Polyglycolic acid (PGA) is a biologically friendly material with a wide range of applications. The production of dimethyl oxalate using coal-based syngas and the hydrogenation of dimethyl oxalate can produce the polymerization raw material of PGA, glycolide, which requires a methyl glycolate polymerization and depolymerization process. The intermediate products of the production process were analyzed using gas chromatogram-mass spectrometry (GC-MS) and Orbitrap mass spectrometry (Orbitrap MS), which revealed the presence of cyclic and linear PGAs with different capped ends. The impurities present in the oligomer were mostly methyl-capped PGA and were retained in the subsequent depolymerization process to glycolide, solvent washing can be used to remove this part of the impurity and ultimately obtain a refined glycolide product. Furthermore, it is proposed that the use of the specialized Kendrick Mass Defect (KMD) to plot and analyze PGA compounds obtained using mass spectrometry can enable the direct classification of PGAs without the need for exact molecular formula assignment.

The input of chlorophyll provides key information for reconstructing paleoproductivity and tracing diagenesis in geological matrices. However, accurate analysis is hampered as chlorophyll readily suffers from demetallation and carbon-chain cleavage, leading to a complex mixture of modified Mg(II) porphyrins and porphins. Here, we developed a copper substitution pretreatment that selectively converts native chlorophyll, its derived Mg(II) porphyrins and porphins (chlorophyll-derived porphyrins) into stable Cu(II) porphyrins, thus enabling a comprehensive qualitative and quantitative analysis of the chlorophyll-derived pool. The method was evaluated using model compounds and ultra-performance liquid chromatography coupled with ultra-high-resolution mass spectrometry (UPLC-Orbitrap MS). It demonstrated >95% conversion of chlorophyll a with CuCl2 and 89% for porphin with Cu sheets, whereas non-target Ni(II), V(IV), and Fe(III) porphyrins remained unaffected. Applied to lake sediments, the pretreatment enabled specific analysis of chlorophyll-derived porphyrins against complex geological matrix. This strategy unifies chlorophyll-derived porphyrins into a single detectable form, offering a selective approach for the accurate reconstruction of initial chlorophyll input and composition in geological samples.