Hello, I have a question regarding unstable retention time. GC conditions are used for hydrocarbon impurity analysis in propylene samples, and use an Al2O3 column. The problem that arises is the difficulty of identifying the components "1,3-butadiene" and "methyl acetylene" which are often imprecise. The retention time range is 15 to 16.6 minutes. Is there a solution to solve this problem?