[Preparation method of polystyrene core-poly (acrylamide-acrylic acid) shell fluorescent microspheres].

OBJECTIVE: To investigate the preparation method of polystyrene core-poly (acrylamide-acrylic acid) shell fluorescent microspheres. METHODS: The polystyrene core-poly (acrylamide-acrylic acid) shell (P-(St-co-AAM)) fluorescent microspheres were prepared using fluorescent microspheres as the core and acrylamide/acrylic as polymerization monomer. Reaction conditions affecting the morphology of core-shell structure including feeding mode, initiator, cross linker, pH, concentration and swelling were studied. RESULT: Fluorescent microscopy showed that the relatively uniform particle sizes were distributed in a range of 7-8 µm. Fourier transform infra-red spectroscopy (FT-IR) proved the existence of poly (acrylamide-acrylic acid) shell and amide group on the surface. The optimal conditions for seeding polymerization: azobisisobutyronitrile was used as the initiator in the absence of cross linker, after a 40 h swelling treatment by using alcohol with the appropriate reaction temperature (70 degree), reaction time (3 h) and pH(6-7). The average dispersion and stability were 25.14 % and 90.21%, respectively. The fluorescein release percentage was kept stable at approximately 30% after 40 h. CONCLUSION: The fluorescent microspheres prepared by this method have core-shell structure and satisfactory fluorescence properties with good dispersion and stability.

[Clustering analysis applied to near-infrared spectroscopy analysis of Chinese traditional medicine].

The present article discusses the clustering analysis used in the near-infrared (NIR) spectroscopy analysis of Chinese traditional medicines, which provides a new method for the classification of Chinese traditional medicines. Samples selected purposely in the authors' research to measure their absorption spectra in seconds by a multi-channel NIR spectrometer developed in the authors' lab were safrole, eucalypt oil, laurel oil, turpentine, clove oil and three samples of costmary oil from different suppliers. The spectra in the range of 0.70-1.7 microm were measured with air as background and the results indicated that they are quite distinct. Qualitative mathematical model was set up and cluster analysis based on the spectra was carried out through different clustering methods for optimization, and came out the cluster correlation coefficient of 0.9742 in the authors' research. This indicated that cluster analysis of the group of samples is practicable. Also it is reasonable to get the result that the calculated classification of 8 samples was quite accorded with their characteristics, especially the three samples of costmary oil were in the closest classification of the clustering analysis.