ACS Instrument Practice Test

In GC, how strongly an analyte is retained depends on how it partitions between the moving gas and the stationary phase. A polar stationary phase provides more sites for interactions with polar analytes, such as dipole–dipole interactions and, where relevant, hydrogen bonding. These stronger interactions make polar compounds spend more time in the stationary phase, increasing their retention times and spreading them out from nonpolar compounds. That increased retention and differential interaction improve separation between polar analytes, making a polar phase a better choice for separating them. The other ideas don’t fit because a polar phase does not shorten retention for polar analytes; it lengthens it. No stationary phase can eliminate all co-eluting peaks regardless of polarity, and the polarity of the stationary phase does influence GC separation.