N;O-bis-trimethylsilyl-trifluoroacetamide: m.w. 257.4; Bp 40°C (12mm Hg); density d20°/4° = 0.961. BSTFA: R = CF3 powerful trimethylsilyl donor with approximately the same donor strength as the non-fluorinated analogue BSA. Advantage of BSTFA over BSA: greater volatility of its reaction products (particularly useful for GC of some lower boiling TMS amino acids. BSTFA is nonpolar (less polar than MSTFA); and can be mixed with acetonitrile for improved solubility. For silylating fatty acid amides; hindered hydroxyls and other compounds; which are difficult to silylate (like secondary alcohols and amines); we recommend BSTFA + 1% trimethylchlorosilane (TMCS); available under the designation SILYL-991.