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1.
PLoS One ; 15(1): e0226761, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-31995571

RESUMO

Spectrophotometers are commonly used to measure the concentrations of a wide variety of analytes in drinking water and other matrixes; however, many laboratories with limited resources cannot afford to buy these very useful instruments. To meet this need, an accurate, precise, and affordable light emitting diode (LED) spectrophotometer was designed and built using best engineering practices and modern circuit design. The cost and performance of this LED spectrophotometer was compared against 4 common commercial spectrophotometers. More specifically, the performance of these spectrophotometers was evaluated from the upper limits of linear range, upper limits of operational range, calibration sensitivities, R2 values, precisions of standards, estimated limits of detection, and percent calibration check standard recoveries for the determinations of iron (Fe), manganese (Mn), and fluoride (F-) in drinking water. This evaluation was done in the United States (U.S.) and India. Our LED spectrophotometer costs $63 United States Dollars (USD) for parts. The 4 commercial spectrophotometers ranged in cost from $2,424 to $7,644 USD. There are no practical differences in the upper limits of linear range, upper limits of operational range, R2 values, precisions of standards, and estimated limits of detection for our LED spectrophotometer and the 4 commercial spectrophotometers. For 2 of the 3 analytes, there is a practical difference in the calibration sensitivities our LED spectrophotometer and the 4 commercial spectrophotometers. More specifically, the calibration sensitivities for Mn and F- using our LED spectrophotometer were 65.2% and 67.0% of those using the 4 commercial spectrophotometers, respectively. In conclusion, this paper describes the design, use, and performance of an accurate, precise, and extremely affordable LED spectrophotometer for drinking water and other testing with limited resources.


Assuntos
Água Potável/análise , Fluoretos/análise , Ferro/análise , Luz , Manganês/análise , Espectrofotometria/instrumentação , Espectrofotometria/métodos , Calibragem , Humanos
2.
Acta Odontol Scand ; 78(1): 31-37, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31349769

RESUMO

Objectives: To determine the baseline perfusion parameters of the alveolar mucosa using laser Doppler flowmetry and tissue spectrophotometry (LDF-TS) in healthy adults.Material and methods: Forty-two healthy adult subjects of either sex were tested. The perfusion of the alveolar mucosa was evaluated using a laser Doppler flowmetry and tissue spectrophotometry using O2C 'oxygen to see' device. The measurements encompassed the maxillary and mandibular mucosa at 20 different points.Results: The O2C device is a reliable method for noninvasive measurement of different perfusion parameters of the oral mucosa. The hemoglobin saturation values (So2 in %), as well as relative amount of hemoglobin in arbitrary units (AU) of the maxillary mucosa demonstrated lower values of that in the mandible. The flow value (AU) exhibited a significant difference in the posterior molar region only, while the velocity value (AU) showed a significant difference across all points except for the anterior region.Conclusion: the present study provides a set of brand-new perfusion parameters of the microcirculation of the alveolar mucosa using LDF-TS. The study suggests a variation of the perfusion parameters between the maxilla and the mandible. Differences in the anatomy of the blood supply, the thickness of the mucosa and the cortical bone, may be attributed to this variation. Further studies using different probes and a combination of ultrasonic measurements and SDF imaging will aid in giving a better overview of the perfusion in the oral mucosa.


Assuntos
Fluxometria por Laser-Doppler/métodos , Mandíbula/irrigação sanguínea , Maxila/irrigação sanguínea , Microcirculação/fisiologia , Mucosa Bucal/irrigação sanguínea , Oxigênio/fisiologia , Espectrofotometria/métodos , Adulto , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Perfusão
3.
Mater Sci Eng C Mater Biol Appl ; 106: 110223, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31753383

RESUMO

A novel molecularly imprinted polymer was synthesized on magnetic halloysite nanotube via surface initiated reversible addition-fragmentation chain transfer polymerization in the presence of 2-aminoethylmethacrylamide, 2-Cyano-2-propyl benzodithioate, ethylene glycol dimethacrylate (EGDMA) and azobis(isobutyronitrile) for sensitive and selective spectrophotometric determination of metoclopramide in urine samples. The synthesized imprinted polymer was characterized by several surface characterization techniques and the results indicated there was a thin polymer network on the magnetic halloysite nanotube. The rebinding properties of the molecularly imprinted magnetic halloysite nanotube were also investigated in detail and the maximum adsorption capacity and imprinting factor were found to be 37.8 mg/g and 4.51, respectively. The application of the proposed method was carried out by enrichment and spectrophotometric determination of metoclopramide via formation of a charge transfer complex between picric acid and eluted metoclopramide. Under the optimized conditions, the calibration curve was linear in the concentration range of 5.0-150.0 ng/mL and the limit of detection and the limit of quantification were calculated to be 1.5 ng/mL and 4.95 ng/mL, respectively. The inter-day and intra-day precisions were below 5% and recoveries were between 92.8% and 99.2%. The results showed that the proposed method increased the sensitivity and selectivity for spectrophotometric determination of metoclopramide.


Assuntos
Metoclopramida/urina , Impressão Molecular/métodos , Nanotubos/química , Polímeros/química , Espectrofotometria/métodos , Adulto , Humanos , Masculino , Espectroscopia Fotoeletrônica , Polimerização
4.
Spectrochim Acta A Mol Biomol Spectrosc ; 224: 117339, 2020 Jan 05.
Artigo em Inglês | MEDLINE | ID: mdl-31344573

RESUMO

An analytical investigation was carried out to study the treatment and amplification of the spectral signals produced by critical concentrations with high accuracy and precision using two advanced approaches. The factorized-spectrum approach was applied through two novel methods which were: absorptivity centering technique via both: factorized zero order absorption spectrum (ACT-FSD0ΔA) and factorized ratio spectrum (ACT-FSRΔP). The proposed methods were found to be linear in the ranges of (15-100 µg/mL) and (3-40 µg/mL) for ASP and MTO, respectively. Those methods were compared to the methods following the geometrical standard addition approach: ratio H-point standard addition method (RHPSAM) and geometrical induced amplitude modulation (GIAM). The approaches were applied for the determination of the minor component metoclopramide in its mixture with the major component aspirin in the challengeable ratio of (1,90) respectively in a white multicomponent system. The results obtained from the proposed approaches were statistically compared with each other. The methods were validated according to ICH guidelines where the results were found to be within the acceptable limits. The methods were found to be accurate and reliable for the determination of metoclopramide critical concentration besides aspirin concentration. The results of single factor ANOVA analysis indicated that there is no significant difference among the developed methods. These methods provided simple resolution of this binary combination from synthetic mixtures and pharmaceutical preparation and can be conveniently adopted for routine quality control analysis.


Assuntos
Preparações Farmacêuticas/análise , Processamento de Sinais Assistido por Computador , Espectrofotometria/métodos , Aspirina/análise , Aspirina/química , Modelos Lineares , Metoclopramida/análise , Metoclopramida/química , Modelos Químicos , Modelos Estatísticos , Preparações Farmacêuticas/química , Reprodutibilidade dos Testes
5.
Talanta ; 206: 120250, 2020 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-31514846

RESUMO

The development of a simple and economical spectrophotometric system based on the use of a device created by 3D printing and the electronics necessary to control the intensity of the radiation source was described. The measurements are made with a low-cost digital webcam. The entire system is only powered through the USB outputs of a computer, which makes the portable and really practical system for the measurements in the field. This method was applied to determine iron (II) in waters using o-phenanthroline as chromogenic reagent giving a red complex, and also to hypochlorite determination using tetramethylbenzidine as the reagent providing a yellow color. The calibration curves were built using a mathematical algorithm making a RGB deconvolution. The intense of colors obtained from a webcam in each concentration of analyte had a relationship with the absorbance values. In order to confirm the accuracy and precision of this method, a traditional spectrophotometer was used for validation.


Assuntos
Computadores , Fotografação/instrumentação , Impressão Tridimensional , Espectrofotometria/instrumentação , Benzidinas/química , Calibragem , Ácido Hipocloroso/análise , Ferro/análise , Limite de Detecção , Fenantrolinas/química , Espectrofotometria/métodos
6.
Allergol. immunopatol ; 47(6): 591-597, nov.-dic. 2019. tab
Artigo em Inglês | IBECS | ID: ibc-186553

RESUMO

Introduction and Objectives: Vitamin D deficiency is associated with increased susceptibility to infections and wheezing. We aimed to evaluate the relation between vitamin D levels, viral infections and severity of attacks in children with recurrent wheezing. Materials and methods: A total of 52 patients who applied with wheezing, at the ages of 12-60 months with a history of three or more wheezing attacks in the last year and 54 healthy children were included. Sociodemographic data, risk factors for recurrent wheezing, and the severity of the wheezing attacks were recorded. 25(OH)D3, calcium, phosphor, alkaline phosphatase and parathormone levels of all children were measured. Nasopharyngeal samples of the patients for viruses were studied by multiplex polymerase chain reaction. Results: For the patient group, being breastfed for six months or less, history of cesarean section, cigarette exposure, humid home environment, and family history of allergic disease were significantly higher compared with the control group. Serum vitamin D levels in the patient group were significantly lower compared to the control group. There was no significant relationship between vitamin D levels and hospitalization, oxygen or steroid therapy. Virus was detected in 38 patients (73%). Rhinovirus (63.2%) was the most frequently detected virus. Coinfection was found in 14 (36.8%) patients. There was no statistically significant difference between detection of virus and vitamin D levels. Conclusions: Cigarette exposure, being breastfed six months or less, humid home environment, history of cesarean section, family history of allergic disease and vitamin D deficiency might be risk factors for recurrent wheezing


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Assuntos
Humanos , Masculino , Feminino , Criança , Adolescente , Adulto Jovem , Adulto , Pessoa de Meia-Idade , Viroses/imunologia , Vitamina D/uso terapêutico , Índice de Gravidade de Doença , Fatores de Risco , Coinfecção/imunologia , Infecções Respiratórias/imunologia , Sons Respiratórios/imunologia , Recidiva , Reação em Cadeia da Polimerase , Anormalidades Congênitas/imunologia , Pulmão/anormalidades , Pulmão/imunologia , Espectrofotometria/métodos , Sons Respiratórios/etiologia , Deficiência de Vitamina D
7.
PLoS One ; 14(12): e0226851, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31887165

RESUMO

BACKGROUND: Due to the current poaching crisis in Africa, increasing numbers of white rhinoceroses (Ceratotherium simum) require opioid immobilisation for medical interventions or management procedures. Alarmingly, the results of both blood gas analysis and pulse oximetry regularly indicate severe hypoxaemia. Yet, the recovery of the animals is uneventful. Thus, neither of the techniques seems to represent the real oxygenation level. We hypothesized that unusual haemoglobin characteristics of this species interfere with the techniques developed and calibrated for the use in human patients. METHODS: Haemoglobin was isolated from blood samples of four adult, white rhinoceroses. Oxygen dissociation curves at pH 7.2 and 7.4 (37°C) were determined based on the absorbance change of haemoglobin in the Soret-region (around 420 nm). Absorbance spectra of oxy- and deoxyhaemoglobin extending into the infrared region were measured. RESULTS: Oxygen dissociation curves of rhinoceros haemoglobin showed the typical high oxygen affinity (p50 of 2.75 ± 0.07 and 2.00 ± 0.04 kPa for pH 7.2 and 7.4, respectively) under near-physiological conditions with respect to pH, temperature and DPG. The infrared absorbance spectra of oxy- and deoxyhaemoglobin showed only marginal deviations from standard human spectra, possibly due to the presence of a few percent of methaemoglobin in vitro. CONCLUSIONS: Our data enables the development of a rhinoceros-specific blood gas analysis algorithm, which allows for species-specific calculation of SaO2 levels in anaesthetized animals. The inconspicuous absorbance spectra do not contribute to the systematic underestimation of SpO2 by pulse-oximetry.


Assuntos
Hemoglobinas/metabolismo , Oxigênio/sangue , Perissodáctilos/sangue , África , Algoritmos , Analgésicos Opioides , Animais , Gasometria/métodos , Gasometria/normas , Hemoglobinas/química , Humanos , Concentração de Íons de Hidrogênio , Oximetria/normas , Espectrofotometria/métodos
8.
J Nutr Sci Vitaminol (Tokyo) ; 65(4): 285-302, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31474678

RESUMO

Recently a new assay method that can quantify the singlet oxygen absorption capacity (SOAC) of antioxidants (AOs) and food extracts was proposed. Singlet oxygen (1O2) quenching rates (kQ) and the relative SOAC values were measured for many carotenoids and phenolic AOs in ethanol/chloroform/D2O (50 : 50 : 1, v/v/v) solution at 35ºC using UV-vis spectrophotometry. It has been clarified that the SOAC method is useful to evaluate the 1O2-quenching activity of lipophilic and hydrophilic AOs having 5 orders of magnitude different rate constants (kQ). Measurements of the kQ and SOAC values were also performed for 39 kinds of food extracts. The results indicate that the SOAC method is useful to evaluate the 1O2-quenching activity of food extracts having two orders of magnitude different kQ values. Further, the kQ values for the reaction of 1O2 with 8 carotenoids and 8 vitamin E homologues were measured in an aqueous Triton X-100 (5.0 wt %) micellar solution (pH 7.4). Results obtained demonstrate that the kQ values of AOs in homogeneous and heterogeneous solutions vary notably depending on (i) polarity (dielectric constant (ε)) of the reaction field between AOs and 1O2, (ii) local concentration of AOs, and (iii) mobility of AOs in solution. Measurements of kQ and SOAC values in a micellar solution may be useful for evaluating the 1O2-quenching activity of AOs in biological systems. Furthermore, measurements of the SOAC values were performed for 32 kinds of food extracts using a microplate reader. The SOAC assay method was validated by inter-laboratory validation study due to 14 laboratories.


Assuntos
Antioxidantes/química , Análise de Alimentos/métodos , Alimentos , Oxigênio Singlete/química , Carotenoides/química , Fenômenos Químicos , Micelas , Fenóis/química , Reprodutibilidade dos Testes , Soluções/química , Espectrofotometria/métodos , Vitamina E/química
9.
Talanta ; 205: 120102, 2019 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-31450421

RESUMO

A disposable and miniaturised optical sensor based on colorimetric solid-phase extraction has been designed using poly(styrene-divinylbenzene) membrane disks modified with the colorimetric reagent pyridoxal salicyloylhydrazone to determine the aluminium concentration in aqueous solutions. The extraction of Al(III) ions by the reagent immobilised onto a disk allows the quantification directly on the adsorbent surface by a miniature portable reflectance spectrometer with an optical fibre at 434 nm. The optimisation of the sensing system was carried out by a fractional factorial design 33-1 considering the extraction pH, amount of ligand immobilised onto the disk and time of immobilisation as experimental factors. The linear dynamic range of the sensor response ranged from 0.18 to 2 mg L-1 Al(III) with a detection limit of 0.18 mg L-1 (n = 10), being the precision of 6.3% for 1 mg L-1 Al(III) (n = 10, confidence level of 95%). The proposed method was successfully applied to the analysis of aluminium in leachates from cookware, antacids and hygienic care products, as contribution to the concern about aluminium as a known systemic toxicant at high doses.


Assuntos
Alumínio/análise , Poluentes Químicos da Água/análise , Antiácidos/análise , Colorimetria/métodos , Desodorantes/análise , Contaminação de Medicamentos/prevenção & controle , Hidrazonas/química , Limite de Detecção , Poliestirenos/química , Piridoxal/análogos & derivados , Extração em Fase Sólida/instrumentação , Extração em Fase Sólida/métodos , Solventes/química , Espectrofotometria/métodos , Água/análise
10.
Talanta ; 205: 120095, 2019 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-31450452

RESUMO

pH value is one of the most important parameters, which show significant application in environmental monitoring, chemistry and biology. Abnormal pH values always associate with some serious diseases, including cancer and Alzheimer's disease. Thus, development of highly sensitive and selective method for pH sensing and imaging is of great importance. In this paper, we synthesized a water-soluble organic probe for pH sensing either through its absorption or through its fluorescent signals. The probe was synthesized from the intermediate containing a phenol group, and the reaction was carried out in concentrated H2SO4 at 90 °C. In this way, the probe can introduce a sulfonic acid group into its structure, and thus improve its water solubility. The synthesized probe is pH-responsive, and the response process is reversible, because that the phenol group in the probe can transfer to deprotonation state with increasing the pH values to improve the intramolecular charge transfer. Meanwhile, the synthesized probe also showed high specificity and excellent biocompatibility, which is suitable for cell imaging applications.


Assuntos
Cumarínicos/química , Corantes Fluorescentes/química , Linhagem Celular Tumoral , Cumarínicos/síntese química , Cumarínicos/toxicidade , Corantes Fluorescentes/síntese química , Corantes Fluorescentes/toxicidade , Humanos , Concentração de Íons de Hidrogênio , Microscopia Confocal/métodos , Solubilidade , Espectrometria de Fluorescência/métodos , Espectrofotometria/métodos , Água/química
11.
J Appl Oral Sci ; 27: e20180351, 2019 Jul 29.
Artigo em Inglês | MEDLINE | ID: mdl-31365707

RESUMO

OBJECTIVE: Since the transmittance of ceramics can influence the degree of conversion (DC) of resin cements, ceramics composition and shade should be considered in the selection of resin cement. This in vitro study aimed to evaluate the effect of the transmittance of different composition, opacities and shades of ceramics on the degree of conversion of two dual-cured resin cements. METHODOLOGY: Sixty discs were prepared from low translucency (LT) and medium opacity (MO) lithium disilicate ceramic, and zirconia ceramic (Z). Each group was subdivided into 5 subgroups (n=4) in shades A2, A3.5, B2, C2 and D3. The transmittance measurement was performed in a spectrophotometer. The Variolink II and Rely X U200 resin cements were photoactivated by LED (1400 mW/cm2) for 40 s through the ceramic discs and without the discs (control group). The DC was measured with infrared FTIR spectroscopy, immediately after light activation. Data were analyzed with Kruskall-Wallis and one-way ANOVA, following post-hoc comparisons by Tukey test and Pearson's correlation test (P<0.05). RESULTS: LT ceramic exhibited higher transmittance values compared to MO and Z ceramics. LTA2 and LTB2 showed statistically higher transmittance values compared to MOA2, MOA3.5 and ZA3.5. For Variolink II, the ceramic interposition did not influence the DC, since there were no statistical differences between groups with ceramic interposition and the control group. For Rely X U200 cement, the interposition of some ceramics types/shades (LTA3.5, MOA2, MOA3.5 and ZA3.5) significantly decreased the DC values compared to control group. A positive correlation was found between the ceramic transmittance and DC values of both tested cements. Conclusions. The transmittance and DC values of the cements were influenced by composition and shades of the ceramics. The higher the transmittance of ceramics, the higher the DC values for both cements.


Assuntos
Porcelana Dentária/química , Cimentos de Resina/química , Zircônio/química , Análise de Variância , Luzes de Cura Dentária , Cura Luminosa de Adesivos Dentários , Teste de Materiais , Transição de Fase , Polimerização , Valores de Referência , Reprodutibilidade dos Testes , Espectrofotometria/métodos , Estatísticas não Paramétricas
12.
Food Chem ; 300: 125177, 2019 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-31323607

RESUMO

A point-of-care testing chip was developed for the colorimetric detection of inorganic mercury ion (Hg2+). The disposable chip fabricated by three-dimensional printing technology contains DNAzymes produced by rolling circle amplification (RCA); a color change caused by the enzymatic reaction between DNAzymes and the peroxidase substrate 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) is measured using a portable spectrophotometer. In the "turn-off"-type RCA reaction, the annealing of the T(12) primer that initiates the RCA reaction is blocked by the interaction of thymine with Hg2+; thus, the amount of amplified DNAzymes causing a color change is decreased depending on Hg2+ concentration. The colorimetric signal is enhanced by amplifying double-repeat DNAzymes from a circular DNA template. The chip detected Hg2+ in tap drinking water samples with high sensitivity (lowest validated value: 3.6 µg/L) and showed better selectivity, precision, and reproducibility than conventional analysis instruments. This low-cost easy-to-use platform can reduce the risk of accidental Hg2+ poisoning.


Assuntos
Colorimetria/instrumentação , Água Potável/análise , Mercúrio/análise , Impressão Tridimensional , Poluentes Químicos da Água/análise , Colorimetria/métodos , DNA Catalítico/química , Desenho de Equipamento , Mercúrio/química , Reprodutibilidade dos Testes , Sensibilidade e Especificidade , Espectrofotometria/métodos
13.
G3 (Bethesda) ; 9(9): 2913-2924, 2019 09 04.
Artigo em Inglês | MEDLINE | ID: mdl-31289023

RESUMO

Kernel methods are flexible and easy to interpret and have been successfully used in genomic-enabled prediction of various plant species. Kernel methods used in genomic prediction comprise the linear genomic best linear unbiased predictor (GBLUP or GB) kernel, and the Gaussian kernel (GK). In general, these kernels have been used with two statistical models: single-environment and genomic × environment (GE) models. Recently near infrared spectroscopy (NIR) has been used as an inexpensive and non-destructive high-throughput phenotyping method for predicting unobserved line performance in plant breeding trials. In this study, we used a non-linear arc-cosine kernel (AK) that emulates deep learning artificial neural networks. We compared AK prediction accuracy with the prediction accuracy of GB and GK kernel methods in four genomic data sets, one of which also includes pedigree and NIR information. Results show that for all four data sets, AK and GK kernels achieved higher prediction accuracy than the linear GB kernel for the single-environment and GE multi-environment models. In addition, AK achieved similar or slightly higher prediction accuracy than the GK kernel. For all data sets, the GE model achieved higher prediction accuracy than the single-environment model. For the data set that includes pedigree, markers and NIR, results show that the NIR wavelength alone achieved lower prediction accuracy than the genomic information alone; however, the pedigree plus NIR information achieved only slightly lower prediction accuracy than the marker plus the NIR high-throughput data.


Assuntos
Genômica/métodos , Modelos Genéticos , Melhoramento Vegetal/métodos , Espectrofotometria/métodos , Bases de Dados Genéticas , Aprendizado Profundo , Genômica/estatística & dados numéricos , Fenótipo , Espectrofotometria/estatística & dados numéricos , Triticum/genética , Zea mays/genética
14.
Acta Pharm ; 69(2): 217-231, 2019 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-31259724

RESUMO

The study presents the application of multivariate curve resolution alternating least squares (MCR-ALS) with a correlation constraint for simultaneous resolution and quantification of ketoprofen, naproxen, paracetamol and caffeine as target analytes and triclosan as an interfering component in different water samples using UV-Vis spectrophotometric data. A multivariate regression model using the partial least squares regression (PLSR) algorithm was developed and calculated. The MCR-ALS results were compared with the PLSR obtained results. Both models were validated on external sample sets and were applied to the analysis of real water samples. Both models showed comparable and satisfactory results with the relative error of prediction of real water samples in the range of 1.70-9.75 % and 1.64-9.43 % for MCR-ALS and PLSR, resp. The obtained results show the potential of MCR-ALS with correlation constraint to be applied for the determination of different pharmaceuticals in complex environmental matrices.


Assuntos
Monitoramento Ambiental/métodos , Preparações Farmacêuticas/análise , Poluentes Químicos da Água/análise , Análise dos Mínimos Quadrados , Análise Multivariada , Espectrofotometria/métodos
15.
Environ Sci Pollut Res Int ; 26(26): 27063-27072, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31313234

RESUMO

In this study, a sensitive and low-cost multi-wavelength spectrophotometric method for the determination of hydrogen peroxide (H2O2) in water was established. The method was based on the oxidative coloration of 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonate) (ABTS) via Fenton reaction, which resulted in the formation of green radical (ABTS•+) with absorbance at four different wavelengths (i.e., 415 nm, 650 nm, 732 nm, and 820 nm). Under the optimized conditions (CABTS = 2.0 mM, CFe2+ = 1.0 mM, pH = 2.60 ± 0.02, and reaction time (t) = 1 min), the absorbance of the generated ABTS•+ at 415 nm, 650 nm, 732 nm, and 820 nm were well linear with H2O2 concentrations in the range of 0-40 µM (R2 > 0.999) and the sensitivities of the proposed Fenton-ABTS method were calculated as 4.19 × 104 M-1 cm-1,1.73 × 104 M-1 cm-1, 2.18 × 104 M-1 cm-1, and 1.96 × 104 M-1 cm-1, respectively. Meanwhile, the detection limits of the Fenton-ABTS method at 415 nm, 650 nm, 732 nm, and 820 nm were respectively calculated to be 0.18 µM, 0.12 µM, 0.10 µM, and 0.11 µM. The absorbance of the generated ABTS•+ in ultrapure water, underground water, and reservoir water was quite stable within 30 min. Moreover, the proposed Fenton-ABTS method could be used for monitoring the variations of H2O2 concentration during the oxidative decolorization of RhB in alkali-activated H2O2 system.


Assuntos
Benzotiazóis/química , Peróxido de Hidrogênio/análise , Espectrofotometria/métodos , Ácidos Sulfônicos/química , Água/análise , Cor , Corantes Fluorescentes/química , Água Doce/análise , Peróxido de Hidrogênio/química , Concentração de Íons de Hidrogênio , Ferro/química , Limite de Detecção , Oxirredução , Rodaminas/química , Água/química
16.
Spectrochim Acta A Mol Biomol Spectrosc ; 223: 117325, 2019 Dec 05.
Artigo em Inglês | MEDLINE | ID: mdl-31280127

RESUMO

We report a facile one step in-situ synthesis of amino-functionalized graphene dots. These quantum dots were employed for the detection of glucose in both standard aqueous solutions and commercially available fruit juice to assess its practicability. The characterization of the quantum dots revealed that they were decorated with amine functionality. Additionally, the interaction between glucose and amine functionalized graphene quantum dots gave enhancement in the UV-vis absorption and photoluminescence (PL) due to aggregation of quantum dots via glucose link. Therefore, the quantum dots were able to detect the concentration of glucose in solution exhibiting linearity from 0.1 to 10 mM and 50-500 mM with a sensitivity transition from 10 mM to 50 mM. The limit of detection for the determination of glucose was found to be 10 µM. This determination was agreed from both UV-Vis absorption and PL spectroscopy. However, the PL emission method of determination was most suited with its very high accuracy of 98.04 ±â€¯1.96% and 97.33 ±â€¯2.67% for the linear range of glucose concentration within 0.1-10 mM and 50-500 mM, respectively. The PL enhancement was highly selective towards glucose in mixture of other form of sugars making it suitable for determining glucose in food samples.


Assuntos
Glucose/análise , Grafite/química , Nitrogênio/química , Pontos Quânticos/química , Espectrofotometria/métodos , Luminescência , Espectroscopia Fotoeletrônica , Pontos Quânticos/ultraestrutura , Espectrofotometria Ultravioleta , Espectroscopia de Infravermelho com Transformada de Fourier
17.
Sensors (Basel) ; 19(13)2019 Jul 08.
Artigo em Inglês | MEDLINE | ID: mdl-31288380

RESUMO

Measuring chlorophyll fluorescence is a direct and non-destructive way to monitor vegetation. In this paper, the fluorescence retrieval methods from multiple scales, ranging from near the ground to the use of space-borne sensors, are analyzed and summarized in detail. At the leaf-scale, the chlorophyll fluorescence is measured using active and passive technology. Active remote sensing technology uses a fluorimeter to measure the chlorophyll fluorescence, and passive remote sensing technology mainly depends on the sun-induced chlorophyll fluorescence filling in the Fraunhofer lines or oxygen absorptions bands. Based on these retrieval principles, many retrieval methods have been developed, including the radiance-based methods and the reflectance-based methods near the ground, as well as physically and statistically-based methods that make use of satellite data. The advantages and disadvantages of different approaches for sun-induced chlorophyll fluorescence retrieval are compared and the key issues of the current sun-induced chlorophyll fluorescence retrieval algorithms are discussed. Finally, conclusions and key problems are proposed for the future research.


Assuntos
Algoritmos , Clorofila/análise , Modelos Teóricos , Tecnologia de Sensoriamento Remoto/métodos , Atmosfera , Fluorescência , Modelos Estatísticos , Folhas de Planta/química , Astronave , Espectrofotometria/métodos
18.
Food Chem ; 298: 125009, 2019 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-31260970

RESUMO

The objective of this study was to develop an accurate and fast method to determine malondialdehyde (MDA) levels in raw and processed meat. This method is based on extraction with trichloroacetic acid (TCA), reaction with 2-thiobarbituric acid (TBA) and quantification with ultraperformance liquid chromatography with a fluorescence detector (UPLC-FLD) with ʎexcitation = 530 nm and ʎemission = 550 nm and with a diode array detector (UPLC-DAD) with ʎabsorbance = 532 nm. The method tested was compared with the TBARS spectrophotometric method with ʎabsorbance = 532 nm. The concentration of MDA was similar for most of the matrices in both UPLC methods, except for cooked ham and frankfurter sausage. The TBARS spectrophotometric method overestimated the MDA concentration in all the matrices. Therefore, the use of both chromatographic methods, especially UPLC-FLD, to determine MDA would be more advisable than the classic TBARS method to avoid overestimation in meat and processed meat products.


Assuntos
Cromatografia Líquida/métodos , Análise de Alimentos/métodos , Malondialdeído/análise , Produtos da Carne/análise , Animais , Fracionamento Químico/métodos , Cromatografia Líquida/instrumentação , Culinária , Fluorescência , Malondialdeído/isolamento & purificação , Carne/análise , Espectrofotometria/métodos , Suínos , Tiobarbitúricos/química , Substâncias Reativas com Ácido Tiobarbitúrico/análise , Ácido Tricloroacético/química
19.
Ultrason Sonochem ; 57: 108-115, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31208605

RESUMO

Efficiency of blue (462 ±â€¯3 nm) light emitting diode (LED) illumination to inactivate Escherichia coli and Staphylococcus aureus in the presence of exogenous photosensitizer (curcumin) was studied in freshly squeezed orange juice. Further, the combinational effect of ultrasound (US), photosensitizer (PS) and blue light (BL) on inactivation of microbes was evaluated. The effect of process parameters such as concentration of PS, US and volume of the juice on E. coli and S. aureus inactivation was also investigated. The US alone and PS + BL treatments resulted in 3.02 ±â€¯0.52 and 1.06 ±â€¯0.13 log reduction of E. coli; 0.18 ±â€¯0.14 and 2.34 ±â€¯0.13 log reduction of S. aureus, respectively. The combination of PS + US + BL treatment at optimized conditions resulted in 2.35 ±â€¯0.16 log reduction of S. aureus. An additive effect on the inactivation of E. coli (4.26 ±â€¯0.32 log reduction) was observed with PS + US + BL combination treatment. The US treatment showed significant change in cloud value, colour and browning index of orange juice. The combinational non-thermal processes (PS + BL and PS + US + BL) did not have any significant effect on total phenolic content, total flavonoid content, and hesperidin content of the orange juice. However, these processes affected ascorbic acid content and antioxidant activity negatively. Thus, this study indicated that photodynamic inactivation of E. coli and S. aureus using LED-based photosensitization in fruit juices could be a potential method for microbial inactivation. Nevertheless, the effect on quality parameters needs to be considered while optimizing the process.


Assuntos
Escherichia coli/efeitos dos fármacos , Escherichia coli/efeitos da radiação , Microbiologia de Alimentos , Sucos de Frutas e Vegetais/microbiologia , Luz , Fármacos Fotossensibilizantes/farmacologia , Staphylococcus aureus/efeitos dos fármacos , Staphylococcus aureus/efeitos da radiação , Ondas Ultrassônicas , Antioxidantes/análise , Ácido Ascórbico/análise , Contagem de Colônia Microbiana , Escherichia coli/isolamento & purificação , Flavonoides/análise , Sucos de Frutas e Vegetais/análise , Hesperidina/análise , Valor Nutritivo , Fenóis/análise , Espectrofotometria/métodos , Staphylococcus aureus/isolamento & purificação
20.
J Sci Food Agric ; 99(13): 5953-5961, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31215031

RESUMO

BACKGROUND: The development of rapid methods for the determination of the soluble solids content (SSC) and total phenolic content (TPC) in fruit juices is of great interest. Soluble solids content is related to sensory attributes, whereas TPC is related to the antioxidant capacity of juices. The aim of this study was to develop and optimize the calibration models for the prediction of the SSC and TPC of strawberry juices from the spectra of fruit and juices. RESULTS: Near infrared (NIR) spectra were measured for strawberry fruit and ultraviolet (UV), visible (VIS), and NIR spectra were measured for juices. The partial least squares regression models were validated using the test sample set and their predictive ability was evaluated on the basis of determination coefficients (R2 P ) and root mean square error of prediction (RMSEP). For SSC the models with high predictive ability were obtained using spectra of fruit (R2 P = 0.929, RMSEP = 0.46%) or juices (R2 P = 0.979, RMSEP = 0.25%) in the NIR range. The optimal models for TPC were obtained using NIR spectra of fruit (R2 P = 0.834, RMSEP = 130.8 mg GA L-1 ) or UV-VIS-NIR spectra of juices (R2 P = 0.844, RMSEP = 126.7 mg GA L-1 ). CONCLUSION: The results show the potential of spectroscopy for predicting quality parameters of strawberry juices from the juice spectra itself or non-destructively from the fruit spectra. They may contribute to the development of fruit sorting systems to optimize their use in juice production, as well as fast-screening methods for quality control of juices. © 2019 Society of Chemical Industry.


Assuntos
Fragaria/química , Sucos de Frutas e Vegetais/análise , Espectrofotometria/métodos , Espectroscopia de Luz Próxima ao Infravermelho/métodos , Calibragem , Frutas/química , Análise dos Mínimos Quadrados , Controle de Qualidade
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