Determination of polyphenols in oats by near-infrared spectroscopy (NIRS) and two-dimensional correlation spectroscopy

Two-dimensional correlation spectroscopy (2DCOS) and near-infrared spectroscopy (NIRS) were used to determine the polyphenol content in oat grain. A partial least squares (PLS) algorithm was used to perform the calibration. A total of 116 representative oat samples from four locations in China were prepared and the corresponding near-infrared spectra were measured. Two-dimensional correlation spectroscopy was employed to select wavelength bands for the PLS regression model for the polyphenol determination. The number of PLS components and intervals was optimized according to the coefficients of determination (R²) and root mean square error of cross validation (RMSECV) in the calibration set. The performance of the final model was evaluated using the correlation coefficient (R) and the root mean square error of validation (RMSEV) in the prediction set. The results showed the band corresponding to the optimal calibration model was between 1350 and 1848?nm and the optimal spectral preprocessing combination was second derivative with second smoothing. The optimal regression model was obtained with an R² of 0.8954 and an RMSECV of 0.06651 in the calibration set and R of 0.9614 and RMSEV of 0.04573 in the prediction set. These measurements reveal the calibration model had qualified predictive accuracy. The results demonstrated that the 2DCOS with PLS was a simple and rapid method for the quantitative determination of polyphenols in oats.     

1H-NMR Profiling Shows as Specific Constituents Strongly Affect the International EVOO Blends Characteristics: The Case of the Italian Oil

Considering the growing number of extra virgin olive oil (EVOO) producers in the world, knowing the influence of olive oils with different geographical origins on the characteristics of the final blend becomes an interesting goal. The present work is focused on commercial organic EVOO blends obtained by mixing multiple oils from different geographical origins. These blends have been studied by ¹H-NMR spectroscopy supported by multivariate statistical analysis. Specific characteristics of commercial organic EVOO blends originated by mixing oils from Italy, Tunisia, Portugal, Spain, and Greece were found to be associated with the increasing content of the Italian component. A linear progression of the metabolic profile defined characteristics for the analysed samples—up to a plateau level—was found in relation to the content of the main constituent of the Italian oil, the monocultivar Coratina. The Italian constituent percentage appears to be correlated with the fatty acids (oleic) and the polyphenols (tyrosol, hydroxytyrosol, and derivatives) content as major and minor components respectively. These results, which highlight important economic aspects, also show the utility of ¹H-NMR associated with chemometric analysis as a powerful tool in this field. Mixing oils of different national origins, to obtain blends with specific characteristics, could be profitably controlled by this methodology.     

Determination of Bitterness of Extra Virgin Olive Oils by Amperometric Detection

A flow injection system with amperometric detection at potentials poised at +0.4 and +0.9 V was used to evaluate intensity of the bitter taste in monovarietal Extra Virgin Olive Oils (EVOO). Results from the proposed method were based on the extraction of the bitter constituents of the virgin olive oil samples in methanol‐water, followed by the direct amperometric measurement. These potentials were selected according to the hydrodynamic voltammogram of oleuropein, one of the most prominent and bitter phenolic compound found in EVOO. The amperometric detection was applied on 32 monovariatal EVOO samples. Results were correlated with the phenolic profile measured by high performance liquid chromatography (HPLC). The amperometric signal at +0.9 V mainly correlated with the total phenols of the samples (R²=0.81), whereas the signal at +0.4 V mainly correlated with oleuropein aglycone (3,4 DHPEA‐EDA, R²=0.79). Bitterness intensity of the samples was evaluated by a trained sensory panel of experts and the results compared to those obtained by the amperometric flow system. The best correlation with the bitter taste was achieved by the sensor at +0.4 V (R²=0.72). A calibration model based on partial least squares was built with three variables, namely the sensors set at +0.4 and +0.9 V and the total phenol content of the EVOO extracts. The model showed a moderate capacity to predict the bitterness of the EVOO samples using leave one out method, (R²=0.75) and in prediction of a test set of samples (R²=0.7). Such approach is very promising for future studies.     

Comparative evaluation of bioactivity of crystalline trypsin for drying by Fourier-transformed infrared spectroscopy

The purpose of this study was to evaluate the enzymatic stability of colloidal trypsin powder during heating in a solid-state by using Fourier transform infrared (FT-IR) spectra with chemoinformatics and generalized two-dimensional (2D) correlation spectroscopy. Colloidal crystalline trypsin powders were heated using differential scanning calorimetry. The enzymatic activity of trypsin was assayed by the kinetic degradation method. Spectra of 10 calibration sample sets were recorded three times with a FT-IR spectrometer. The maximum intensity at 1634 cm⁻¹ of FT-IR spectra and enzymatic activity of trypsin decreased as the temperature increased. The FT-IR spectra of trypsin samples were analyzed by a principal component regression analysis (PCR). A plot of the calibration data obtained was made between the actual and predicted trypsin activity based on a two-component model with γ² = 0.962. On the other hand, a 2D method was applied to FT-IR spectra of heat-treated trypsin. The result was consistent with that of the chemoinformetrical method. The results for deactivation of colloidal trypsin powder by heat-treatment indicated that nano-structure of crystalline trypsin changed by heating reflecting that the β-sheet was mainly transformed, since the peak at 1634 cm⁻¹ decreased with dehydration. The FT-IR chemoinformetrical method allows for a solid-state quantitative analysis of the bioactivity of the bulk powder of trypsin during drying.     

Mechanism of propagation and degenerate chain branching in the oxidation of polypropylene and polyethylene

Samples of polypropylene with adjacent and isolated hydroperoxide groups have been prepared. The rate constants of free-radical formation from solid hydroperoxides were measured by the inhibitor method. It was found that the free radicals yielded by adjacent hydroperoxide groups are formed more rapidly. The main reaction of free-radical formation in oxidized polypropylene is of the type: ROOH + ROOH → RO + H₂O + RO₂^˙. The average yield of free radicals from polypropylene hydroperoxide is 2–4%. Oxygen has no effect on the yield of free radicals. However, the pressure of oxygen Po₂ affects the rate of degenerate chain branching in polypropylene. The number of adjacent hydroperoxide groups and the rate of initiation increase with Po₂. Consequently, a reaction of the type, R^˙, + RH → RH + R^˙, plays an important part in transport of free valence through solid polymer. This reaction is very fast in polyethylene, and no adjacent hydroperoxide groups are formed. The free radicals from polyethylene hydroperoxide are found to form by a reaction of the type: ROOH → RO^˙ + HO^˙.     

Kinetic study of thermal breakdown of triglycerides contained in extra-virgin olive oil

Thermal decomposition of extra-virgin olive oil (EVOO) was investigated by thermogravimetry (TG) and derivative thermogravimetry (DTG) up to 550°C at different heating rates (from 5 to 12.5°C min⁻¹). The thermal degradation study of four unsaturated or saturated esterified C18 fatty acids with glycerol (i.e., glyceryl-tristearate (C18:0),-trioleate (C18:1),-trilinoleate (C18:2) and-trilinolenate (C18:3)) was also carried out under the same experimental conditions. A deconvolution procedure applied only to the first two overlapping steps of EVOO and C18:1 enabled the activation energy of decomposition to be determined both by the Kissinger and the Ozawa-Flynn-Wall isoconversional method for the two deconvoluted steps of EVOO and C18:1, as well as for the only single step of the other three C18 triglycerides. Practically constant activation energy for the first deconvoluted step of EVOO and C18:1 and for the single step of C18:0 was found in good agreement with the results obtained with the Kissinger method, while a similar increasing trend was observed for the second decomposition step of EVOO and C18:1 and for the single steps of C18:2 and C18:3 triglycerides.     

Multivariate monitoring of soybean oil ethanolysis by FTIR

In this work, an analytical procedure was developed to monitor the ethanolysis of degummed soybean oil (DSO) using Fourier-transformed mid-infrared spectroscopy (FTIR) and methods of multivariate analysis such as principal component analysis (PCA) and partial least squares regression (PLS). The triglycerides (reagents) and ethyl esters (products) involved in ethanolysis were shown to have similar FTIR spectra. However, when the FTIR spectra derived from seven standard mixtures of triolein and ethyl oleate were treated by PCA at the region that represents the CO stretching vibration of ester groups (1700-1800 cm⁻¹), only two principal components (PC) were shown to capture 99.95% of the total spectral variance (92.37% for the former and 7.58% for the latter PC). This observation supported the development of a multivariate calibration model that was based on the PLS regression of the FTIR data. The prevision capability of this model was measured against 40 reaction aliquots whose ester content was previously determined by size exclusion chromatography. Only small discrepancies were observed when the two experimental data sets were treated by linear regression (R²=0.9837) and these deviations were attributed to the occurrence of non-modeled transient species in the reaction mixture (reaction intermediates), particularly at short reaction times. Therefore, the FTIR/PLS model was shown to be a fast and accurate method to predict reaction yields and to follow the in situ kinetics of soybean oil ethanolysis.     

Kinetic study of the solution polymerization of methacrylamide initiated with potassium persulfate using in situ Raman spectroscopy and band‐target entropy minimization

In this paper, the use of in situ Raman spectroscopy together with a novel multivariate data analysis method, band‐target entropy minimization (BTEM), is discussed to monitor the solution polymerization of methacrylamide in aqueous medium. Although FTIR spectroscopy is a more popular spectroscopic technique for polymer characterization and in situ polymerization monitoring, Raman spectroscopy is selected over FTIR in the current study. This is because water has very strong and broad infrared absorption bands and thus masks most of the other infrared signals contributed from monomer and polymer. On the contrary, water has very weak Raman scattering and thus it does not interfere the other Raman signals. The polymerization was initiated with potassium persulfate (KPS). A series of experiments were carried out varying initial monomer concentration, initial KPS concentration, and polymerization temperature. In situ Raman spectroscopy was used to monitor the polymerizing mixture and measure the compositions. The collected reaction spectra were subjected to BTEM to elucidate the pure component spectra, and then determine the conversion of monomer. The conversion data was then used to obtain kinetic parameters for the polymerization. The rate of consumption of monomers was found to follow the expression R = k_eff [I]^0.55[M]^1.41. The activation energy of the system was estimated at 121 kJ/mol. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5697–5704, 2007     

Direct determination of polymerized triglycerides in deep-frying olive oil by attenuated total reflectance–Fourier transform infrared spectroscopy using partial least squares regression

A partial least squares (PLS) regression model based on attenuated total reflectance–Fourier transform infrared spectra of heated olive oil samples has been developed for the determination of polymerized triacylglycerides (PTGs) generated during thermal treatment of oil. Three different approaches for selection of the spectral regions used to build the PLS model were tested and compared: (1) variable selection based on expert knowledge, (2) uninformative variable elimination PLS, and (3) interval PLS. Each of the three variable selection methods provided PLS models from heated olive oil samples with excellent performance for the prediction of PTGs in fried olive oils with comparable model statistics. However, besides a high coefficient of determination (R ² of 0.991) and low calibration, validation, and prediction errors of 1.14%, 1.21%, and 1.40% w/w, respectively, variable selection based on expert knowledge gave additionally almost identical low calibration (−0.0017% w/w) and prediction (−0.0023% w/w) bias. Furthermore, it was verified that the determination of PTGs was not influenced by the type of foodstuff fried in the olive oil.     

Determination of biodiesel content when blended with mineral diesel fuel using infrared spectroscopy and multivariate calibration

In this work, multivariable calibration models based on middle- and near-infrared spectroscopy were developed in order to determine the content of biodiesel in diesel fuel blends, considering the presence of raw vegetable oil. Soybean, castor and used frying oils and their corresponding esters were used to prepare the blends with conventional diesel. Results indicated that partial least squares (PLS) models based on MID or NIR infrared spectra were proven suitable as practical analytical methods for predicting biodiesel content in conventional diesel blends in the volume fraction range from 0% to 5%. PLS models were validated by independent prediction set and the RMSEPs were estimated as 0.25 and 0.18 (%, v/v). Linear correlations were observed for predicted vs. observed values plots with correlation coefficient (R) of 0.986 and 0.994 for the MID and NIR models, respectively. Additionally, principal component analysis (PCA) in the MID region 1700 to 1800 cm^− 1 was suitable for identifying raw vegetable oil contaminations and illegal blends of petrodiesel containing the raw vegetable oil instead of ester.     

Silica Hybrid Containing （ R ）-2, 2＇-Binaphtho-20-crown-6 Moieties via the Sol-Gel Process

(R)-6,6‘-Bis(triethoxysilylethen-2-yl)-2,2-‘binaphtho-20-crown-6(precursor,R-2) derived form(R)-2,2-BINOL derivative was synthesized by Pd-catelyzed Heck reaction of (R)-6-6‘-dibromo-2,2‘-binaphtoh-20-crown-6(R-1) intermediate with vinyltriethoxysilane. The hydrolysis and polycondensatlon ofthe precursor gave rise to the corresponding xerogei. Both pre cursor and xerogei were analysed by NMR, FT-IR, UV, CD spectra, fluorescent spectroscopy, polarimetry and elemental analysis. The precursor and xerogei can emit strong blue fluorescenee and are expected to have the potential appficatiou inthe separation of chiral molecules as fluorescent sensor. The precursor exhibits strong Cotton effect in its circular dichroism (CD) spectrum indicating that it is a highly rigid structure.     

Accelerator mass spectrometry (AMS) of the inhibitory effect of six dietary constituents on nicotine-hemoglobin adduction in mice

Summary Accelerator mass spectrometry (AMS) is an ultra-sensitive method to monitor and trace the environmental exposure levels of ¹⁴C-labeled molecules in vivo. Nicotine [3-(1-methyl-2-pyrrolidinyl)-pyridine], a major alkaloid in tobacco products, has proven to be a potential genotoxic compound. Using ¹⁴C-labeled nicotine and AMS, we have investigated the inhibitory effect of curcumin, garlic squeeze, grapeseed extract, tea polyphenols, vitamin C and vitamin E, respectively, on nicotine-hemoglobin (Hb) adduction in vivo. The results demonstrated that these dietary constituents induced remarkable decrease of nicotine-Hb adducts. The inhibitory fact may afford an important clue of the chemoprevention of the potential nicotine-induced carcinogenesis.     

Stand-off Raman spectroscopy: a powerful technique for qualitative and quantitative analysis of inorganic and organic compounds including explosives

A pulsed stand-off Raman system has been built and optimised for the qualitative and quantitative analysis of inorganic and organic samples including explosives. The system consists of a frequency doubled Q-switched Nd:YAG laser (532 nm, 10 Hz, 4.4 ns pulse length), aligned coaxially with a 6″ Schmidt–Cassegrain telescope for the collection of Raman scattered light. The telescope was coupled via a fibre optic bundle to an Acton standard series SP-2750 spectrograph with a PI-MAX 1024RB intensified CCD camera equipped with a 500-ps gating option for detection. Gating proved to be essential for achieving high signal-to-noise ratios in the recorded stand-off Raman spectra. In some cases, gating also allowed suppression of disturbing fluorescence signals. For the first time, quantitative analysis of stand-off Raman spectra was performed using both univariate and multivariate methods of data analysis. To correct for possible variation in instrumental parameters, the nitrogen band of ambient air was used as an internal standard. For the univariate method, stand-off Raman spectra obtained at a distance of 9 m on sodium chloride pellets containing varying amounts of ammonium nitrate (0–100%) were used. For the multivariate quantification of ternary xylene mixtures (0–100%), stand-off spectra at a distance of 5 m were used. The univariate calibration of ammonium nitrate yielded R ² values of 0.992, and the multivariate quantitative analysis yielded root mean square errors of prediction of 2.26%, 1.97% and 1.07% for o-, m- and p-xylene, respectively. Stand-off Raman spectra obtained at a distance of 10 m yielded a detection limit of 174 μg for NaClO₃. Furthermore, to assess the applicability of stand-off Raman spectroscopy for explosives detection in “real-world” scenarios, their detection on different background materials (nylon, polyethylene and part of a car body) and in the presence of interferents (motor oil, fuel oil and soap) at a distance of 20 m was also investigated.     

Simultaneous determination of total polyphenols and caffeine contents of green tea by near-infrared reflectance spectroscopy

This paper indicates the possibility to use near infrared (NIR) spectroscopy as a rapid method to predict quantitatively the content of caffeine and total polyphenols in green tea. A partial least squares (PLS) algorithm is used to perform the calibration. To decide upon the number of PLS factors included in the PLS model, the model is chosen according to the lowest root mean square error of cross-validation (RMSECV) in training. The correlation coefficient R between the NIR predicted and the reference results for the test set is used as an evaluation parameter for the models. The result showed that the correlation coefficients of the prediction models were R = 0.9688 for the caffeine and R = 0.9299 for total polyphenols. The study demonstrates that NIR spectroscopy technology with multivariate calibration analysis can be successfully applied as a rapid method to determine the valid ingredients of tea to control industrial processes.     

Electron density distributions in substituted 2,3,4,5-tetraphenyl-1-germacyclopenta-2,4-dienes studied by NMR spectroscopy

The signals in the¹³C NMR spectra of 2,3,4,5-tetraphenyl-1-germacyclopenta-2,4-dienes (R¹=R²=H, Me,cyclo-C₃H₅, SiMe₃, SnMe₃, R¹=Me, R²=H, Cl) were completely assigned using 2D NMR spectroscopy. The pattern of the variation of the chemical shifts in the¹³C NMR spectra indicates that the effects of substituents R¹ and R² on the heterocycle and on the phenyl groups are of inductive rather than mesomeric origin and include the direct through-space polarization of bonds (field effect). Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 1962–1965, November, 1997.     

Polymer‐based fluorescence sensors incorporating chiral binaphthyl and benzo[2,1,3]thiadiazole moieties for Hg2+ detection

Three chiral polymers P‐1 , P‐2 , and P‐3 could be obtained by the polymerization of (R)‐6,6′‐dibutyl‐3,3′‐diiodo‐2, 2′‐binaphthol (R‐M‐1) , (R)‐6,6′‐dibutyl‐3,3′‐diiodo‐2,2′‐bisoctoxy‐1,1′‐binaphthyl ( R‐M‐2 ), and (R)‐6,6′‐dibutyl‐3,3′‐diiodo‐2,2′‐bis (diethylaminoethoxy)‐1,1′‐binaphthyl ( R‐M‐3 ) with 4,7‐diethynyl‐benzo[2,1,3]‐thiadiazole ( M‐1) via Pd‐catalyzed Sonogashira reaction, respectively. P‐1 , P‐2 , and P‐3 can show pale red, blue–green, and orange fluorescence. The responsive optical properties of these polymers on various metal ions were investigated by fluorescence spectra. Compared with other cations, such as Co²⁺, Ni²⁺, Ag⁺, Cd²⁺, Cu²⁺, and Zn²⁺, Hg²⁺ can exhibit the most pronounced fluorescence response of these polymers. P‐1 and P‐2 show obvious fluorescence quenching effect upon addition of Hg²⁺, on the contrary, P‐3 shows fluorescence enhancement. Three polymer‐based fluorescent sensors also show excellent fluorescence response for Hg²⁺ detection without interference from other metal ions. The results indicate that these kinds of tunable chiral polybinaphthyls can be used as fluorescence sensors for Hg²⁺ detection. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 997–1006, 2010     

Synthesis and optical properties of cis‐dibenzothiazolyldibenzo‐24‐crown‐8

New crown ether carrying two fluorionophores of cis‐dibenzothiazolyldibenzo‐24‐crown‐8 was synthesized from cis‐diformyldibenzo‐24‐crown‐8 and 2‐aminobenzenethiol. The binding behavior and the optical properties of the crown ether were examined through UV‐visible spectroscopy and fluorescence spectroscopy. When complexed with Na⁺, K⁺, Rb⁺, and Cs⁺ ions, it led to intramolecular charge transfer and caused the changes of the fluorescence spectra. The protonation of the crown ether was also studied. With protonation using CF₃COOH, the absorption bands and the fluorescence spectroscopy changed, the maximal fluorescence wavelengths red shifted and the fluorescence intensity with the maximum at 433 nm enhanced strongly. J. Heterocyclic Chem., (2011).     

(5R*, 9S*)- and (5R*, 9R*)-2,2,9-Trimethyl-1,6-dioxaspiro[4.4]non-3-ene and their Dihydro Derivatives as New Constituents of Geranium Oil

(5 R^*,9S^*)- and (5R^*,9R^*)-2,2,9-Trimethyl-1,6-dioxaspiro [4.4]non-3-ene ( 1a and 1b resp.) and their dihydro derivatives 2a and 2b are described as new constituents of geranium oil. The structures and configurations of 1a , 1b , 2a , and 2b , are based on spectra interpretation and syntheses. Also some other monoterpenoid constituents identified in the same boiling range are discussed.     

Different radical scavenging tests in virgin olive oil and their relation to the total phenol content

Four different antioxidant tests (ABTS⁺, DPPH, ORAC, β-carotene-linoleate model system) were used to determine the free-radical scavenging activity of 39 extra virgin olive oils (EVOO) and compare the total phenol content by the Folin-Ciocalteu method. The correlation between the total phenols and antioxidant capacities measured by the four methods was very high, and highest with ABTS⁺ (R² = 0.9905). Some of these methods of measurement were applied to olive-oil samples (OO), with approximately a 50% decrease in the value of the antioxidant capacity in comparison with values found for EVOO. In conclusion, the results show that all the methods tested were suitable for determining the antioxidant capacity of olive oil. The Picual variety of extra-virgin olive oil showed high antioxidant activity.     

Lipofuscin and A2E Accumulate with Age in the Retinal Pigment Epithelium of Nrl−/− Mice†

Lipofuscin is a fluorescent material with significant phototoxic potential that accumulates with age in the retinal pigment epithelium (RPE) of the eye. It is thought to be a factor in retinal degeneration diseases. The most extensively characterized lipofuscin component, N‐retinylidene‐N‐retinylethanolamine (A2E), has been proposed to be a byproduct of reactions involving the visual pigment chromophore. To examine the impact of the visual pigment and photoreceptor cell type on lipofuscin accumulation, we analyzed the RPE from Nrl^?/? mice of various ages for lipofuscin fluorescence and A2E levels. The photoreceptor cells of the Nrl^?/? retina contain only cone‐like pigments, and produce cone‐like responses to photostimulation. The cone‐like nature of these cells was confirmed by the presence of RPE65. Lipofuscin was measured with fluorescence imaging, whereas A2E was quantified by UV/VIS absorbance spectroscopy coupled to HPLC. The identity of A2E was corroborated with tandem mass spectrometry. Lipofuscin and A2E accumulated with age, albeit to lower levels compared with wild type mice. The emission spectra of RPE lipofuscin granules from Nrl^?/? mice were similar to those from wild type mice, with λ_maxca 610 nm. These results demonstrate that cone visual pigments can contribute to the production of lipofuscin and A2E.