S. Singhawangcha

Substituted benzeneboronic acids for the gas chromatographic determination of bifunctional compounds with electron-capture detection

Abstract Seven aromatic boronic acids have been prepared and evaluated as selective analytical reagents for the gas chromatographic analysis of bifunctional compounds. The introduction of halogen atoms into the aromatic ring provides volatile derivatives which can be determined with an electron-capture detector at the picogram level.

New electron-capturing pentafluorophenyldialkylchlorosilanes as versatile derivatizing reagents for gas chromatography

Abstract Flophemesyl, ISP-flophemesyl, tert.-buflophemesyl and CM-flophemesyl derivatives of a wide range of organic functional groups can be prepared and have good gas chromatographic and electron-capture detector properties. The derivatives are compared in terms of volatility, hydrolytic stability, detector response and mass spectral properties. Bis(pentafluorophenyl)chloromethylmethylsilane is evaluated as a reagent for preparing derivatives of strong nucleophiles. CM-flophemesyl chloride is evaluated as a cyclizing reagent for preparing derivatives of β- and γ-hydroxyamines. The flophemesyl derivative of N-nitrosodiethanolamine is shown to be suitable for detecting this compound at trace levels.

The determination of steroids with and without natural electrophores by gas chromatography and electron-capture detection

The response of the electron-capture detector to organic compounds is poorly defined, and the steroids are no exception to this observation. For those steroids which are naturally electron-capturing, the structures of the electrophores will be defined. Other steroids can be made electron-capturing by the formation of appropriate derivatives. Some new or infrequently used reagents for this purpose (flophemesyl ethers,t-buflophemesyl ethers, pentafluorophenylhydrazone derivatives and halogensubstituted aromatic boronic acids) are described.

tert.-butylpentafluorophenylmethylchlorosilane as a reagent for the formation of hydrolytically stable alkylsilyl derivatives with electron-capturing properties

The synthesis of a new silylating reagent, tert.-butylpentafluorophenylmethylchlorosilane (tert.-buflophemesyl chloride) is described. The reagent forms volatile derivatives of alcohols, phenols, carboxylic acids, thiols and amines which are suitable for gas chromatography with electron-capture detection. The tert.-buflophemesyl derivatives are many-fold more stable towards hydrolysis than the flophemesyl derivatives to conditions such as partitioning between organic solvents and acid or base, thin-layer chromatography and column chromatography. The mass spectra of the derivatives show characteristics of both the flophemesyl and tert.-butyldimethylsilyl derivatives and are suitable for compound identification.

Profiles of organic volatiles in biological fluids as an aid to the diagnosis of disease

The transevaporator sampling technique is described for the solvent stripping of the organic volatile fraction from 5–500-µl samples of biological fluids prior to analysis by capillary column gas chromatography. The reproducible nature of the isolation and separation technique enables quantitative comparisons to be made between normal and pathological samples and marker substances of use for the diagnosis of the diseased state to be identified. Electron-capture detector profiles provide complementary information to the flame-ionisation detector that may prove to be very useful in developing biological correlations.

Comparison of elelctron-capturing boronic acids for the selective analysis of bifunctional compounds

Abstract The preparation and chromatographic properties of 2,6-dichlorobenzeneboronic, 2,4,6-trichlorobenzeneboronic and 3,5-di(trifluoromethyl)benzeneboronic acids are described. These reagents are compared with seven other electron-capturing boronic acids on the basis of their range of application, relative volatility, electron-capture sensitivity and derivative stability to establish some criteria for the selection of the most useful reagents. It is proposed that the four boronic acids 3,5-di(trifluoromethyl)benzeneboronic, 2,4-dichlorobenzeneboronic, 4-bromobenzeneboronic and 4-iodobutaneboronic acid are sufficient to meet the needs of most analytical problems.

Determination of bifunctional compounds : VII. Ethylphosphonothioic dichloride as a selective reagent for the trace analysis of bifunctional compounds by gas chromatography with phosphorus-specific detection☆

Abstract Ethylphosphonothioic dichloride reacts selectively with bifunctional compounds containing OH, NH2 and COOH groups to form derivatives which are stable to gas chromatography. These derivatives can be determined at the low picogram level with nitrogen—phosphorus detector or with the flame photometric detector. The cyclic ethylphosphonothioic derivatives produce characteristic mass spectra with prominent molecular ions. The derivatives are suitable for identification purposes by gas chromatography—mass spectrometry and the prominent ion [M  C2H5S]+ should be useful for trace analysis by single ion monitoring.

The determination of bifunctional compounds. Part 1. Boronic acids with electron-capturing properties

Summary3,5-dichlorobenzeneboronic acid and 3-nitrobenzeneboronic acid have been evaluated as selective reagents for the derivatization of proximinal bifunctional compounds. Their gas chromatographic properties and response to the electron-capture detector are described.

The determination of bifunctional compounds : IX. A selective reaction for the determination of guaifenesin in plasma by gas chromatography☆

Guaifenesin after extraction from plasma with an organic solvent can be selectively derivatized with 2,4-dichlorobenzeneboronic acid and determined by gas chromatography with electron-capture detection. The detection limit for guaifenesin was 15 ng ml-1 for a 2.0-ml plasma sample. The mass spectra of the boronate derivatives of guaifenesin and mephenesin, used as internal standard, show good molecular ions with characteristic modes of fragmentation useful for their identification.