The use of near infrared reflectance spectroscopy in the control of flour protein content

Near infrared reflectance spectroscopy (NIR) is a rapid (50s) and non-destructive method of analysis of a wide variety of solid, semi-solid and liquid samples. Since no sample preparation is required for many sample types, particularly powders, NIR is an ideal technique for process control. The use of NIR to monitor the protein content of flour in order to optimise the milling conditions and the composition of the grist is described. Control of the blending of flours or supplementation with wheat gluten to achieve a composite flour of a given protein content is proposed.     

Gasoline classification by source and type based on near infrared (NIR) spectroscopy data

In this paper, we have tried to classify 382 samples of gasoline and gasoline fractions by source (refinery or process) and type. Three sets of near infrared (NIR) spectra (450, 415, and 345 spectra) were used for classification of gasolines into 3 or 6 classes. We have compared the abilities of three different classification methods: linear discriminant analysis (LDA), soft independent modeling of class analogy (SIMCA), and multilayer perceptron (MLP) - to build effective and robust classification model. In all cases NIR spectroscopy was found to be effective for gasoline classification purposes. MLP technique was found to be the most effective method of classification model building.     

The characterization of coal macerals by diffuse reflectance infrared spectroscopy

Diffuse reflectance Fourier transform infrared (DRIFT) spectroscopy was applied to study the structure of vitrinites, liptinites and fusinites isolated from different rank coals (77.0-91.5%C) using a centrifugal float-sink procedure. Among the macerals separated from a given coal, liptinites are characterized by the highest proportion of aliphatic CH groups, occurring principally as CH₂, and fusinites by the most aromatic structure. Macerals separated from the low rank coals show comparable content of hydroxyl groups that occur as free OH or form similar types of hydrogen bonds. Carbonyl groups appear not only as conjugated ketones and quinones in vitrinites, but also as carboxylic groups in liptinites and low rank fusinites. CH_ar/CH_al ratio does not vary with carbon content in liptinites, but increases in vitrinites and fusinites. In the case of liptinites and vitrinites, a linear relationship between CH_ar/CH_al and reflectance is observed up to vitrinite R₀ value of 1.80%. For all macerals, the ratio CH_ar/CC increases with reflectance, but at different rates. Structural parameters CH_ar/CH_al and CH_ar/CC calculated from DRIFT spectra are very helpful in monitoring the differences among macerals of given coal and following structural rearrangement occurring with rank.     

Diffuse reflectance Fourier transform infrared spectroscopy of oleic acid adsorption on silicic acid

Diffuse reflectance Fourier transform infrared spectroscopy was used to observe adsorption complexes of oleic acid and isopropanol (IPA) on silicic acid in hexane. The spectra provide definite evidence of the molecular nature of the surface interaction. In addition, the effect on oleic acid adsorption of modifying the solvent with IPA, which competes for adsorption sites and modifies the solvent polarity, was studied. Oleic acid adsorption was reduced in the presence of an equimolar IPA concentration in hexane, relative to that from hexane alone. This could be explained by a combination of competitive adsorption of IPA and IPA interacting with oleic acid in solution. IPA, in solution, and silica are probably competing for the lipid. This is additional evidence that suggests that lipid adsorption onto silicic acid is influenced by competitive adsorption. The adsorption of oleic acid and IPA, from a mixture of the two in hexane, was controlled by (i) the equilibrium between surface-bound species and molecules in solution and (ii) the polar interaction between oleic acid and IPA in solution. Thus, washing pre-bound oleic acid with hexane removed only a small amount of oleic acid, while washing with a solution of IPA in hexane removed most of the pre-bound oleic acid.     

Motor oil classification by base stock and viscosity based on near infrared (NIR) spectroscopy data

In this paper we have tried to build effective model for classification of motor oils by base stock and viscosity class. Three (3) sets of near infrared (NIR) spectra (1125, 1010, and 1050 spectra) were used for classification of motor oils into 3 or 4 classes according to their base stock (synthetic, semi-synthetic, and mineral), kinematic viscosity at low temperature (SAE 0W, 5W, 10W, and 15W) and kinematic viscosity at high temperature (SAE 20, 30, 40, and 50). The abilities of three (3) different classification methods: regularized discriminant analysis (RDA), soft independent modelling of class analogy (SIMCA), and multilayer perceptron (MLP) - were also compared. In all cases NIR spectroscopy was found to be quite effective for motor oil classification. MLP classification technique was found to be the most effective one.     

Diffuse reflectance fourier transform infrared spectroscopy of phospholipid adsorption onto silicic acid

Diffuse reflectance Fourier transform infrared spectroscopy was used to study the mode of adsorption of phosphatidylcholine (PC) in hexane onto silicic acid (SA). PC adsorption was mainly through the charged phosphate group with minimal binding through the ester carbonyl. When the SA surface with adsorbed PC is washed with hexane, containing a small concentration of isopropanol, the desorbed PC is recovered without structural change, i.e., there is no evidence of PC hydrolysis in the adsorption process. Adsorbent misture probably promotes PC adsorption due to the increased availability of surface water hydroxyl groups for interaction with the PC phosphate groups. Isopropanol promoted PC binding by destabilizing PC reverse miscelles in solution, thus promoting its adsorption.     

Recent progress in diffuse reflectance spectroscopy of supported metal oxide catalysts

Diffuse reflectance spectroscopy is a suitable technique for studying heterogeneous catalysts, as both d–d and charge transfer transitions of supported transition metal ions can be probed. Within the past several years, new developments have resulted in a more detailed understanding of the surface chemistry of supported metal oxide catalysts. In this review, the fundamental advances of the use of diffuse reflectance spectroscopy in the field of heterogeneous catalysis will be discussed. It will be shown that (1) oxidation states can be spectroscopically quantified in well-defined conditions; (2) chemometrical techniques are crucial for an unbiased analysis of the spectra; (3) in situ spectroscopy, in combination with experimental design and on line catalytic measurements, allows the development of relevant structure–activity relationships, and (4) the reduction kinetics of supported metal oxides can be evaluated.     

Nonlinear observers for parameter estimation in a solution polymerization process using infrared spectroscopy

Adaptive and high gain nonlinear observers are used for state and parameter estimation in an industrial polymerization process. The solution homopolymerization of acrylic acid is considered. The process is monitored online by near infrared spectroscopy giving the residual amount of monomer. Using this measurement, a continuous adaptive observer is first constructed to estimate the concentration of radicals. A second high gain continuous-discrete observer uses off-line measurements of the polymer molecular weight to estimate the termination rate coefficient that might be time varying due to the gel effect. The transfer to solvent rate coefficient is estimated under steady-state conditions and is assumed to be constant during the reaction. The identified model is validated by varying the process parameters: the concentrations of solvent, monomer, radicals and the residence time in the reactor with interest of their impact on the polymer molecular weight.     

Simultaneous determination of lodine value and trans content of fats and oils by single-bounce horizontal attenuated total reflectance fourier transform infrared spectroscopy

A method for the simultaneous determination of iodine value (IV) and trans content from the Fourier transform infrared (FTIR) spectra of neat fats and oils recorded with the use of a heated single-bounce horizontal attenuated total reflectance (SB-HATR) sampling accessory was developed. Partial least squares (PLS) regression was employed for the development of the calibration models, and a set of nine pure triacylglycerols served as the calibration standards. Regression of the FTIR/PLS-predicted IV and trans contents for ten partially hydrogenated oil samples against reference values obtained by gas chromatography yielded slopes close to unity and SD of <1. Good agreement (SD<0.35) also was obtained between the trans predictions from the PLS calibration model and trans determinations performed by the recently adopted AOCS FTIR/SBHART method for the determination of isolated trans isomers in fats and oils.     

近红外光谱技术在烟草行业的应用进展

介绍了近红外光谱技术在烟草化学成分分析、烟气分析、烟叶类型与产地判别及物理指标测定、卷烟辅料分析、卷烟真伪识别、卷烟配方识别及设计、在线检测等方面的应用。近红外光谱技术是一种简便、快捷的分析方法,在烟草行业中正扮演着越来越重要的角色,而且具有十分广阔的应用前景。     

Use of pyrogenic silicas for petroleum oil polar fraction characterisation. Fourier transform infrared spectroscopy and microelectrophoresis studies

In the power transformer, the presence of polar or charged species in the insulating oil can cause failure and electric discharges. Solid substrates such as silica can be used to extract the polar species and to refine the oil in order to prevent future failure in the power transformer. However, the use of silica for petroleum oil separation and refining will depend on the silica characteristics such as surface charge, surface composition, specific surface area and particle size.Various pyrogenic silicas having various specific surface areas (49-200 m² g⁻¹) and particle sizes (207-500 nm) were used to extract the polar fractions from the neat transformer insulating oils (a new, NO, and used, UO2, oils). The oil covered silica samples were investigated by diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy in the range 4000-600 cm⁻¹. The bare silica surfaces present two main hydroxyl components, a sharper peak at 3745 cm⁻¹, I₃₇₄₅, due to isolated silanols and a second broad, which spreads over 3745-3000 cm⁻¹, I_3745-3000, due to H-bonded silanols. The relative intensities of the two components, I₃₇₄₅/I_3745-3000, varied for the bare and the oil covered silicas depending on the solid surface characteristics. The adsorption of the NO polar fraction onto silica leads to strong reduction in intensity of the sharper peak in favour of the broad one. However, the adsorption of the UO2 polar fraction onto silica leads in all cases to the decrease in the intensity of the both silica OH components. Further, the UO2 adsorption on the silica leads to the apparition of a broad peak at low frequency in the region 3250-3300 cm⁻¹ which, is due to the associated phenolic groups of UO2 oil polar fraction. The analysis of the DRIFT spectra for various samples indicates that the oil polar fraction resembles to asphaltenes compounds.The microelectrophoresis method used to investigate the surface charge at the water/oil polar fraction covered silica interface, indicates negatively charged particles. Further, the negative charge increased with the pH, as resulting from the increase of the ionisation and/or the amount of the oil polar carboxylic and phenolic groups. The oil polar fraction, i.e. the asphaltene components, in contact with both the silica surface and water at high pH values rearrange, due to their amphiphilic character.Finally, the use of the silica substrates seems to be suited to extract and analyse polar species present in petroleum oil. A correlation is found between the nature of the oil, its functionalities, and the magnitude of its zeta potential value at the water/oil covered silica interface.     

Monitoring a progressing transesterification reaction by fiber-optic near infrared spectroscopy with correlation to 1H nuclear magnetic resonance spectroscopy

Biodiesel is a promising alternative diesel fuel obtained from vegetable oils, animal fats, or waste oils by transesterifying the oil or fat with an alcohol such as methanol. In an extension of previous work, fiber-optic near infrared spectroscopy was used to quantitatively monitor the transesterification reaction (6-L scale) of a vegetable oil (soybean oil) to methyl soyate. The results were correlated with ¹H nuclear magnetic resonance spectroscopy. The method described here can be applied to the transesterification of other vegetable oils.     

SIBR微观结构的红外光谱定量分析

采用聚苯乙烯、聚丁二烯和聚异戊二烯标准样品复配,建立了利用红外光谱工作曲线来测定苯乙烯-异戊二烯-丁二烯橡胶(SIBR)中苯乙烯、丁二烯反式-1,4结构、丁二烯顺式-1,4结构、丁二烯-1,2结构、异戊二烯-1,2结构、异戊二烯3,4-结构和异戊二烯-1,4结构等7种微观结构的定量分析方法,解决了使用红外光谱联立解方程组法来测定SIBR多种微观结构含量的困难。该方法方便、准确、可靠,也适用于嵌段共聚物SIBS的微观结构测定。     

Application of near infrared diffuse reflectance spectroscopy for on-line measurement of coal properties

The applicability of the Multi-wavelength Near-infrared sensor to analyze coal properties such as proximate analysis (moisture, ash, volatile matter, fixed carbon), ultimate analysis (carbon, hydrogen, nitrogen, oxygen, sulfur) and heating value is discussed. The most useful wavelengths (1,680, 1,942, 2,100, 2,180, 2,300 nm) for determining coal properties concentration were chosen by analyzing the NIR spectrum according to coal properties. Absorbances at the characteristic wavelength obtained from 128 mixed coal samples, which are using at a conventional thermal power plant, were correlated to the coal properties by using multiple regression analysis. The accuracy of coal analysis was examined by calculating the RMSEC (%), RMSEP (%), comparing the error with ASTM/ISO tolerance and performing paired Student’s T-test. The result of on-line coal analysis for all moisture, volatile matter, fixed carbon, carbon, hydrogen and heating value is not different from that of ASTM/ISO traditional methods at 90% confidence level. The technology appears suitable for the determination of several coal prorperties. If calibrated periodically, this on-line analysis of coal properties is helpful to efficiently operate a coal fired power plant.     

Characterization of edible oils,butters and margarines by Fourier transform infrared spectroscopy with attenuated total reflectance

The combination of attenuated total reflectance (ATR) and mid-infrared spectroscopy (MIRS) with statistical multidimensional techniques made it possible to extract relevant information from MIR spectra of lipid-rich food products. Wavenumber assignments for typical functional groups in fatty acids were made for standard fatty acids: Absorption bands around 1745 cm⁻¹, 2853 cm⁻¹, 2954 cm⁻¹, 3005 cm⁻¹, 966 cm⁻¹, 3450 cm⁻¹ and 1640 cm⁻¹ are due to absorption of the carbonyl group, C−H stretch, =CH double bonds of lipids and O−H of lipids, respectively. In lipid-rich food products, some bands are modified. Water strongly absorbs in the region of 3600–3000 cm⁻¹ and at 1650 cm⁻¹ in butters and margarines, allowing one to rapidly differentiate the foods as function of their water content. Principal component analysis was used to emphasize the differences between spectra and to rapidly classify 27 commercial samples of oils, butters and margarines. As the MIR spectra contain information about carbonyl groups and double bonds, the foods were classified with ATR-MIR, in agreement with their degree of esterification and their degree of unsaturation as determined from gas-liquid chromatography analysis. However, it was difficult to differentiate the studied food products in terms of their average chainlength.     

Calibration of NIRS for the Estimation of Fatty Acids in Brassica Juncea

This study was done to test whether near infrared reflectance spectroscopy (NIRS) could be used as a quick substitute for measuring quality characteristics, i.e., a fatty acid profile over gas liquid chromatography. Near infrared reflectance spectroscopy is a multi‐trait technique. In the present study, the fatty acid profiles of seeds of 200 genotypes of Brassica juncea were analysed by gas liquid chromatography. Near infrared reflectance spectra of intact seeds of the same samples were collected (400–2500 nm) on a NIR systems Model 6500 spectrophotometer. The spectra were subjected to scanning, mathematical processing, and statistical analysis using Win ISI software. Data were scored to remove redundancy. Spectra were treated as outliers with H > 3.0 (global H) and similar samples with H < 0.6 (neighbourhood H). Cross validation of the spectra was done using a modified partial least‐square method to develop the calibration equation. The calibration equation had good R² values for oleic acid (R² = 0.91), linoleic acid (R² = 0.83), and erucic acid (R² = 0.88). The internal validation was done to test the goodness of fit of the developed equation. The equation provided reliable estimations of these traits in internal validation with R² values of 0.77, 0.68, 0.81 for the above quoted fatty acids, respectively. The external validation results also showed higher R² values for oleic acid (0.89), linoleic acid (0.69), and erucic acid (0.90). The equation was less reliable for linolenic acid, which had R² values of 0.53 in cross validation, 0.25 for internal validation, and 0.20 for external validation. The results indicated that NIRS could be used to rapidly determine oleic acid, linoleic acid, and erucic acid in intact B. juncea seeds.     

近红外光谱分析技术在PA6生产中的应用

介绍了实际工作中采用近红外光谱分析技术建模时应注意的要点,以及使用Thermo Fisher近红外光谱仪对PA6生产中调配用添加剂不同组分进行光谱分析与检测。通过对比理论值与实际测试结果,确定光谱分析技术在调配工艺中的可行性;经过实际建立模型、校正、实际样品检测等过程后对模型进行验证和评价。     

ABS接枝聚合物红外光谱分析的制样方法研究

由于丙烯腈一苯乙烯一丁二烯共聚物（ABS）橡胶含量较高,采用传统KBr压片法制备的样品测试效果不理想,探索一种准确高效的制样方法,对于ABS接枝聚合物红外定性或定量分析具有重要意义。本文研究了ABS接枝聚合物红外光谱分析过程中不同制样方法对分析结果的影响,通过对比涂膜法、裂解法、热压片法等制样过程以及相应的红外光谱分析结果,寻求一种最佳的制样分析方法。结果表明,裂解法适合高橡胶含量的ABS接枝聚合物制样,该方法制样快捷,红外光谱分析结果重复性较好。     

Characterization of clays used in the ceramic manufacturing industry by reflectance spectroscopy: An experiment in the São Simão ball-clay deposit, Brazil

The characterization of clays from the physical, chemical, and ceramic standpoint in pre-and-within mining stages is a necessary step. However, succinct mining planning, lack of industry-oriented standards and the usual bond to empirical discrimination of clays as regards their use, imply in mixing chemically and technologically different materials, with serious consequences to the mining and manufacturing process. Taking the alluvium-derived, ball-clay deposit of São Simão (SS) as a case study, this works aims to evaluate the potential of reflectance spectroscopy (RS) as a method to define types, purity and crystallinity of clays and to seek a possible relation between spectral characteristics of clays and their use in the ceramic industry. The SS deposit hosts three types of clays that were spectrally set apart based on RS. The technique indicated that the white clays comprise highly ordered kaolinite, mica, smectite and lepidocrosite (first finding in Brazilian alluviums). The brown clays are also rich in well-ordered kaolinite and contain abundant Fe-bearing minerals, as goethite, hematite and siderite (rarely found in alluviums). The gray clays are kaolinite-poor and are abundant in organic matter and smectites. Each of the clay classes typified in the SS deposit has a specific application in the fine ceramic industry, indicating the prominent potential of RS to characterize industrial materials.     

红外和核磁共振法鉴定聚醚型聚酯的组成结构

利用红外吸收光谱及核磁共振波谱仪的一维和二维技术对一种未知聚合物试样进行鉴定。由核磁共振二维技术分析得出聚醚酯的序列结构及其分布。结果表明:该未知聚合物试样为聚醚酯弹性体,由对苯二甲酸、间苯二甲酸、新戊二醇、乙二醇、聚四氢呋喃醚共聚而成。