals for toxin quantification by N2A cell-based assay. However, a test method for unambiguous confirmation of exposure of marine animals or humans to ciguatoxins is still needed. In the present study, we adopted the acetonitrile extraction method and added sample clean-up in the sample preparation for the determination of Pacific ciguatoxins CTX1B (aka P-CTX-1), 52-epi-54-deoxyCTX1B (aka P-CTX-2), and CTX3C (aka P-CTX-3C) in blood plasma by LC-MS/MS. We investigated sample clean-up, LC mobile phases, LC solvent programming, and settings of the two mass spectrometers (4000 Q TRAP and AB SCIEX Triple Quad 5500) in order to improve the ability to detect the Pacific ciguatoxins at ppt level. Rat blood plasma was used for the method development. Average recoveries of the three toxins in the rat plasma samples ranged from 90% to 116% with relative standard deviations of less than 15%. The method detection limits were still not low enough for the determination of the Pacific ciguatoxins in individual blood samples from Hawaiian monk seals with the two LC-MS systems. The methods were applied to a pooled sample of blood plasma collected from Hawaiian monk seals for confirmation of toxin exposure. This study will benefit monitoring of Pacific ciguatoxins in marine mammals and potentially humans by LC-MS/MS.


Assuntos
Cromatografia Líquida/métodos , Ciguatoxinas/sangue , Espectrometria de Massas em Tandem/métodos , Acetonitrilos/química , Animais , Limite de Detecção , Ratos , Focas Verdadeiras/sangue , Solventes
20.
Sci Adv ; 6(10): eaay4109, 2020 03.
Artigo em Inglês | MEDLINE | ID: mdl-32181345

RESUMO

The contamination of indoor nonsmoking environments with thirdhand smoke (THS) is an important, poorly understood public health concern. Real-time THS off-gassing from smokers into a nonsmoking movie theater was observed with online and offline high-resolution mass spectrometry. Prominent emission events of THS tracers (e.g., 2,5-dimethylfuran, 2-methylfuran, and acetonitrile) and other tobacco-related volatile organic compounds (VOCs) coincided with the arrival of certain moviegoers and left residual contamination. These VOC emission events exposed occupants to the equivalent of 1 to 10 cigarettes of secondhand smoke, including multiple hazardous air pollutants (e.g., benzene and formaldehyde) at parts-per-billion concentrations. Nicotine and related intermediate-volatility nitrogen-containing compounds, which vaporized from clothes/bodies and recondensed onto aerosol, comprised 34% of observed functionalized organic aerosol abundance. Exposure to THS VOC emission events will be considerably enhanced in poorly ventilated or smaller spaces in contrast with a large, well-ventilated theater-amplifying concentrations and potential impacts on health and indoor chemistry.


Assuntos
Poluição do Ar em Ambientes Fechados/análise , Benzeno/análise , Furanos/análise , Nicotina/análise , Poluição por Fumaça de Tabaco/análise , Compostos Orgânicos Voláteis/análise , Acetonitrilos/análise , Acetonitrilos/química , Aerossóis , Benzeno/química , Formaldeído/análise , Formaldeído/química , Furanos/química , Alemanha , Humanos , Espectrometria de Massas , Filmes Cinematográficos , Nicotina/química , Compostos Orgânicos Voláteis/classificação
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