蔬菜叶片中叶绿素a和叶绿素b的阶导数分光光度法测定

本文提出用一阶导数分光光度法同时测定蔬菜叶片中叶绿素ａ和叶绿素ｂ的含量。讨论了同时存在于蔬菜叶片中的类胡萝卜素对两者测定的影响，并提出用适当浓度的类胡萝卜素丙酮溶液作为参比溶液，用以消除类胡萝卜素对叶绿素测定的影响。     

蔬菜叶片中叶绿素a和叶绿素b的一阶导数分光光度法测定

本文提出用一阶异数分光光度法同时测定蔬菜叶片中叶绿素ａ和叶绿素ｂ的含量。讨论了同时存在于蔬菜叶片中的类胡萝卜素对两者测定的影响，并提出用适当浓度的类胡萝卜素丙酮溶液作为参比溶液，用以消除类胡萝卜素对叶绿素测定的影响。     

间接光度法测定植物叶片中叶绿素含量

将植物叶试样置于研钵中用无水乙醇研磨,使植物叶中叶绿素溶入乙醇中。分取部分此乙醇溶液用石油醚萃取,使叶绿素溶入石油醚中。石油醚相用1 mol.L-1盐酸反萃取,使镁离子从叶绿素分子中被氢离子置换而进入水溶液中。然后用光度法以偶氮氯膦Ⅰ为显色剂测定镁量并用以计算叶绿素的含量。     

分光光度法快速测定玉米叶片中的叶绿素

以玉米叶片为材料,利用双波长双光束紫外可见分光光度计,用最大决定系数增量回归算法,研究了叶片叶绿素a、b及SPAD值同时、快速测量方法.结果表明,用3个波长点建立的模型可以达到良好的预测效果,预测叶绿素a、b及SPAD值的相关系数分别为0.9919、0.9816和0.9757;标准差分别为1.52、0.43和1.96;预测相对标准差分别为4.64%、5.50%和4.88%.同时研究了仪器波长误差和带宽变化对测定结果的影响, 发现波长偏移超过0.2 nm,误差快速增大,且波长向长波方向偏移时对测量的影响要大于向短波方向偏移的影响;仪器带宽变大,预测误差也就越大.     

导数分光光度法同时测定叶绿素a和叶绿素b

1 引言 本文采用一阶导数分光光度法同时测定叶绿素(Chl)a和b,检测下限分别为14.3ng/ml和37.8ng/ml,测定范围分别为0.5～20μg/ml和0.5～10μg/ml,相对标准偏差分别为1.01%和1.44％。 2 方法要点 取适量Chl a或Chl b的90％丙酮溶液,在美国Beckman DU-7HS型分光光度计上以600nm/min的扫描速度绘制吸收光谱,并转换成一阶导数谱图(△λ=4)。由该谱图可知,Chl b在467.0nm处有一个导数     

铜绿微囊藻液中提取叶绿素a作为基准物用于荧光光度法测定叶绿素含量

用乙醇从铜绿微囊藻中提取叶绿素a并用分光光度法测得提取液中叶绿素a的质量浓度为1 902.5μg·L-1,以叶绿素a作为标准物质,用荧光光度法测定叶绿素含量。叶绿素a的质量浓度在30~1 800μg·L-1范围内与荧光强度呈线性关系。试验表明:该提取液在冰箱4℃条件下保存,5h内其荧光值的相对误差为±2.5%;在pH 3~9范围内应用时,荧光值的相对误差为±5.0%;在温度5℃~30℃范围中使用时,荧光值的相对误差为±3.0%,证明提取液的稳定性能满足使用要求。与叶绿素标准品同时测定了5个水样中的叶绿素含量,经t检验所得结果之间无显著差异,说明可用叶绿素a代替叶绿素标准品作为荧光光度法中的基准物质。     

用植物叶片中重金属元素含量指示大气污染的研究

通过对潮州市区交通繁忙路段和对照区 (红山森林公园 )不同植物叶片重金属元素 (Pb、Cd、Cu、Zn)的含量研究 ,探讨了重金属含量与城市大气污染之间的关系。结果表明 ,植物叶片中的重金属元素富积量和大气中污染指数正相关。植物叶片的重金属元素富积量可较好和客观地指示市区大气的重金属污染状况。该研究为城市规划和环境保护提供了科学依据     

流动注射—分光光度法测定植物中钼

本文将流动注射分析(FIA)引入Mo-SCN~--RhB三元缔合体系测定痕量Mo。不需萃取,反应迅速,重现性好。0～1.6μg/ml Mo符合比耳定律,检测限0.02μg/ml。用预混线圈R_1可克服Fe~(3+)等元素与SCN~-络合的干扰。测定了植物中Mo,结果满意。     

分光光度法测定水体中叶绿素a的浓缩方法的改进

<正>浮游植物中叶绿素a的含量是估算水域初级生产力的一个重要指标,近几十年来,随着水体富营养化问题的日益加剧,精确测定水体中叶绿素a的含量意义重大。目前测定水体中叶绿素a的国家标准方法为分光光度法[1],该方法所用萃取溶剂为丙酮,其萃取效率较差且有毒,操作还较繁琐。对此,科研工作者先后从萃取溶剂[2-3]、提取方法[4-5]和滤膜的选择[6-7]等方面对分光光度法进行了改进,效果显     

偏最小二乘法及主组分回归法用于药物组分的测定

本文研究了多元校准方法——偏最小二乘法(PLS)和主组份回归法(PCR)在药物多组份光度分析中的应用,获得了较满意的结果。而且在系列校准样品的实验设计、交叉证实法确定最佳因子数以及空缺组份体系的分析等方面进行了探讨。     

Simultaneous Spectrophotometric Determination of Iron and Cobalt in Micellar Medium by Using a Principal Component Artificial Neural Network and Multivariate Calibration

A simple and reliable method for simultaneous spectrophotometric determination of iron(II) and cobalt(II) has been established. The method is based on complex formation with 1‐(2‐pyridylazo)‐2‐naphtol (PAN) in a micellar medium. Despite a spectral overlap, Fe²⁺ and Co²⁺ have been simultaneously determined with chemometric approaches involving principal component artificial neural network (PC‐ANN), principal component regression (PCR) and partial least squares (PLS). Various synthetic mixtures of iron and cobalt were assessed and the results obtained by the applications of these chemometric approaches were evaluated and compared. It was found that the PC‐ANN method afforded relatively better precision than that of PCR or PLS. The proposed method permits detection limits of 0.05 and 0.07 ng mL^?1 for Co and Fe, respectively. The influences of pH, ligand amount, solvent percentage and time on the absorbance were also investigated. The proposed method was also applied satisfactorily for the determination of Fe(II) and Co(II) in real and synthetic samples.     

Resolution of Differential Pulse Voltammetric Peaks Using Genetic Algorithm Based Variable Selection‐Partial Least Squares and Principal Component‐Artificial Neural Networks

Differential Pulse Voltammetry has been used for the simultaneous determination of cysteine, tyrosine and trptophan on the unmodified glassy carbon electrode. In the analysis of these analytes in the same samples, the main difficulty is the high degree of overlapping of voltammograms. The relationships between the currents and the concentrations are complex and highly nonlinear. The predictive ability of principal component regression (PCR), partial least squares regression (PLS), genetic algorithm‐partial least squares regression (GA‐PLS) and principal component‐artificial neural networks (PC‐ANNs) were examined for simultaneous determination of three amino acids. For a regression model, everything that could not help in constructing the model may be considered as noise without further specification. PC‐ANN and GA‐PLS use significant data and show superiority over other applied multivariate methods. The proposed method was also applied satisfactorily to determination of analytes in some synthetic samples.     

Improvement of multivariate calibration techniques applied to 1-to-N component mixtures through an optimized experimental design

This work describes a novel experimental design aimed at building a calibration set constituted by samples containing a different number of components. The algorithm performs a reiteration process to maintain the number of samples at the lower value as possible and to ensure an homogeneous presence of all the concentration levels. The mixture design was applied to a drug system composed by one-to-four components in different combination. The resolution of the system was performed by three multivariate UV spectrophotometric methods utilizing principal component regression (PCR) and partial last squares (PLS1 and PLS2) algorithms. The calibration set was composed by 61 references on four concentration levels, including 15 samples for each quaternary, ternary and binary composition and 16 one-component samples. The calibration models were optimized through a careful selection of number of factors and wavelength zones, in such a way as to remove interferences from instrumental noise and excipients present in the pharmaceutical formulations. The prediction power of the regression models were verified and compared by analysis of an external prediction set. The models were finally used to assay pharmaceutical specialities containing the studied drugs in one-to-four formulations.     

同时测定合成样中铜钴镍钒含量的分光光度法--主成分回归法和偏最小二乘法比较

研究了主成分回归和偏最小二乘方法在多组分分光光度法分析中的应用,以５－Ｂｒ－ＰＡＤＡＰ（２〔５－溴－２－吡啶）－偶氮〕５－二乙氨基苯酚）为显色剂,ＯＰ（聚乙二醇辛基苯基醚）作为增溶增稳剂,在ｐＨ＝３．６的条件下,用主成分回归及偏最小二乘分光光度法同时测定了合成样中的铜、钴、镍、钒４组分含量,测定相对误差在－６．００％～４．００％之间。实验证明,对于加和性不好的体系偏最小二乘分光光度法要优于主成分回     

Simultaneous Kinetic‐Spectrophotometric Determination of Hydrazine and its Derivatives by Partial Least Squares and Principle Component Regression Methods

Simultaneous kinetic‐spectrophotometric determination of a ternary mixture of hydrazine (HZ) and its derivatives by principal component regression (PCR) and partial least squares (PLS) calibration is described. The methods were based on the difference observed in the reduction rate of iron(III) with HZ, thiosemicarbazide (TSCZ) and phenylhydrazine (PHZ) in the presence of 2,2′‐bipyridine (Bpy). The colored complex of [Fe(Bpy)₃]²⁺ was formed in sodium dodecyl sulfate (SDS) as micellar media, and then monitored at 520 nm. The results showed that simultaneous determination of HZ, TSCZ and PHZ could be performed in their concentration ranges of 1.0–70.0, 0.2–6.0 and 0.1–10.0 μg mL^?1, respectively. The root mean squares errors of prediction (RMSEP) of HZ, TSCZ and PHZ were 0.719, 0.164 and 0.105 (for PLS) 0.788, 0.166 and 0.993 (for PCR), respectively. Both methods (PCR and PLS) were validated using a set of synthetic sample mixtures and then applied for simultaneous determination of HZ, TSCZ and PHZ in water samples.     

氨基酸结构描述子矢量VHSE及其在肽QSAR中的应用

从20种天然氨基酸的50个物化性质出发，按照疏水、立体和电性特征将其分类后分别进行主成分分析，并将产生的得分矢量即VHSE(principal component score vector of hydrophilicity,steric，and electronic properties)作为氨基酸结构描述子用于肽的定量构效关系研究。与已有方法相比，VHSE描述子具有物化意义明确、结果更易解释等特点。应用该描述子并结合逐步回归变量筛选和偏最小二乘建模方法，在对苦味二肽和血管舒缓激肽促进剂等体系的定量构效关系研究中，均取得了优于已有文献的结果。     

Simultaneous spectrophotometric determination of ethinylestradiol and levonorgestrel by partial least squares and principal component regression multivariate calibration

Two spectrophotometric methods for the determination of Ethinylestradiol (ETE) and Levonorgestrel (LEV) by using the multivariate calibration technique of partial least square (PLS) and principal component regression (PCR) are presented. In this study the PLS and PCR are successfully applied to quantify both hormones using the information contained in the absorption spectra of appropriate solutions. In order to do this, a calibration set of standard samples composed of different mixtures of both compounds has been designed. The results found by application of the PLS and PCR methods to the simultaneous determination of mixtures, containing 4–11 μg ml⁻¹ of ETE and 2–23 μg ml⁻¹ of LEV, are reported. Five different oral contraceptives were analyzed and the results were very similar to that obtained by a reference liquid Chromatographic method.     

化学计量学方法用于多组分的分光光度分析——合成样品中钡锶钙的同时测定

近年来,随着现代化学测量仪器的大量涌现及计算机科学的进步,化学计量学在我国取得了重大发展[1],为多组分同时测定提供了一个重要的研究手段。特别是对于白色分析体系,一般情况下,分析化学计量学均可给出令人满意的定量解析结果。白色分析体系指定性组成已知,需对各组分进行定     

A Robust Near-Infrared Calibration Model for the Determination of Chlorophyll Concentration in Tree Leaves with a Calibration Transfer Method

A method based on piecewise direct standardization was developed to directly predict leaf chlorophyll concentrations by correction of near-infrared spectra to construct a robust calibration model. Chinar, camphor, and gingko leaves collected from two growth intervals were evaluated. Spectral pretreatment methods and wavelength selection were investigated. The first derivative combined with stability competitive adaptive reweighted sampling before piecewise direct standardization provided the best performance. Under the optimized parameters, the root mean square error of prediction was significantly reduced by using piecewise direct standardization. This study demonstrates that the calibration model may be used to rapidly characterize chlorophyll concentrations across species and growth intervals.