A trimethylsilyl donor with donor strength comparable to BSA and BSTFA
Reacts to replace labile hydrogens on a wide range of polar compounds with a -Si(CH3)3 group
Used to prepare volatile and thermally stable derivatives for GC and MS
Primary advantage of MSTFA is the volatility of its byproduct, N-methyltrifluoroacetamide; MSTFA is the most volatile TMS-amide available, and N-methyltrifluoroacetamide has an even lower retention time than MSTFA
Often TMS derivatives of small molecules can be analyzed when derivatized with MSTFA because the byproducts and reagent itself usually elute with the solvent front
Addition of TMCS aids derivatization of amides, secondary amines and hindered hydroxyls not derivatized by MSTFA alone
Applications
Excellent reagent for use when analyzing drugs of abuse (Amphetamines, Morphine, LSD and THC Metabolites)
MSTFA is an effective trimethylsilyl donor similar to BSA and BSTFA. MSTFA reacts to replace labile hydrogens on a wide range of polar compounds with a -Si(CH3)3 group and is used to prepare volatile and thermally stable derivatives for gas chromatography and mass spectrometry.
One advantage of MSTFA over other silylating reagents is the volatility of its byproduct, N-methyltrifluoroacetamide. MSTFA is the most volatile TMS-amide available and N-methyltrifluoroacetamide has an even lower retention time than MSTFA. TMS derivatives of small molecules can often be analyzed using MSTFA, because byproducts and the reagent usually elute with the solvent front. Silylating reagents containing the trifluoroacetyl moiety, such as MSTFA, act as cleaning agents for flame ionization detectors. When a large number of TMS derivatives is to be analyzed using FID, silicone deposits from the excess derivatizing reagent tend to form on the detector and reduce its sensitivity. This buildup is minimized when derivatizing with reagents based on trifluoroacetic acid because the silicone is volatilized as SiF4, therefore, BSTFA and MSTFA are recommended rather than BSA for these applications.
MSTFA may be used at full strength or diluted with a solvent such as pyridine. In most applications, at least a 1-2 molar ratio of MSTFA per active hydrogen is used. Best results are obtained when the products of the silylation reaction are soluble in the final reaction mixture. Amides, many secondary amines and hindered hydroxyls will not be derivatized by MSTFA alone; however, when a catalyst such as TMCS is added, many of these compounds can be readily derivatized. TMCS is added at concentrations from 1-10% to enhance the reactivity of MSTFA.
References
1. Donike, M. et al. (1969). Quantitative determination of saturated and unsaturated fatty acids as trimethyl esters by gas chromatography.J. Chromatogr. 42: 103 2. Kourou-Daley, S. et al. (1981). A gas chromatographic and mass spectral approach to the analysis of the anticancer drug methyl-G as the trimethylsilyl derivative. Biomed. Mass Spectrosc. 8(5):219 3. Hoffmann, K. et al. (1988). The use of alkoxycarbonyl derivatives for the mass spectral analysis of drug-thioether metabolites. Studies with the cysteine, mercapturic acid and glutathione conjugates of acetaminophen. Biomed. Environ. Mass Spectrom. 15: 637. 4. Ren, S., et al. (1992). O-acetylated gangliosides in bovine buttermilk. Characterization of 7-O-acetyl, 9-O-acetyl, and 7,9-di-O-acetyl GD3. J. of Biol. Chem. 267:12632. 5. Wu, A.H., et. al. (1993). Extraction and simultaneous elution and derivatization of 11-nor-9-carboxy-delta 9-tetrahydrocannabinol using Toxi-Lab SPEC prior to GC/MS analysis of urine. J. Anal. Toxicol. 17:215-217. 6. Mitchell, K., et. al. (2003). Insight into the mechanism of aromatic hydroxylation by toluene 4-monooxygenase by use of specifically deuterated toluene and p-xylene. PNAS 100(7):3784-89. 7. Moriya, F., et. al. (1994). Testing for drugs of abuse in meconium of newborn infants. J. Anal. Toxicol. 18:41-45. 8. Yoo, Y., et. al. (1995). Determination of nalbuphine in drug abusers' urine. J. Anal. Toxicol. 19:120-123.
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