Determination of Sudan I in chilli powder from solvent components gradual change-visible spectra data using second order calibration algorithms

It was discovered that a second order spectra data matrix of Sudan I produced from the solvent components gradual change-visible absorption spectra can be expressed as the combination of two bilinear data matrices. Based on this discovery, a new method for the determination of Sudan I in gray systems using second order calibration algorithms has been developed. The second order calibration algorithms were based on the popular parallel factor analysis (PARAFAC) and rank annihilation factor analysis (RAFA), respectively. In the method described here, the components of the solvent were changed gradually by adding ethanol into cyclohexane, the absorption spectra of Sudan I and chilli samples in a series of cyclohexane-ethanol mixed solvents with various ethanol volume fractions were recorded, and then the second order data were obtained from the solvent components gradual change-visible absorption spectra. Thus, the concentration of Sudan I in a gray system could be determined from the spectra matrices using second order calibration algorithms. This method is simple, convenient and dependable. The method has been used to determine Sudan I in chilli powder with satisfactory results.     

三维荧光二阶校正法用于未知混合物中苯酚含量的测定

将三维荧光光谱技术与秩消失因子分析、广义秩消失因子分析和交替三线性分解3种二阶校正方法相结合,建立了测定未知混合物中苯酚含量的三维荧光二阶校正新方法。设定在激发波长240~280 nm和发射波长280~360 nm范围内测定未知混合物中苯酚的三维荧光光谱,构建三维响应数据阵,运用基于三线性分解的二阶校正算法进行解析。结果表明,当模拟样品的组分数为2时,秩消失因子分析、广义秩消失因子分析和交替三线性分解3种方法测定苯酚的预测均方根误差分别为0.33,1.18和0.15,平均回收率分别为101.6%,115.6%和101.9%;当组分数为3时,3种方法的预测均方根误差则分别为1.61,1.80和0.51,平均回收率分别为134.2%,133.9%和107.1%;将其分别应用于实际样品中苯酚的测定,结果满意,且交替三线性分解法的测定结果优于秩消失因子分析法和广义秩消失因子分析法。     

一种测定中药复方制剂中活性成分的计算分析方法

提出了一种测定中药复方制剂中活性成分含量的计算分析新方法。该方法将主 成分分析和广义秩消因子分析集成用于处理HPLC／DAD数据，并改进了传统的IND因 子指示函数，适用于定量计算分析复杂混和物体系中的待测成分。将其用于测定复 方丹参制剂中三七皂苷R1的含量，计算分析结果表明，本方法明显优于广义秩消因 子法，同时证明IND函数的改进提高了计算分析准确度。     

Spectrophotometric determination of acidity constants by two-rank annihilation factor analysis

Annihilation of the contribution of one chemical component from the original data matrix is a general method in rank annihilation factor analysis (RAFA). However, RAFA is not applicable for studying the protonation equilibria of multiprotic acids. In this work, a two-rank annihilation factor analysis (TRAFA) method was proposed for determination of the acidity constants of diprotic acids. After recording the electronic absorbance spectra of the acids at different pH, the contributions of both H₂A and A²⁻ were annihilated from the absorbance data, which made feasible the determination of two successive acidity constants. The method was validated by analysis of simulated data and its application to the determination of the acidity constants of calmagite, as a reference compound. A close agreement was obtained between the resulted values by TRAFA and the declared values. Indeed, the method was used for determination of the acidity constants of two new chromenone derivatives in binary solvents mixtures of methanol and water. The effects of changing solvent composition on acidity constant data were explained by linear solvation free energy relationships (LSFER) utilizing solvatochromic parameters.     

Molecular fluorescence excitation-emission matrices relevant to tissue spectroscopy

In vivo and ex vivo studies of fluorescence from endogenous and exogenous molecules in tissues and cells are common for applications such as detection or characterization of early disease. A systematic determination of the excitation-emission matrices (EEM) of known and putative endogenous fluorophores and a number of exogenous fluorescent photodynamic therapy drugs has been performed in solution. The excitation wavelength range was 250-520 nm, with fluorescence emission spectra collected in the range 260-750 nm. In addition, EEM of intact normal and adenomatous human colon tissues are presented as an example of the relationship to the EEM of constituent fluorophores and illustrating the effects of tissue chromophore absorption. As a means to make this large quantity of spectral data generally available, an interactive database has been developed. This currently includes EEM and also absorption spectra of 35 different endogenous and exogenous fluorophores and chromophores and six photosensitizing agents. It is intended to maintain and extend this database in the public domain, accessible through the Photochemistry and Photobiology website (http://www.aspjournal. com/).     

Application of GRAM and TLD to the resolution and quantitation of real complex multicomponent mixtures by fluorescence spectroscopy

The application of the generalised rank annihilation method (GRAM) and the trilinear decomposition (TLD) method to the resolution and quantitation of fluorescence excitation-emission matrices of a ternary mixture of pesticides, carbendazim, fuberidazole, and thiabendazole, with overlapped spectra is described. The results obtained with both methods are compared and evaluated using measures of similarity (correlation coefficients) between the real and estimated spectra. Both approaches have been tested using augmented data matrices containing only two samples, but none of these methods succeeded completely in resolution of the system. When TLD was applied to augmented data matrices containing more than two samples better performance was achieved. To illustrate the application of both algorithms to real samples, they were used in the analysis of water samples containing the target pesticides. Again, TLD had an advantage over GRAM because the ability to analyse data from multiple (more than two) samples simultaneously allowed the resolution of the mixtures.     

Variable-angle synchronous fluorescence spectrometry and rank annihilation methods for mixture resolution

The potential of variable angle synchronous spectroscopy (VASS) for fluorescent mixtures resolution was assessed and compared with the rank annihilation method (RAM). For this purpose, a set of excitation-emission matrices from three standard cyclodextrin fluorescence-enhanced solutions of the pesticides aminocarb, carbendazim and coumatetralyl and a mixture of them was obtained. Careful selection of the spectral routes to be scanned provides analyte signals that are free of interferences. Application of the rank annihilation method to excitation-emission matrices (EEMs) obtained by conventional scanning spectrofluorimetry gives quantitative results that show poor precision and accuracy when compared to those of VASS. The recoveries from ternary mixtures by VASS are within 99-104% and by RAM within 84-130%.     

Limit of detection estimator for second-order bilinear calibration

A new approach is developed for estimating the limit of detection in second-order bilinear calibration with the generalized rank annihilation method (GRAM). The proposed estimator is based on recently derived expressions for prediction variance and bias. It follows the latest IUPAC recommendations in the sense that it concisely accounts for the probabilities of committing both types I and II errors, i.e. false positive and false negative declarations, respectively. The estimator has been extensively validated with simulated data, yielding promising results.     

类石墨碳修饰提高ZnO纳米棒阵列光催化活性和光稳定性的研究

半导体光催化是一种理想的太阳能化学转化绿色技术,可以实现水分解制氢和CO2光还原制备碳氢化合物燃料.氧化锌 (ZnO) 作为一种直接带隙半导体材料,一方面具有性能优异、价格低廉、易制备等优点; 另一方面因光腐蚀而不稳定,大大限制了该材料的实际应用.本文提出了一种简单易行的类石墨碳修饰方法,可以有效提高 ZnO 用于CO2光还原的光催化活性和稳定性.首先采用水热法在金属锌片基底上生长 ZnO 纳米棒阵列 (ZnO-NRA),然后通过葡萄糖水热法进行不同含量的类石墨碳 (C-x) 修饰,形成 ZnO-NRA/C-x 纳米复合结构,同步实现碳包覆和碳掺杂.X 射线衍射结果表明,ZnO 纳米棒及ZnO-NRA/C-x 纳米复合结构都具有良好的纤锌矿型 (Wurtzite) 结构; 而拉曼散射则清楚地证实了类石墨碳的存在.扫描电子显微观察显示,生长的 ZnO 纳米棒长度大约 2-5 μm,直径为 400-700 nm,沿方向[0001]生长,端部由六个规则的 (103)晶面组成,进一步直观佐证了 ZnO 的典型纤锌矿型结构特征.透射电子显微分析结果表明,ZnO-NRA/C-x 纳米复合结构中类石墨碳包覆层厚度大约为 8 nm.ZnO-NRA/C-x 纳米复合结构的 X 射线光电子谱分析结果验证了 C-C,C-O 和 C=O键的存在与碳的包覆层相对应; 而 C-O-Zn键的出现则是由于碳在 ZnO 中掺杂所引起.从紫外-可见吸收谱上可观察到ZnO 的典型吸收带边位置约为 385 nm,而碳的包覆和掺杂导致 ZnO-NRA/C-x 纳米复合结构的吸收带边发生红移,并且吸收背底明显提高.电化学阻抗谱测试结果清楚地显示,ZnO-NRA/C-x 纳米复合结构比单纯 ZnO-NRA 的电化学阻抗明显降低,说明类石墨碳包覆层大幅度提高了电导性能,从而有利于光生载流子的分离和传输.荧光分析结果也表明,与单纯的 ZnO-NRA 相比,ZnO-NRA/C-x 纳米复合结构的荧光强度大幅度下降,进一步证实了 ZnO-NRA/C-x 纳米复合结构比单纯的 ZnO-NRA更有利于光生载流子的分离和传输.光电化学测试结果表明,ZnO-NRA/C-x 纳米复合结构的瞬态光电流 4 倍于单纯的ZnO-NRA,而 CO2 光还原性能测试也得到一致的结果.长时间多循环 CO2 光还原实验证实,ZnO-NRA/C-x 纳米复合结构具有稳定的光催化活性和极好的光稳定性.综上,我们利用一种简单易行的水热法进行类石墨碳修饰,成功开发了 ZnO-NRA/C-x 纳米复合结构,该结构因其优异的光生电子和空穴的分离和迁移性能,从而具有显著提升的CO2光还原活性和光稳定性.本工作证明,类石墨碳修饰是一种可以广泛借鉴的有效提升半导体材料光催化活性和光稳定性的可行方法.     

Calibration transfer for excitation-emission fluorescence measurements

The main part of the wide array of different calibration transfer methods found in literature is dedicated to two-way data arrangements (m×n matrices). Less work has been done within the area of calibration transfer for three-way data structures (m×n×l tensors) such as calibrations made for excitation-emission-matrix (EEM) fluorescence spectra. There are two possible ways to attack the problem for EEM transfer. Either the tensors are unfolded to two-way data, whereby the existing methods can be applied, or new methods dedicated to three-way calibration transfer have to be developed. This paper presents and compares both. It was possible to make a local linear pixel-based model that could be used for transfer of EEM's. This new method has a similar performance to the classical methods found in literature, direct- and piecewise direct standardization. The three-way advantages made it possible to use as few as four samples to build useable transfer models. Care has to be taken though when choosing the samples. When subset recalibration of the systems is compared to calibration transfer, better performance is seen for the transferred calibrations. Overall the three-way calibration transfer methods have a slightly better performance than the two-way methods.