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The Solvent Shield: The Role of the Solvent in Blocking Active Sites

9 Feb 2009

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A recent project afforded me the chance to observe the role a solvent can play in blocking surface activity in inlet liners and, as a consequence, lowering degradation for some analytes. In my case, the analytes of interest were endrin and 4,4'-DDT. I examined solutions made in three different solvents: methanol, MTBE, and hexane. All other things being equal, there was a marked difference in the observed degradation for both compounds that was solvent-dependent. Endrin breakdown consistently decreased as solvent polarity increased. One rationale is that polar solvents like methanol will hydrogen-bond to active silanol groups on the liner surface, reducing the acid-catalyzed opening of endrin’s epoxide moiety. 4,4'-DDT more or less followed the same trend, though the breakdown mechanism must certainly be different in its case. I’d love to hear from colleagues who have used this to their advantage! If you’d like information about analytical conditions, please write.