Acylation reagents for GC - Bisacylamides

For improved volatility, better thermal stability or low limit of detection in gas chromatography prerequisite: quantitative, rapid and reproducible formation of only on derivative halogen atoms introduced by derivatisation (e.g. trifluoroacetates) allow specific detection (ECD) with the advantage of high sensitivity elution order and fragmentation patterns in MS can be influenced by a specific derivatisation.
Reagents for silylation - alkylation (methylation) - acylation are available.

Acylation with fluorinated acid amides is recommended for alcohols, primary and secondary amines as well as for thiols under mild, neutral conditions. MBTFA also forms very volatile derivatives with carbohydrates.

by-products: corresponding neutral acylamides, which can be easily removed due to their high volatility; because of neutral conditions and favourable chromatographic properties often removal of the bisacylamide is not necessary. Thus sample preparation is much more convenient.

MBTFA / MBHFBA
N-methyl-bis(trifluoroacetamide) MBTFA
m.w. 223.08, Bp 123 - 124°C (760mm Hg), density d20°/4° = 1.55,
CF₃ - CO - N(CH₃) - CO - CF₃