大豆异黄酮指纹图谱中保留时间漂移的校正研究

选取5个极性不同的化合物作为标准样品,在不同仪器及不同色谱柱上采用已建立的大豆异黄酮高效液相色谱(HPLC)指纹图谱条件进行测定,以它们在不同色谱仪(或柱)上的保留时间进行线性回归,并用得到的线性方程对相同条件下测得的大豆异黄酮指纹谱中峰面积为总峰面积1.5%以上的色谱峰的保留时间进行校正,通过校正使保留时间的最大绝对误差由5.868 min减小为0.854 min。采用该方法可以校正相同色谱条件但不同实验室间指纹图谱保留时间的漂移,提高HPLC指纹图谱的重现性。     

反相高效液相色谱中流动相线性梯度洗脱条件下溶质保留时间预测的新方法

 在计算溶质的梯度保留时间时 ,根据流动相在色谱柱内的分布规律 ,对溶质在色谱柱内的迁移距离和流动相梯度同时进行校正 ,从而建立了一种预测溶质线性梯度洗脱条件下保留时间的新方法。该方法在不同的仪器系统中 ,对于弱保留和强保留溶质在不同线性梯度洗脱条件下保留时间的预测 ,都具有良好的准确度。以 15种氨基酸和 8种苯的同系物为例 ,该方法对于弱保留溶质保留时间的预测 ,相对平均误差分别为 3 70 %和 4 90 % ,远小于文献方法得到的结果 (2 3 6 1%和 31 16 % ) ;对于强保留溶质保留时间的预测 ,相对平均误差分别为 0 2 1%和6 0 1% ,略小于文献 。     

径向基函数网络在近红外人体无创伤血糖浓度检测基础研究中的应用

在近红外无创伤血糖浓度检测的基础研究中，对于多组分的混合物的分析，常因光谱与样品浓度之间呈现非线性响应，使得基于线性模型的校正方法失效。本文讨论了非线性校正方法径向基函数神经网络( RBFN )的有效性，并与线性校正方法中的主成分分析和偏最小二乘法作了对比研究。验证实验所用样品为①葡萄糖水溶液②包含牛血红蛋白和白蛋白的葡萄糖水溶液，结果表明：在①实验中PLS模型和RBFN预测标准偏差分别为8．2、8．9；在②实验中分别为15．6、8．8。可见在样品组分增多时，RBFN算法较线性PLS方法建立的模型预测能力强。     

基于遗传算法优化的约束背景双线性分解算法用于改进高效液相色谱灰色分析体系的校正结果

该文采用约束背景双线性分解算法(CBBL)对以高效液相色谱(HPLC)方法分离分析的灰色分析体系进行了多元校正研究。针对采用包括CBBL在内的矩阵校正方法处理HPLC灰色分析体系的固有缺陷,即在相关组分的色谱保留时间重现性较低的情形下多元校正的结果不理想,对CBBL方法进行了改进,即将待测组分的浓度与组分的色谱保留时间同时作为优化的参量引入CBBL,并采用遗传算法(GA)优化CBBL,对于模拟的组分保留时间飘移严重的HPLC灰色分析体系及保留时间重现性不佳的多种酚类化合物组成的实际HPLC灰色分析体系进行了多元校正分析,成功克服了经典CBBL的固有缺陷,取得了较理想的多元校正结果。另外,该研究所建议的方法的校正结果也显著优于传统的残差双线性分解法(RBL)以及秩消失因子分析法(RAFA)。     

黄芪中黄酮类组分的高效液相色谱分离条件的快速优化

以黄芪为研究对象,对黄芪中乙酸乙酯部位的化学成分进行了高效液相色谱分析并对其色谱操作条件进行了快速优化。根据几个线性梯度下的保留时间来计算各组分的保留参数,然后利用重叠分辨图法确定其最佳分析条件。在选定的最佳条件下各组分分离情况良好。利用梯度保留时间计算保留参数比较方便快速,并可以有效地避免以往等度线性回归法遇到的峰识别问题。该方法更适用于实际复杂样品色谱分析条件的优化。     

基于非线性化学指纹图谱技术测定婴幼儿羊奶粉中掺假牛奶粉含量

采用非线性化学指纹图谱技术,及最小二乘一元线性回归方法对婴幼儿羊奶粉中掺假牛奶粉进行定量分析。首先测定具有不同掺杂百分比的混合奶粉标样非线性化学指纹图谱,利用其停波时间相对于掺杂牛奶粉含量之间的一元线性关系,通过最小二乘法建立测定混合奶粉中掺杂牛奶粉含量的校正模型;然后用该模型和混合奶粉试样指纹图谱的停波时间来计算混合奶粉中掺杂牛奶粉的含量;最后根据掺杂牛奶粉的含量来鉴别和定量评价奶粉质量。实验表明:该方法相关系数为0.9945,相对标准偏差(RSD)为0.53%~2.18%,回收率在95.3%~107.0%范围,检出限为1.09%。方法准确度高,重现性好,操作简单,是一种切实可行的测定婴幼儿羊奶粉中掺杂牛奶粉含量的方法。     

主成分回归残差神经网络校正算法用于近红外光谱快速测定汽油辛烷值

根据汽油辛值预测体系本身的非线性特点,提出主成分回归残差神经网络校正算法（principal component regression residual artificial neural network,PCRRANN)用于近红外测定汽油辛烷值的预测模型校正,该方法给合了主成分回归算法（PC）,与经典的线性校正算法（PLS（Partial Least Square),PCR, 以及非线性PLS（NPLS,Non-linear PLS)等相比,预测明显的改善,文中还讨论了PCR主成分数及训练参数对预则模可能的影响。     

用局部拟合主成分回归计算光度分析法测定黄连生物碱

针对具有样本数据非无匀分布和非线性特点的光度分析问题，提聘种局部拟合 主成分回归法，用于中药多组分计算测定。该方法根据待测样本与各已知样本光度 分析数据的欧式距离确定相应的权值，将部分权值较大的样本组成校正集，并用分 段线性拟合算法建立待测样本的校正预测模型，将其用于分析黄连的药根碱、巴巴 亭和小檗碱等三种生物碱，所得预测均方根误差分别为0.023,0.0400和0.052，优 于主成分回归法、偏最小二乘法以及人工神经元网络法所得结果。这表明，本方法 用于中药光度分析能获得较为准确的计算分析结果。     

InGaAs探测器中的双孔法非线性校正技术

探测器的非线性误差是影响光谱仪器精度的主要因素,采用双孔法解决InGaAs探测器的非线性校正问题,消除了InGaAs探测器非线性误差对水红外分析仪吸光度示值的影响。实验结果表明,水红外分析仪经非线性校正后的吸光度偏差明显小于校正前的吸光度偏差,提高了仪器测定结果的准确度。     

基于选择离子集成谱的中药质量评价新方法

采用液相色谱-质谱(LC-MS)联用技术建立了不同产地的双丹方(丹参和丹皮)煎剂的指纹图谱, 并提出一种将二维的LC-MS数据转化为一维的选择离子集成谱(ISIC)的方法. 通过主成分分析考察了ISIC与总离子流色谱图(TIC)和保留时间校正后的TIC对不同产地药材的区分能力. 结果表明, ISIC能全面反映不同产地的丹参和丹皮成分间的差异; 而TIC由于色谱峰重叠严重, 对不同产地的药材无区分能力, 保留时间校正后的TIC仅能反映不同产地丹参成分间的差异. 该方法运算速度快, 适于大批量样本分析, 生成的ISIC信息量大, 且不需校正保留时间, 可直接用于后续的统计分析.     

梯度液相色谱中任意等度、线性和阶梯梯度组合下的保留时间公式

基于线性溶剂强度模型,应用特征线分析的方法求解梯度洗脱模式下的理想液相色谱模型。在考虑到梯度延迟时间会对溶质的保留时间造成影响的情况下,得到适合于梯度液相色谱中任意等度、线性和阶梯梯度组合条件下的保留时间推导公式。应用这些公式计算任意的梯度条件下的保留时间,并将得到的结果与数值计f算的结果进行比较,二者完全一致,从而验证了推导得到的保留时间公式的正确性。由于这些公式具有形式简单、适用范围广等优点,因此可方便地应用于实际应用中,具有较高的实用价值。     

非线性色谱保留时间与进样量关系的实验分析

随着制备色谱的发展,对非线性色谱的研究日益深入,非线性色谱中保留时间与进样量的关系是非线性色谱研究中的重要课题.非线性色谱理论研究从40年代开始,主要工作是数学模型的求解与分析.结合理论的实验研究工作较少,关于非线性色谱中进样量与保留时间关系的研究更是这样.对于柱效为无限的理想情形,Aris 与Amundson 曾从理论上作过详细分析,在理想条件下,色谱方程为     

Alignment of retention time obtained from multicapillary column gas chromatography used for VOC analysis with ion mobility spectrometry

Multicapillary column (MCC) ion mobility spectrometers (IMS) are increasingly in demand for medical diagnosis, biological applications and process control. In a MCC-IMS, volatile compounds are differentiated by specific retention time and ion mobility when rapid preseparation techniques are applied, e.g. for the analysis of complex and humid samples. Therefore, high accuracy in the determination of both parameters is required for reliable identification of the signals. The retention time in the MCC is the subject of the present investigation because, for such columns, small deviations in temperature and flow velocity may cause significant changes in retention time. Therefore, a universal correction procedure would be a helpful tool to increase the accuracy of the data obtained from a gas-chromatographic preseparation. Although the effect of the carrier gas flow velocity and temperature on retention time is not linear, it could be demonstrated that a linear alignment can compensate for the changes in retention time due to common minor deviations of both the carrier gas flow velocity and the column temperature around the MCC-IMS standard operation conditions. Therefore, an effective linear alignment procedure for the correction of those deviations has been developed from the analyses of defined gas mixtures under various experimental conditions. This procedure was then applied to data sets generated from real breath analyses obtained in clinical studies using different instruments at different measuring sites for validation. The variation in the retention time of known signals, especially for compounds with higher retention times, was significantly improved. The alignment of the retention time—an indispensable procedure to achieve a more precise identification of analytes—using the proposed method reduces the random error caused by small accidental deviations in column temperature and flow velocity significantly.     

New uniform algorithm to predict reversed phase retention values under different gradient conditions

A new numerical emulation algorithm was established to calculate retention parameters in RP-HPLC with several retention times under different linear or nonlinear binary gradient elution conditions and further predict the retention time under any other binary gradient conditions. A program was written according to this algorithm and nine solutes were used to test the program. The prediction results were excellent. The maximum relative error of predicted retention time was less than 0.45%.     

Formulation of Risperidone as Self-Nanoemulsifying Drug Delivery System in Form of Effervescent Tablets

Risperidone is an atypical antipsychotic drug used to treat schizophrenia. This study aims to formulate risperidone as effervescent tablets to improve patient compliance. Different nanoemulsion combinations were loaded with risperidone to improve its poor water solubility then adsorbed on Aeroperl. The formula showing highest drug dissolution was formulated as effervescent tablets. Factorial design was applied for different tablet formulation variables and the prepared formulae were tested for different criteria in comparison with their corresponding formulae containing drug without nanoemulsion formulation. Statistical analysis was used to determine the most desirable tablet formula considering its Carr index, effervescence time, and drug release.     

Direct minimization of the energy functional in LCAO–MO calculations

In this paper we obtain formulae useful in methods for the direct minimization of the energy functional in the LCAO -MO -MC -SCF approach. The formulae are appropriate for dealing with variations in both the linear and nonlinear parameters. We include formulae for the usual closed- and open-shell problems as special cases.     

Preliminary chemometric study of minerals and trace elements in Spanish infant formulae

The concentrations of minerals (Na, K, P, Ca and Mg) and trace elements (Fe, Zn, Cu, Mn, Se, Al, Cd and Pb) in a total of 105 different infant formulae (starter, follow-up, premature, specialised and soya formulae) marketed in Spain were determined by atomic spectrometry (flame and electrothermal) and inductively coupled plasma emission spectroscopy after acid-microwave decomposition. On the basis of the elements distribution, a preliminary chemometric study with the use of pattern recognition methods was carried out. Hierarchical cluster analysis (HCA), principal component analysis (PCA), as unsupervised exploratory techniques, and linear discriminant analysis (LDA), were applied to characterise, classify and distinguish the different types of infant formulae. The HCA results showed that mineral and trace element content data support adequate information to obtain the infant formula differentiation. PCA permitted the reduction of 13 variables to four principal components accounting for 61.9% of the total variability. This four-factor model interprets reasonably well the correlations of these studied elements. The obtained element associations may be attributed to the composition of matrix ingredients, the contamination during elaboration, the additives and mineral supplements added and the present tendency of standardization in the manufacture of infant formulae. The application of LDA gave a 77.1% of infant formulae correctly assigned with three clearly differentiated and two overlapped groups. The use of discriminant functions, as a complementary tool, to distinguish the different types depending on protein matrix of infant formula, is also discussed. This survey shows that HCA, PCA and LDA techniques appear useful tools for the characterisation and classification of infant formulae using their elemental profile.     

Nonlinear alignment of chromatograms by means of moving window fast Fourier transfrom cross‐correlation

The preprocessing of chromatograms is essential to modern chromatography for further qualitative and quantitative analysis, especially when chromatographic instruments are used for herb products analysis involving large number of samples. To accurately compare and analyze the obtained chromatograms, it is necessary to preprocess, especially align retention time shifts. Here moving window fast Fourier transform (FFT) cross‐correlation is introduced to perform nonlinear alignment of high‐throughput chromatograms. Since elution characteristics of chromatograms will produce local similarity in retention time shifts, moving window procedure seems to be a better substitute of segmentation steps. The retention time shifts can be calculated and accelerated by FFT cross‐correlation. The artifacts can be detected and eliminated from the retention time shifts profile since the continuity of moving window procedure. The proposed method is demonstrated in comparison with recursive alignment by FFT on chromatographic datasets from herb products analysis. It is shown that the proposed method can address nonlinear retention time shift problem in chromatograms with the simple moving window procedure, which will not introduce segments size optimization problem. In additional, the parameters are intuitive and easy to adjust, which makes it off‐the‐shelf toolbox for alignment of chromatograms.     

Applicability of linear and nonlinear retention‐time models for reversed‐phase liquid chromatography separations of small molecules,peptides, and intact proteins

The applicability and predictive properties of the linear solvent strength model and two nonlinear retention‐time models, i.e., the quadratic model and the Neue model, were assessed for the separation of small molecules (phenol derivatives), peptides, and intact proteins. Retention‐time measurements were conducted in isocratic mode and gradient mode applying different gradient times and elution‐strength combinations. The quadratic model provided the most accurate retention‐factor predictions for small molecules (average absolute prediction error of 1.5%) and peptides separations (with a prediction error of 2.3%). An advantage of the Neue model is that it can provide accurate predictions based on only three gradient scouting runs, making tedious isocratic retention‐time measurements obsolete. For peptides, the use of gradient scouting runs in combination with the Neue model resulted in better prediction errors (<2.2%) compared to the use of isocratic runs. The applicability of the quadratic model is limited due to a complex combination of error and exponential functions. For protein separations, only a small elution window could be applied, which is due to the strong effect of the content of organic modifier on retention. Hence, the linear retention‐time behavior of intact proteins is well described by the linear solvent strength model. Prediction errors using gradient scouting runs were significantly lower (2.2%) than when using isocratic scouting runs (3.2%).