Determination of the Hydroxyl Value of Soybean Polyol by Attenuated Total Reflectance/Fourier Transform Infrared Spectroscopy

A rapid method for the quantitative determination of the hydroxyl value (OHV) of hydroxylated soybean oils by HATR/FTIR spectroscopy is described. Calibration standards were prepared by the formic acid/hydrogen peroxide method and OH values were determined by the official method of AOCS Tx 1a-66, covering an analytical range of 3.5–125 mg of KOH/g of sample. A partial least squares (PLS) calibration model for the prediction of the hydroxyl value (OHV) was developed based on eight different spectral subregions between 3,150 and 990 cm⁻¹ and combinations of them. On average, 36 samples were used for the modeling and 17 were used for external validation. The resulting calibration was linear over the analytical range and had a standard deviation of 2.334. Validation of the method was carried out by comparing the OHV of a series of hydroxylated soybean oils predicted by the PLS model to the values obtained by the AOCS standard method. A correlation coefficient of R ² = 0.9843 and RMSEC and RMSEP values of, respectively, 3.393 and 3.643 were obtained. After the calibration of the spectrometer, the OHV could be obtained in 2–3 min per sample, a major improvement over conventional wet chemical methods. The advantages of these methodologies are that they do not destroy the sample, have a lower cost, expedite the analysis and do not produce residues. Therefore, they may yield excellent results when used to quantify OHV of soybean polyols obtained by hydroxylation reaction.     

偏最小二乘-近红外光谱测定抚顺石油二厂汽油辛烷值

对来自抚顺石油二厂的汽油样品进行近红外光谱分析,使用偏最小二乘算法建立近红外谱图与辛烷值的关联模型.检测表明,用近红外光谱检测石油二厂汽油样品辛烷值的误差在标准方法规定的再现性要求之内,证明了用近红外光谱技术分析石油二厂汽油辛烷值的可行性.     

气相色谱法测定分子筛生产循环废水中的三乙胺及杂质含量

采用气相色谱-质谱仪对晶化母液处理回收工艺流程中的三乙胺及杂质含量进行了定性分析,确定了三乙胺的杂质种类,为建立气相色谱分析方法确立了目标组分。在筛选色谱柱和优化色谱条件的基础上,选用十六烷醇柱CP7448(0.32 mm×60 m×0.5μm),TCD检测器,测定回用三乙胺产品的纯度和杂质含量,实验结果表明,目标组分分离效果良好。以校正面积归一法对三乙胺及杂质的质量分数进行定量,各组分重复测定5次的相对标准偏差均小于1.8%,回收率在98.5%~103.0%之间,表明方法的精密度和准确度良好,并具有快速、可靠的特点。     

Raman and IR studies of surface metal oxide species on oxide supports: Supported metal oxide catalysts

Raman and infrared spectroscopy provide complementary information about the nature of the surface metal oxide species present in supported metal oxide catalysts. This paper reviews the type of fundamental information that is typically obtained in Raman and IR characterization studies of supported metal oxide catalysts. The molecular structures of the surface metal oxide species are reflected in the terminal M=O and bridging M-O-M vibrations. The location of the surface metal oxide species on the oxide supports is determined by directly monitoring the specific surface hydroxyls of the support that are being titrated. The surface coverage of the surface metal oxide species on the oxide supports can be quantitatively obtained since at monolayer coverage all the reactive surface hydroxyls are titrated and additional metal oxide results in the formation of crystalline metal oxide particles. The nature of surface Lewis and Brønsted acid sites present in supported metal oxide catalysts are determined by adsorbing basic probe molecules like pyridine. Information about the behavior of the surface metal oxide species during catalytic reactions are provided by in situ characterization studies. Such fundamental information is critical for the development of molecular structure-reactivity relationships for supported metal oxide catalysts. This paper will be limited to supported metal oxide catalysts containing group V-VII transition metal oxides (e.g., V, Nb, Cr, Mo, W and Re) on several different oxide supports (alumina, titania, zirconia, niobia and silica).     

Quantitative Monitoring of the Amidation Reaction Between Coconut Oil and Diethanolamine by Attenuated Total Reflectance Fourier Transform Infrared Spectrometry

An analytical procedure was developed to monitor the batch reaction of coconut oil and diethanolamine which also would determine the cocodiethanolamide (CDEA) content of the final product. The method was based on attenuated total reflectance Fourier transform infrared spectrometry utilizing partial least squares regression. The calibration was modeled in the 1,781–1,714 and 1,658–1,639 cm⁻¹ spectral regions for coconut oil and CDEA respectively. The models were then applied to predict the amidation process yield and to monitor the in situ kinetics of reactions between coconut oil and DEA. The root mean square error of prediction was 0.590 and 0.336 for coconut oil and CDEA respectively. The proposed method can also be successfully applied to the determination of purity in commercial grade CDEA samples and would give reliable results in comparison with the potentiometric titration reference method.

Rapid Determination of Free Fatty Acid in Extra Virgin Olive Oil by Raman Spectroscopy and Multivariate Analysis

We introduce a visible Raman spectroscopic method for determining the free fatty acid (FFA) content of extra virgin olive oil with the aid of multivariate analysis. Oleic acid was used to increase the FFA content in extra virgin olive oil up to 0.80% in order to extend the calibration span. For calibration purposes, titration was carried out to determine the concentration of FFA for the investigated oil samples. As calibration model for the FFA content (FFA%), a partial least squares (PLS) regression was applied. The accuracy of the Raman calibration model was estimated using the root mean square error (RMSE) of calibration and validation and the correlation coefficient (R ²) between actual and predicted values. The calibration curve of actual FFA% obtained by titration versus predicted values based on Raman spectra was established for different spectral regions. The spectral window (945–1600 cm⁻¹), which includes carotenoid bands, was found to be a useful fingerprint region being statistically significant for the prediction of the FFA%. High R ² and small RMSE values for calibration and validation could be obtained, respectively.     

A rapid method for the analysis of hydrogenated fats by GC with IR detection

A rapid method for analysis of trans and cis FA in hydrogenated fats has been developed. The method is based on a single anlaysis by CG with IR detection. Multivariate partial least squares regression is applied on the IR spectra to predict the number of cis and trans double bonds. For each chain length the method provides information about the amount of the saturated FA, the amount of trans monoenes, the amount of cis monoenes, the amount of PUFA, and the average number of cis and trans double bonds in PUFA. The method has been validated by summing the values to a total trans value and total unsaturation. These sum values were compared with total trans unsaturation, as determined by AOCS method Cd 14-95, and iodine value, as determined by AOCS Cd 1d-92.     

近红外光谱结合化学计量学方法快速鉴别一种汞污染植物

结合红外光谱法和化学计量学,建立汞污染植物千里光和未受污染千里光的快速鉴别模型,并考察其作为筛查土壤汞污染替代指标的可行性。分别在铜仁市汞矿周边和远离汞矿地区对千里光进行代表性采样,以ICP-AES对千里光汞含量进行分析。根据千里光粉末的漫反射红外光谱数据,建立化学计量学分类模型,对不同汞含量的千里光进行快速鉴别。ICP-AES结果表明,汞矿周边和远离汞矿地区的千里光中汞元素的差别显著,分别为0~0.2和10.0~19.7 mg/kg。基于原始近红外光谱、二阶导数光谱和标准正态变换(SNV)光谱的偏最小二乘判别分析(PLSDA)模型对两组千里光样品的预测准确率分别为0.886、0.943和0.900。近红外二阶导数光谱结合化学计量学建模可快速准确识别千里光的汞含量水平。该方法快速经济,可为土壤汞污染快速筛查提供一种替代指标。     

Detection of Extra Virgin Olive Oil Adulteration With Edible Oils Using Front‐Face Fluorescence and Visible Spectroscopies

Synchronous front‐face fluorescence and visible spectroscopies are utilized for the simple, rapid, and nondestructive quantification of extra virgin olive oil (EVOO) adulteration with corn, soybean, and sunflower oils. For each adulterant, 42 adulterated EVOO samples in the adulterant amount in the range 1.0–50 g/100 g were prepared. The partial‐least‐squares regression was executed for quantification. Both full (leave‐one‐out) cross‐validation and external validation were performed to evaluate the predictive ability. The plots of observed vs. predicted values exhibit high linearity. The coefficient of determination (R²) values are larger than 0.99. The root mean square errors of both cross‐validation and prediction are no more than 2%. The detection limits for the three seed oils using fluorescence and visible spectroscopies are in the range of 1.5–2.2% and 1.8–2.4%, respectively. The merit of this method is that both the front‐face fluorescence and visible spectroscopies are recorded toward neat oils, avoiding any sample pretreatment including dilution.     

A New Strategy for Quantitative Proportions in Complex Systems of Blended Oils by Triacyglycerols and Chemometrics Tools

Many oils sold in China and India are a blend of various oils to improve performance, stability, and nutritional characteristics, which are required in their respective markets. Quantitative analysis of the proportions of constitutive components is fundamental to the conformity and adulteration checking of edible blended oil products. A multi linear regression model with constrained linear least squares and exhaustion calculation was applied in this study. The source of the varieties in the model is a database (614 pure oils) of triacylglycerols (TAGs) collected by GC–FID and HPLC–RID. There were 20 groups of binary and ternary blended oils consisting of two or three oils out of five kinds, namely soybean, corn, peanut, rapeseed, and sunflower, which were analyzed and processed separately. Results showed that the method was able to predict the proportions of constitutive components in the edible blended oils, given that relative errors required less than 20%, the accuracy was 98.2% for the binary system if the proportion of each oil in blended oils was more than 20%, while the accuracy was 84.7% for the ternary system if the proportion of each oil in blended oils was more than 10%. The quantitative method is based on a simple analysis to determine the TAGs composition and thus it is useful for quick segregation and quality control of blended oils in routine analysis.     

Prediction of properties of diesel/biodiesel blends by infrared spectroscopy and multivariate calibration

Partial least squares models (PLS) using near and middle infrared spectrometry were developed to predict quality parameters of diesel/biodiesel blends (density, sulphur content and distillation temperatures). Practical aspects are discussed, such as calibration set composition; model efficiency using different infrared regions and spectrometers; and the calibration transfer problem. The root mean square errors of prediction, employing both regions and equipment, were comparable with the reproducibility of the corresponding standard method for the properties investigated. Calibration transfer between the two instruments, using direct standardization (DS), yielded prediction errors comparable to those obtained with complete recalibration of the secondary instrument.     

便携式拉曼光谱仪内标法快速测定乙酸浓度

利用激光拉曼散射原理,研究得到乙酸的特征峰(892cm(-1)附近),以硝酸的特征峰为内标,建立了一种醋酸浓度测定的新方法.在醋酸浓度为1%～60%范围内,线性关系良好,线性方程为I=4.4886x+0.34312,相关系数r=0.9997.该方法加标回收率为96%～107%.对样品进行了测试,相对标准偏差分别为0.5...     

近红外漫反射分析技术在测定聚丙烯粉料中二甲苯可溶物方面的应用

文章探讨了利用近红外分析技术快速判断聚丙烯粉料中的二甲苯可溶物含量的应用。用近红外漫反射法收集了样品的近红外光谱图。参照化学计量学分析方法测定聚丙烯样品的二甲苯可溶物含量。利用偏最小二乘法线性回归法建立了聚丙烯二甲苯可溶物的近红外光谱预测模型。将近红外法测定结果与化学分析方法测定结果进行了比较,对光谱测量的重复性进行了考察。结果表明,利用近红外光谱法与化学分析法的测定结果无显著差异。     

近红外光谱法快速检测单基发射药中的二苯胺含量

采用近红外光谱法快速测定了单基发射药中二苯胺(DPA)的含量。评价了多个光谱预处理方法的优化效果,采用反向偏最小二乘法(biPLS)优选了建模波段(4 698~4 991、6 464~6 761和9 414~9 708cm-1),并根据光谱分析结果和回归系数图解释了波段的选择。基于建模参数优化结果建立了二苯胺定量模型,并对模型进行了重复性验证。研究了环境温度对模型预测结果的影响。结果表明,确定的最佳光谱预处理方法是标准正态变换(SNV)、一阶导数和平滑的组合;模型校正相关系数(Rc)和验证相关系数(Rp)分别为0.995 3和0.988 5,预测均方根误差RMSEP为0.163 5;重复性极差和标准偏差均低于0.1%;环境温度的变化对模型预测的影响不显著。该方法可用于快速检测单基发射药中的二苯胺含量。     

Evaluation of the Performance of a Portable Mid-Infrared Analyzer for the Rapid Determination of Total Trans Fat in Fast Food

The performance of a novel, transmission‐mode, portable, Fourier transform infrared (FTIR) analyzer was evaluated and compared to that of a benchtop attenuated total reflection (ATR)‐FTIR spectrometer. The total concentration of trans fatty acids in the fat extracted from 19 representative fast foods was rapidly (<5 min) quantified in a single measurement after conversion to fatty acid methyl esters (FAME). While the FTIR determination is rapid, the time required for extraction and derivatization is not. For all extracts, the total trans FAME concentration varied from approximately 0.5 to 11 % (of total FAME) as determined using the portable FTIR analyzer. The trans fat contents (mean ± SD), expressed in grams per serving and calculated on the basis of total fat content and FTIR determination of trans fat content, were found to be 1.00 ± 0.42 for hamburgers, 0.67 ± 0.78 for chicken tenders, 1.00 ± 1.24 for French fries, and 0.27 ± 0.23 for apple pies. Determinations of total trans‐unsaturated FAME were consistent with those obtained by use of ATR‐FTIR and GC official methods (AOCS Cd 14e‐09 and AOCS Ce 1j‐07, respectively). These results indicate that the portable FTIR analyzer is suitable for the rapid and routine quantification of total trans fat measured as FAME prepared from fats extracted from fast foods.     

<Superscript>1</Superscript>H NMR and Multivariate Calibration for the Prediction of Biodiesel Concentration in Diesel Blends

In this work, the use of ¹H-NMR spectroscopy and a statistical approach to the analysis of biodiesel concentrations in blends with conventional diesel is described. For this, we performed ¹H-NMR analyses using distinct mixtures of biodiesel from soybean and castor oil in mineral diesel, in concentrations ranging from 0.5 to 30%, and then we applied partial least squares regression (PLS) and principal components regression (PCR) to such data. So, six models were designed and they were evaluated through statistical parameters and through the analysis of four samples prepared in the laboratory. Briefly, a PLS model, obtained through the selection of aromatic, aliphatic and methoxy spectral regions, was quite suitable for the prediction of biodiesel concentrations greater than 2.0%. Deviations of real and predicted values were found to B2 commercial blends, indicating that this model can only be applied to blends exceeding a 2.0% level of biodiesel in petroleum diesel. In conclusion, the ¹H-NMR-PLS method is fairly useful for the quality control of biodiesel–diesel blends, whose commercialisation has increased in the last few years.     

Fatty Acid Profiles of Garuga floribunda,Ipomoea pes‐caprae,Melanolepis multiglandulosa and Premna odorata Seed Oils

The fatty acid profiles of the seed oils of four species from four plant families for which no or only sparse information on the fatty acid profiles is available are reported. The four seed oils are Garuga floribunda of the Burseraceae family, Ipomoea pes‐caprae, of the Convolvulaceae family, Melanolepis multiglandulosa of the Euphorbiaceae family, and Premna odorata of the Labiatae (Lamiaceae) family. Linoleic acid is the most abundant in three seed oils, except I. pes‐caprae in which oleic acid is most abundant. These two acids are overall the most abundant in all four seed oils studied. Of the four seed oils investigated, only G. floribunda contains minor amounts of a cyclic fatty acid (dihydrosterculic acid).     

胺菊酯·高效氯氰菊酯气雾剂的气相色谱分析

介绍了 0 .2 8 %胺菊酯·高效氯氰菊酯气雾剂的气相色谱分析方法。选用 5 %SE - 30 ChromsorbWAW -DMCS(15 0～ 180um)色谱柱 ,以邻苯二甲酸二正辛酯为内标物进行定量分析测定 ,该方法简单、快速、准确、适用。结果表明胺菊酯和高效氯氰菊酯的标准偏差分别为 0 .2 4 %和 0 .11% ;变异系数分别为 0 .94 %和 1.74 % ;平均回收率分别为 99.6 4 %和 99.95 % ;线性回归系数分别为 0 .9999和 0 .9998。     

FT-NIR快速测定烟叶及卷烟烟丝中挥发碱的含量

采用傅立叶变换近红外光谱技术采集烤烟烟叶和卷烟烟丝样品的近红外光谱,结合水蒸汽蒸馏法测定样品中挥发碱含量的数据,采用偏最小二乘法(PLS)分别建立了预测烤烟烟叶和国内品牌卷烟烟丝中挥发碱含量的近红外模型,两种模型的相关系数分别为0.95396和0.96558。进行了准确性和重复性实验。实验表明,近红外光谱法与标准方法之间不存在显著性差异,可以很好的应用于两类样品挥发碱含量的快速检测。     

偏最小二乘光度法同时测定白油中单环及多环芳烃含量

白油中存在着单环芳烃和多环芳烃物质,其吸收光谱相互重叠,在测定波长260～300 nm范围内,采用偏最小二乘回归(PLS)法同时测定白油中单环芳烃和多环芳烃的含量,当残差平方和PRESS达到最小值时,确定PLS回归中二组分的主成分数均为4,分析结果表明,样品中单环芳烃和多环芳烃的回收率在93.73%～101.31%,线...