Flophemesyl, ISP-flophemesyl, tert.-buflophemesyl and CM-flophemesyl derivatives of a wide range of organic functional groups can be prepared and have good gas chromatographic and electron-capture detector properties. The derivatives are compared in terms of volatility, hydrolytic stability, detector response and mass spectral properties. Bis(pentafluorophenyl)chloromethylmethylsilane is evaluated as a reagent for preparing derivatives of strong nucleophiles. CM-flophemesyl chloride is evaluated as a cyclizing reagent for preparing derivatives of β- and γ-hydroxyamines. The flophemesyl derivative of N-nitrosodiethanolamine is shown to be suitable for detecting this compound at trace levels.