将粗苯均四甲酸二酐(PMDA)样品与甲醇回流2 h,冷却后用甲醇将甲醇回流液稀释至100 mL,分取20 μL进样,用高效液相色谱法测定其中苯均四甲酸含量。采用的色谱柱为Agilent RP18柱(4.6 mm×200 mm,10 μm),流动相为磷酸(0.1+99.9)溶液与甲醇以体积比为80比20组成的混合溶液,流量为1.0 mL·min-1,紫外检测波长为220 nm。在此条件下,粗苯均四甲酸二酐中共存的4种组分,苯均四甲酸二酐酯化产物、1,2,4-苯三甲酸酐、邻苯二甲酸、苯均四甲酸可得到有效分离。

Sample of Crude pyromellitic dianhydride (PMDA) was refluxed with methanol for 2 h, and after cooling the methanol extract was diluted to 100 mL with the same solvent. 20 μL of the solution were introduced into the instrument and content of pyromellitic acid (PMA) was determined under the following chromatographic conditions: ① chromatographic column: Agilent RP18 column (4.6 mm×200 mm, 10 μm); ② mobile phase: mixture of methanol and H3PO4 (0.1+99.9) solution (20+80 by vol.); ③ flow-rate: 1.0 mL·min-1; ④ wavelength of UV-detection: 220 nm. Under the optimized conditions mentioned above, effective separation was achieved among the 4 components present together with the crude PMDA, i.e., the esterification product of PMDA, 1,2,4-benzenetricarboxylic-1,2-anhydride, phthalic acid and pyromellitic acid.