Twenty-fifth anniversary of the retention index system in gas—liquid chromatography

Synthesis and characterization of authentic standards for the reductive-cleavage method. The positional isomers of partially methylated and acetylated or benzoylated 1,4-anhydro-L-fucitol

Described herein is the synthesis of all positional isomers of methylated and acetylated or benzoylated 1,4-anhydro-L-fucitol. The benzoates are generated simultaneously from 1,4-anhydro-L-fucitol by sequential partial methylation and benzoylation or sequential partial benzoylation and methylation. The individual isomers are obtained in pure form by high-performance liquid chromatography. Debenzoylation and acetylation provided the corresponding acetates. The 1H NMR spectra of the benzoates and the electron-ionization mass spectra of the acetates and the tri-O-methyl derivative are reported herein as are the linear temperature programmed gas-liquid chromatography retention indices of the acetates and the tri-O-methyl derivative on three different capillary columns.

Authentic standards for the reductive-cleavage method. The positional isomers of partially methylated and acetylated or benzoylated 1,4-anhydro-D-xylitol

Described herein is a general method for the synthesis of all positional isomers of methylated and acetylated or benzoylated 1,4-anhydro-D-xylitol. The benzoates are generated simultaneously from 1,4-anhydro-D-xylitol by sequential partial methylation and benzoylation or sequential partial benzoylation and methylation. The individual isomers are obtained in pure form by high-performance liquid chromatography. Debenzoylation and acetylation provided the corresponding acetates. The 1H NMR spectra of the benzoates and the electron ionization mass spectra of the acetates and the tri-O-methyl derivative are reported herein as are the linear temperature programmed gas-liquid chromatography retention indices of the acetates and the tri-O-methyl derivative on three different capillary columns.

Authentic standards for the reductive-cleavage method. The positional isomers of partially methylated and acetylated or benzoylated 1,5-anhydro-D-mannitol

Described herein is an efficient method for the synthesis of the sixteen positional isomers of methylated and acetylated or benzoylated 1,5-anhydro-D-mannitol. The compounds are generated simultaneously by partial methylation of 1,5-anhydro-D-mannitol and subsequent benzoylation, and the individual isomers are obtained in pure form by high-performance liquid chromatography. Debenzoylation of the latter and acetylation yielded the desired acetates. The the benzoates and the electron-ionization mass spectra of the acetates and the tetra-O-methyl derivative are reported herein as are the linear temperature-programmed gas-liquid chromatography retention indices of the acetates and the tetra-O-methyl derivative on three different capillary columns.

Authentic standards for the reductive-cleavage method. The positional isomers of partially methylated and acetylated or benzoylated 1,5-anhydro-D-glucitol

Described is an efficient method for the synthesis of the sixteen positional isomers of methylated and acetylated or benzoylated 1,5-anhydro-D-glucitol. The compounds are generated simultaneously by partial methylation of 1,5-anhydro-D-glucitol and subsequent benzoylation, and the individual isomers are obtained in pure form by high-performance liquid chromatography. Debenzoylation of the latter and acetylation yielded the desired acetates. Reported are the 1H NMR spectra of the benzoates and the electron-ionization mass spectra of the acetates and the tetra-O-methyl derivative. Also reported for the acetates and the tetra-O-methyl derivative are their linear temperature programmed gas-liquid chromatography retention indices on three different capillary columns.

Authentic standards for the reductive-cleavage method. The positional isomers of partially methylated and acetylated or benzoylated 1,5-anhydro-D-galactitol

Described herein is an efficient method for the synthesis of the sixteen positional isomers of methylated and acetylated or benzoylated 1,5-anhydro-D-galactitol. The compounds are generated simultaneously by partial methylation of 1,5-anhydro-D-galactitol and subsequent benzoylation, and the individual isomers are obtained in pure form by high-performance liquid chromatography. Debenzoylation and acetylation yielded the desired acetates. Reported herein are the 1H NMR spectra of the benzoates and the electron-ionization mass spectra of the acetates and the tetra-O-methyl derivative. Also reported for the acetates and the tetra-O-methyl derivative are their linear temperature-programmed gas-liquid chromatography retention indices on three different capillary columns.

Retrieval of structure information from retention index

The chromatographic identity of a compound can be determined by four parameters, namely, I, A, Z and (GRF). These are interrelated in a linear regression equation, given in the paper as Eq. 8. The retrieval of structural information from retention data requires the introduction of a new meaning to the Kováts retention index, the use of column difference (delta I) to characterize functional groups, the redefinition of the role of electronegative oxygen and nitrogen atoms, and the division of retention index (I) into contributions from atoms and from functional groups. The separation of retention index (I) into molecular and interaction contributions is a necessary condition for retention index prediction from structure and also for structure information retrieval from retention data. According to Eq. 8 the retention index is uniquely determined by three parameters, namely A, Z and (GRF). For prediction of retention index, the A value is assigned a value of 100 index units (i.u.), the Z value is obtained directly from the compound, and the (GRF) value is pre-calibrated. In Eq. 10, the m and n values represent the pre-calibrated terms for a quantitative structure-retention index relationship. These terms account for the positive and negative retention contributions from polar and polarizable atom groups. All atom groups that are different from methylene and methyl groups will interact with the stationary phase and contribute to retention. The m and n values for various functional, polar and polarizable atom groups and their column differences (delta I values) are the results of interactions between the solute and the stationary phase and are structure dependent. The interaction increases with increasing polarities of the solute and the stationary phase. The column difference not only reflects the strength of the interaction, but is also characteristic of the functional and polarizable groups. The retrieval of structural information from retention data is equivalent to obtaining Z and (GRF) values from known I and delta I values, which is straightforward for monofunctional compounds. For multi-functional compounds, additional data will be needed for retrieval of structural information. These can be obtained from derivatization of the unknown compound, from its chemical reactions with other reagents, from GC-MS analysis and from structure match using internal or external standards. The additional data required will depend upon the complexity of the unknown structure. This approach demonstrates that a system can be devised to utilize GC retention characteristics uniquely for structure elucidation.

Authentic standards for the reductive-cleavage method. The positional isomers of partially methylated and acetylated or benzoylated 1,5-anhydro-D-fucitol

Described herein is an efficient method for the synthesis of the eight positional isomers of methylated and acetylated or benzoylated 1,5-anhydro-D-fucitol. The compounds are generated simultaneously by partial methylation of 1,5-anhydro-D-fucitol and subsequent benzoylation, and the individual isomers are obtained in pure form by high-performance liquid chromatography. Debenzoylation of the latter and acetylation yielded the desired acetates. Reported herein are the 1H NMR spectra of the benzoates and the electron-ionization mass spectra of the acetates and the tri-O-methyl derivative. Also reported for the acetates and the tri-O-methyl derivative are their linear temperature programmed gas-liquid chromatography retention indices on three different capillary columns.

Use of M-series retention index standards in the identification of trichothecenes by electron impact mass spectrometry

A method for the reliable identification of a series of trichothecenes as their trifluoroacetate esters in porridge flake samples is described. The esters were separated by gas chromatography and identified from their retention times relative to n-alkyl-bis(trifluoromethyl)phosphine sulphide (M-series) retention index standards and their electron impact mass spectra. The relative retention times offer an independent identification method by which the reliability of the identification can be improved. The mass spectra and the relative retention times were obtained from the same gas chromatographic-mass spectrometric run. Detection limits were of the order to 0.005-0.05 mg/kg. All the flake samples including oats (ten of fourteen samples studied) contained deoxynivalenol (0.01-0.2 mg/kg) and one oat flake sample contained HT-2 toxin (0.008 mg/kg). The other trichothecenes monitored were not found.

Gas chromatographic retention indices of sulfur vesicants and related compounds

Temperature-programmed retention indices, relative to a n-alkane homologous series, were determined for 37 sulfur vesicant or vesicant-related compounds using DB-1, DB-5 and DB-1701 fused-silica capillary columns. Many of the compounds, including long chain dichloro, vinylchloro, vinylalcohol and macrocyclic compounds have either not been previously identified or have not been associated with sulfur vesicant analysis. Reproducibility of the retention indices, based on Van den Dool's equation, was excellent over the course of the study. In addition, changes in retention index (delta RI), which may enable the prediction of uncharacterized homologue chromatographic behaviour, were calculated for several homologous series.

Gas chromatographic data for 187 nitrogen- or phosphorus-containing drugs and metabolites of toxicological interest analysed on methyl silicone capillary columns

Retention data, retention indices and retention times relative to diazepam, associated with 187 nitrogen- or phosphorus-containing drugs and metabolites likely to be found in toxicological analysis, are presented. The work was carried out with cross-linked methyl silicone, siloxane-deactivated fused-silica capillary columns in different gas chromatographs equipped with nitrogen-phosphorus flame ionization detectors and a gas chromatograph-mass spectrometer. Results show the high reproducibility offered by the capillary system, which permits the reduction of identification problems and analysis time.