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1.
Anal Bioanal Chem ; 411(27): 7095-7104, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31673753

RESUMO

A candidate reference measurement procedure (RMP) based on isotope dilution coupled with liquid chromatography-tandem mass spectrometry (ID-LC-MS/MS) was developed and validated for the quantification of 17α-hydroxyprogesterone (17-OHP) in human plasma. 17-OHP spiked with a deuterium-labeled internal standard was extracted from plasma by liquid-liquid extraction with 1 mL n-hexane/ethyl acetate (3:2, v/v). Reversed-phase chromatography and positive electrospray ionization were used in the ID-LC-MS/MS. Gradient elution coupled with use of a C18-packed ultrahigh-performance liquid chromatography column allowed complete baseline resolution of 17-OHP from its structural analogue desoxycorticosterone in 6 min. To determine the 17-OHP level in human plasma, a bracketing calibration method was used to give higher accuracy and precision. The limit of detection and the lower limit of the measuring interval for the candidate RMP were 2.1 pg/mL (6.4 pmol/L) and 4.6 pg/mL (13.9 pmol/L), respectively. Extraction recovery was determined to be (96.08 ± 3.03)% (n = 3). Imprecision (intra-assay and interassay) was 4.03% or less at 0.83, 15.19, 64.22, and 313.46 ng/mL (2.51, 45.97, 194.34, and 948.56 nmol/L, respectively). Recoveries ranged from 98.05% to 102.24%. When comparing our RMP results with those obtained with an established RMP via International Federation of Clinical Chemistry and Laboratory Medicine external quality assessment scheme for reference laboratories in laboratory medicine (RELA) samples, we found that the biases ranged from -1.99% to 3.08% against the targets. No interference was observed, and the linear response ranged from 0.47 to 958.63 ng/mL (1.42 to 2900.90 nmol/L). Moreover, the candidate RMP was used to measure the concentration of 17-OHP in human plasma and was compared with an immunoassay using 40 plasma samples. The performance of the method meets the needs of an RMP (total coefficient of variation of 5% or less and bias of 3.08% or less). This method can be used for reference material value assignment of 17-OHP in human plasma matrix. It could also serve as an accurate reference baseline for routine methods to increase the accuracy and precision of certain clinical laboratory measurements. Graphical abstract Selected ion chromatograms obtained by liquid chromatography-tandem mass spectrometry with a C18 column for 17α-hydroxyprogesterone (17-OHP) from a plasma sample.


Assuntos
17-alfa-Hidroxiprogesterona/sangue , Cromatografia Líquida de Alta Pressão/métodos , Espectrometria de Massas em Tandem/métodos , Calibragem , Cromatografia Líquida de Alta Pressão/normas , Deutério/sangue , Humanos , Técnicas de Diluição do Indicador , Marcação por Isótopo , Padrões de Referência , Valores de Referência , Reprodutibilidade dos Testes , Espectrometria de Massas em Tandem/normas
2.
Food Chem ; 300: 125175, 2019 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-31323606

RESUMO

Despite the ban of nitrofurans (NFs) for use in food production in many countries in the 1990s, NF metabolites in food are still regularly detected during import control testing. We have developed a confirmatory routine method for the detection and quantification of NF metabolites in seafood using LC-MS/MS and validated the method according to the strict criteria in European legislation and Codex Alimentarius. Method characteristics were found to fulfill the criteria. We report for the first time a new false positive for 1-amino-2,4-imidazolidinedione (AHD), the metabolite of Nitrofurantoin (NFT). By using optimized washing procedures, the non tissue bound false positives can be minimized. The results from the validation on both lean and fatty fish and crustaceans, results from proficiency tests and routine use over many years, demonstrates that the method is fit for purpose to determine NF metabolites in the seafood category.


Assuntos
Cromatografia Líquida/métodos , Contaminação de Alimentos/análise , Nitrofurantoína/análise , Alimentos Marinhos/análise , Espectrometria de Massas em Tandem/métodos , Animais , Reações Falso-Positivas , Análise de Alimentos/métodos , Técnicas de Diluição do Indicador , Nitrofurantoína/metabolismo
3.
Anaesthesia ; 74(12): 1551-1557, 2019 12.
Artigo em Inglês | MEDLINE | ID: mdl-31228255

RESUMO

Particulate corticosteroids have been described to lead to greater pain improvement compared with their non-particulate counterparts when used in epidural injections. It is hypothesised that filtering may significantly impact their concentration and long-term efficacy. We investigated if passing particulate suspensions through different commonly-used filters affects drug dosage. Two particulate corticosteroid formulations, triamcinolone acetonide and methylprednisolone acetate, were mixed at different concentrations with either bupivacaine hydrochloride or 0.9% sodium chloride. Solutions were passed through a 5-µm and a 0.2-µm filter. Mass spectroscopy results indicated a complete loss of corticosteroid from the solutions using both filters, and light microscopy imaging demonstrated agglomerate formation, suggesting that filtering interferes with drug dosage. The choice of diluents must also be considered to reduce large agglomerate formation. Clinicians should be aware of the consequences of filtering particulate suspensions and carefully consider the selection of diluent when considering treatment plans.


Assuntos
Corticosteroides/administração & dosagem , Corticosteroides/química , Química Farmacêutica , Composição de Medicamentos , Filtração , Técnicas de Diluição do Indicador , Injeções Epidurais , Metilprednisolona/administração & dosagem , Metilprednisolona/química , Tamanho da Partícula , Material Particulado , Suspensões , Triancinolona Acetonida/administração & dosagem , Triancinolona Acetonida/química
4.
BMC Bioinformatics ; 20(1): 295, 2019 May 30.
Artigo em Inglês | MEDLINE | ID: mdl-31146686

RESUMO

BACKGROUND: The real-time quantitative polymerase chain reaction (qPCR) is routinely used for quantification of nucleic acids and is considered the gold standard in the field of relative nucleic acid measurements. The efficiency of the qPCR reaction is one of the most important parameters in data analysis in qPCR experiments. The Minimum Information for publication of Quantitative real-time PCR Experiments (MIQE) guidelines recommends the calibration curve as the method of choice for estimation of qPCR efficiency. The precision of this method has been reported to be between SD = 0.007 (three replicates) and SD = 0.022 (no replicates). RESULTS: In this article, we present a novel approach to the analysis of qPCR data which has been obtained by running a dilution series. Unlike previously developed methods, our method, Pairwise Efficiency, involves a new formula that describes pairwise relationships between data points on separate amplification curves and thus enables extensive statistics. The comparison of Pairwise Efficiency with the calibration curve by Monte Carlo simulation shows the two-folds improvement in the precision of estimations of efficiency and gene expression ratios on the same dataset. CONCLUSIONS: The Pairwise Efficiency nearly doubles the precision in qPCR efficiency determinations compared to standard calibration curve method. This paper demonstrates that applications of combinatorial treatment of data provide the improvement of the determination.


Assuntos
Reação em Cadeia da Polimerase em Tempo Real/métodos , Animais , Calibragem , Linhagem Celular , Análise de Dados , Técnicas de Diluição do Indicador , Camundongos , Método de Monte Carlo
5.
Environ Sci Pollut Res Int ; 26(21): 22051-22060, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31144184

RESUMO

The analytical procedure for reference measurements of Hg in marine environmental samples based on cold vapour generation (CVG) inductively coupled plasma quadrupole mass spectrometry (ICP-QMS) and isotope dilution calibration strategy (ID) is described in the present study. The procedure was applied on different matrices and varying mass fractions for mercury in oyster, marine sediment and costal seawater samples. The use of CVG for sample introduction resulted in sensitivity enhancement, reduction of blank levels, minimization of matrix interferences and the elimination of memory effects. The entire measurement process was described by mathematical equations, and all factors influencing the final results were systematically investigated. The expanded uncertainty on results was estimated following the ISO/Guide to the Expression of Uncertainty in Measurement guidelines, and all major contributions were identified. Modelling of the entire measurement process and the use of primary method of measurements ID ICP-MS related obtained values for total mercury in different types of marine matrices to the international system of units SI. Obtained results for mercury mass fractions in biota and marine sediments were used as the International Atomic Energy Agency's  contribution in the certification campaigns for marine reference materials and were in excellent agreement with the assigned reference values.


Assuntos
Monitoramento Ambiental/métodos , Mercúrio/análise , Poluentes Químicos da Água/análise , Animais , Calibragem , Gases , Sedimentos Geológicos/química , Técnicas de Diluição do Indicador , Isótopos/análise , Espectrometria de Massas/métodos , Ostreidae , Valores de Referência , Espectrofotometria Atômica , Análise Espectral
6.
Food Chem ; 292: 58-65, 2019 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-31054692

RESUMO

The current food safety concern for food integrity demands the availability of an accurate, easy and reliable analytical tool for assay development of nisin A in cheese. To address this, we report the application of isotopically labelled peptide sequence MSTKDFNLDLVSVSKKDSGASP(R) (without thioether bridges) as internal standard for determination of nisin A in cream cheese, mascarpone, processed cheese and ripened cheese without the need for matrix-matched calibration by triple-quadrupole mass spectrometry. Full method validation was performed according to the modified Commission Decision 2002/657/EC criteria and method robustness was checked on 10 random cheese samples. Internal standard provided significant improvement (p < 0.05) in method precision for determination of nisin A in all four types of cheese. Significant losses (p < 0.05) for Nisin A in cheese was observed one week later. A fit-for-purpose method using internal standard procedure for accurate quantitation of Nisin A in cheese becomes available.


Assuntos
Queijo/análise , Cromatografia Líquida/métodos , Técnicas de Diluição do Indicador , Nisina/análise , Espectrometria de Massas em Tandem/métodos , Calibragem , Análise de Alimentos/métodos , Conservantes de Alimentos/análise , Soroalbumina Bovina
7.
J Agric Food Chem ; 67(22): 6414-6422, 2019 Jun 05.
Artigo em Inglês | MEDLINE | ID: mdl-31088051

RESUMO

The C13-norisoprenoid aroma compounds 1,1,6-trimethyl-1,2-dihydronaphthalene (TDN) and isomeric 2,10,10-trimethyl-6-methylene-1-oxaspiro[4.5]dec-7-enes, so-called vitispiranes, are considered to be biosynthetically related. They occur at higher concentrations in bottle-aged Riesling wines especially and are important contributors to the varietal aroma of Riesling wines. Because of the variation of the quantitative methods and data reported in the literature, a redetermination of concentration levels for both free and total TDN and isomeric vitispiranes, especially in German Riesling wines, was performed using a stable-isotope-dilution assay (SIDA). For this purpose, a novel six-step synthetic route to TDN and deuterium-labeled TDN was developed. A standardized sample preparation for TDN and vitispiranes and a rapid acid-hydrolysis method at genuine wine-pH conditions for the conversion of the precursors into TDN and vitispiranes were also developed. Automated HS-SPME was applied to 250 wine samples from two wine competitions, and analysis was performed by gas chromatography-mass spectrometry with selected-ion monitoring (GC-SIM-MS) as well as selected-reaction monitoring (GC-SRM-MS).


Assuntos
Deutério/química , Naftalenos/química , Norisoprenoides/química , Vinho/análise , Cromatografia Gasosa-Espectrometria de Massas , Técnicas de Diluição do Indicador , Isomerismo , Naftalenos/síntese química , Vitis/química
8.
J Agric Food Chem ; 67(23): 6650-6657, 2019 Jun 12.
Artigo em Inglês | MEDLINE | ID: mdl-31094514

RESUMO

The use of the synthetic antioxidant ethoxyquin (1,2-dihydro-6-ethoxy-2,2,4-trimethylquinoline, EQ) as a flame retardant in fish meal transported by sea is required by international authorities to prevent self-ignition. Because of extensive carry-over within the food chain, selective and sensitive analytical methods are required for investigations on human exposure and the safety of EQ and its metabolites. Therefore, a simple, fast, and rugged liquid-chromatography (LC) method was developed for the detection of EQ and its metabolites in fish and fishery products after liquid-liquid extraction using QuEChERS. For screening purposes, a fluorescence detector was used (LC-FLD) with the EQ-analogue methoxyquin serving as an internal standard. For stable-isotope dilution analysis by liquid chromatography-tandem mass spectrometry (SIDA-LC-MS/MS), deuterated analogues of EQ and its metabolites were synthesized for the first time and allowed for sensitive quantification and thus confirmation of screening results. Both methods were validated and successfully applied to commercially available fish samples.


Assuntos
Antioxidantes/química , Cromatografia Líquida/métodos , Etoxiquina/química , Produtos Pesqueiros/análise , Peixes/metabolismo , Técnicas de Diluição do Indicador , Espectrometria de Massas em Tandem/métodos , Animais , Antioxidantes/metabolismo , Etoxiquina/metabolismo , Fluorescência , Alimentos Marinhos/análise
9.
J Pharm Biomed Anal ; 170: 228-233, 2019 Jun 05.
Artigo em Inglês | MEDLINE | ID: mdl-30933898

RESUMO

The development of a chemometric method for monitoring the pharmaceutical dissolution, under green analytical chemistry principles, was reported. Meloxicam (MEL) and pridinol (PRI) were employed as a combination model. Multivariate curve resolution with alternating least squares (MCR-ALS) was proposed to resolve UV spectra of the analytes during pharmaceutical dissolution. Empowering UV-vis spectrophotometry, which is considered an economical, ecological and fast technique, but poor in terms of selectivity. The developed method was validated in accordance to ICH guidelines, fulfilling acceptance criteria for linearity (r > 0.99 in the ranges 3.5-19.6 mg L-1 and 0.81-5.41 mg L-1 for MEL and PRI, respectively), accuracy (96.3% and 100.6% recoveries for MEL and PRI respectively), and precision (RSD < 10%) were evaluated using an independent validation set. Using a commercial sample, the method's accuracy was evaluated against HPLC analysis. Dissolution profiles were obtained using both methods. A point-to-point comparison with Moore and Flanner's factors (f1 and f2) were calculated. Specificity was evaluated by spectral correlation (R2>0.950). Additionally, the developed method works on-line and forgoes organic solvents and dilutions, lending itself to automation.


Assuntos
Meloxicam/química , Piperidinas/química , Calibragem , Cromatografia Líquida de Alta Pressão/métodos , Técnicas de Diluição do Indicador , Análise dos Mínimos Quadrados , Análise Multivariada , Sensibilidade e Especificidade , Solubilidade
10.
Transfusion ; 59(S2): 1512-1517, 2019 04.
Artigo em Inglês | MEDLINE | ID: mdl-30980760

RESUMO

BACKGROUND: Many transfusion services determine the titer of potentially incompatible plasma-containing products by performing a one-dilution titer at their selected titer threshold. This study compared the results of immediate spin (IS) one-dilution titers determined by three methods with a reference standard method. METHODS: Plasma-containing products from group A and O donors were titered using the participant's routine IS one-dilution titer method. No time or temperature incubations were performed, and antihuman globulin reagent was not used. The samples were then tested using a reference method, which was a saline tube test with a 1-hour room temperature incubation; antihuman globulin was not used in the reference method. The results of the one-dilution titer were then compared to that obtained in the reference method. RESULTS: Nine centers participated in this study. There were 698 antibodies from 374 units tested by the manual IS tube one-dilution titer method; sensitivity was 0.88 (95% confidence interval [CI], 0.83-0.92), and specificity was 1.00 (95% CI, 0.98-1.00). There were 412 antibodies from 206 units tested by the manual and automated IS buffered gel card one-dilution titer method; sensitivity was 0.95 (95% CI, 0.91-0.98), and specificity was 0.87 (95% CI, 0.81-0.91). There were 98 antibodies from 49 units tested by an automated microplate IS one-dilution titer method; sensitivity was 0.76 (95% CI, 0.71-0.93), and specificity was 0.96 (95% CI, 0.92-0.99). All three methods had an accuracy rate of 90% or greater. CONCLUSION: The manual and automated one-dilution titer methods are suitable for screening plasma-containing units, although more evaluation of the automated microplate method might be required.


Assuntos
Sistema do Grupo Sanguíneo ABO/sangue , Incompatibilidade de Grupos Sanguíneos/sangue , Isoanticorpos/sangue , Manejo de Espécimes/métodos , Feminino , Humanos , Técnicas de Diluição do Indicador , Masculino
11.
Anal Bioanal Chem ; 411(16): 3553-3560, 2019 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-31028409

RESUMO

This study presents a novel size exclusion chromatography-inductively coupled plasma-mass spectrometry (SEC-ICP-MS) method for the characterisation and quantification of immunoassays with lanthanide-labelled antibodies. SEC-ICP-MS in combination with a double isotope dilution approach enabled facile validation of the antibodies' integrity, the determination of the batch to batch labelling efficiency, monitoring of each labelling step, and quantification of the immunocomplexes after incubation with the target protein. The addition of oxygen into the dynamic reaction cell improved the detection of sulphur as a marker for the antibodies and target protein via mass-shifting (LOD = 3.7 ng/mL), whilst maintaining sufficient sensitivity for the analysis of the lanthanides. Ultra-high performance liquid chromatography (UHPLC) SEC ensured a rapid chromatographic method with separation times under 7 min of the labelled and unlabelled antibodies, the immunocomplexes, and the unconjugated polymer used to lanthanide-label the antibodies. SEC calibration estimated the molecular weights of all peaks and provided valuable insights in immunochemical reactions and the stoichiometry of the reactants and products. A novel on-line isotope dilution analysis (IDA) enabled absolute quantification of sulphur and lanthanide signals and the protein of interest. The chromatographic separation of immunocomplexes and labelled antibodies allowed the simultaneous determination of the antibody/metal stoichiometry and target protein concentration from a single mass flow chromatogram. An immunoglobulin protein was quantified after incubation with an 153Eu-labelled primary polyclonal antibody. The procedure was validated with direct labelling of the target protein with 156Gd for parallel, simultaneous quantification. The concentration determined via direct labelling of the protein deviated 1.9% from the immunochemical approach employing 153Eu-labelled polyclonal antibodies. Graphical abstract.


Assuntos
Cromatografia em Gel/métodos , Imunoensaio/métodos , Espectrometria de Massas/métodos , Anticorpos/imunologia , Cromatografia Líquida de Alta Pressão/métodos , Técnicas de Diluição do Indicador , Elementos da Série dos Lantanídeos/química , Limite de Detecção
12.
Bioresour Technol ; 283: 53-58, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-30901588

RESUMO

In this work, hydrolysis of spoiled wheat grains using dilute acid (5, 10%; 1 N HCl) was investigated and the effect of hydrolysis conditions on reducing sugars, soluble proteins, rheology and infrared spectra of the hydrolysates was determined. Hydrolysis with 10% acid concentration released more quantities of reducing sugar (16.47 mg/mL) at shorter hydrolysis times whereas 5% acid concentration produced higher protein content (28.74 mg/mL) for similar durations. Flow characteristics demonstrated an increased apparent viscosity of the hydrolysates retrieved after 4.5 h of hydrolysis possibly due to breakdown of hemicelluloses and lignin into sugars. Infrared spectroscopy showed release of carbonates after 1.5 h and 5.5 h of hydrolysis perhaps due to oxidation of lignin or a reaction between acid and sugars. The study highlights that acid hydrolysis would be a rapid and cost effective approach to produce fermentable hydrolysates for bio-processing industry applications while generating an avenue for waste grain utilization.


Assuntos
Grão Comestível/química , Triticum/química , Ácidos/química , Hidrólise , Técnicas de Diluição do Indicador , Lignina/química , Polissacarídeos/química , Reologia , Açúcares/química , Viscosidade
13.
Food Chem ; 288: 154-161, 2019 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-30902276

RESUMO

The complex nature of human breast milk (HBM) makes samples difficult to analyze, requiring several extraction techniques and analytical platforms to obtain high metabolome coverage. In this work, we combined liquid-liquid extraction (LLE) and solid-phase extraction (SPE) techniques to prepare HBM samples to overcome the challenge of low- and high-abundance lipid species, enabling the semiquantitative analysis of total HBM lipids in one liquid chromatography-mass spectrometry (LC-MS) run. A nonorganic fraction obtained during the LLE step was used to analyze small polar metabolites. This analytical approach allows extensive metabolome coverage, especially for low-abundance glycerophospholipids and sphingolipids. The method was applied to monitor short-term metabolome changes in HBM composition within individual mothers and the results showed variable metabolite composition patterns. Simultaneous detection of high-abundance glycerolipids and low-abundance but not less significant phospholipids in one LC-MS run saves time, decreases cost, and enables comprehensive insight into the dynamics of HBM composition.


Assuntos
Metaboloma , Leite Humano/metabolismo , Fosfolipídeos/metabolismo , Cromatografia Líquida , Feminino , Humanos , Técnicas de Diluição do Indicador , Lactente , Extração Líquido-Líquido , Metabolômica , Extração em Fase Sólida , Espectrometria de Massas em Tandem
14.
Bioresour Technol ; 282: 475-481, 2019 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-30897485

RESUMO

Distillers' dried grains with solubles (DDGS) is the by-product of bioethanol production from starch-rich grains through dry-mill fermentation. In this study, dilute sulfuric acid hydrolysis, aqueous ammonia, and steam explosion as the pre-treatment methods were optimized. The central composite response surface methodology (RSM) design was used for optimization of dilute acid pretreatment, aqueous ammonia pretreatment. The steam explosion trials were evaluated. The results show that the dilute acid pretreatment at 121 °C is the most effective way of obtaining simple fermentable sugars (0.382 g/g DDGS). The levels of furfural and HMF was also 5.2 mg/g DDGS) and 1.6 mg/g DDGS, respectively, in the dilute sulfuric acid pretreated DDGS. On the other hand, maximum sugar yield for ammonia pretreatment was 0.129 g/g DDGS and 0.055 g/g DDGS for the steam pretreatment, while no significant amounts of furfural and HMF were observed for these two pretreatment methods.


Assuntos
Amônia/química , Fermentação , Ácidos Sulfúricos/química , Zea mays/metabolismo , Reatores Biológicos , Metabolismo dos Carboidratos , Carboidratos , Explosões , Furaldeído/metabolismo , Hidrólise , Técnicas de Diluição do Indicador , Vapor , Zea mays/química
15.
Food Chem ; 286: 710-714, 2019 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-30827668

RESUMO

A high-precision isotope dilution GC-MS method was employed for the determination of nitrate in processed vegetables. The samples were extracted in water, derivatized with triethyloxonium tetrafluoroborate and analyzed by headspace GC-MS (15 samples/h). The method was applied to estimate the effect of drying on the content of nitrate in vegetables. The absolute amount of nitrate in a spinach sample before and after drying did not change even when the material was baked at 105 °C. Elevated levels of nitrate were found in commercial vegetable powders where the nitrate mass fraction exceed the percent level: 1.2-2.3% NO3- was found in spinach powders, 1.3-1.6% in kale powders, and 1.4% in a beetroot powder. The likely reduction of the antioxidant properties seen in vegetable powders along with their high nitrate content suggest the need to study the risk of endogenous N-nitrosation associated with these products.


Assuntos
Cromatografia Gasosa-Espectrometria de Massas/métodos , Nitratos/análise , Verduras/química , Antioxidantes/análise , Boratos/química , Brassica/química , Análise de Alimentos/métodos , Técnicas de Diluição do Indicador , Pós/análise , Spinacia oleracea/química , Água
16.
Bioresour Technol ; 278: 460-463, 2019 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-30704901

RESUMO

An efficient hybrid pretreatment method was developed for butanol production from corn stover using dilute sulfuric acid (DA) and aqueous ammonia (AA). With the optimized AA concentration, treatment temperature and time of 10% AA, 80 °C and 24 h, the hybrid pretreatment could effectively dissolve hemicellulose and lignin with solid recovery rate of 37.45% and lignin reduction rate of 86.77% compared to those of 57.75% and 45.84% from single DA pretreatment. By washing 1 time after each step treatment, sugar yield and butanol production were increased to 401.76 mg/g-CS and 10.89 g/L from 346.04 mg/g-CS and 9.33 g/L obtained without washing. Compared with conventional single DA and AA pretreatment methods, wastewater generation was reduced to 0.83 L/g-butanol from 2.11 and 3.46 L/g-butanol, indicating this hybrid pretreatment could be an effective approach for improving butanol production from lignocellulosic feedstocks.


Assuntos
Amônia/química , Butanóis/química , Ácidos Sulfúricos/química , Águas Residuárias/química , Zea mays/química , Hidrólise , Técnicas de Diluição do Indicador , Lignina/química , Polissacarídeos/química
17.
Bioresour Technol ; 278: 318-328, 2019 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-30711840

RESUMO

This study aimed to evaluate the effectiveness of microwave-assisted pretreatment in production of cellulosic bioethanol from maize distillery stillage. High glucose concentration (104.4 ±â€¯0.4 mg/g dry weight) and the highest yield of enzymatic cellulose hydrolysis (75.8 ±â€¯0.9%) were obtained for microwave pretreatment characterized by the following parameters: 300 W, 54 PSI, 15 min. Such pre-treatment parameters allowed the obtaining of not only a high concentration of glucose, but also a low concentration of fermentation inhibitors, i.e. 5-hydroxymethylfurfural (6.8 ±â€¯0.4 mg/g of DW) and furfural (6.0 ±â€¯1.2 mg/g dry weight). Optimal dose of yeast, Saccharomyces cerevisiae strain Ethanol Red which gave a high attenuation was 2 g/L of cellulose fermentation medium. Detoxification of cellulose hydrolysates with activated carbon enabled achieving high fermentation yield (approximately 77% of the theoretical yield). Microwave processing can be an effective pretreatment method in production of cellulosic ethanol from maize distillery stillage, but this process requires careful selection of parameters.


Assuntos
Celulose/metabolismo , Etanol/metabolismo , Micro-Ondas , Ácidos Sulfúricos/química , Zea mays/metabolismo , Etanol/química , Fermentação , Hidrólise , Técnicas de Diluição do Indicador , Saccharomyces cerevisiae/metabolismo
18.
Food Chem ; 284: 100-107, 2019 Jun 30.
Artigo em Inglês | MEDLINE | ID: mdl-30744833

RESUMO

Key odorants of Guojing sesame-flavor Baijiu were identified using the concept of molecular sensory science, including aroma extract dilution analysis (AEDA) based on gas chromatography-olfactometry (GC-O) combined with gas chromatography-mass spectrometry (GC-MS). A total of 509 volatile compounds were detected by comprehensive two-dimensional gas chromatography/time-of-flight mass spectrometry (GC × GC-TOF-MS). Sixty-one aroma-active compounds were identified via AEDA. Among them, two compounds with strong roasted aroma showed the highest flavor dilution (FD) factors of 19,683 and 6561. By using pure standards, aroma tests, and GC-MS, the compound with FD = 19683 was identified as benzenemethanethiol, which is reported for the first time in Baijiu. Sixty compounds were quantified by means of internal standard curve method, and 39 of them had odor activity values (OAVs) ≥ 1. Ethyl hexanoate, ethyl octanoate, and dimethyl trisulfide showed the highest OAVs, indicating that they contribute significantly to the aroma of Guojing sesame-flavor Baijiu.


Assuntos
Aromatizantes/química , Análise de Alimentos , Odorantes/análise , Sesamum , Cromatografia Gasosa-Espectrometria de Massas/métodos , Técnicas de Diluição do Indicador , Olfatometria/métodos , Compostos Orgânicos Voláteis/química
19.
BMC Infect Dis ; 19(1): 164, 2019 Feb 14.
Artigo em Inglês | MEDLINE | ID: mdl-30764767

RESUMO

BACKGROUND: Herpes simplex virus type 1 (HSV1), establishes life-long latency and can cause symptoms during both first-time infection and later reactivation. The aim of the present study was to describe a protocol to generate a reliable and discriminative avidity index (AI) for anti-HSV1 IgG content in human sera. METHODS: Human serum from two distinct cohorts; one a biobank collection (Betula) (n = 28), and one from a clinical diagnostics laboratory at Northern Sweden University Hospital (NUS) (n = 18), were assessed for presence of IgG antibodies against HSV1 by a commercially available ELISA-kit. Addition of urea at the incubation step reduces effective binding, and the ratio between urea treated sample and non-treated sample was used to express an avidity index (AI) for individual samples. RESULTS: AI score ranged between 43.2 and 73.4% among anti-HSV1 positive biobank sera. Clinical samples ranged between 36.3 and 74.9%. Reproducibility expressed as an intraclass correlation coefficient (ICC) was estimated at 0.948 (95% CI: 0.900-0.979) and 0.989 (95% CI 0.969-0.996) in the biobank and clinical samples, respectively. CONCLUSION: The method allows for AI scoring of anti-HSV1 IgG from individual human sera with a single measurement. The least significant change between two measurements at the p < 0.05 level was estimated at 5.4 and 3.2 points, respectively, for the two assessed cohorts.


Assuntos
Anticorpos Antivirais/análise , Afinidade de Anticorpos/efeitos dos fármacos , Herpesvirus Humano 1/imunologia , Imunoglobulina G/análise , Testes Sorológicos/métodos , Ureia/farmacologia , Adulto , Idoso , Idoso de 80 Anos ou mais , Anticorpos Antivirais/sangue , Anticorpos Antivirais/efeitos dos fármacos , Ensaio de Imunoadsorção Enzimática/métodos , Feminino , Humanos , Imunoglobulina G/metabolismo , Imunoglobulina M/sangue , Técnicas de Diluição do Indicador , Masculino , Pessoa de Meia-Idade , Kit de Reagentes para Diagnóstico , Reprodutibilidade dos Testes
20.
Food Chem ; 282: 153-163, 2019 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-30711100

RESUMO

Toona sinensis (A. Juss.) M. Roem. (TS) possesses a unique and pleasant flavor and is consumed as a popular seasonal vegetable in certain parts of eastern and southeastern Asia. The potent odorants in raw and cooked TS were identified by combined sensory and instrumental analysis techniques, including sensory descriptive aroma profiling and two complimentary volatile isolation methods combined with gas chromatography-olfactometry (GC-O) techniques. Highly volatile odorants were determined by static headspace dilution analysis (SHDA)-GC-O, while those of intermediate- and semi-volatility were determined by solvent-assisted flavor evaporation-aroma extract dilution analysis (SAFE-AEDA). Among the numerous odorants identified by SHDA and SAFE-AEDA, (E,E)-bis-(1-propenyl) disulfide was found to be predominant in both raw and cooked TS. In agreement with results of sensory descriptive analysis, hexanal, (Z)-3-hexenal, (E)-2-hexenal and (Z)-3-hexen-1-ol contributed green, grassy and leafy aroma notes; while hydrogen sulfide, methyl thiirane, (E,E)-bis-(1-propenyl) disulfide and (E,Z)-bis-(1-propenyl) disulfide contributed pungent, sulfurous and alliaceous notes in TS.


Assuntos
Meliaceae/química , Odorantes/análise , Olfatometria/métodos , Cromatografia Gasosa , Cromatografia Gasosa-Espectrometria de Massas , Temperatura Alta , Técnicas de Diluição do Indicador , Meliaceae/metabolismo , Compostos Orgânicos Voláteis/análise , Volatilização
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