可见-近红外光谱结合CARS优化模型预测棕榈油碘值

采用可见-近红外透射光谱结合CARS变量优选方法优化模型,对棕榈油碘值进行近红外定量分析。通过将使用不同预处理方法产生的建模效果进行比较,找到了理想的预处理方法,通过CARS变量选择方法优选出与棕榈油碘值相关的有效波点共60个,利用60个有效波点建立棕榈油碘值优化模型。根据优化模型的建模集相关系数(R_c=0.9814)和预测集相关系数(R_p=0.9806),得到的建模均方根误差(RM SEC=0.0398)和预测均方根误差(RM SEP=0.0406)优于采用全波段建立的模型得到的系数误差。利用可见近红外透射光谱结合CARS变量优选方法,简化了棕榈油碘值模型,并能够保证碘值预测的准确度。     

声光可调滤光器-近红外光谱法快速测定苗药水冬瓜根皮药材中总黄酮和浸出物的含量

取48批次水冬瓜根皮鲜药材于50℃分别烘干后粉碎至通过孔径0.23mm的样筛。混匀后装于样品瓶中制备成48个样品,编号为G1～G48,其中42个样品(G1～G42)作为校正集,6个样品(G43～G48)为验证集。应用声光可调滤光器(AOTF)-近红外光谱仪(NIR)采集每个样品的原始光谱。确定NIR光谱预处理方式为一阶微分导数,在1 100～2 200nm波段构建该药材中总黄酮及浸出物含量快速测定的分析模型。采用化学计量学分析软件将校准集样品的光谱信息和上述两测定项目的参考值作数据关联,分别建立该药材中总黄酮和浸出物快速测定的分析模型。用G1样品重复采集其NIR光谱6次,按上述方法作预处理及测定,结果获得总黄酮及浸出物测定值的相对标准偏差(n=6)分别为3.9%,2.8%。仍取G1样品于12h内先后采集其红外光谱8次,按上述相同方法分析,两项测定结果的相对标准偏差分别为2.1%,2.3%,说明12h内样品的稳定性良好。最后将6个验证样品的原始光谱经预处理所得的数据导入化学计量学分析软件作模型预测,两项目的预测值与参考值的相对误差分别在1.6%～6.3%和0.60%～4.3%之间。表明所建模型验证效果良好,应用此方法分析单个样品只需2～5s。     

独立分量分析预处理法提高苹果糖度模型预测精度研究

为了提高苹果近红外光谱糖度预测模型精度,利用独立分量分析方法(ICA)对苹果近红外光谱进行了预处理,并且建立了糖度的偏最小二乘(PLS)预测模型。结果表明,独立分量分析不但能分离出噪声信号,而且所分离出来的光谱信号也比原始光谱信号光滑。在预处理后的最佳PLS糖度模型校正时的相关系数rc和标准偏差SEC分别为0.9549和0.3361,用于预测时的相关系数rp和标准偏差SEP分别为0.9071和0.4355。与普通的平均处理法的PLS模型相比,其精度有所提高,且模型更加简洁。     

基于近红外光谱分析技术的食品包装塑料的定性分析

该文基于近红外漫反射光谱分析技术对食品包装材料聚乙烯、聚丙烯进行定性判别试验研究,选取不同波段范围、采用不同光谱预处理方法,使用主成分分析法(Principal component analysis,PCA)结合SIMCA、贝叶斯判别、K-近邻3种模式识别方法建立定性预测模型,并根据正确识别率比较了各模型预测性能。结果表明：使用SIMCA方法、贝叶斯判别、K-近邻3种方法建立的定性校正模型均在1 050~1 550 nm波长范围内效果较好;采用矢量归一化、标准正态变量变换、中心化、滑动均值滤波、多项式平滑滤波、一阶微分6种光谱预处理方法和上述3种模式识别方法对塑料样品近红外光谱进行了数据处理,其中在1 050~1 550 nm范围内,主成分因子数为3,采用原始光谱建立的K-近邻定性校正模型较优,对样品校正集和预测集的正确识别率均为100%。可为食品包装材料聚乙烯、聚丙烯的快速鉴别研究提供参考。     

icPL-ANN近红外光谱分析方法在航空燃料中的应用研究

以航空燃料的闪点预测为例,针对数据分布分散不连续,与光谱信息的线性关联偏弱的情况,提出一种将波段间隔组合与线性-人工神经网络(icPLANN)相结合的近红外光谱定量分析方法。该方法利用分段建模考核进行波段优选,最大程度地提取了有效信息,并结合PL-ANN方法建立了近红外光谱定量分析模型。最终把预测结果与间隔组合偏最小二乘法(icPLS)的实验结果进行了对比。结果表明,间隔组合PL-ANN模型的校正标准偏差(SEC)为0.75,预测标准偏差(SEP)为0.86,而间隔组合偏最小二乘法SEC为1.48,SEP为1.08,因此前一种方法的预测精度更高,预测决定系数(Rp2)能达到0.8971。可见,针对分散不连续数据与近红外光谱的复共线性影响预测模型准确度和稳定性的问题,间隔组合PL-ANN方法是一种有效的近红外光谱定量方法。     

废旧涤/棉混纺织物近红外定量分析模型的建立及预测

将中红外光谱筛选出的598个纯涤、纯棉及涤/棉混纺样本采用GB/T 2910.11-2009法测定其涤、棉准确含量,其中校正集样本252个,验证集样本346个。使用便携式近红外光谱仪获取样本的原始近红外光谱(NIRS)。校正集样本依据回归系数的分布趋势和范围选取最佳建模谱区,并采用差分一阶导、S-G平滑和均值中心化相结合的方法对原始光谱进行预处理,利用偏最小二乘法(PLS)建立涤/棉混纺织物中涤含量的近红外(NIR)定量分析模型。同时分析了样本颜色对NIRS的影响,探讨了斜线光谱样本、奇异样本和不同组织结构织物对模型预测效果的影响。结果表明:利用PLS法建立的涤/棉混纺织物定量分析模型最优组合包含1个光谱区间和9个主成分因子,校正集相关系数(RC)为0.998,标准偏差(SEC)为0.908。为验证所建模型的有效性和实用性,对346个未参与建模的涤棉样本进行了预测,并将预测结果与国标法测定值进行方差分析,两种方法结果无显著差异,预测正确率达97%以上。模型的建立为废旧涤/棉混纺织物快速、无损分拣提供了基础数据库。     

近红外光谱分析原油中水分和硫含量模型的建立及验证

取原油样品120个,分别按照GB/T 11133-2015和GB/T 17040-2008中所述方法测定了上述原油样品中的水分和硫的含量。通过优化的近红外光谱(NIRS)条件采集了上述原油样品的NIR光谱图。采用杠杆值算法剔除4个异常样品。在建立水分含量分析模型时,采用的条件为:用Savitzky-Golay法对光谱进行滤波预处理,建模光谱区间为6 200～8 200cm-1,主成分数为6,用偏最小二乘回归法(PLS)交叉验证建立分析模型。硫含量分析模型的建立条件为:采用二阶导数-Norris Derivative对光谱进行预处理,建模光谱区间为4 400～4 700cm-1,主成分数为6,用PLS交叉验证建立分析模型。水分和硫含量模型的预测值与测定值的相关性较好。水分模型的决定系数(R2c)为0.989 9,校正标准偏差(RMSEC)为0.084 2,说明其预测效果较好,可用于原油中水分含量的预测。硫含量模型的R2c为0.996 3,RESEC为0.069 6,说明此模型的预测效果也较好,可用原油中硫含量的预测。应用所建立的两个模型对10个未知原油样品中水分和硫含量进行了预测,并与其测定值比较,结果表明两者之间的相对偏差均小于10%。     

高效液相色谱法测定方便面中丙烯酰胺

建立了一种检测方便面中丙烯酰胺的液相色谱方法。萃取剂选择1g/L的蚁酸溶液,将萃取液以12000r/min,2℃离心18min,上清液再以14500r/min,0℃离心18min,可分离基质中淀粉、蛋白质、脂肪等干扰物;方法采用ZORBAX SB-C18(250mm×4.6mm,5μm)色谱柱,流动相为A(乙腈∶水=1∶24(V/V))和B(乙腈),流速0.5mL/min,在丙烯酰胺的最大吸收197nm处检测,提高了方法的检出限及回收率。该方法有良好的线性关系(r=1.00000),检出限为48.0μg/kg。回收率94.4%～109.8%,相对标准偏差为4.9%～5.6%。     

不同偏最小二乘法在化学需氧量近红外光谱特征波段选择中的应用

通过近红外光谱法对生活废水样本中的化学需氧量(COD)进行分析,将全谱波段等分为30、20、15、12个子区间,选用间隔偏最小二乘法(iPLS)、后向间隔偏最小二乘法(BiPLS)以及前向间隔偏最小二乘法(FiPLS)建立COD光谱特征波段的选择。结果显示:全波段所建立的PLS模型最差,iPLS、FiPLS、BiPLS模型均有所改进,且BiPLS算法的模型最好。当全波长分为30个子区间时,所选特征波段第22、18、23、25、24、4、2、19、17组合区间建立的模型为最佳,其预测集标准偏差(RMSEP)与交叉验证均方差(RMSECV)分别为15.9mg·L-1和16.8mg·L-1。     

2,4-二硝基氯苯衍生高效液相色谱法测定饮品中牛磺酸含量

建立了饮品中牛磺酸的高效液相色谱(HPLC)测定方法。采用2,4-二硝基氯苯90℃下衍生30 min,冷至室温后离心,取上清液10μL进样分析。以甲醇-KH2PO4为流动相梯度洗脱,360nm紫外检测,柱温20℃,流速1 mL/min。结果显示牛磺酸至少在0.02～200 mg/L范围内线性良好(r=0.999),回收率在97.5%～114.0%之间,保留时间和峰面积的相对标准偏差(RSD)(n=6)分别为0.40%和5.8%,方法已用于饮品中牛磺酸含量的测定。     

A methodology for choosing parameters for ESR readout of alanine dosimeters for radiotherapy

Spectrometer settings for ESR readout of alanine dosimeters for radiotherapy have been investigated. Several ESR parameters were studied and determined. The main reason for this work is to choose the suitable parameters to increase signal-to-noise ratio and to reduce the uncertainty on ESR readout, which is one of the main components of uncertainty of alanine/ESR dosimetry system for radiotherapy. The new spectrometer settings have been applied for ESR readout of alanine dosimeters irradiated from 1 to 10 Gy. A higher signal-to-noise ratio has been achieved compared to our old spectrometer settings. The extended uncertainty (k=2) has been evaluated in the dose range 2–10 Gy (maximum uncertainty of 4.9% for 2 Gy, while minimum uncertainty of 1.4% for 10 Gy), which implies that the alanine/ESR dosimetry system can be applied to radiotherapy dose level that needs a global accuracy of 5%.     

Potential of FTIR spectroscopy for analysis of tears for diagnosis purposes

It has been widely reported that the tear film, which is crucially important as a protective barrier of the eye, undergoes biochemical changes as a result of a wide range of ocular pathology. This tends to suggest the possibility of early detection of ocular diseases on the basis of biochemical analysis of tears. However, studies of tears by conventional methods of biomolecular and biochemical analysis are often limited by methodological difficulties. Moreover, such analysis could not be applied in the clinic, where structural and morphological analyses by, mainly, slit-lamp biomicroscopy remains the recommended method. In this study, we assessed, for the first time, the potential of FTIR spectroscopy combined with advanced chemometric processing of spectral data for analysis of raw tears for diagnosis purposes. We first optimized sampling and spectral acquisition (tears collection method, tear sample volume, and preservation of the samples) for accurate spectral measurement. On the basis of the results, we focused our study on the possibility of discriminating tears from normal individuals from those of patients with different ocular pathologies, and showed that the most discriminating spectral range is that corresponding to variations of CH₂ and CH₃ of lipid aliphatic chains. We also report more subtle discrimination of tears from patients with keratoconus and those from patients with non-specific inflammatory ocular diseases, on the basis of variations in spectral ranges attributed notably to lipid and carbohydrate vibrations. Finally, we also succeeded in distinguishing tears from patients with early-stage and late-stage keratoconus on the basis of spectral features attributed to protein structure. Therefore, this study strongly suggests that FTIR spectral analysis of tears could be developed as a valuable and cost-saving tool for biochemical-based detection of ocular diseases, potentially before the appearance of the first morphological signs of diseases. Combined with supervised modelling methods and with use of a spectral data base acquired for representative patients, such a spectral approach could be a useful addition to current methods of clinical analysis for improvement of patient care.

Application of thermal analysis for investigations of polymer powders for coatings

Polypropylene coatings obtained by the fluidized bed method were investigated. It was proved that the application of thermal analysis methods for their characterization gave many useful data, as a consequence of the similar conditions of thermal measurements and plastics powder processing. Significant correlations were found between the thermal properties and the standard coating poperties.

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Zusammenfassung Durch Fluidisationsverfahren erhaltene Polypropylenbeschichtungen wurden untersucht. Es wurde festgestellt, daß infolge der ähnlichen Bedingungen von thermischen Messungen und Plastpulverisierungsverfahren die Anwendung von thermischen Untersuchungsmethoden zu deren Charakterisierung viele nützliche Angaben liefern. Es konnten eindeutige Beziehungen zwischen thermischen Eigenschaften und Standardbeschichtigungseigenschaften gefunden werden.

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New method for prefractionation of plasma for proteomic analysis

The depth of proteome analysis is severely limited in complex samples with a wide dynamic range of protein abundance such as plasma. Removal of high‐abundance proteins should reveal the signal of lower abundance plasma proteins. However, smaller proteins may be part of larger protein complexes and hence the removal of proteins involved in complexes with high‐abundance proteins such as albumin may inhibit the search for disease biomarkers. Prefractionation of a sample divides it into fractions of reduced complexity, allowing improved detection of lower abundance proteins. Using a prefractionation device, which employs Gradiflow? technology, we were able to separate small volume plasma samples into multiple fractions based on the molecular weight and/or charge. The resulting samples of reduced complexity were directly compatible with 2‐DE. The use of this prefractionation machine may therefore be useful in the hunt for disease biomarkers.     

Prospects for development of a technology for production of butene-1

Industrial technologies for production of butene-1 are described, including the most promising process for recovery of butene-1 of polymerization purity from C₄ fractions formed in pyrolysis and catalytic cracking of hydrocarbons. It is shown that this technology can be improved and suggested to use as a raw material the recycle butene fraction formed from these C₄ fractions upon isolation of 1,3-butadiene and isobutene. A technological scheme for recovery of butene-1 of polymerization purity is suggested.     

Preparation of PVA membrane for immobilization of GOD for glucose biosensor

A membrane was prepared using polyvinyl alcohol (PVA) with low and high degree of polymerization (DOP), acetone, benzoic acid (BA) and was cross-linked by UV treatment. Membrane composition was optimized on the basis of swelling index. Membrane prepared with 12% low DOP and 8% high DOP of PVA, 2% BA, dissolved in buffer containing 20% acetone and cross-linked with UV treatment exhibited lower swelling index. Fourier transform infrared (FTIR) study of the membranes showed appearance of a strong band at approximately 2337 cm(-1) when UV was used for cross-linking in the presence of benzoic acid. Scanning electron microscope (SEM) study revealed that membrane cross-linked with UV treatment was smoother. Glucose oxidase (GOD)-PVA membrane was associated with the dissolved oxygen (DO) probe for biosensor reading. Glucose was detected on the basis of depletion of oxygen, when immobilized GOD oxidizes glucose to gluconolactone. A wide detection range, 0.9-225 mg/dl was estimated from the linear range of calibration plot of biosensor reading. Membranes were reused for 32 reactions without significant loss of activity and stored for 30 days (approximately 90% activity) at 4 degrees C. Membranes were also used with real blood samples.     

Piperazine-based buffers for liposome coating of capillaries for electrophoresis

Anionic liposomes can be coated on fused-silica capillaries for electrophoresis in the presence of N-(hydroxyethyl)piperazine-N'-(2-ethanesulfonic acid) (HEPES) as background electrolyte (BGE) solution. In this work, the interaction of various compounds with zwitterionic and anionic phospholipid coatings was studied with HEPES at pH 7.4 as BGE solution. The chromatographic and electrophoretic behavior of three test sample solutions (anionic, cationic, and neutral) was investigated for evaluation of the phospholipid coatings. Our results show that hydrophobic interactions between analytes and the phospholipid coating are important for the migration of charged analytes. In addition, the performances of other piperazine-based buffers, i.e., N-(2-hydroxyethyl)piperazine-N'-(2-hydroxypropanesulfonic acid), piperazine-N,N'-bis(2-ethanesulfonic acid), and piperazine-N,N'-bis(hydroxypropane sulfonic acid), at pH 7.4, as liposome solvent and BGE solution were evaluated and compared with the performance of HEPES at pH 7.4. The anionic liposome solution comprised 80/20 mol% phosphatidylcholine/phosphatidylserine. A simple test solution was selected and the chromatographic and electrophoretic migration behavior of the analytes was evaluated. The results show that, in addition to HEPES, other piperazine-based buffers at pH 7.4 are suitable for coating of fused-silica capillaries with anionic liposomes.     

Adhesives for assembly procedures for products of radioelectronic industry

A list of adhesive materials, sealants, and potting compounds used at the enterprise is given. The basic properties of these materials are discussed, and particular process procedures in which they are employed are described.     

缓冲溶液pH计算公式的推导

酸碱缓冲溶液在分析化学中的应用是多方面的 ,因此酸碱缓冲溶液 ｐＨ的计算是分析化学中必不可少的一个内容。目前 ,高师院校的分析化学多采用华中师范大学等校编的《分析化学》(第 2版 ) ,笔者在几年的教学中 ,发现该教材在缓冲溶液 ｐＨ计算的公式推导中存在疏漏。为此 ,在比较其他教材中该章节的内容后 ,从酸碱平衡最本质的内容ＰＢＥ出发 ,提出一种新的缓冲溶液ｐＨ计算公式推导方法。1　华中师范大学版教材中的问题[1]　　以一元弱酸及其共轭碱体系进行讨论 ,设弱酸ＨＡ浓度为ｃａ,共轭碱ＮａＡ浓度为ｃｂ。将ＨＡ Ａ-体系以Ｈ2 Ｏ作媒…     

Rules for selection of oxide catalysts for oxidative dehydrocombination of hydrocarbons

Based on the mechanism of oxidative dimerization of hydrocarbons the rules for the selection of catalysts for this kind of reactions has been discussed. It has been shown that an efficient dehydrodimerization catalyst must contain on its surface electron acceptor centers (metal cations) of moderate strength, strongly bound nucleophilic oxygen, and possess the corresponding collective properties. The elements have been discussed, the oxides of which satisfy the above requirements.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 24, No. 3, pp. 366–370, May–June, 1988.