Authentication of cassia seeds on the basis of two-wavelength HPLC fingerprinting with the use of chemometrics

<正>High performance liquid chromatographic(HPLC) fingerprints of Cassia seed,a traditional Chinese medicine(TCM),were developed by means of the chromatograms at two wavelengths of 238 and 282 nm.Then,the two data sets were combined into one matrix.The application of principal component analysis(PCA) for this data matrix showed that the samples were clustered into four groups in accordance with the plant sources and preparation procedures.Furthermore,partial least squares(PLS),back propagation artificial neural network(BP-ANN),and radial basis function artificial neural network(RBF-ANN) were effectively applied to predict the category of the four different samples in the test set.     

Extra-pair sires as identified by means of standardized across-gel comparisons of multilocus DNA fingerprints

Molecular analyses of genetic parentage in wild bird populations demonstrate that extra-pair paternity (EPP) is common, even in socially monogamous species. After having identified extra-pair offspring (EPO), an important step is to uncover the identity of extra-pair sires (EPS). Studies relying on multilocus DNA fingerprinting face the problem that simple between-gel comparisons of fingerprint banding patterns are imprecise in assigning parentage across gels. To tackle this problem, we developed a method to identify EPS by means of standardized across-gel comparisons of multilocus DNA fingerprints and applied it in a socially monogamous bird species with high levels of EPP, the coal tit (Parus ater). Scanned DNA fingerprint gels and standard image-editing software allowed to screen and reliably identify EPS. Overall, EPP was successfully assigned to 32 different EPS for 143 out of 210 (68.1%) EPO detected. This corresponds well to extra-pair parentage assignment rates revealed by microsatellite-based studies in congeneric species. Our approach proves especially useful whenever multilocus DNA fingerprints for parentage exclusion exist while microsatellite markers are not available.     

Retention behaviour of some coumarins in normal-phase high-performance thin-layer and column chromatography

Summary A number of coumarins, furocoumarins and pyranocoumarins were investigated using HPTLC and HPLC systems consisting of silica gel and binary and ternary solvents containing a polar modifier (acetonitrile, dioxane, diisopropyl ether, methyl ethyl ketone, ethyl acetate, 2-propanol or tetrahydrofuran) and a non-polar or weakly polar diluent (n-heptane or dichloromethane). The experimental results obtained on thin layers, under isocratic conditions, showed a linear relationship between the R_M values and the log of the concentration of the polar modifier.The influence of the modifier and the individual substituents in the solute molecule on retention is presented as chromatographic spectra by plotting the R_M and logk values against the mobile phase used.Preliminary communication of this work was presented at the 46th International Congress of Pharmaceutical Sciences, in Helsinki, Finland, 1–5 September, 1986.     

Preparation of reversed-phase high-performance thin-layer plates by in situ reaction with monochlorosilanes

The condition for in situ chemical modification of commercially available thin-layer plates have been varied and the influence thereof upon reversed phase plate properties has been studied. The reaction variables studied were: average silica pore size, silica water content, use of tri- or monochlorosilanes as modifiers, reaction temperature, and addition of base. Coverage and activity of residual silanol groups was studied on modified plates. Desired plate properties are high speed of development in aqueous solvents and low content of active residual silanol groups. Under the conditions tested, the lowest amount of residual silanols was achieved at the expence of the speed of development in aqueous media and vice versa.     

Fingerprinting bacterial strains using ion mobility spectrometry

Ion mobility spectrometry (IMS) is currently in widespread use for the detection and identification of narcotic and explosive compounds without prior sample clean-up or concentration steps. IMS analysis is rapid, less than a minute, and sensitive, with detection limits in the nanogram to picogram range, depending on the target analyte. Our studies indicate that this technique has potential for detection of specific components of bacterial cells and for identification and differentiation of bacterial strains and species within a minute, and with no specialized test kits or reagents required. When microgram quantities of whole bacterial cells are thermally desorbed, complex positive or negative ion patterns (plasmagrams) are obtained. These plasmagrams differ reproducibly for different strains and species and for different conditions of growth, and can be used for the classification and differentiation of specific strains and species of bacteria, including pathogens. Methods for improved ion peak detection, most notably sequential sample desorption at stepped increases in temperature (programmed temperature ramping), are described.     

Optimization of a scanning densitometer for fluorescence detection in high performance thin-layer chromatography

Conditions for maximizing resolution and signal-to-noise ratios in fluorescence scanning densitometry of separations obtained by high performance thin-layer chromatography are described. Resolution was found to be independent of most instrument parameters with a small decrease observed at wide slit widths. Signal was found to be markedly dependent on experimental parameters such as slit width, slit height, sensitivity setting, and the time constant of electronic filters. For recording chromatograms a slit width of 1.00 mm, a slit height slightly greater than the spot diameter, a low sensitivity setting (50 mV), electronic filtering, and a scan rate of 24 or 48 mm min^?1 are commensurate with minimum recording time and maximum sample detectability without incurring a significant decrease in resolution.     

Quantitative evaluation of thin-layer chromatograms. 4. Calculation of fluorescence using Bodó equations

Changes in fluorescence intensity at the far and near side for various spot locations in a sorbent are calculated using a multilayer model and Bodó equations for each sublayer. Flow charts are given for evaluation of reflectance transmission, and fluorescence.     

Quantitative evaluation of thin-layer chromatograms. 1. The calculation of remission and transmission using multilayer models

Quantitative evaluation of TLC by direct photometric scanning is a promising method, in view of the development of cheap microprocessors: soon instruments for digital scanning will be commercialy available. In this paper we describe a multilayer model which seems to be a good approximation for solving the radiation transfer equation in the case of layer models with a gradient in an inward direction. Changes of remitted and transmitted light, in cases where a band lies in different layers, are presented. Examples shown are: the absorbance profile of a chromatographed band in the direction of scanning is approximated to that of an isosceles triangle; the concentration of the band is uniform, e.g. 0.3 A. U.; the concentration of the band is changing from 0 to 2.0 A. U. These results will serve to set up the correct algorithms for digital scanning and simultaneous determination in TLC.