Trifluoroacetyl deriv for

The relative response of the electron-capture detector to some haloalkylacyl derivatives is sumi rized in Table 8.17 [451]. In general terms, the monochloroacetyl and chlorodifluoroacetyl derivatives provide a greater response than the trifluoroacetyl derivatives. Increasing the fluorocarbon chain length of the fluorocarbonacyl derivatives increases t ir electron-capture detector response without inconveniently increasing their retention times. The heptafluorobutyryl and pentafluoropropionyl derivatives are considered to be the best compromise between detector sensitivity and volatility for most applications. 

Fan et al. [106] developed a high performance capillary electrophoresis method for the analysis of primaquine and its trifluoroacetyl derivative. The method is based on the mode of capillary-zone electrophoresis in the Bio-Rad HPE-100 capillary electrophoresis system effects of some factors in the electrophoretic conditions on the separation of primaquine and trifluoroacetyl primaquine were studied. Methyl ephedrine was used as the internal standard and the detection was carried out at 210 nm. A linear relationship was obtained between the ratio of peak area of sample and internal standard and corresponding concentration of sample. The relative standard deviations of migration time and the ratio of peak area of within-day and between-day for replicate injections were <0.6% and 5.0%, respectively. 

Molecular ions were observed by gas chromatography-mass spectrometry (GC-MS) analysis for trifluoroacetyl 58 and trimethylsilyl 60 derivatives of mesocarb (sydnocarb) 59 (Section 5.03.12) <1999JMP1079>. Unlike the silyl derivative 60 and sydnones <1996CHEC-II(4)165>, no [M+—NO] ion was observed for trifluoroacetyl derivative 58. The characteristic ions PhCH2(Me)CH+ (m/z 119) and PhCH2+ (tn/z 91) were observed for both derivatives 58 and 60. 

A sensitive method for primary amines is shown in reaction 2, leading to the corresponding 7V-benzenesulfonyl-/V-trifluoroacetyl derivatives. These can be determined by GC-ECD using SE-30 columns LOD 1-5 pg, which is about 200 times more sensitive than GC-FID. The method was applied for determination of phenethylamine (33) in urine110. This analysis was performed also by LLE into n-pentane, derivatization to the benzenesulfonamide and GC-FPD using a capillary column recoveries of aliphatic primary amines in urine were 91-107%, RSD 0.2-4.5%111,112. Amines in environmental waters and sediments were determined after LLE with dichloromethane, derivatization with benzenesulfonyl chloride and GC-SIM-MS LOD 0.02-2 pg/L of water and 0.5-50 ng/g of sediment113. 

A gas chromatographic method was described for the determination of isoxsuprine after its extraction from plasma [32]. The method is based on the reaction of the analyte with trifluoroacetic anhydride to form the trifluoroacetyl derivative. The GLC analysis was carried out a 3% OV-17... 

The energy barriers and relative conformer stabilities have also been obtained and interpreted for a number of N-trifluoroacetyl derivatives (84BSB927) 119 in all those examined the Z-conformer prevails. 

Gas chromatography and capillary column GC represent by far the most developed and most used analytical techniques for the determination of multiple trichothecenes, especially in view of the possibility of employing MS for confirmation of the peaks. The available methods, such as the Scott and Ware methods (90,91), differ in sample extraction, sample cleanup, and the derivatization step. Heptafluorobutyryl (HFB), trimethylsilyl (TMS), and trifluoroacetyl derivatives are frequently used, coupled with electron capture detection. A GC method (92) has recently been collaboratively tested in barley and malt and accepted by the American Society of Brewing... 

Diamide Chiral Separations. The first chiral stationary phase for gas chromatography was reported by Gil-Av and co-workers in 1966 (113) and was based on Al-tfifluoroacetyl (ZV-TFA) L-isoleucine lauryl ester coated on an inert packing material. It was used to resolve the trifluoroacetylated derivatives of amino acids. Related chiral selectors used by other workers included -dodecanoyl-L-valine-/-butylamide and... 

In an alternative route employing fewer overall steps, Borbas and Lipt k119 synthesized the trisaccharide hapten as a 4-aminophenyl glycoside protected as the (V-trifluoroacetyl derivative 13 for potential conjugation to protein.108 Ethyl 1-thio-a-L-rhamnopyranoside as the 2,3-O-diphenylmethylene acetal 23 was the precursor for both rhamnosyl residues. Condensation of 23 with glycosyl bromide 24 with silver triflate as promoter, followed by O-deacetylation and O-benzyliden-... 

Finally, we have encountered situations where carbon-14 from a labeled pesticide has been incorporated into normal natural products including amino acids. We were interested in seeing if we could separate the normal amino acids from a protein hydrolysate on a single column with sufficient resolution to identify separate amino acids. Figure 11 shows a radiochromatogram of the separation of sixteen standard C-amino acids. Were this a product of a metabolism study, we could then isolate any of these fractions, convert the residual amino acid to the N-trifluoroacetyl 0-butyl derivative for gas chromatography ar.d further confirmation of structure. 

The electronegative trifluoroacetyl group would strengthen this interaction accounting for the difference in reactivity between the acetyl and trifluoroacetyl derivatives. 

Of halogenated acetyl derivatives, trifluoroacetyl derivatives are mainly used for the sensitive analysis of amines, particularly owing to their better chromatographic properties despite their ECD response being lower than that of chloroacetyl derivatives (cf., Table 4.7, p. 69). Trifluoroacetyl derivatives were exploited for the GC separation of a mixture of saturated and unsaturated homologues of amines up to C22 on conventional packed columns [71]. Mori et al. [72] developed a method for the quantitative and qualitative GC analysis of m- and p-xylenediamines in polyamides in the form of their t N -trifluoro-acetyl derivatives. An analogous method was elaborated for the analysis of ethanolamine for the presence of mono-, di- and triethanolamine [73]. A 1-ml volume of TFA anhydride is stoppered in a 2-ml vial, which is evacuated with the aid of a 10-ml injection syringe. 

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