Determination of monomer residues in polylactic acid by gas chromatography - Master's thesis - Dissertation

1206RGB (single)

Single chip microcomputer STM32L151CCU6

WIFI test head can be customized for other specifications

Test - lowercase jpg

Kaixin micro test

1 Introduction

Polylactic acid has broad application prospects in the field of biomedical engineering because of its good biocompatibility and biodegradability. The polylactic acid we synthesized uses lactide as a monomer. In order to effectively control the quality of the product, it is necessary to check the monomer residue of this product [1-3]. The current method for determining lactide residues is hydrogen nuclear magnetic resonance, but it cannot be quantified. Therefore, it is necessary to establish a simple and practical analytical method for the determination of residual monomers of polylactic acid, which is necessary for the research and development of polylactic acid and the control of production process.

We used capillary gas chromatography to determine the lactide monomer residues in polylactic acid.

2 instruments and reagents

Beijing Puri GC-7800 gas chromatograph; column: 30QC3/AC20-0.5 capillary column, 30m × 0.32mmI.D. (bonded phase is polyethylene glycol); FID detector; carrier gas is high purity nitrogen; Lactide is a domestic analytical reagent.

3 methods and results

3.1 chromatographic conditions

Capillary column: 30m × 0.32mmI.D. The bonded phase is polyethylene glycol; column temperature: 150 ° C; inlet temperature is 280 ° C; detector temperature is 150 ° C; nitrogen (N2) pressure is 150 kPa, The hydrogen (H2) pressure was 100 kPa; the combustion gas (air) pressure was 50 kPa, and the base pressure was 300 kPa. Direct injection, injection volume: 1μl. The chromatogram is shown in Figures 1 and 2.

3.2 Preparation of reference solution

Weigh accurately 0.1022g of lactide, place it in a 10ml volumetric flask with a small amount of chloroform, shake it, add chloroform to the mark, and use it as a reference stock solution 5.

3.3 line shape and range

Precisely measure 5ml of the reference stock solution, place it in a 10ml volumetric flask, add chloroform to the scale, and use it as No. 4 solution; accurately measure 1, 5ml in the sample liquid of No. 4, place it in a 10ml volumetric flask, add trichlorochloride. Methane was used as the No. 2 and No. 3 solution; 1 ml was accurately weighed in the No. 2 solution, placed in a 10 ml volumetric flask, and chloroform was added to the mark to prepare the No. 1 solution. Each precision was taken in 1 μl and injected directly.

The linear regression is performed with the concentration C as the abscissa and the peak area A as the ordinate. The regression equation of the PLA monomer is obtained as follows:

A=1.04951×10-6C+0.003048

R=0.99999

As can be seen from the above, the linear relationship between the respective peak areas in the range of 0.01022 to 10.22 mg/ml is good, as shown in Table 1. Table 1 lactide linear relationship

3.4 Minimum detection limit determination

With standard solution 0.01022mg/ml, continuously diluted, each dilution, sample injection, GC, requires: S / N ≥ 3, the minimum detection limit of PLA monomer measured is 3.413μg / ml.

3.5 precision test

Accurately measure 5 ml of No. 3 solution in a 10 ml volumetric flask, add chloroform to the mark, and test according to the above chromatographic conditions. The RSD of the peak area of ​​the lactide was measured to be 4.8%, as shown in Table 2. Table 2 lactide precision test

3.6 recovery test

Accurately weigh PLA (lot number 2008111801) about 1g, and accurately measure 2ml stock solution (I), put it in the same volumetric flask, add chloroform to volume, dissolve, shake, and accurately measure 1μl for direct injection According to the above chromatographic conditions, the average recovery of lactide was calculated to be 99.8%, and the RSD was 0.18%.

3.7 Determination of sample residue

Sample: Precision weighed PLA1.0031g in a 10ml volumetric flask, add chloroform to volume, control: precision weighed reference substance 0.9956g in a 10ml volumetric flask, add chloroform on the scale.

Separately weigh 1μl, direct injection according to the Chinese Pharmacopoeia 2005 edition two appendix VIIIP second method, according to the method of repeatability to determine the peak area of ​​the sample reference solution; according to the external standard method to calculate the peak area. The peak area of ​​the sample was determined to be 51387, the monomer residue was 0.049%, the peak area of ​​the reference product was 443,440, and the monomer residue was 0.42%.

4 Conclusion

In summary, by gas chromatography analysis, under the chromatographic conditions determined in this study, the residual amount of lactide monomer in polylactic acid can be quickly and accurately analyzed.