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1.
Food Chem ; 370: 131004, 2022 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-34525425

RESUMO

A step-by-step approach to easily adapt and use a GC-FID as an olfactometer, as well as a detailed description of acquisition and interpretation of olfactometric data by the OSME (from the Greek word for odor, ὀσµÎ®) method. A Merlot wine was used to exemplifly this strategy and its volatiles were characterized, rendering 43 volatiles in 1D-GC/MS and 142 in GCxGC/MS. GC-O showed the presence of 24 odor-active compounds and GCxGC/MS indicated aditional 14 odor-active compounds, which were found as coelutions. Six compounds (isoamyl acetate, ethyl octanoate, ethyl decanoate, 3-methylthio-1-propanol, carvone, benzyl alcohol and nonanoic acid) were described in 1D-GC-O analyses as having distinct odors by the same and by different assessors. This fact indicated the presence of coeluting bands, which were resolved by GCxGC/MS. The adapted GC-O in combination with the use of GCxGC/MS may be a tool to more accurate investigation of the odor-active compounds of wine.


Assuntos
Compostos Orgânicos Voláteis , Vinho , Cromatografia Gasosa , Odorantes/análise , Olfatometria , Compostos Orgânicos Voláteis/análise , Vinho/análise
2.
Food Chem ; 366: 130526, 2022 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-34274705

RESUMO

An in-house method, employing magnetic stirring-assisted aqueous extraction combined with gas chromatography-flame ionization detector, for determination of ethanol in different foods and beverages was validated according to the ISO/IEC 17025 standard. Validation parameters, including selectivity, method limits of detection (approx. 0.006 mg/g) and quantification (approx. 0.02 mg/g), linearity (R2 of >0.999), trueness (relative biases of <3%), accuracy (recoveries of 96-105%), and precision (relative standard deviations of <5%), were satisfactory. The proposed method was as accurate and precise as and more sensitive than the AOAC method 2016.12, with estimated relative expanded uncertainties of around 8% for all samples. The validated method was successfully applied for determination of ethanol in 108 commercially processed foods and beverages, and it could be used for halal verification. Accordingly, this study provided a reliable method for routine quantitative analysis of ethanol in processed foods and beverages to ensure their halal integrity prior to halal certification.


Assuntos
Bebidas , Etanol , Bebidas/análise , Cromatografia Gasosa , Fenômenos Magnéticos , Água
3.
Meat Sci ; 183: 108658, 2022 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-34482216

RESUMO

The flavour profiles of beef jerky separately inoculated with different autochthonous lactic acid bacteria (LAB) strains (Lactobacillus sakei BL6, Pediococcus acidilactici BP2, and Lactobacillus fermentum BL11) and a non-inoculated control were analysed using electronic nose (E-nose) and gas chromatography-ion mobility spectrometry (GC-IMS). GC-IMS results revealed a total of 42 volatile compounds in beef jerky. Inoculation of the three LAB strains decreased the levels of lipid autoxidation-derived aldehydes (e.g., hexanal, heptanal, octanal, and nonanal). In addition, inoculation of P. acidilactici BP2 increased the levels of esters. Principal component analysis of the E-nose and GC-IMS results could effectively differentiate non-inoculated beef jerky and beef jerky separately inoculated with different LAB strains. Furthermore, there was a high correlation between the E-nose and GC-IMS results, providing a theoretical basis for the identification of different beef jerky formulations and selection of autochthonous starter cultures for beef jerky fermentation.


Assuntos
Lactobacillales/fisiologia , Produtos da Carne/análise , Compostos Orgânicos Voláteis/análise , Animais , Bovinos , Cromatografia Gasosa , Nariz Eletrônico , Espectrometria de Mobilidade Iônica , Produtos da Carne/microbiologia , Análise de Componente Principal
4.
Food Chem ; 369: 130944, 2022 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-34464834

RESUMO

A headspace-solid phase microextraction - gas chromatography-flame ionisation detector (HS-SPME-GC/FID) method was developed for the simultaneous determination of furan, 2-methylfuran and 2-furaldehyde in thermally processed Mopane worms, corn, and peanuts. The optimal HS-SPME conditions with polydimethylsiloxane/carboxen/divinylbenzene (PDMS/CAR/DVB) fiber were 30 °C, 40 min and 600 rpm stirring speed. The recoveries, detection and quantification limits for the analytes in food samples were 67-106%, 0.54-3.5 µg kg-1, and 1.8-12 µg kg-1, respectively. These results showed that the developed method was accurate, reproducible, and sensitive for the determination of furan, 2-methylfuran and 2-furaldehyde in complex food matrices with limited interference from other components. The optimised analytical method was applied for monitoring the presence of the furanic compounds in heat-processed South African foods. Although 2-furaldehyde was not detected in food samples, the maximum concentrations of 24 and 95 µg kg-1 were found for furan and 2-methylfuran, respectively.


Assuntos
Microextração em Fase Sólida , Zea mays , Arachis , Cromatografia Gasosa , Furaldeído , Reprodutibilidade dos Testes
5.
Food Chem ; 371: 130995, 2022 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-34537610

RESUMO

The quantification of fatty acids (FA) in meat products is frequently carried out by two-stage methylation procedures followed by long gas chromatography (GC) runs. This work aimed to simplify this methodology by means of a one-stage transmethylation method and a fast GC run, evaluating the influence of sample preparation, reagents and type of heating on the amount of FA in different meat products and optimizing a fast GC-FID (flame ionization detector) run. This allowed to establish the optimum combination of parameters (methanol + chlorotrimethylsilane, lyophilized samples and oven heating) to achieve the quantification of the highest possible amount of FA and to reduce the time of GC run from 60 to 10 min. The quality evaluation of this method obtained satisfactory results. Thus, the quantification of FA in meat products was achieved in a straightforwardly and quickly way by using a one-stage transmethylation procedure followed by a fast GC-FID run.


Assuntos
Produtos da Carne , Cromatografia Gasosa , Ácidos Graxos , Ionização de Chama , Produtos da Carne/análise
6.
J Pharm Biomed Anal ; 207: 114425, 2022 Jan 05.
Artigo em Inglês | MEDLINE | ID: mdl-34656936

RESUMO

A novel gas chromatography (GC) method for quantitation of volatile organic compounds (VOCs) in 18F- and 11C-radiopharmaceuticals listed in the European Pharmacopoeia (Ph. Eur.) was proposed. Optimized chromatographic parameters were used for separation of ethanol, acetone, acetonitrile, tetrahydrofuran (THF), dibromomethane (DBM), 2-dimethylaminoethanol (deanol), N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) which could be detected in radioactive drug samples. The calculated peak resolutions (RS) were higher than 2.0 at ethanol concentration of up to 11 m/m%. Reproducible results could be obtained using base deactivated fused silica wool as packing material of inlet liner. Validation parameters showed excellent linearity (r2 ≥0.9998) in the range from 10 to at least 120% of concentration limit of solvents. The accuracy was determined as recovery of concentrations which ranged from 99.3% to 103.8%. Additionally, the relative standard deviation (RSD) of each solvent for inter-day and intra-day precision were in the range of 0.5-4.2% and 0.4-4.4%, respectively. The limit of quantitation (LOQ) for ethanol, acetone, acetonitrile, THF, DBM, deanol, DMF and DMSO was 0.48, 0.42, 0.43, 0.46, 4.35, 0.73, 0.68 and 0.50 mg/L, respectively. The developed procedure was successively applied for quantitation of ethanol, acetone, acetonitrile and deanol in radioactive drug samples of [11C]methionine, [11C]choline, 2-deoxy-2-[18F]fluoro-D-glucose ([18F]FDG) and O-(2-[18F]fluoroethyl)-L-tyrosine ([18F]FET). The proposed GC method applying flame ionization detection (FID) could be adapted in routine quality control of most frequently used positron emission tomography (PET) radiopharmaceuticals to perform the determination of residual solvents with analysis time of 12 min.


Assuntos
Tomografia por Emissão de Pósitrons , Compostos Radiofarmacêuticos , Cromatografia Gasosa , Compostos Radiofarmacêuticos/análise , Reprodutibilidade dos Testes , Solventes/análise
7.
Anal Chim Acta ; 1189: 339254, 2022 Jan 02.
Artigo em Inglês | MEDLINE | ID: mdl-34815033

RESUMO

Sulfolane is explored as a novel stationary phase for use in analytical separations by capillary column gas chromatography with flame ionization detection (GC-FID). Stainless steel capillaries were found to provide a good substrate for coating and retaining a sulfolane phase, whereas fused silica tubing did not perform well for this. In general, the phase was found to be stable for several hours of use when using elevated carrier gas pressures (90 psi) and a small restriction (25 µm I.D. tubing) at the outlet. This normally provided good performance at temperatures up to about 200 °C with very little background interference in the FID. Given its separation properties, a short 2 m × 100 µm I.D. column was found to be preferable for most separations in this study. Measurements indicated the coating procedure yielded a sulfolane film near 4 µm thick on this column, which produced 4400 plates for benzene with a sample capacity near 30 µg. The sulfolane phase yielded good retention and peak shape for many analytes including alkanes, aromatics, alcohols, bases, sulfides, phosphites, thiols, and others. Compared to longer conventional GC columns, the relatively short sulfolane column was found to offer improved selectivity in the separation of unsaturated, aromatic, and alkane test analytes. As such the method was successfully applied to the analysis of aromatics in gasoline headspace. Results suggest that sulfolane could be a potentially useful stationary phase to further explore in GC separations.


Assuntos
Alcanos , Tiofenos , Cromatografia Gasosa , Ionização de Chama
8.
BMC Plant Biol ; 21(1): 506, 2021 Nov 02.
Artigo em Inglês | MEDLINE | ID: mdl-34727870

RESUMO

BACKGROUND: Nitrogen (N) fertilizer is commonly considered as one of the most important limiting factors in the agricultural production. As a result, a large amount of N fertilizer is used to improve the yield in modern tea production. Unfortunately, the large amount of N fertilizer input has led to increased plant nitrogen-tolerance and decreased amplitude of yield improvement, which results in significant N loss, energy waste and environment pollution. However, the effects of N-deficiency on the metabolic profiles of tea leaves and roots are not well understood. RESULTS: In this study, seedlings of Camellia sinensis (L.) O. Kuntze Chunlv 2 were treated with 3 mM NH4NO3 (Control) or without NH4NO3 (N-deficiency) for 4 months by sandy culture. The results suggested that N-deficiency induced tea leaf chlorosis, impaired biomass accumulation, decreased the leaf chlorophyll content and N absorption when they were compared to the Control samples. The untargeted metabolomics based on GC-TOF/MS approach revealed a discrimination of the metabolic profiles between N-deficient tea leaves and roots. The identification and classification of the altered metabolites indicated that N deficiency upregulated the relative abundances of most phenylpropanoids and organic acids, while downregulated the relative abundances of most amino acids in tea leaves. Differentially, N-deficiency induced the accumulation of most carbohydrates, organic acids and amino acids in tea roots. The potential biomarkers screened in N-deficient leaves compared to Control implied that N deficiency might reduce the tea quality. Unlike the N-deficient leaves, the potential biomarkers in N-deficient roots indicated an improved stress response might occur in tea roots. CONCLUSIONS: The results demonstrated N deficiency had different effects on the primary and secondary metabolism in tea leaves and roots. The findings of this study will facilitate a comprehensive understanding of the N-deficient tea plants and provide a valuable reference for the optimized N nutrient management and the sustainable development in the tea plantations.


Assuntos
Camellia sinensis/química , Camellia sinensis/crescimento & desenvolvimento , Camellia sinensis/metabolismo , Nitrogênio/deficiência , Nitrogênio/metabolismo , Folhas de Planta/metabolismo , Raízes de Plantas/metabolismo , Cromatografia Gasosa , Produtos Agrícolas/química , Produtos Agrícolas/crescimento & desenvolvimento , Produtos Agrícolas/metabolismo , Espectrometria de Massas , Metaboloma , Metabolômica , Folhas de Planta/química , Folhas de Planta/crescimento & desenvolvimento , Raízes de Plantas/química , Raízes de Plantas/crescimento & desenvolvimento
9.
Se Pu ; 39(12): 1340-1346, 2021 Dec.
Artigo em Chinês | MEDLINE | ID: mdl-34812006

RESUMO

Determination of fatty acid compositions and contents in Chinese mitten crabs is of great significance to evaluate its nutritional value and quality. However, in the face of a wide range of fatty acid extraction and methyl esterification reagents, the measurement results are uneven, and it is difficult to accurately quantify the rich fatty acids in Chinese mitten crabs. In this paper, four kinds of oil extraction reagents and two kinds of methylating reagents, were investigated. Chloroform-methanol (1∶1, v/v) was used as the extraction solvent, and methanol containing 2% sulfuric acid was used as the derivatization reagent. A method for the determination of fatty acids in the muscle of Chinese mitten crabs by gas chromatography was established. The experiment was carried out under the condition of programmed temperature rise, 37 kinds of fatty acids were separated on a DM-2560 capillary column (100 m×0.25 mm×0.20 µm), detected by hydrogen flame ionization detector (FID) and quantified by external standard method. The linear relationships of the 37 fatty acids were good in the range of 0.5-100.0 µg/mL. The correlation coefficients (R2) were 0.9981-0.9999. The limits of detection (LODs) and limits of quantification (LOQs) were 0.01-0.02 mg/100 g and 0.04-0.06 mg/100 g, respectively. The methodology was validated by palmitic acid and stearic acid. The recoveries were 76.0%-97.5%, and the relative standard deviations (RSD, n=5) were 3.31%-7.90% at the spiked levels of 1, 2 and 10 mg/100 g. The method was applied to the determination of fatty acid compositions and contents in the muscle of Chinese mitten crabs. A total of 31 kinds of fatty acids were detected. The length of carbon chain ranged from 12 to 24, and the total content of fatty acids reached 281.03 mg/100 g. Oleic acid, docosahexaenoic acid and eicosapentaenoic acid were the main fatty acids in the muscle of Chinese mitten crabs. Thus, this method provided accurate and reliable theoretical data for the determination of fatty acids in Chinese mitten crabs. This method has the advantages of simple operation, small amount of reagent and sample, reliable qualitative, accurate quantitative, detection of more fatty acid types. It is suitable for the rapid detection of fatty acid compositions and contents in muscle tissue of Chinese mitten crabs.


Assuntos
Ácidos Graxos , China , Cromatografia Gasosa , Ionização de Chama , Cromatografia Gasosa-Espectrometria de Massas
10.
Anal Chim Acta ; 1185: 339042, 2021 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-34711315

RESUMO

The nitro functional group (NO2) features strongly in compounds such as explosives, pharmaceuticals, and fragrances. However, its gas phase absorbance characteristics in the vacuum UV region (120-200 nm) have not been systematically studied. Gas chromatography/vacuum UV spectroscopy (GC/VUV) was utilized to study the gas phase VUV spectra of various nitrated compounds (e.g., nitrate esters (-R-O-NO2), nitramines (R-N-NO2), nitroaromatics (Ar-NO2), and nitroalkanes (R-NO2)). The nitro absorption maximum appeared over a wide range (170-270 nm) and its wavelength and intensity were highly dependent upon the structure of the rest of the molecule. For example, the nitroalkanes exhibited a trend in that the ratio of the relative absorption intensity between these two absorption features between the alkyl group (<150 nm) and the nitro group (200 nm) increases as the molecular weight increases. It was observed that the addition of multiple nitro functional groups on benzene or toluene resulted in an increase in intensity and blue shift from approximately 240 nm-210 nm. Nitrate esters exhibited an absorption between 170 nm and 210 nm and absorbance increased with increasing nitrogen content. The relative diversity of the spectra obtained was analyzed by Principal Component Analysis (PCA) and Linear Discriminant Analysis (LDA). These calculations revealed that the spectra of all the compounds analyzed could be reliably differentiated without any misclassifications.


Assuntos
Ésteres , Cromatografia Gasosa , Análise Discriminante , Espectrofotometria Ultravioleta , Vácuo
11.
Anal Chim Acta ; 1184: 339040, 2021 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-34625251

RESUMO

Carbon dioxide (CO2) and methane (CH4) are two climate-sensitive components of gases migrating within sediments and emitted into the water column on continental margins. They are involved in several key biogeochemical processes entering into the global carbon cycle. In order to perform onboard measurements of both the molecular and stable carbon isotope ratios (δ13C) of CH4 and CO2 of natural gases during oceanic cruises, we have developed a novel approach coupling gas chromatography (GC) with cavity ring-down spectroscopy (CRDS). The coupled devices are connected to a small sample isotope module (SSIM) to form a system called GC-SSIM-CRDS. Small volumes of natural gas samples (<1 mL) are injected into the GC using a headspace autosampler or a gas-tight syringe to separate the chemical components using a Shincarbon ST packed column and for molecular quantification by thermal conductivity detection (TCD). Subsequently, CO2 from the sample is trapped in a 7 mL loop at 32 °C before being transferred to the CRDS analyzer for sequential determination of the stable carbon isotope ratios of CH4 and CO2 in 24 min. The loop is an open column (without stationary phase). This approach does not require the use of adsorbents or cooling for the trapping step. Optimization of the separation step prior to analysis was focused on the influence of two key separation factors 1) the flow of the carrier gas and 2) the temperature of the oven. Our analytical system and the measurement protocol were validated on samples collected from gas seeps in the Sea of Marmara (Turkey). Our results show that the GC-SSIM-CRDS system provides a reliable determination of the molecular identification of CH4 and CO2 in complex natural gases, followed by the stable carbon isotope ratios of methane and carbon dioxide.


Assuntos
Expedições , Gás Natural , Isótopos de Carbono/análise , Cromatografia Gasosa , Gases , Análise Espectral
12.
Adv Exp Med Biol ; 1336: 139-157, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34628631

RESUMO

This chapter discusses the fundamentals of gas chromatography (GC) to improve method development for metabolic profiling of complex biological samples. The selection of column geometry and phase ratio impacts analyte mass transfer, which must be carefully optimized for fast analysis. Stationary phase selection is critical to obtain baseline resolution of critical pairs, but such selection must consider important aspects of metabolomic protocols, such as derivatization and dependence of analyte identification on existing databases. Sample preparation methods are also addressed depending on the sample matrix, including liquid-liquid extraction and solid-phase microextraction.


Assuntos
Metabolômica , Cromatografia Gasosa
13.
Sensors (Basel) ; 21(20)2021 Oct 13.
Artigo em Inglês | MEDLINE | ID: mdl-34696013

RESUMO

A microfluidic film bulk acoustic wave resonator gas sensor (mFBAR) adapted specifically as an in-line detector in gas chromatography was described. This miniaturized vapor sensor was a non-destructive detector with very low dead volume (0.02 µL). It was prepared by enclosing the resonator in a microfluidic channel on a chip with dimensions of only 15 mm × 15 mm × 1 mm. The device with polymer coating showed satisfactory performance in the detection of organophosphorus compound, demonstrating a very low detection limit (a dozen parts per billion) with relatively short response time (about fifteen seconds) toward the simulant of chemical warfare agent, dimethyl methylphosphonate. The in-line detection of the mFBAR sensor with FID was constructed and employed to directly measure the concentration profile on the solid surface by the mFBAR with the controlled concentration profile in the mobile phase at the same time. The difference of peak-maximum position between mobile phase and solid phase could be a convenient indicator to measure mass transfer rate. With the response of the mFBAR and FID obtained in one injection, an injection mass-independent parameter can be calculated and used to identify the analyte of interest.


Assuntos
Substâncias para a Guerra Química , Microfluídica , Substâncias para a Guerra Química/análise , Cromatografia Gasosa , Gases , Som
14.
Nutrients ; 13(10)2021 Sep 29.
Artigo em Inglês | MEDLINE | ID: mdl-34684472

RESUMO

Oleanolic acid (OA), a triterpene that is highly present in olive leaves, has been proposed as a component of functional foods for the prevention of metabolic syndrome, due to its anti-inflammatory activity. We analyzed the effects of OA on inflammatory parameters and signaling proteins in LPS-stimulated THP-1 macrophages. Thus, THP-1 macrophages were incubated with LPS for 48 h after pretreatment with OA at different concentrations. Pretreatment with OA was significantly effective in attenuating IL-6 and TNF-α overproduction induced by LPS in macrophages, and also improved the levels of AMPK-α. We also evaluated the effects of human triglyceride-rich lipoproteins (TRLs) derived from individuals consuming an OA-enriched functional olive oil. For this purpose, TRLs were isolated from healthy adolescents before, 2 and 5 h postprandially after the intake of a meal containing the functional olive oil or common olive oil, and were incubated with THP-1 macrophages. THP-1 macrophages incubated with TRLs isolated at 2 h after the consumption of the OA-enriched olive oil showed significant lower levels of IL-6 compared to the TRLs derived from olive oil. Our results suggest that OA might have potential to be used as a lipid-based formulation in functional olive oils to prevent inflammatory processes underlying metabolic syndrome in adolescents.


Assuntos
Interleucina-6/biossíntese , Lipoproteínas/metabolismo , Macrófagos/metabolismo , Ácido Oleanólico/química , Azeite de Oliva/química , Azeite de Oliva/farmacologia , Triglicerídeos/metabolismo , Biomarcadores , Composição Corporal , Linhagem Celular , Sobrevivência Celular/efeitos dos fármacos , Células Cultivadas , Cromatografia Gasosa , Citocinas/biossíntese , Ácidos Graxos/metabolismo , Humanos , Mediadores da Inflamação/metabolismo , Metabolismo dos Lipídeos/efeitos dos fármacos , Período Pós-Prandial , Proteínas Proto-Oncogênicas c-akt/metabolismo
15.
J Chromatogr A ; 1657: 462575, 2021 Nov 08.
Artigo em Inglês | MEDLINE | ID: mdl-34601254

RESUMO

This work reports a selective and inert triptycene-based stationary phase (TPT) combining the triptycene framework with tocopheryl polyethylene glycol succinate (TPGS) units for capillary gas chromatography (GC). The TPT stationary phase was physically coated onto a capillary column by static coating method with the column efficiency of 4200 plates/m and moderate polarity. As demonstrated, the TPT column exhibited high inertness towards organic bases, including basic heterocycles, aliphatic and aromatic amines, showing distinct advantages over the TPGS and commercial columns. Also, the TPT column displayed high-resolution performance towards the isomers of methylpyridines, toluidines, xylidines and alkanes (C6-C8). Moreover, it showed excellent separation repeatability and reproducibility with RSD values in the range of 0.03%-0.07% for run-to-run, 0.12%-0.18% for day-to-day and 2.3%-3.6% for column-to- column (n = 4). Its applications to purity test of chemical products and to GC-MS analysis of the essential oil of Artemisia annua L. demonstrated its good potential for practical analyses. The present work has novelty in constructing highly selective and inert stationary phases and providing a feasible strategy for concurrently addressing the related problems in GC analyses. Its methodology and findings is of important value in terms of fundamental researches and practical applications.


Assuntos
Fenóis , Polietilenoglicóis , Antracenos , Cromatografia Gasosa , Fenóis/análise , Reprodutibilidade dos Testes , Succinatos
16.
J Chromatogr A ; 1657: 462576, 2021 Nov 08.
Artigo em Inglês | MEDLINE | ID: mdl-34601255

RESUMO

Today, labs that carry out chemical analyses for regulation, food safety, health, forensics, or even security purposes are looking for ways to accelerate the analytical process. Slow procedures are costly because the necessary instruments are expensive and require maintenance and a highly trained staff to operate them. One of the more ubiquitous instruments in such labs is a Gas Chromatograph (GC), which accepts a solution and outputs each of the compounds within it in a gaseous form, one by one to be further analyzed and identified, usually by a Mass Spectrometer (MS). This separation process in a GC can be rather time-consuming, partly due to the slow heating and cooling of the GC column through which the compounds move, which happens inside a box-shaped oven. This paper describes a controller developed for a unique Open Probe Fast GC instrument that enables, among other things, high-speed and controlled heating and cooling of a gas-carrying capillary transfer line. Fast heating is achieved by precisely controlling the electrical current flowing through the small inner-diameter steel tube through which the GC column passes. The fast cooling occurs by exposing the low-mass heated tube to room temperature, along with the assistance of a simple fan that carries the heated air away. This technology also supports control of other system parts, including a unique quick sampling device called an Open Probe that allows for an even faster analysis cycle. Our design is based entirely on a digital signal processor (DSP) and digital control. The use of pulse width modulation (PWM) control enables a compact and efficient system.


Assuntos
Calefação , Temperatura Alta , Cromatografia Gasosa , Gases , Humanos
17.
J Chromatogr A ; 1657: 462556, 2021 Nov 08.
Artigo em Inglês | MEDLINE | ID: mdl-34601256

RESUMO

Ionic liquid bonded polysiloxanes (PILs) are a class of polysiloxanes whose side chains contain ionic liquid (IL) moieties. They not only inherit the character of "dual nature" from ILs but also inherit the excellent film-forming ability and thermal stability from polysiloxanes. In this paper, the solvation parameter model is introduced to investigate the interaction characteristics of PILs. The experimental results show that the b values of PILs occur in a wider range than those previously reported for the stationary phases. The hydrogen bond acidity can be effectively adjusted by varying the ionic liquid content or substituents. Hindering the formation of the hydrogen-bonded networks and increasing the exposed hydrogens may be intrinsic to the strong hydrogen bond acidity of PILs. Subsequently, the separation performances of these PIL stationary phases were demonstrated by separating various mixed samples of aromatic isomers, dichloroanilines, substituted alkanes, alcohols, esters, etc. The results show that the PILs with strong hydrogen bond acidity have excellent selectivity performances for aromatic position isomers, alcohols, and substituted alkanes. This study is significant for understanding the hydrogen bond acidity and broadening the range of hydrogen bond acidity of ionic liquid stationary phases.


Assuntos
Líquidos Iônicos , Alcanos , Cromatografia Gasosa , Ligação de Hidrogênio , Siloxanas
18.
J Chromatogr A ; 1658: 462611, 2021 Nov 22.
Artigo em Inglês | MEDLINE | ID: mdl-34666270

RESUMO

This work presents the investigation of using the amphiphilic triblock copolymer composed of poly(ethylene oxide)(PEO)-poly(propylene oxide) (PPO)-poly(ethylene oxide) (PEO) (denoted as EPE) as the stationary phase for gas chromatographic (GC) analyses. The EPE capillary column exhibited moderate polarity and column efficiency of 4348 plates/m determined by naphthalene at 120 °C (k = 11.52). Different from the PEG and polysiloxane homopolymers, it showed high-resolution performance towards a wide range of aliphatic and aromatic isomers in terms of polarity and acid-base properties. Particularly, the EPE column displayed distinct advantages for separating the critical isomers of alkanes, anilines and phenols and the components of the lemon essential oil over the commercial PEG and polysiloxane columns. In addition, the EPE column exhibited excellent separation repeatability and reproducibility with the relative standard deviation (RSD) values in the range of 0.03% - 0.08% for run-to-run, 0.14% - 0.61% for day-to-day and 3.1% - 4.0% for column-to-column, respectively. Moreover, the EPE column was investigated in terms of thermal stability, the minimum allowable operating temperature (MiAOT) and sample loadability. Its application to GC-MS analysis of the essential oil demonstrated its feasibility for practical analyses. This work demonstrates the promising future of triblock copolymers as a new class of selective stationary phases for GC analyses, which is barely reported up to date. The findings of this work is of important value for fundamental researches and practical applications.


Assuntos
Óleos Voláteis , Alcanos/análise , Cromatografia Gasosa , Isomerismo , Reprodutibilidade dos Testes
19.
Molecules ; 26(19)2021 Oct 06.
Artigo em Inglês | MEDLINE | ID: mdl-34641597

RESUMO

Ubiquitous occurrences of phthalic acid esters (PAEs) or phthalates in a variety of consumer products have been demonstrated. Nevertheless, studies on their occurrence in various types of bottled drinks are limited. In this study, fifteen PAEs were analyzed in six categories of bottled drinks (n = 105) collected from the Chinese market, including mineral water, tea drinks, energy drinks, juice drinks, soft drinks, and beer. Among the 15 PAEs measured, DEHP was the most abundant phthalate with concentrations ranging from below the limit of quantification (LOQ) to 41,000 ng/L at a detection rate (DR) of 96%, followed by DIBP (DR: 88%) and DBP (DR: 84%) with respective concentration ranges of below LOQ to 16,000 and to 4900 ng/L. At least one PAE was detected in each drink sample, and the sum concentrations of 15 PAEs ranged from 770 to 48,004 ng/L (median: 6286 ng/L). Significant differences with respect to both PAE concentrations and composition profiles were observed between different types of bottled drinks. The median sum concentration of 15 PAEs in soft drinks was over five times higher than that detected in mineral water; different from other drink types. Besides DEHP, DBIP, and DBP, a high concentration of BMEP was also detected in a tea drink. The estimated daily dietary intake of phthalates (EDIdrink) through the consumption of bottled drinks was calculated based on the concentrations measured and the daily ingestion rates of bottled drink items. The EDIdrink values for DMP, DEP, DIBP, DBP, BMEP, DAP, BEEP, BBP, DCP, DHP, BMPP, BBEP, DEHP, DOP, and DNP through the consumption of bottled mineral water (based on mean concentrations) were 0.45, 0.33, 12.5, 3.67, 2.10, 0.06, 0.32, 0.16, 0.10, 0.09, 0.05, 0.81, 112, 0.13, and 0.20 ng/kg-bw/d, respectively, for Chinese adults. Overall, the EDIdrink values calculated for phthalates through the consumption of bottled drinks were below the oral reference doses suggested by the United States Environmental Protection Agency (U.S. EPA).


Assuntos
Bebidas/análise , Exposição Dietética/análise , Ácidos Ftálicos/análise , China , Cromatografia Gasosa , Ingestão de Líquidos , Disruptores Endócrinos/análise , Ésteres/análise , Humanos
20.
Chemosphere ; 282: 131109, 2021 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-34470161

RESUMO

Liquid crystals (LCs) are widely used in the modern society, but their environmental fate and related human health effects remain inadequately recognized. To assist in better understanding the environmental fate of LCs, the octanol-air partition coefficients (KOA) of 21 target LCs were determined with a gas chromatography-retention time (GC-RT) approach. Four classes of traditional organic pollutants, including polycyclic aromatic hydrocarbons, organochlorides, polybrominated diphenyl ethers, and polychlorinated biphenyls were employed as reference or calibration compounds. Cluster analysis indicated that the reference and calibration compounds somewhat influenced the relative and absolute magnitudes of GC-RT results. A quantitative structure-property relationship (QSPR) model was constructed from the experimental results and outperformed a widely-used model, KOAWIN, in estimating log KOA of LCs. This model was used to predict log KOAs for 116 LCs with the same element compositions and similar structures as the target LCs. Overall persistence and long-range transport potential were predicted based on the measured and estimated log KOA values, yielding consistent results. Several LCs were shown to have comparable characteristic travel distances and transport efficiencies as the traditional organic pollutants, suggesting they are potential environmental pollutants and the QSPR model is applicable in predicting the environmental fate of LCs.


Assuntos
Poluentes Ambientais , Cristais Líquidos , Bifenilos Policlorados , Cromatografia Gasosa , Poluentes Ambientais/análise , Humanos , Octanóis , Bifenilos Policlorados/análise
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