Determination of Monomer Residues in Poly(lactide-co-glycolide) as Carrier of Sustained Release Preparation by Gas Chromatography with Sample Injection after Dissolving-Precipitation

In order to reduce the effect of poly(lactide-co-glycolide) (PLGA) on the determination of monomer residue, the work as mentioned by the article was done, using dichloromethane as solvent and n-hexane as precipitant. About 0.1 g of sample was dissolved in 7 mL dichloromethane (solvent), and then the solution was placed into a 10 mL-volumetric flask and n-hexane (precipitant) was added to dilute to the scale. After shaking and centrifuging, the supernatant was taken as the test solution. Agilent HP-INNOWax capillary column was used for separation and FID was used for detection, and the two monomers of glycolide and lactide in the above solution were determined by gas chromatography. As shown by the results, the dissolving-precipitation method could effectively reduce the system pollution caused by direct injection method and greatly improve the detection accuracy. Linear relationships between values of peak area and mass concentration of two monomers were found in the range of 0.005-0.060 g·L^-1, with detection limits (3S/N) of 2.0 mg·L^-1 for glycolide and 1.0 mg·L^-1 for lactide. The spiked recoveries were 97.0% and 101%, respectively. The precision test of the mixed reference solution and the test solution were carried out, with RSDs (n=6) of the determined values less than 3.0%. The method was applied to analysis of three batches of samples, and the residues of two monomers were less than 0.050%.