A Simple and Highly Sensitive Method for Quantitative Detection of Methyl Paraben and Phenol in Cosmetics Using Derivative Spectrophotometry and Multivariate Chemometric Techniques

This paper presents a simple and sensitive method for the simultaneous determination of methyl paraben (MP ) and phenol (PO ) based on the application of successive projections algorithm (SPA ) to the first derivative spectra (200–350 nm). SPA is used for variables selection in order to obtain multiple linear regression (MLR ) models using a small subset of wavelengths. The starting vector and the number of variables are optimized and the best variables are selected according to the sequence of projection operations on the spectral data matrix of the calibration set. Principal component regression and partial least squares models are also developed for comparison. The best models are found to be SPA‐MLR using seven wavelengths from the first‐derivative spectra with a root‐mean‐square error of prediction (RMSEP) of 0.08 for MP and eight wavelengths with RMSEP of 0.31 for the determination of PO . The accuracy of the proposed method is confirmed by spiked recovery test on cosmetic samples with satisfactory results (86–110%). Analysis results of the cosmetic samples are also statistically compared with those obtained from the HPLC method, showing no significant difference regarding accuracy and precision. The results indicate the potential of SPA‐MLR and derivative spectrophotometry for rapid and sensitive analysis of cosmetic samples.     

Zn2-xGeO4-x-3yN2y催化剂的制备、表征及可见光催化性能

通过氮化Zn2GeO4制备了Zn2-xGeO4-x-3yN2y催化剂,其带边吸收由400nm的紫外光区扩展到600nm的可见光区。光催化产氧性能的结果表明,氮化温度为800℃时,制备的催化剂具有最大活性。不同助催化剂对产氧活性的影响研究表明,担载助催化剂能大大提高产氧活性,其中担载Co2O3的产氧活性可达未担载的3.8倍。     

气相色谱灰色分析体系中未知组分保留指数的预测

提出在部分组分已知的气相色谱灰色体系中,利用已知组分的保留指数和保留时间推算死时间和正构烷烃的保留时间,再计算未知组分保留时间的方法,结果显示,在已知组分不是太少的情况下,该方法计算的死时间和正构烷烃的保留时间与实验值吻合,预测的保留指数也有较高的精度.     

Aromatic Higher Alcohols in Wine: Implication on Aroma and Palate Attributes during Chardonnay Aging

The higher alcohols 2-phenylethanol, tryptophol, and tyrosol are a group of yeast-derived compounds that have been shown to affect the aroma and flavour of fermented beverages. Five variants of the industrial wine strain AWRI796, previously isolated due to their elevated production of the ‘rose-like aroma’ compound 2-phenylethanol, were characterised during pilot-scale fermentation of a Chardonnay juice. We show that these variants not only increase the concentration of 2-phenylethanol but also modulate the formation of the higher alcohols tryptophol, tyrosol, and methionol, as well as other volatile sulfur compounds derived from methionine, highlighting the connections between yeast nitrogen and sulfur metabolism during fermentation. We also investigate the development of these compounds during wine storage, focusing on the sulfonation of tryptophol. Finally, the sensory properties of wines produced using these strains were quantified at two time points, unravelling differences produced by biologically modulating higher alcohols and the dynamic changes in wine flavour over aging.     

总氮测定过程中空白吸光值偏高的原因分析

使用HJ 636-2012测定水质总氮时,空白吸光值往往偏高.为了寻找最佳的实验条件,使用多元线性回归模型定性评价过硫酸钾和氢氧化钠的纯度、实验用水、碱性过硫酸钾溶液的存放时间、消解条件、冷却时间、消解器皿等因素对空白吸光值的重要性.结果表明:过硫酸钾纯度对空白吸光值影响最显著.为了保证总氮空白吸光值小于0.030,测...     

一种新的氨基酸描述符及其在肽QSAR中的应用

从20种天然氨基酸的41个randic molecular profiles非零描述符、44个eigenvalue based indices非零描述符和47个walk and path counts非零描述符分别进行主成分分析,得出一种新的氨基酸描述符-SVREW。将其应用于血管紧张素转化酶(ACE)抑制二肽和ACE抑制三肽、苦味二肽和苦味四肽、后叶催产素类似物、HLA-A*0201限制性CTL表位肽的结构表征,应用多元线性回归(MLR)建立定量构效关系模型,同时采用内部与外部双重验证的方法验证模型的稳定性。所建ACE抑制二肽、ACE抑制三肽、苦味二肽、苦味四肽、后叶催产素类似物、HLA-A*0201限制性CTL表位肽的模型复相关系数(R2cum)分别为0.994,0.797,0.948,0.878,0.686,0.720;留一法交互校验复相关系数(R2cv)分别为0.955,0.859,0.879,0.958,0.796,0.843;外部样本校验相关系数(Q2ext)分别为0.990,0.954,0.890,0.950,0.748,0.773。经研究表明SVREW描述符用于肽分子结构表征所建模型的稳定性与预测能力均较好,有望成为多肽定量构效关系研究中一种有效的结构表征方法,可对新药物的发现和研究提供指导。     

苯甲醛衍生物的结构与其半波电位关系的研究

以半经验分子轨道方法计算苯甲醛衍生物的分子结构参数，以多元线性回归方法研究了苯甲醛衍生物的半波电位与其分子结构参数间的关系。研究发现，在所选择的２３个分子结构参数中，基态双中心总能量（ＥＴ（ｔｗｏ）、电离势（Ｉｐ）及分子的生成热（Ｈｆ）与其半波电位有较好的相关性。其回归方程为：ｙ＝－５．４２３２＋０．５４７７８Ｉｐ－３．３３１＊１０＾－３Ｅｔ（ｔｗｏ）－１．６７０＊１０＾－３Ｈｆ（ｒＲＣ＝０．９２     

应用多元线性回归法测定黄河口不同粒径悬浮物中的有机碳含量

悬浮颗粒物(TSS)粒径与颗粒有机碳(POC)含量的关系研究,是河口淡、咸水混合过程中有机碳形态变化及其输送过程和输运通量研究的基础。在沉降法分级的基础上,结合激光粒度仪粒度测定,用多元线性回归分析法处理所得数据,校正了由于沉降分级的粒径交错现象而导致POC测定中小粒径TSS的POC含量偏低、大粒径TSS的POC含量偏高的问题,获得了样品中不同粒径TSS的POC含量。实验发现,黄河口水体中POC含量随TSS粒径的增加显著递减,80%以上的颗粒有机碳集中在<16μm的TSS中,而粒径<32μm的悬浮物承载了95%以上的颗粒有机碳的入海量。     

Synthesis,Characterization and Thermal Degradation of Substituted Acetophenone Based Terpolymers Having Biological Activities

The terpolymer resins have been synthesized by the condensation of p- hydroxyacetophenone and p-chloroacetophenone with formaldehyde/furfuraldehyde in the presence of catalyst in 1:1:5 molar proportions of reactants. The molecular structures were confirmed by FT-IR and Pyrolysis GC-MS. The number average molecular weights of these resins were determined by conductometric titration in non-aqueous medium. Viscometric measurements in tetrahydrofuran (THF) have been carried out with a view to ascertaining the characterstic functions and constant. Detailed thermal degradation studies of the terpolymer have been carried out to ascertain its thermal stability. A multiple linear regression (MLR) method has been used to calculate activation energies and frequency factor. Formaldehyde based terpolymer (E _a= 22.3 KJ/mol, Z = 0.77) has a greater activation energy and frequency factor as compared to furfuraldehyde based terpolymer (E _a=18.8 KJ/mol, Z = 0.25). Thermodynamic parameters such as free energy (ΔG), entropy change (ΔS*) and rate constant (k _r) have also been evaluated on the basis of data of the Ozawa, Flynn and Wall method. All the synthesized polymers have shown excellent antimicrobial activities as compared to the standard Ciprofloxacin and Amphotericin-B drugs.     

Evaluation of Anthocyanin Profile and Color in Sweet Cherry Wine: Effect of Sinapic Acid and Grape Tannins during Aging

Cherries are rich in bioactive phenolic compounds and are often fermented into cherry wines. The degradation of anthocyanins during storage will cause color deterioration. The study aimed to utilize sinapic acid and grape tannins in cherry wine to maintain a high fraction in the colored forms of anthocyanins, in order to maximize the color intensity, the latter being associated with good product quality. The effects on the anthocyanin profile and on color parameters of copigments, utilizing spectral measurement combined with UPLC-MS quantitative analysis, have been evaluated in sweet cherry wines. The copigmentation effect of sinapic acid and grape tannin was accompanied by the bathochromic shift and the hyperchromic effect, which lead to an increase in color intensity (lower L*, higher a* and b*). During the aging process, sinapic and grape tannin increased the content of pyranoanthocyanins in cherry wine, especially the addition of sinapic acid makes the cherry wine generate 10-syringyl-pyranocyanidin-3-rutinoside. These results demonstrate that sinapic acid is suitable for adding before alcohol fermentation, while grape tannins can be added before aging.     

Simulation of aerated lagoon using artificial neural networks and multivariate regression techniques

The aim of this study was to develop an empirical model that provides accurate predictions of the biochemical oxygen demand of the output stream from the aerated lagoon at International Paper of Brazil, one of the major pulp and paper plants in Brazil. Predictive models were calculated from functional link neural networks (FLNNs), multiple linear regression, principal components regression, and partial least-squares regression (PLSR). Improvement in FLNN modeling capability was observed when the data were preprocessed using the PLSR technique. PLSR also proved to be a powerful linear regression technique for this problem, which presents operational data limitations.     

Prediction of anti-HIV activity and cytotoxicity of pyrimidinyl and triazinyl amines: A QSAR study

A QSAR study on a series of pyrimidinyl and triazinyl amines was performed to explore the physico-chemical parameters responsible for their anti-HIV activity and cytotoxicity. Physico-chemical parameters were calculated using WIN CAChe 6.1. Stepwise multiple linear regression analysis was carried out to derive QSAR models which were further evaluated for statistical significance and predictive power by internal and external validation. The selected best QSAR models showed correlation coefficient R of 0.914 and 0.901, and cross-validated squared correlation coefficient Q ² of 0.685 and 0.691 for anti-HIV activity and cytotoxicity, respectively. The developed significant QSAR model indicates that hydrophobicity of the whole molecule plays an important role in the anti-HIV activity and cytotoxicity of pyrimidinyl and triazinyl amine derivatives. When hydrophobicity is increased, anti-HIV activity of the present series of compounds is decreased leading to high cytotoxicity.     

生物质固体成型燃料热值和碳元素预测模型的建立

建立生物质固体成型燃料热值和碳元素预测模型。利用秸秆类生物质固体成型燃料的测试数据,以工业分析中的水分、灰分、挥发分和固定碳含量指标为4个自变量,分别以低位热值、高位热值和碳元素分析为因变量,通过多元线性回归模型(MLR)方法建立多元线性回归预测模型。内部检验和外部检验说明3组模型在应用域范围内均具有理想的预测能力,拟合效果良好,其中高位热值预测模型的R^2和R^2_(prep)分别为0.900和0.730,与已有研究相比,相对残差范围减小为–2.59%~2.26%,可为工业用途的生物质固体成型燃料的热值和碳元素分析快速做出反映。     

Qualitative and semi-quantitative analysis in ICP-AES using multivariate calibration

This paper describes a two step algorithm for qualitative and semiquantitative analysis in inductively coupled plasma—atomic emission spectroscopy (ICP-AES) including the preceding data acquisition. Sample and calibration spectra were recorded in 0.05 nm spectral windows centered about the most prominent lines of the 49 covered elements. In the first step of the analysis of an unknown sample spectrum it is decided which of these elements can be excluded from further operations because of the absence of their most prominent lines applying a multivariate criterion for peak detection. For the remaining elements quantitative analysis is performed via multivariate calibration taking into consideration the most prominent line of each element and possibly interfering lines of those elements which were not found absent during the first step. After the estimation of the element concentrations multivariate detection limits are used as criterion for the presence of an element. Results for six synthetic samples of increasing complexity prepared from standard solutions and three standard reference materials are given.     

化学计量学辅助紫外分光光度法同时测定洛美沙星和司帕沙星

在pH：3．0的B-R缓冲溶液中,洛美沙星（LMX）和司帕沙星（SPFX）的最大吸收波长分别为286nm和296nm,两者吸收光谱严重重叠．本文用多元线性回归（MLR）、K-矩阵（AKC）、P-矩阵（CPA）等计算方法辅助紫外分光光度法,同时测定了模拟样中LMX和SPFX的含量。发现CPA法明显优于MLR和AKC,LMX和SPFX的平均回收率分别达99．5％和99．9％,相对标准偏差RSD分别为0．59％和0．85％.     

La2—xSrxCuO4和La2—xNdxCuO4＋y的键共价性计算

使用复杂晶体化学键理论计算了Ｌａ２－ｘＳｒｘＣｕＯ４和Ｌａ２－ｘＮｄｘＣｕＯ４＋ｙ中各键的健共价性,讨论了键性随着掺杂的变化规律,研究表明,对于２１４结构,没有发现明显的化学键性与超导温度的关系,因此２１４结构中有关超导现象产生的机理还有待于进一步研究。