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CN-121994941-A - Separation qualitative and quantitative detection method for L-lactide, D-lactide and Meso-lactide

CN121994941ACN 121994941 ACN121994941 ACN 121994941ACN-121994941-A

Abstract

The invention relates to a method for qualitatively and quantitatively detecting separation of L-lactide, D-lactide and Meso-lactide, which belongs to the field of lactide optical purity detection and comprises the following steps of firstly, respectively establishing standard curves of various lactide with different configurations, wherein the concentration range of the standard curves is 10-1000mg/L, the various lactide with different configurations comprises one or more of L-lactide, D-lactide and Meso-lactide, secondly, detecting and quantitatively calculating a lactide to be detected by using a gas chromatography-mass spectrometer, and the concentration range of the lactide to be detected is 200-1000 mg/L.

Inventors

  • LIU ZHONGSHI
  • WANG SIZHI
  • XIONG FENG
  • ZHOU XUDONG

Assignees

  • 中石油(上海)新材料研究院有限公司
  • 中国石油天然气股份有限公司

Dates

Publication Date
20260508
Application Date
20241105

Claims (10)

  1. 1. The qualitative and quantitative detection method for the separation of L-lactide, D-lactide and Meso-lactide is characterized by comprising the following steps: Step one, respectively establishing standard curves of various lactide with different configurations, wherein the concentration range of the standard curves is 10-1000mg/L, and the various lactide with different configurations comprises one or more of L-lactide, D-lactide and Meso-lactide; Detecting and quantitatively calculating a lactide to-be-detected object by using a gas chromatography-mass spectrometer, wherein the concentration range of the lactide to-be-detected object is 200-1000mg/L; The gas chromatography mass spectrometry technology has the following conditions: The chromatographic column is a full methylation-beta-cyclodextrin chromatographic column, and has the specification of (25-50) m multiplied by 0.25mm multiplied by 0.25 mu m; The spacer purge flow is 3mL/min; The temperature of the chromatographic column is raised in such a way that the initial temperature is 50-120 ℃, the temperature is raised to 180-200 ℃ at the rate of 10-20 ℃ per minute, and the chromatographic column is kept for 5-15min; the equilibrium time of the chromatographic column is 0.5-2min; the temperature of the sample inlet is 180-200 ℃; the carrier gas is helium; The flow rate of the carrier gas is 1.0-2.0mL/min; The split ratio is 20-50:1; the sample injection amount is 0.1-1uL; A mass spectrum scanning mode, namely a total ion scanning mode or a selective ion scanning mode; the temperature of a mass spectrum transmission line is 200-220 ℃; ion source temperature 230 ℃; the temperature of the four-stage rod is 150 ℃; The solvent delay time is 4-6min; The scanning quality range is 12-600m/z; the scanning speed is 1562u/s; Selecting an ion scanning mode, wherein the quantitative ion selection mass-to-charge ratio is 56, and the auxiliary quantitative ions are 144 and 45; The ion residence time is 80-100ms.
  2. 2. The method for qualitative and quantitative detection of L-lactide, D-lactide and Meso-lactide according to claim 1, wherein in the first step, when the relative proportion of a certain configuration of lactide is lower than 1%, the concentration range of the standard curve is adjusted to 10-200mg/L so as to reduce the fitting error of the standard curve of lactide.
  3. 3. The method for qualitative and quantitative detection of L-lactide, D-lactide and Meso-lactide according to claim 1, wherein in the second step, when the chemical purity P chemical or the major optical configuration content P majoroptical of the lactide to be detected is lower than 50%, the concentration range of the lactide to be detected is increased to 1/P chemical or 1/P majoroptical times of the original concentration range.
  4. 4. The method for qualitative and quantitative detection of L-lactide, D-lactide and Meso-lactide according to claim 1, wherein in the second step, when the concentration of the lactide analyte is less than 7.0mg/L, the mass spectrum scanning mode adopts a selective ion scanning mode.
  5. 5. The qualitative and quantitative detection method for separation of L-lactide, D-lactide and Meso-lactide according to claim 1, wherein in the second step, the inner diameter of the chromatographic column is 0.25mm, the length of the chromatographic column is 50m, and the thickness of the stationary phase film is 0.25um.
  6. 6. The qualitative and quantitative detection method for separation of L-lactide, D-lactide and Meso-lactide according to claim 1, wherein the good solvent for dissolving a plurality of lactide and lactide to be detected with different configurations is one or a mixture of methanol, ethanol, ethyl acetate, acetonitrile, acetone and chloroform.
  7. 7. The qualitative and quantitative detection method for separation of L-lactide, D-lactide and Meso-lactide according to claim 6, wherein the solution of lactide and lactide to be detected with different configurations dissolved in good solvent is filtered to remove insoluble impurities.
  8. 8. The qualitative and quantitative detection method for the separation of L-lactide, D-lactide and Meso-lactide according to claim 7, wherein an organic filter membrane is selected in the filtration process, and the organic filter membrane is one or more of a nylon membrane, a polypropylene membrane and a polytetrafluoroethylene membrane with a filter diameter of 0.22-0.45 um.
  9. 9. The qualitative and quantitative detection method for the separation of L-lactide, D-lactide and Meso-lactide according to claim 1, wherein in the second step, when organic acid residues exist in the lactide to be detected, 20 to 50uL of N-methyl-N- (trimethylsilyl) trifluoroacetamide containing 1% trimethylchlorosilane is additionally added when the lactide to be detected is dissolved, and a 40 to 50 ℃ thermostatic water bath is used for 5 to 15 minutes.
  10. 10. The method for qualitative and quantitative detection of L-lactide, D-lactide and Meso-lactide according to claim 1, wherein the lactide to be detected is crude lactide which has not been purified by distillation.

Description

Separation qualitative and quantitative detection method for L-lactide, D-lactide and Meso-lactide Technical Field The invention relates to the field of lactide optical purity detection, in particular to a qualitative and quantitative detection method for separation of L-lactide, D-lactide and Meso-lactide. Background Since the fifties of the last century, the total world plastic production has exceeded 78 million tons, with about 79% of plastic products being landfilled or disposable causing serious soil, marine environmental pollution problems, only about 21% being disposed of by recycling and incineration. With the increasing severity of the 'white pollution', various laws and regulations for limiting and forbidding plastic are actively promoted in various countries around the world. The bio-based degradable material replacing the traditional plastic becomes one of the new research and development hot spots in the global academia and industry. Polylactic acid is a bio-based degradable aliphatic polyester, and an unstable ester bond of the polylactic acid can be hydrolyzed under the combined action of acid-base catalysis and microbial degradation enzymes, so that carbon dioxide and water are finally generated. Polylactic acid has excellent mechanical properties, physical properties, biocompatibility and air permeability, so that the polylactic acid has wide market demands in the fields of express packaging, textile clothing, biological medicine, degradable agricultural films and the like. The lactide ring-opening polymerization method is a main process route for polylactic acid synthesis at present. The lactic acid is dehydrated and condensed into low molecular weight poly-D, L-lactic acid, the poly-D, L-lactic acid is catalyzed by a tin-based catalyst to carry out back biting reaction and depolymerization under the condition of high temperature and high vacuum to generate lactide, and the lactide is subjected to ring-opening polycondensation after rectification and purification to obtain a polylactic acid product. Lactide is an important polymerization intermediate in the ring-opening polymerization process, and the chemical purity and the optical purity of the lactide directly influence the performance index and the production cost of polylactic acid products. L-lactic acid and D-lactic acid randomly arranged in the oligomeric lactic acid chain produce three optical isomers, L-lactide, D-lactide, meso (Meso) -lactide during depolymerization. Taking L-polylactic acid (PLLA) as an example, D-lactide and MESO-lactide impurities in the L-lactide raw material can reduce the crystallinity and crystallization rate of polylactic acid, further weaken the mechanical property and processing property of the polylactic acid, and reduce the melting point, glass transition temperature and biodegradation rate of the material. Therefore, the optical purity detection of the lactide has important significance for regulating and controlling the performance of the polylactic acid product and the industrial production cost. The current method for detecting the optical purity of lactide is mainly divided into the following steps: CN113292531A, CN104837889A quantitatively integrates methyl or methylene peaks according to chemical displacement difference of L-lactide and MESO-lactide by using a nuclear magnetic method, so as to obtain the ratio of the L-lactide to the MESO-lactide; the method has the disadvantages that the nuclear magnetic hydrogen spectrometry cannot separate enantiomer L-lactide and D-lactide with the same chemical environment, and the quantitative accuracy of the method is influenced by the magnetic field intensity of a magnet and the integral error caused by overlapping of an impurity peak and a peak to be detected. The quadruple peaks of L-lactide and MESO-lactide methylene partially overlap at 5.2ppm, are not suitable for accurate quantification, and are easy to be interfered by methyl signals in the oligolactic acid, water and impurities although the methyl peak has good separation degree at 1.5ppm, so that the quantification error of lactide samples with lower chemical purity is larger. CN106153418A, CN114478470A used methyl polysiloxane and polyethylene glycol based chromatography column for GC-FID quantitative analysis of L-lactide and MESO-lactide. The method has the disadvantage that the separation capability is poor through the comparison test, and the shoulder peak appears between the signal peaks of the L-lactide and the MESO-lactide. The lobe information of the acromion mass spectrogram is characterized as lactide, and the integration attribution of the acromion can have serious influence on the quantitative accuracy. The specific optical rotation method is another commonly used L/D-lactide ratio analysis method, and is commonly used for assisting the method to make up for the defect of weak enantiomer separation capability, but the optical rotation of the oligomeric lactic acid impurity in the