Simultaneous Determination of Hydrocortisone and Zn-Bacitracin by Spectrophotometric Derivative and Multivariate Methods

 Four spectrophotometric methods are described and applied to resolve binary mixtures of the corticosteroid hydrocortisone and the antibacterial polypeptide Zn-Bacitracin. The simultaneous determination of the two compounds was accomplished by means of derivative methods, which were satisfactory used to determine synthetic mixtures of these compounds in different ratios and in pharmaceutical preparations (only for hydrocortisone). Direct absorption spectra of compounds were used to optimise the spectral data set performs the calibration by PLS-1, PLS-2 and PCR algorithms. These calibration models were evaluated through internal validation (prediction of compounds in its own designed training set of calibration), cross-validation (obtaining statistical parameters that show the efficiency for a calibration fit model) and external validation over synthetic and pharmaceutical mixtures. The four described procedures do not require any separation step. Precision studies were achieved over two series of ten standards for each compound showing no significant differences at 95% confidence level in the two spectrophotometric methods. The results found in commercial products were compared with those obtained by means of MEKC method and similar values were found. Correspondence: Department of Analytical Chemistry and Food Technology, Universidad de Castilla-La Mancha, 13071 Ciudad Real, Spain. e-mail: JoseMaria.Lemus@uclm.es Received January 25, 2002; accepted October 22, 2002     

多波长线性回归法校正火焰原子吸收光谱干扰

用多波长线性回归法校正了火焰原子吸收分析中Ｇａ４０３．２９８ｎｍ对Ｍｎ４０３．３０７ｎｍ的吸收线重叠干扰，对合成样中Ｍｎ和Ｇａ含量的测定，结果令人满意。     

岭回归法解析病态光谱体系数据及其在复方维生素B分析中的应用

当多组分体系的吸收光谱出现严重重叠而构成病态体系时，用以最小二乘估计的各种化学计算学方法算其含量时，往往导致偏差，本文用岭回归法处理复方维生素Ｂ四组分体系的光谱数据，所得分析结果表明优于最二乘法。     

ICP—AES分析的线性回归校准曲线

本文对ICP-AES分析中2种线性回归方法的校准曲线作了比较和讨论。对大多数元素而言,用加权法得到的校准曲线的斜率比不加权校准曲线的斜率略大,减小3校准曲线在低浓度部分的弯曲,曲线明显优于不加权校准曲线。将2种方法得到的校准曲线进行比较时,应将剩余标准偏差(或剩余变差平方和)及曲线截距等加以综合考虑。用含零标的标准系列制作校准曲线可使曲线的截距更接近原点,有利于提高在低浓度部分校准分析的准确性。     

线性回归间接极谱络合滴定

本文提出的方法是，根据一定的络合平衡和物料平衡，将间接极谱和线性回归应用于络合滴定，旨在扩大络合滴定的应用范围。文中对测定误差作了分析和计算，探讨了滴定点及权重选择问题。     

Statistical evaluation of potash-lime-silica glass weathering

Two potash-lime-silica model glasses with compositions similar to those of medieval stained glass were exposed at 26 test sites all over Europe and in North America for 3–6 years. The objectives of this large-scale field exposure programme were: (a) a qualitative analysis of the weathering products formed on the surface of the samples in the (environmental) scanning electron microscope in combination with energy dispersive X-ray microanalysis (ESEM/EDX or SEM/EDX, respectively); (b) a statistical evaluation of the weathering phenomena by applying a multiple linear regression (MLR) analysis to find correlations between the degree of weathering, which was measured in terms of surface coverage with reaction products, and environmental parameters such as the concentration (c) of the acidifying gases SO₂, NO₂ and O₃, the temperature (T) and the relative humidity (RH); and (c) the calculation of a time-dependence function of the weathering process of these glasses. Mainly sulfates of calcium and potassium such as gypsum (CaSO₄·2 H₂O), arcanite (K₂SO₄) and syngenite (CaSO₄·K₂SO₄·H₂O) could be identified in the SEM and ESEM. Carbonates, nitrates and many particles deposited on the glass surface were found as well. MLR calculations exhibit significant dependencies of the degree of weathering on T, RH, c(NO_x), c(SO₂) and c(O₃). Applying a time-dependence function of the general form y=a·t^b (t=time) results in a value of approximately 0.42 for the exponent b, which comes close to values expected from various studies in the literature.     

Multivariate analytical sensitivity in the determination of selenium, copper, lead and cadmium by stripping voltammetry when using soft calibration

A new approach to the multivariate sensitivity concept based on the determination of the capability of discrimination of a method of analysis is shown. Thus the analytical sensitivity is defined in this work by the analyte concentration that a analytical method is able to discriminate, which implies the estimation of the ‘false noncompliance’ and ‘false compliance’. In this approach the estimation of the multivariate analytical sensitivity is independent of scale factors and calibration models, and allows one to study the behavior of a analytical method for several concentrations and matrix. The estimation of this parameter in the simultaneous determination of selenium, copper, lead and cadmium by stripping voltammetry when using soft calibration is carried out, showing that different multivariate analytical sensitivities are obtained for each metal.     

多波长线性回归紫外吸光光度法同时测定炼油厂污水中苯酚和苯胺

提出用多波长线性回归紫外吸光光度法同时测定炼油厂污水中的苯酚和苯胺.方法省去了萃取、蒸馏、显色等步骤,操作简单.对合成水样进行测定,相对标准偏差≤4.57%,相对误差≤±2.3%.对炼油厂水样进行测定并进行加标回收试验,苯酚和苯胶的回收率分别为99.4%～103.0%和97.2%～104.0%,结果良好.苯酚和苯胶的最低检出限分别为0.010和0.048μg·ml~(-1).