Abstract: The polymeric grade isoprene produced by the extraction and distillation method with dimethylformamide (DMF) contains trace impurities such as cyclopentadiene, 2-butyne, iso-pentenylene, 1-pentyne, cis-1,3-pentadiene, trans-1,3-pentadiene, DMF, and p-tert-butylcatechol (TBC). A gas chromatography method was developed for the determination of these eight trace impurities by central cutting technique with HP-1 as the main analytical column and CP-Al₂O₃/Na₂SO₄ as the auxiliary analytical column. The results showed that 8 kinds of trace impurities could be separated and analyzed on a set of chromatograms by this method; the recovery rates were 95.6%-104.9%, the relative standard deviation was less than 2.2%, indicating high accuracy and reliability. Compared with the general method, the sensitivity of isoprene analysis was significantly improved by changing the packed column chromatography system to the capillary column system, it could meet the analysis requirements of isoprene and butyl rubber raw materials, and the accuracy of analysis results could be improved by using external standard method. It could simultaneously measure the content of DMF and TBC, saving analytical instrument resources and reducing workload. This method has been used for daily quality monitoring of isoprene, and its stability and reliability have been fully verified.

Key words: central cut gas chromatography, polymer-grade isoprene, trace impurities, external standard method, gas chromatography