AIM: To synthesize biodegradable poly lactic acid (PLA) through the optimization and selection of process and catalyst.METHODS: This experiment was performed at the Research Center for Green Chemistry and Technology in the School of Municipal and Environmental Engineering of Harbin Institute of Technology from February 2003 to October 2004. Biodegradable poly L-lactic acid (PLLA) was synthesis by melt polycondensation using L-lactic acid (LA) as material. Firstly, oligo L-lactic acid (OLLA) was prepared by dehydrating aqueous solution of LA without catalyst. And then, the mixture of OLLA and catalyst was heated at a certain temperature and pressure for a period of time to get the product of PLLA. The structure of PLLA was characterized by Fourier transform infrared (FTIR) spectra and 1H- nuclear magnetic resonance (1H-NMR) spectra. The polydispersity was determined by gel permeation chromatography (GPC).RESULTS: OLLA with the viscosity average molecular weight (Mη) of 6 500 g/mol was prepared by the following steps: the solution of LA without catalyst was dehydrated at 140 ℃, first at reduced pressure of 30 kPa for 2 hours, and then at 5 kPa for 4 hours. SnCl2-p-toluenesulfonic acid (TSA) system was the effective catalyst for the polycondensation of OLLA. After the mixture of OLLA and catalysts polycondensed at 165 ℃ and 5 kPA for about 8 hours, PLLA with the Mη of 65 000 g/mol was obtained by using SnCl2-TSA system as catalyst with the SnCl2 amount of 0.4wt% to OLLA and equal mol ratio of SnCl2 and TSA.CONCLUSION:PLLA with a certain practicability was obtained under the optimal process and catalyst. Oligomerization of LA played an important role on improving the molecular weight of PLLA.

A simple and sensitive capillary electrophoresis method with field-enhanced stacking concentration for the analysis of protocatechuic aldehyde, protocatechuic acid, danshensu, rosmarinic acid and salvianolic acid B in Salvia miltiorrhiza var. miltiorrhiza f. alba was developed. The separation was achieved with a fused-silica capillary (75 microm x 50.2 cm, effective length was 40 cm) and a running buffer 15 mmol x L(-1) borax (pH 10.0) containing 20% CH3 OH. The UV detection wavelength was 210 nm. The applied voltage was 28 kV, and the cartridge temperature was 25 degrees C. Water plug was introduced from the anode by 0.5 psi x 4 s before injection. Sample was injected by electrokinetic injection - 8 kV x 3 s. The linear range of protocatechuic aldehyde is 3.0-60.00 mg x L(-1) (R2 = 0.999 8); that of protocatechuic acid, danshensu, rosmarinic acid and salvianolic acid B are 1.0-20.00 mg x L(-1) (R2 are 0.999 1, 0.999 4, 0.998 9 and 0.999 8, respectively), and the limits of detection of five analyts are 0.55, 0.40, 0.25, 0.32, 0.38 microg x L(-1), respectively, Stacking factor is higher and precision is satisfactory. The recoveries ranges were from 97.3% to 99.8%. The proposed method was used to determine the protocatechuic aldehyde, protocatechuic acid, danshensu, rosmarinic acid and salvianolic acid B in S. miltiorrhiza var. miltiorrhiza f. alba. The proposed method is simple, rapid, accurate and high sensitivity, and can be used to control of the quality of S. miltiorrhiza var. miltiorrhiza f. alba.
Benzaldehydes ; analysis ; Benzofurans ; analysis ; Catechols ; analysis ; Cinnamates ; analysis ; Depsides ; analysis ; Electrophoresis, Capillary ; methods ; Hydroxybenzoates ; analysis ; Lactates ; analysis ; Plant Extracts ; analysis ; Quality Control ; Salvia miltiorrhiza ; chemistry ; Sensitivity and Specificity ; Solubility ; Water