查看更多>>摘要：Advances in food monitoring benefit tremendously from the naked-eye observation and device-miniaturization of colorimetric and fluorometric methods. Intelligent food packaging, containing a built-in sensor inside food bags, is capable of real-time monitoring of food quality by visibly discernible out-put signals, which effectively ensures food safety. We synthesized a donor-pi-acceptor (D-pi-A) compound DPABA, and disclosed its fluorescence response to amines. According to quantum chemical calculations, DPABA is apt to D-A coupling in aggregated state, causing the formation of exciplex/excimer together with intermolecular charge/energy transfer to the disadvantage of light emission; while the evasion of amine vapors would decouple the intermolecular D-A interactions to induce stronger emission with shorter wavelength. Utilizing the amine vapor generated by fish, DPABA can serve as an indicator for freshness monitoring. To create an intelligent food package, the compound was made into cellulose film, which was further cut into smart labels to be encapsulated into food bags. The as-prepared smart label exhibits red color under ambient light and glows weak red emission under UV light, while it turns into faint yellow color in response to putrid fish, and its emission changes to bright cyan. The output signals can be accurately recorded by instrument, and detected by naked eye, suggesting high signal contrast. In addition, the smart label exhibits different changing scope in response to different degree of freshness, showing high potential for in-field detection. (C) 2021 Elsevier B.V. All rights reserved.
查看更多>>摘要：Hazelnut oil (HO), which is not widely used because its healthy properties are not fully known yet, is an excellent nutrient due to its high content of monounsaturated fatty acids and antioxidants. In this study, the effects of thermal processing on the quality of HO in comparison to extra virgin olive oil (EVOO), which is one of the healthiest and heat-resistant oils, were investigated using Attenuated Total Reflection-Fourier Transform Infrared (ATR-FTIR) spectroscopy. Oil samples were heated at a frying temperature (180 degrees C) for 24 h in periods of 8 h per day and alterations in the spectra of these oils sampled every 2 h were evaluated. The heating process caused decreases in the areas of the bands at 3007 and 722 cm(-1) and the area ratios of 3007/2854 and 722/2854 cm(-1) and increases in the areas of the bands at 987 and 965 cm(-1) and the area ratio of 965/2854 cm(-1) in both oils suggesting the conjugation and cis-trans isomerization of unsaturated fatty acids. In addition, heating caused increases in the areas of the bands at 3475 and 1744 cm(-1) and the ratios of 3475/2854 cm(-1) and 1744/2854 cm(-1), a shift to a lower value in the wavenumber and a broadening of the 1744 cm(-1) band indicating the formation of primary and secondary oxidation products in the heated oils, which were also supported by chemical studies. Most of these changes began earlier in EVOO and all occurred to a higher extent, revealing that HO has a higher thermal stability than EVOO. Principal component analysis and hierarchical cluster analysis confirmed that HO is more resistant to heat than EVOO. These results showed that HO is superior to EVOO and it could be used for frying as a healthier and cheaper oil alternative. This study also indicated that oil oxidation could be monitored easily and rapidly via ATR-FTIR spectroscopy. (C) 2021 Elsevier B.V. All rights reserved.
查看更多>>摘要：The popular medicinal mushroom Ganoderma lucidum was often cultivated by the natural-log. Generally the short log after cultivation were discarded and became pollutant. Rapid and less destructive method of analysis technical by Fourier Transform Infrared (FTIR) and Two-dimension Infrared (2DIR) correlation spectroscopy were selected to determine the composition changes of the logs after G. lucidum cultivation after first year to fifth year. The FTIR accumulated spectra formed without processed baseline showed the samples relied upon a sequenced increase of higher level than spectrum control Q (Q = Quercus acuttisima) from L + Q-5 (L = Lingzhi), L + Q-3, L + Q-1 to L + Q-2. The spectrum L + Q-4 has the optimum highest peak at box B, C and E from this lumped spectral view. The split spectra pinpointed on the fingerprint region of a sample begins from peak 1737 cm(-1). ascribed C = 0 stretching vibration on acetyl and carboxyl hemicellulose group bonding gradually faded from L + Q-1 to L + Q-4 but appeared again on L+ Q-5, possibly due to the degradation of hemicellulose. The absorption of peak around 1626 cm 1,1318-cm(-1) and 781 cm(-1) could be the characteristic absorption peak of calcium oxalate monohydrate. The correlation table indicated, most of the original structure of the building block of the wooden part was deteriorated and marked the lowest correlation value of the 4th year sample with control Q. The sudden changing pattern of 2nd derivative spectrum L + Q-3 to more flatten pattern spectrum L + Q-4 ascribed the changing contents of cellulose and hemicellulose included the lignin within one year during the G. lucidum cultivation. The 2DIR spectrum of the raw material sample precisely showed that the active site with red color was clustered with the area around 1800-1700 cm(-1),1450-800 cm(-1) and 750-400 cm(-1). In between, the range 1450-800 cm(-1) was the most active cluster. Each of the sample showed the different sequence of autopeak comparison. This study has examined the impact of G. lucidum on the degradation of Q. acuttisima in term of their ecosystem life chain. The components of healthy Q. acuttisima wood including lignin, cellulose, hemicellulose and calcium oxalate monohydrate underwent changes after different years of G. lucidum cultivation. (C) 2021 Elsevier B.V. All rights reserved.
查看更多>>摘要：Nitroaromatic compounds (NACs) can lead to various environmental pollution healh problems. In order to effectively recognize and sense NACs, a novel coordination polymers (CPs) with fluorescent characteristic [Zn-3(btc)(2)(tPt)(H2O)(2)]center dot 4H(2)O (1) (tpt = tris(4-pyridyl)triazine, H(3)btc = 1,3,5-benzenetricarboxylic acid) has been triumphantly prepared as an fluorescence probe by solvothermal method. 1 possesses remarkable PH stability ranging from 2.0 to 12.0 and is also stable in different pure organic solvents. It should be noted that 1 manifests a fluorescence quenching response against the detection of selectivity and sensitivity towards 2,4,6-trinitrophenol (TNP) in aqueous solution. It also makes analysis on the limit of detection towards TNP, which is as low as 0.94 mu M compared with most reported CPs sensors for TNP. Therefore, 1 can become a satisfactory sensor for TNP detection with remarkable selectivity, strong anti-interference and favorable recyclability. In addition, the quenching mechanisms were also discussed. It was supposed that the mechanisms of photoinduced electron transfer (PET) as well as resonance energy transfer (RET) might be the main influencing factors. (C) 2021 Elsevier B.V. All rights reserved.
Sidorov, N., VPalatnikov, M. N.Gorelik, V. S.Sverbil, P. P....
5页
查看更多>>摘要：Additional bands have been discovered for the first time in the Raman spectra of terbium doped lithium niobate crystals. The bands have been determined in the high-frequency region and have been attributed to the overtone states of the second order of polar fundamental modes of the crystal lattice. It has been established that Raman spectrum of terbium doped lithium niobate contains bands with frequencies exceeding the overtones of the highest-frequency fundamental polar modes of A(1)(Z) and E(X, Y) symmetry types. The observed features of the second-order Raman spectra have been interpreted as a manifestation of bound states of phonons - biphonons. (C) 2021 Published by Elsevier B.V.
查看更多>>摘要：We investigated the vibrational density of states of sodium carboxymethyl starch (CM-starch) by terahertz (THz) time-domain spectroscopy. The CM-starch showed a broad peak at-3 THz. The structure of the peak was similar to those corresponding to glucose-based polymer glasses possessing hydrogen bonds. The boson peak (BP) appeared at 1.16 THz at the lowest temperature and disappeared because of the existence of excess wing at higher temperatures. However, based on our novel BP frequency determination method using the inflection point of the extinction coefficient, the BP frequency showed almost no dependence on temperature. Further, the chain length dependence of the BP frequency of the glucose based glasses showed that the BP frequency of the polymer glass was slightly lower than that of the monomer glass. The power law behaviour of the absorption coefficient suggested the existence of fractons, and the fractal dimension was estimated to be 2.33. (c) 2021 Elsevier B.V. All rights reserved.
查看更多>>摘要：Rice Blast is the most devastating rice disease which poses a serious threat to the safe production of rice. The most effective way to prevent rice blast is to cultivate the rice varieties that have resistance to the disease, however, traditional resistance testing requires professional personnel, a tedious process, long determination time and high cost. In order to quickly identify different resistant rice seeds which are difficult to distinguish with the naked eye, a rapid non-destructive identification method based on NearInfrared Spectroscopy (NIRS) was proposed. Four different types of resistant rice seeds (high resistance, high susceptibility, susceptibility and resistance) came from in HeiLongjiang province of China were selected as the research objects. A total of 240 spectral data (60 from each variety) were scanned by the NIR spectrometer. The BP neural network (BP), Support Vector Machines (SVM), Probabilistic Neural Network (PNN) models were established based on the original spectral data in the fullspectrum (11520-4000 cm(-1)). Among all, Raw-BP has the best identification accuracy which reaches 100% with an iteration time of 869 s. After extracting the feature wavelengths by successive projections algorithm (SPA) on the spectral data, Raw-SPA-BP, Raw-SPA-SVM and Raw-SPA-PNN models were established. The accuracy of these three models didn't improve. But the iteration time of the SPA-BP model was shortened to 791 s. Another group of BP, SVM, and PNN models were established after using different spectral pretreatment methods and the SPA feature extraction. After Multivariate Scatter Correction (MSC), the accuracy of the MSC-SPA-BP model was still 100% and the iteration time was shortened to 840 s, which is 1/30 of the time at which the original data model was formed. The accuracy of the MSC-SPA-PNN model increased from 60% to 90% and the accuracy of the MSC-SPA-SVM model increased from 60% to 85%. Based on the comparison analysis of the models mentioned above, a best neural network identification model of the MSC-SPA-BP with 513 inputs, 8 hidden layers and 4 outputs was established. Its classification accuracy reached 100% with an iteration time of 29 s, indicating that the MSCSPA-BP model can completely achieve identification of four different resistant rice seeds. Therefore, the proposed method of the BP neural network identification model based on NIRS can be fully applied to the non-destructive rapid identification of rice seeds. Meanwhile, it provides a reference for the rapid identification of other crop seeds. (C) 2021 Elsevier B.V. All rights reserved.
查看更多>>摘要：The feasibility analysis of fluorescence hyperspectral imaging technology was studied for the detection of lead content in lettuce leaves. Further, Monte Carlo optimized wavelet transform stacked auto-encoders (WT-MC-SAE) was proposed for dimensionality reduction and depth feature extraction of fluorescence spectral data. The fluorescence hyperspectral images of 2800 lettuce leaf samples were selected and the whole lettuce leaf was used as the region of interest (ROI) to extract the fluorescence spectrum. Five different pre-processing algorithms were used to pre-process the original ROI spectral data including standard normalized variable (SNV), first derivative (1st Der), second derivative (2ndDer), third derivative (3rd Der) and fourth derivative (4th Der). Moreover, wavelet transform stacked auto-encoders (WT-SAE) and WT-MC-SAE were used for data dimensionality reduction, and support vector machine regression (SVR) was used for modeling analysis. Among them, 4th Der tends to be the most useful fluorescence spectral data for Pb content detection at 0.067 similar to 1.400 mg/kg in lettuce leaves, with R-c(2) of 0.9802, RMSEC of 0.02321 mg/kg, R-p(2) of 0.9467, RMSEP of 0.04017 mg/kg and RPD of 3.273, and model scale (the number of nodes in the input layer, hidden layer and output layer) was 407-314-286-121-76 under the fifth level of wavelet decomposition. Further studies showed that WT-MC-SAE realizes the depth feature extraction of the fluorescence spectrum, and it is of great significance to use fluorescence hyperspectral imaging to realize the quantitative detection of lead in lettuce leaves. (C) 2021 Published by Elsevier B.V.
查看更多>>摘要：Aspirin and omeprazole combining has proven their effectiveness clinically in the treatment and prevention of cardiovascular diseases in patient with gastric diseases and gastric ulcers. Simultaneous determination of omeprazole and aspirin in their combination is a challenge due to the overlapping spectra of these drugs. Six smart and different spectrophotometric methods were developed for the analysis of omeprazole and aspirin in binary mixture and pharmaceutical dosage form. These smart methods characterized by simplicity and accuracy. The first two methods based on minimal mathematical data processing based on the zero order absorption spectra were; dual wavelength and advanced absorbance subtraction methods. The third method is first and second derivative spectrophotometric method that based on derivative spectra. The last three methods based on ratio spectra manipulation are named; ratio difference, mean centering and derivative ratio spectrophotometric methods. The linearity range of omeprazole was 2-20 mu g/mL for dual wavelength method and 2-30 mu g/mL for the other ones, while aspirin showed a good linearity over a range of 2.5-30 mu g/mL for all methods. The correlation coefficients were greater than 0.999. The results of the developed methods are statistically compared with each other and with the results of the reported HPLC method showing no significant difference. The greenness of the developed methods was assessed using eco-scale scoring method revealing excellent greenness of the applied methods. This spectrophotometric methods is more sensitive and greener with comparing by the reported one so, these developed methods are considered eco-friendly to the environment. (C) 2021 Elsevier B.V. All rights reserved.
Lalaouna, Abd El DjalilHadef, YoucefNekkaa, AmineTitel, Faouzi...
11页
查看更多>>摘要：The development of analytical chemistry is omnipresent in all fields, this leads to considerable consumption of organic solvents and hazardous reagents with an increase in the production of waste to be treated. In this work, we developed simple, fast, cost-effective and above all environmentally friendly methods for the analysis of Acetaminophen (ACT) and Ascorbic acid (ASC) in synthetic mixtures and pharmaceutical formulation, using UV spectroscopy. Four chemometric methods were studied, including PLS-1 with full-spectrum (Full-PLS) and PLS-1 using three variable selection methods, namely subset selection through a genetic algorithm (GA), uninformative variable elimination using iterative predictor weighting (IPW), and variable selection by sub-window permutation analysis (SwPA). The accuracy of the developed methods was evaluated through the root mean square error of prediction (RMSEP), the mean absolute percentage error (MAPE) and the recovery values. All methods showed more accurate prediction results in comparison with full-PLS calibration. Furthermore, the results indicate that the GA-PLS models showed the highest prediction accuracy among all other models with RMSEP and MAPE values of (0.0494 and 0.610) and (0.0163 and 0.321) for the estimation of ACT and ASC, respectively. The proposed methods were successfully applied to the determination of ACT and ASC in their combined dosage form. In addition, the results obtained were statistically compared to those of the conventionally used HPLC method and were found to be in good agreement.
NSTL
Elsevier