Trimethylanilinium hydroxide

A brief comment should be made concerning the technique of "on-column" methylation. This is a technique wherein a methylating agent is injected along with the drug into the gas chromatograph whose temperatures initiate and complete derivatization. Trimethylanilinium hydroxide is the most commonly employed reagent and has been used to form the 1,3-dimethyl derivatives of barbiturates which do not form stable TMS derivatives (29). 

Skinner et al. (55) used GC/MS in their analyses of barbiturates. Samples were methylated (1,3-dimethyl derivatives) on-column using trimethylanilinium hydroxide. The analysis was conducted on 3% OV-1 on Gas Chrom Q. Temperature was programmed from 120 to 220°C at 10°C/min. 

FS Tanaka, RG Wien. Gas chromatography of substituted phenylureas by flash-heater methylation with trimethylanilinium hydroxide. J Chromatogr 87 85-93,1973. 

L Ogierman. Analysis of phenylurea herbicides by formation of methylated derivatives in the gas-liquid chromatograph using trimethylanilinium hydroxide. Fresenius Z Anal Chem 320 365-368, 1985. 

E. Brochmann-Hanssen and T. O. Oke, Gas chromatography of barbiturates, phenolic alkaloids, and xanthine bases Flash-heater methylation by means of trimethylanilinium hydroxide, J. Pharm. Sci., 55 370(1969). 

Methylation of the phenolic OH in the product of Emde degradation decinine (32) with trimethylanilinium hydroxide (24) resulted in cleavage the lactone ring to yield derivative 33. 

Our original method for A9-THC explored this problem to some extent. Rather than attempt the synthesis of deutero labeled A9-THC we decided to analyze A9-THC as its own methyl ether (Fig. 2). Our internal standard would be l-0-perdeuteriomethyl-A9-THC. It was proposed to convert A9-THC to its 1-0-methyl ether for the analysis. This was effected by the co-injection of trimethylanilinium hydroxide and A9-THC. At the elevated temperatures of the injector port the phenol is converted to its methyl derivative. This conversion is both reproducible and quantitative. It is therefore suitable for use in any analytical technique. ... 

The problem of lipophiles remained and here again we could make use of the acid functionality of the phenols. With less lipid soluble phenols such as the steroids, simple back extraction from organic solvent into strong base would have been sufficient. However, the high lipid solubility of A9-THC necessitated that extraction be carried out with Brodie s solvent (hexane and isoamyl alcohol) and that back extraction be done with Claisen s alkali, which is a mixture of KOH, methanol, and water. After acidification of the Claisen s alkali, A9-THC could be recovered by extraction. The external standard and the trimethylanilinium hydroxide were added and the extracted phenol (i.e. A9-THC) was converted to the 1-0-methyl derivative in the injector port and the determination carried out... 

We attempted to approach the determination of ll-hydroxy-A9-THC in the same way. Preliminary experiments showed that ll-hydroxy-A9-THC was not very soluble in Brodie s solvent and the metabolite was unstable to methylation with trimethylanilinium hydroxide. 

Some substrates can pyrolyse irreproducibly into a number of products at a high temperature of the injection port. The use of trimethylanilinium hydroxide with the injection port temperature being only 265°C [19] was therefore suggested. Dimethylaniline is... 

The thermal decomposition of tetramethylammonium salts of barbiturates is a procedure used extensively for their methylation [512-515]. Decomposition is performed at 240°C (temperature of the injection port) with analysis on SE-30, QF-1 and similar stationary phases. The use of trimethylanilinium hydroxide leads to better reproducibility of the preparation of the phenobarbital derivatives and to an improvement in the quantitative results [516,517]. The disadvantage of this procedure is the dependence of the course of the reaction on several parameters, e.g., geometry of the injection port, temperature. 

Gas Chromatography. This can be used to detect these compounds using 3% SE-30 on 80-100 mesh Chromosorb G (System GD, p. 194). The compounds should be converted to their methyl derivatives by heating the Acid Fraction obtained from the solvent extraction of horse urine (see above) in a sealed tube at 100 for 30 minutes with 180 il of iodomethane and 50 mg of potassium carbonate. Trimethylanilinium hydroxide is not recommended for methylating these compounds. 

The use of trimethylanilinium hydroxide can cause a problem. Highly polar material which has not been fully methylated can lie dormant on a column for a long period of time, but can be released by a subsequent injection of trimethylanilinium hydroxide, thus yielding a false positive result. 

Figure 9.1 GC-MS data obtained for laboratory standard and casework samples of phenobarbitone, derivatized with trimethylanilinium hydroxide (a) gas chromatogram of standard 166 s) (b) gas chromatogram of casework sample (t, 164 s) (c) mass spectrum of standard (d) mass spectrum of casework sample.

Hydration of vasicine (184) to the dihydroxypyrroloquinazoline 191 proceeded in aqueous solution in a sealed tube at 140- 150 C during 16 hr. Methylation of this produce (191) with trimethylanilinium hydroxide resulted in a mixture of the pyrrolo[2,l- >]quinazolines 426 and 427, which were then acetylated with acetic anhydride. ... 

The aromatic hydroxy group of vasicinolone (188) was methylated with trimethylanilinium hydroxide, and that of the pyrido[2,l- )]quinazoline 211 (R = OH) was ethylated with ethyl iodide in dimethylformamide in the presence of potassium carbonate. ... 

Midha and Charette carried out quantitative determinations of quinidine in plasma and whole blood. Cinchonidine was added to the plasma sample to be analyzed as an internal standard. The alkaloids were extracted with benzene at pH 12.0. The residue from the extract was mixed with 25 yl of trimethylanilinium hydroxide in methanol, and aliquots (1-2 ul) were injected into the gas chromatograph in which the injection port was held at 350°C. The methyl derivatives of quinidine and the internal standard gave well separated symmetrical peaks. Detection by flame ionization gave a linear response over the range 0.2-12.0 vg quinidine/ml plasma. The limit of detectability was 0.05 ug/ml and the method was adequate for following blood profiles of 200 mg quinidine sulphate doses in humans. The recovery of quinidine... 

Valentine et al. applied, in principle, the method of Midha and Charette for a quantitative assay of quinidines (quinidine and hydroquinidine) in plasma, using methylene chloride instead of benzene for the extraction of a small volume of plasma after basification. To the extract was added the internal standard, cinchonine evaporation to dryness and reconstituting in a methanolic solution of trimethylanilinium hydroxide followed. An aliquot of this solution was analyzed by GLC via on-column methylation reaction. Evaluation of the method over the range 0.5 - 10 ug/ml in human plasma gave a precision and accuracy overall of 4.5 %... 

Because theobromine and theophylline have very low volatility and low solubility in most solvents, and are difficult to gas chromatograph without considerable adsorption losses, Brochmann-Hanssen and Oke preferred to convert both compounds into caffeine on flash-heater methylation by means of trimethylanilinium hydroxide. Caffeine can be readily gas chromatographed. To a screw-cap containing the substance to be gas chromatographed, trimethylanilinium hydroxide was added in approximately 100 % excess. The solution was diluted with methanol when necessary, and 1 pi containing 0.2 to 1.0 pg of the compound was injected into the flash heater with a micro syringe. The temperature of the flash heater was 275°C and the column temperature 137°C. A packed column of 3 % SE-30 on Gas Chrom Q was used. 

Because the peak shape of theophylline can be poor in gas chromatography, as also can be the sensitivity of the method, Dusci et al.17 preferred to convert theophylline with on-column methylation by means of trimethylanilinium hydroxide to caffeine. In that manner they... 

An on-column methylation of dimethylphosphorothioate in urine samples used trimethylanilinium hydroxide in acetone (Moody et al. 1985). 

Various acyl derivatives (31)-(35) of schumannificine (28) detailed in Table 6 have been prepared by standard methods using the appropriate acyl anhydride or chloride [41,43]. Schumannificine has also been methylated at C-7 and C-5 by treatment with trimethylanilinium hydroxide in methanol to yield (36),(37) [43]. 

The method (27) describes the measurement of clonidine in human plasma and urine by combined gas chromatography-mass spectrometry with ammonia chemical ionization. Addition of [ 84] clonidine to plasma or urine is followed by ethylacetate extraction of clonidine from alkaline medium, back extraction into acid extraction into ethyl ether from alkaline medium and evaporation of the extract to dryness. Trimethylanilinium hydroxide is added to the residue, and dimethyl derivatives of clonidine are formed by on column methylation with an injection-port temperature of 250 for g.c. -70-eV m.s., the glass column (1.8 m X 2 mm) packed with 3% of OV-17 on Gas-Chrom Q (100 to 120 mesh) is operated at 245 . With He s carrier gas (15 ml min" ) NH3 is admitted to an ion-source pressure of 0.2 Torr, and ions are monitored at m/e 258 and 264. Graphs of peak height ratios (m/e 258 to 264) vs amounts of clonidine in urine (up to 40 ng ml-i) and in plasma (up to 5 ng ml i) are rectilinear. The precision for assay of clonidine in plasma is 11% at 0.25 ng ml" and 5% at 0.5 ng ml" and the lower limit of determination is 0.1 ng ml. ... 

In most cases the extraction of thiopental was achieved using procedures described in section 5.1. When required, methylation was the favored method of derivatization with reagents including trimethylphenyl artmumium l droxide [TMPAH, 38], trimethylanilinium hydroxide (IMAH, 40] and iodomethane [43]. 

Holzer et al. employed Curie-point pyrolysis to analyze microbial fatty acid by in situ methylation with trimethylanilinium hydroxide (TMAH). The fatty acid methyl ester profiles produced during pyrolysis of the whole cell agreed well with the analysis of lipid extracts from the same microorganism. Dworzanski et al. also used pyrolytic methylation-GC to profile fatty acids in whole cells of E. coli, Mycobacterium tuberculosis, and B. subtilis. Curie-point pyrolysis coupled to GC/ion trap MS was used by Snyder et al. " to characterize 14 strains representing 9 bacterial species for their lipid biomarker content. A quartz tube Pyroprobe from... 

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