Rapid monitoring of grapevine reserves using ATR–FT-IR and chemometrics

Predictions of grapevine yield and the management of sugar accumulation and secondary metabolite production during berry ripening may be improved by monitoring nitrogen and starch reserves in the perennial parts of the vine. The standard method for determining nitrogen concentration in plant tissue is by combustion analysis, while enzymatic hydrolysis followed by glucose quantification is commonly used for starch. Attenuated total reflectance Fourier transform infrared spectroscopy (ATR–FT-IR) combined with chemometric modelling offers a rapid means for the determination of a range of analytes in powdered or ground samples. ATR–FT-IR offers significant advantages over combustion or enzymatic analysis of samples due to the simplicity of instrument operation, reproducibility and speed of data collection. In the present investigation, 1880 root and wood samples were collected from Shiraz, Semillon and Riesling vineyards in Australia and Germany. Nitrogen and starch concentrations were determined using standard analytical methods, and ATR–FT-IR spectra collected for each sample using a Bruker Alpha instrument. Samples were randomly assigned to either calibration or test data sets representing two thirds and one third of the samples respectively. Signal preprocessing included extended multiplicative scatter correction for water and carbon dioxide vapour, standard normal variate scaling with second derivative and variable selection prior to regression. Excellent predictive models for percent dry weight (DW) of nitrogen (range: 0.10–2.65% DW, median: 0.45% DW) and starch (range: 0.25–42.82% DW, median: 7.77% DW) using partial least squares (PLS) or support vector machine (SVM) analysis for linear and nonlinear regression respectively, were constructed and cross validated with low root mean square errors of prediction (RMSEP). Calibrations employing SVM-regression provided the optimum predictive models for nitrogen (R² = 0.98 and RMSEP = 0.07% DW) compared to PLS regression (R² = 0.97 and RMSEP = 0.08% DW). The best predictive models for starch was obtained using PLS regression (R² = 0.95 and RSMEP = 1.43% DW) compared to SVR (R² = 0.95; RMSEP = 1.56% DW). The RMSEP for both nitrogen and starch is below the reported seasonal flux for these analytes in Vitis vinifera. Nitrogen and starch concentrations in grapevine tissues can thus be accurately determined using ATR–FT-IR, providing a rapid method for monitoring vine reserve status under commercial grape production.     

Application of Fourier-transform infrared (FT-IR) transmission spectroscopy for the estimation of roxithromycin in pharmaceutical formulations

A quick and reliable analytical method for the quantitative assessment of roxithromycin in pharmaceutical formulations was developed using Fourier-transform infrared (FT-IR) transmission spectroscopy for routine quality control. The sample preparation was avoided except grinding for pellet formation and eliminated the use of toxic solvents. For the determination of roxithromycin, conventional KBr was used in the form of pellets for acquisition of the FT-IR spectra of standards and samples. The calibration model was developed based on simple Beer's law using the FT-IR carbonyl region (CO) from 1765 to 1705 cm⁻¹. The excellent coefficient of determination (R²) was achieved (0.9992) with 0.01 mg standard error of calibration. This work clearly revealed the capability of the transmission FT-IR spectroscopy and extended its application for determining the exact quantity of roxithromycin to control the processing formulation and quality of finished product with the analysis time of less than 3 min using the neat solid samples.     

Studies on the Structure of Gel during Preparing ZnO Thin Films by Sol-gel Method

<正>Transparent thin films of ZnO have been prepared on ordinary glass substrates by the inorganic sol-gel method using citric acid as chelating agent and zinc nitrate as the starting material.A novel structure on zinc citrate complex was put forward by using DTA-TG and FT-IR absorbance spectrum of citrate gels.Phase formation,morphology and optical properties of ZnO films are investigated by XRD,AFM and UV-vis transmittance spectra.The experimental results show that ZnO thin films derived from zinc citrate sol-gel method showed a(002)oriented hexagonal wurtzite structure,good crystalline property,a uniform range of grain size(40 nm), smooth surface of films,band gap of 3.28 eV and optical transmittances ratio over 90%in the visible range.     

Electric field standing wave effects in FT-IR transflection spectra of biological tissue sections: Simulated models of experimental variability

The so-called electric field standing wave effect (EFSW) has recently been demonstrated to significantly distort FT-IR spectra acquired in a transflection mode, both experimentally and in simulated models, bringing into question the appropriateness of the technique for sample characterization, particularly in the field of spectroscopy of biological materials. The predicted effects are most notable in the regime where the sample thickness is comparable to the source wavelength. In this work, the model is extended to sample thicknesses more representative of biological tissue sections and to include typical experimental factors which are demonstrated to reduce the predicted effects. These include integration over the range of incidence angles, varying degrees of coherence of the source and inhomogeneities in sample thickness. The latter was found to have the strongest effect on the spectral distortions and, with inhomogeneities as low as 10% of the sample thickness, the predicted distortions due to the standing wave effect are almost completely averaged out. As the majority of samples for biospectroscopy are prepared by cutting a cross section of tissue resulting in a high degree of thickness variation, this finding suggests that the standing wave effect should be a minor distortion in FT-IR spectroscopy of tissues. The study has important implications not only in optimization of protocols for future studies, but notably for the validity of the extensive studies which have been performed to date on tissue samples in the transflection geometry.     

Incorporation of FT-IR spectral data in a computer-assisted prediction of globular protein structure

Currently, much effort is being directed to the determination of the three-dimensional structure of proteins. Two classes of research are of interest; spectrometric techniques which include Fourier transform infrared (FT-IR) spectrometry, and non-spectrometric prediction schemes. The spectra obtained using FT-IR spectrometry, are analyzed to determine the percentages of alpha-helices, beta-pleated sheets, and non-structured coils in a protein. Unfortunately, FT-IR, as well as other spectrometric techniques, cannot be used to determine the exact secondary structure of a protein reliably. Non-spectrometric prediction methods yield information on the exact secondary structure, but are not always accurate. Most prediction methods relate the primary amino acid sequence to the secondary structure of a protein, allowing sequential secondary structure information for the protein examined to be obtained. The goal of this research is to incorporate FT-IR with a prediction method, resulting in an improvement in the accuracy of the prediction.     

FT-IR spectroscopic study on the variations of molecular structures of some carboxyl acids induced by free electron laser

Free electron laser has been developed as tunable lasers over a wide range of wavelengths. Devices irradiating in the region of 6-16 microm (1666-625 cm-1) are operable in the Beijing free electron lasers facilities (BFEL). For understanding the interactions between FEL and biological tissues, in this study wavelength-selective infrared-induced structure changes of substances under irradiation by FEL were measured using FT-IR spectroscopy. The carboxyl acids and carboxylates samples investigated include salicylic acid, sulfosalicylic acid, cholic acid, deoxycholic acid, sodium cholate and sodium deoxycholate. The changes of the FT-IR spectra of the molecules prove that the spectral variations of the samples induced by FEL are closely related to their hydrogen bond networks.     

Completely automated open-path FT-IR spectrometry

Atmospheric analysis by open-path Fourier-transform infrared (OP/FT-IR) spectrometry has been possible for over two decades but has not been widely used because of the limitations of the software of commercial instruments. In this paper, we describe the current state-of-the-art of the hardware and software that constitutes a contemporary OP/FT-IR spectrometer. We then describe advances that have been made in our laboratory that have enabled many of the limitations of this type of instrument to be overcome. These include not having to acquire a single-beam background spectrum that compensates for absorption features in the spectra of atmospheric water vapor and carbon dioxide. Instead, an easily measured “short path-length” background spectrum is used for calculation of each absorbance spectrum that is measured over a long path-length. To accomplish this goal, the algorithm used to calculate the concentrations of trace atmospheric molecules was changed from classical least-squares regression (CLS) to partial least-squares regression (PLS). For calibration, OP/FT-IR spectra are measured in pristine air over a wide variety of path-lengths, temperatures, and humidities, ratioed against a short-path background, and converted to absorbance; the reference spectrum of each analyte is then multiplied by randomly selected coefficients and added to these background spectra. Automatic baseline correction for small molecules with resolved rotational fine structure, such as ammonia and methane, is effected using wavelet transforms. A novel method of correcting for the effect of the nonlinear response of mercury cadmium telluride detectors is also incorporated. Finally, target factor analysis may be used to detect the onset of a given pollutant when its concentration exceeds a certain threshold. In this way, the concentration of atmospheric species has been obtained from OP/FT-IR spectra measured at intervals of 1 min over a period of many hours with no operator intervention.     

Seafood freshness determination through vapour phase Fourier transform infrared spectroscopy

A new vapour-phase manifold has been developed to determine trimethylamine (TMA) in fish and cephalopod samples by Fourier transform infrared (FT-IR) spectroscopy. Samples were treated off-line for 1 h with trichloroacetic acid (TCA), filtered and washed. The obtained extracts were aspirated and alkalinized with NaOH 2.0 M, in an on-line system. TMA was separated from the solution in a gas phase separator and then transported by means of a nitrogen carrier into a home made 10 cm pathlength IR gas cell, where the corresponding FT-IR spectra were acquired by accumulating 30 scans per spectrum with 2 cm⁻¹ nominal resolution. The method was applied to the determination of TMA in natural samples providing concentration values statistically comparables with those obtained by a head space gas chromatography (HS-GC) reference procedure. The sample throughput by FT-IR is increased by a factor of 6 as compared with HS-GC.     

Applying Fourier-transform infrared spectroscopy and chemometrics to the characterization and identification of lactic acid bacteria

The infrared absorption spectra of 55 lactic acid bacteria belonging to the genera Lactobacillus, Weissella and Carnobacterium were obtained and mathematically analyzed. Sixteen reference strains and 39 food strains isolated from meat and meat products and belonging to the genera Lactobacillus (6 species), Weissella (3 species) and Carnobacterium (2 species) were processed under standardized conditions and their medium infrared spectra obtained using Fourier-transform infrared (FT-IR) spectroscopy. Reproducibility indexes and similarities between FT-IR spectra were calculated using modified correlation coefficients to detect the ranges with the best reproducibility and discrimination properties. Hierarchical cluster analysis and stepwise discriminant analysis (SDA) were subsequently carried out to detect classes and create library groups. Reference strains could be distinguished on the basis of their spectral data and their clustering was in agreement with differences in chemical composition of the cell wall. For the 39 food isolates, the capability of two identification systems was compared. Unknown strains were identified (a) using the linear functions obtained from SDA (canonical variables) of the variables that provide the best discrimination of spectra, and (b) by calculating a differentiation index when a range of the unknown's transformed IR spectrum was compared to all spectra included in a reference library. The system based on the differentiation index obtained a higher rate of identification, allowing for detection of outliers. FT-IR spectroscopy is shown to afford additional information to phenotypic and genotypic data which may help to establish a more robust taxonomic classification.     

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.     

A novel direct coupling of simultaneous thermal analysis (STA) and Fourier transform-infrared (FT-IR) spectroscopy

Evolved gas analysis (EGA) from thermal analyzers such as thermogravimetry (TG) or simultaneous thermal analysis (STA) which refers to simultaneous TG–DSC is well established since it greatly enhances the value of TG or TG–DSC results. The sensitive and selective FT-IR technique is in particular useful for the analysis of organic molecules but also for infrared active permanent gases evolved during most decomposition processes. The coupling interface between thermal analyzers and FT-IR spectrometers usually consists of heated adapters and a flexible, heated transfer line. In this work, a novel direct coupling of an STA instrument and an FT-IR spectrometer without a transfer line is presented. A very small FT-IR spectrometer is directly mounted on top of the STA furnace leading to a compact and fully integrated STA–FT-IR coupling system. The possibilities and the value of simultaneous STA–FT-IR measurements are demonstrated for organic, biomass, and ceramic samples in the temperature range between room temperature and about 1,500 °C. Various samples from the field of inorganics and organics—especially polymers—were furthermore measured showing the advantages of the direct STA–FT-IR coupling compared to state-of-the-art STA–FT-IR coupling using a heated transfer line: we found that the time delay caused by the volume of the transfer line itself is rather negligible whereas a significantly better correlation between gas detection and TG results was observed in case of some highly condensable decomposition gases. Aspects of quantification of evolved gases are furthermore discussed as well as the known nonlinearity of FT-IR detection at higher gas concentrations.     

用原位红外光谱法研究NiB和NiP非晶态合金的还原和苯加氢反应过程

 用化学还原法制备了NiB和NiP非晶态合金催化剂,并用XRD,DSC,SEM和TEM鉴定了样品的非晶性,用ICP测定了样品的组成．在脉冲微反－色谱装置上考察了这两种催化剂催化苯加氢反应的活性．采用在线漫反射傅里叶变换红外光谱研究了这两种催化剂的还原及苯加氢反应过程．结果表明,所制备的NiB和NiP合金均为非晶态,且都是纳米尺度．NiB的粒度要比NiP小,晶化温度也比NiP低,表明Ni与B之间同Ni与P之间的相互作用不同．对苯加氢反应,NiB非晶态合金具有更大的优势,原位红外光谱结果证实催化剂的活性中心与还原态镍有关．     

The use of FT-IR as a screening technique for organic residue analysis of archaeological samples

A range of archaeological samples have been examined using FT-IR spectroscopy. These include suspected coprolite samples from the Neolithic site of Catalh?yük in Turkey, pottery samples from the Roman site of Silchester, UK and the Bronze Age site of Gatas, Spain and unidentified black residues on pottery sherds from the Roman sites of Springhead and Cambourne, UK. For coprolite samples the aim of FT-IR analysis is identification. Identification of coprolites in the field is based on their distinct orange colour; however, such visual identifications can often be misleading due to their similarity with deposits such as ochre and clay. For pottery the aim is to screen those samples that might contain high levels of organic residues which would be suitable for GC-MS analysis. The experiments have shown coprolites to have distinctive spectra, containing strong peaks from calcite, phosphate and quartz; the presence of phosphorus may be confirmed by SEM-EDX analysis. Pottery containing organic residues of plant and animal origin has also been shown to generally display strong phosphate peaks. FT-IR has distinguished between organic resin and non-organic compositions for the black residues, with differences also being seen between organic samples that have the same physical appearance. Further analysis by GC-MS has confirmed the identification of the coprolites through the presence of coprostanol and bile acids, and shows that the majority of organic pottery residues are either fatty acids or mono- or di-acylglycerols from foodstuffs, or triterpenoid resin compounds exposed to high temperatures. One suspected resin sample was shown to contain no organic residues, and it is seen that resin samples with similar physical appearances have different chemical compositions. FT-IR is proposed as a quick and cheap method of screening archaeological samples before subjecting them to the more expensive and time-consuming method of GC-MS. This will eliminate inorganic samples such as clays and ochre from GC-MS analysis, and will screen those samples which are most likely to have a high concentration of preserved organic residues.     

Detergent Powder: Investigation for Feasible Retrospective Dosimetry Using ESR Technique

An Electron Spin Resonance (ESR) study of radiation induced free radicals in the commonly used detergent powder (Surf), was conducted to examine its potential application for retrospective/high level dosimetry, including possible dating of the accidents. The radical ions present in the irradiated detergent powder were identified as arising predominantly from sodium tri poly phosphate (Na₃P₅O₁₀) and sodium sulphate (Na₂SO₄). The physical mixture of sodium tri poly phosphate and sodium sulphate in 4:1 ratio was found to give an ESR response, similar to that of the detergent powder. These results suggest that the detergent powder can be used as a dosimeter in the 20 Gy to 18 kGy dose range, spanning over 3 orders of magnitude. The second derivative ESR spectra of the detergent powder irradiated to different doses showed that the relative yield of the radicals is independent of irradiation dose. The decay pattern of radicals when followed as a function of post irradiation days, lead to the idea about the contrasting decay characteristics of the radicals. From the ESR signals of the irradiated detergent samples, it is shown that radiation dose can be evaluated and the radiation incident can be dated with an accuracy of ±10%.     

Infrared dielectric mirrors based on thin film multilayers of polystyrene and polyvinylpyrrolidone

Thin film polymer multilayers were prepared by spin coating alternating layers of polystyrene and polyvinylpyrrolidone. Samples with 10, 20, 30, 40, and 50 layers were prepared with individual layer thickness values in the range 223–508 nm. These samples were measured using a Fourier transform infrared spectrometer and were found to display narrow photonic band gaps (～ 0.04 to 0.06 μm wide) in their spectral response over the wavelength range 1.6 ? 2.6 μm. The position of the photonic band gaps was controlled by varying the thickness of the individual layers within the multilayer structures. This was achieved by varying the spin speed used during the deposition of the polymer layers. The peak reflectance of the multilayers was controlled by varying the number of layers within the multilayer samples giving values in the range 20–80% (corresponding to transmittances of 80–20%). Calculated transmittance spectra were also obtained using an optical transfer matrix method. These calculated spectra were shown to be in good agreement with the experimental data obtained. These experiments demonstrate a facile approach to the production of low cost dielectric mirrors that have tailored photonic properties over a range of wavelengths that are currently important for applications in fibre optic based telecommunications. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011     

Thermal Degradation and Kinetic Studies of New Flame-Retardant Phosphorus-Containing Polymers with Liquid Crystalline Properties

In this study, two new thermotropic liquid crystalline phosphorus-containing polymers were prepared by polycondensation reaction of 1,4-phenylene-bis((6-oxido-6H-dibenz[c,e][1,2]oxaphosphorinyl)carbinol) with two different phosphonic dichlorides, namely ethyl dichlorophosphate and phenyl dichlorophosphate. The polymers were characterized by means of FT-IR, ¹H NMR, differential scanning calorimetry, polarized light microscopy, wide-angle X-ray diffraction, and thermogravimetric analysis. Thermogravimetric analysis was performed in nitrogen atmosphere by heating the samples over a range of temperatures from 25° to 700°C using five different heating rates. The kinetic processing of data was achieved using the Freeman-Carroll, ASTM E1641, and Kissinger methods.     

Preparation and characterization of nanosized ZSM-5 zeolite using kaolin and investigation of kaolin content, crystallization time and temperature changes on the size and crystallinity of products

Nano sized ZSM-5 zeolite samples were synthesized successively from kaolin clay as alumina source having a large amount of quartz (39%) and silicic acid as silica source by hydrothermal treatment with NaOH in the presence of tetrapropylammonium hydroxide as a template. Then the effect of kaolin content, crystallization temperature and time on the size and crystallinity of the products were investigated. The prepared samples were characterized using XRD, SEM, EDS and FT-IR techniques. The results showed that the synthesized ZSM-5 zeolite samples were almost pure and their crystallization was almost complete. The average particle size, as determined by Debye-Scherrer equation, was in the range of 20-42 nm. Increasing kaolin content on crystal size was more effective than increase in crystallization temperature and time. Additional evidences for the nano sized ZSM-5 zeolite were the asymmetric stretch vibration band at 1225 cm^-1 in the FT-IR spectra and TEM images. The scanning electron micrographs of the synthesized zeolites showed that they are spherical shape crystals.     

Rapid analysis of grape aroma glycoconjugates using Fourier-transform infrared spectrometry and chemometric techniques

The varietal aroma of most wines from non-aromatic grapes is partly dependent on the qualitative and quantitative composition of glycosidic precursors in grapes. The only rapid method to assess these glycoconjugates (Red-Free Glycosyl-Glucose (G-G) method) allows only their total quantitation. We developed a new method using Fourier-transform infrared spectrometry (FT-IR) and chemometric techniques allowing these glycosidic precursors to be determined more finely. Vitis vinifera cv. Melon B. grapes grown in different areas of Muscadet vineyard (Northwest France) and harvested at different maturity stages were used to demonstrate the potentiality of this analysis method. Predictive partial least squares (PLS) regressions were established using 39 samples, representative of the glycoside variability. These models allowed the total levels of C13-norisoprenoidic and monoterpenic glycoconjugates, the most relevant aroma glycoconjugates for Muscadet wines, to be determined with a predictive error of 14 and 15%, respectively, and the total levels of the other classes of glycoconjugates with predictive errors ranging from 22% for volatile phenols to 36% for aliphatic and aromatic alcohols.     

用傅里叶变换红外光谱差减技术自动监测大气毒物的软件及应用

本文介绍了大气毒物傅里叶变换红外光谱自动差减定量软件，介绍了方法的原理和软件的结构与功能。该技术能够进行数据库的实时咨询，差减谱位的智能搜索和光谱自动差减定量，实现了大气毒物自动定量分析。运用于实际样品分析，快速准确，优于其它的傅里叶变换红外光谱定量技术。     

Determination of detergents in washing machine wastewater with a voltammetric electronic tongue

A voltammetric electronic tongue (ET) and a conductivity meter were used to predict amounts of detergents in process water from washing machines. The amount of detergent in over sixty samples was also determined by a HPLC reference method. Prediction was more accurate for the electronic tongue, but both techniques could be used. The composition of the detergent, e.g. supporting electrolyte, is an important factor for the ability to predict the detergent quantity by conductivity. Also two different surfactants, alkyl benzyl sulfonate (ABS) and etoxylated fatty alcohol (EOA), were fingerprinted by the HPLC. Their behaviour during the wash cycle differs from each other, ABS rinses away in the same proportions as the supporting electrolyte, but EOA appears to stay within the machine and laundry. Prediction models for ABS are accurate both with ET and conductivity meter, mostly due to the correlation with supporting electrolyte. The behaviour of EOA, with almost no correlation to the supporting electrolyte makes it difficult to predict using conductivity but ET prediction models give promising indications of its capabilities.