Fluoroacetate samples

Emptage M, J Tabinowski, JM Odom (1997) Effect of fluoroacetates on methanogenesis in samples from selected methanogenic environments. Environ Sci Technol 31 732-734. 

The method developed for sodium fluoroacetate is based on collection of the sample with cellulose ester filters especially low in extractables (Toyo-cel cellulosic ester membrane filters from Nuclepore were used). The samples were extracted with water and analyzed by ion chromatography. Other MCE filters contained high levels of extractables Cfrom wetting agents, surfactants) that... 

Few of these have been found so far, the first not until 1944, in a poisonous South African plant, Gifblaar . The toxic principle of this was identified44 as fluoroacetic acid. A recent summary45 indicates that some 10 fluorinated natural products have now been isolated (in small amounts) largely from other plant sources, their formation being rationalized from the metabolism of fluoroacetate. The exception is nucleocidin (1), an antibiotic from a microbial source (Streptomyces calvus), originating in an Indian soil sample, and which has a ribose moiety carrying fluorine at C4. 

Koryagina, N.L., Savelieva, E.I., Khlebnikova, N.S., Goncharov, N.V., Jenkins, R.O., Radilov, A.S. (2006). Determination of fluoroacetic acid in water and biological samples by GC-FID and GC-MS in combination with solid-phase microextraction. Anal. Bioanal. Chem. 386 1395-1400. 

Mori, M., Nakajima, H., Seto, Y. (1996). Determination of fluoroacetate in aqueous samples by headspace gas chromatography. J. Chromatogr. A 736 229-34. 

Sporkert, F., Pragst, F., Huebner, S., Mills, G.G. (2002). Head-space solid-phase microextraction with 1-pyrenyldiazo-methane on-fibre derivatisation for analysis of fluoroacetic acid in biological samples. J. Chromatogr. B 772 45-51. 

Fig. 2 illustrates the partition coefficient (K) values for these dicarboxylic acid samples in the polar two-phase solvent systems composed of methyl f-butyl ether (MBE)/l-butanol/acetonitrile (AcN)/aqueous 0.1% tri-fluoroacetic acid (TFA), at various volume ratios. K... 

After addition of sample wash with 4 mL of 0.025 M phosphate buffer (pH 7) and elute with 2 x 0.5 mL isopropanol/water/tri-fluoroacetic acid (60 40 0.1). 

Etherification of lower organic acids improves their chromatographic properties and enhances the detection sensitivity. To determine sodium fluoroacetate, Stahr [135] devised a method based on preliminary formation of methyl fluoroacetate. The fluoroacetate was extracted from the sample with methanol, and the water was removed by heating after adding a certain amount of an alkali in order to prevent volatilization of the fluoroacetate. The dehydrated sample was etlierifled in a sulphuric acid—methanol solution, yielding 85% of ethyl ether. The latter was analysed by GC. The detection limit was 1 10" %. 

The mobile phase consists of one or more solvents that are pumped through the chromatographic system, resulting in the separation of analytes. Mobile phases may also contain modifiers. Examples of frequently used solvents include hexane, methanol, 2-propanol, acetonitrile (ACN), and water. Examples of modifiers include tri-fluoroacetic acid, acetic acid, or formic acid. In general, the composition of the mobile phase should be kept simple. Factors that influence the choice of mobile phase include the solubility of the sample in the mobile phase, the polarity of the mobile phase, ultraviolet absorption wavelength, refractive index, and viscosity of the solvents. The purity of the solvents in the mobile phase is also important because the region of UV that is used for the detection of lipids (200-215 nm) must be free of interferences. For phospholipids, the most popular solvent systems are transparent to UV in the range of 200-215 nm they include... 

An efficient procedure for converting polysaccharides into their monosaccharide constituents is by hydrolysis at 121° for 1 hr with 2N tri-fluoroacetic acid. Trifluoroacetic acid is volatile and can be easily removed from the hydrolyzed samples by evaporation in a stream of air. The monosaccharides are converted to the corresponding alditols by reduction with sodium borohydride and the alditols are acetylated with acetic anhydride in the presence of a weak base, such as sodium acetate. The steps involved in converting a polysaccharide into its constituent alditol acetates are summarized in Fig. 1. 

A sample pre-treatment was evaluated to enable the production of intact cationic species of synthetic polymers holding a phosphonate group using MALDI-mass spectrometry. Thus, the polymer (496) obtained by nitroxide-mediated polymerisation was stirred for a few hours in tri-fluoroacetic acid to induce the substitution of a tert-butyl group on the nitrogen of the nitroxide end-group by a hydrogen atom (Scheme 166). 

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