Gas-liquid chromatography of isopropylidene-glucose and glucose as their trimethylsilyl derivatives

Summary This paper describes the gas chromatographic separation of the mixture of di- and mono-O-isopropylidene-D-glucose and D-glucose as their trimethylsilyl derivatives. The use of OV-101 as liquid phase provides a complete separation for the all components in the mixture. Quantative analysis was performed using xylitol as the internal standard for di- and mono-O-isopropylidene-D-glucose, and sorbitol as the internal standard for -and -glucose.     

Analysis of hydroxy fatty acids as pentafluorobenzyl ester,trimethylsilyl ether derivatives by electron ionization gas chromatography/mass spectrometry

Electron ionization (EI) gas chromatography/mass spectrometry (GC/MS) analysis of pentafluorobenzyl ester-trimethyl sllyl ether (PFB-TMS) derivatives of hydroxy-subshtuted fatty acids provides structural information comparable to that obtained in analysis of methyl ester-trimethyl silyl ether (Me-TMS) derivatives. Use of this derivative eliminates the need to prepare two separate derivatives, the PFB-TMS derivative for molecular weight determination by electron capture ionization (negative ions) analysis and the Me-TMS derivative for structural determination by EI GC/MS analysis. The relative abundance of fragment ions observed during EI GC/MS analysis of these derivatized unsaturated fatty acids indicates the location of the —OTMS substituents relative to double bond positions in those cases studied. The most abundant fragment ions are observed when the compound contains an unsaturation two carbon atoms removed from the —OTMS ether carbon (the β-OTMS position). The “saddle effect” observed in the GC/MS analyses of some derivatized monohy— droxy unsaturated fatty acids is suggested to be due to a thermally allowed pericyclic double bond rearrangement and indicates the presence of a conjugated diene one carbon atom removed from the —OTMS ether carbon (the α-OTMS position). The saddle effect is most prominent for fatty acids that contain additional unsaturation separated by a single methylene unit from the conjugated diene moiety.     

Capillary gas chromatography of amino acids as their tert-butyldimethylsilyl derivatives in the analysis of serum amino acids in metabolic diseases

Reaction of amino acids with N-methyl-N-(tert-butyldimethylsilyl)trifluoroaceamide (MTbSTFA) in acetonitrile affords good yields of amino acid derivatives with excellent gas chromatographic and mass spectrometric properties. The single-step derivatization procedure is highly reproducible. The TBDMS amino acids are stable at room temperature for at least three days. Only a single peak is observed for each amino acid. The procedure allows simultaneous analysis of asparagine and glutamine together with other serum amino acids. Separation is achieved on a borosilicate glass capillary coated with OV-1. The mass spectra of the TBDMS amino acids possess characteristic diagnostic ions. These properties were used in the sensitive detection by GC-MS and SIM-GC-MS of GABA and pipecolic acid in the serum of a newborn suspected of a Zellweger-type syndrome, which could not be detected by other methods.     

Gas-liquid chromatography of isopropylidene monosaccharides and their trimethylsilyl derivatives

Summary This paper describes the gas chromatographic separation of the mixture of isopropylidene monosaccharides, and their trimethylsilyl derivatives. Based on the total analysis time and resolution the best stationary phase was SF-96 using Chromosorb G as the solid support and temperature programming.     

O-trimethylsilylquinoxalinol derivatives of aromatic alpha-keto acids. Mass spectra and quantitative gas chromatography

As an extension of earlier work on aliphatic alpha-keto acids, a method is described for the quantitative gas chromatographic determination of urinary aromatic alpha-keto acids. The keto acids are derivatized with o-phenylenediamine to yield the quinoxalinols. These compounds are chromatographed after trimethylsilylation. The aromatic keto acids are stabilized by sodium dithionite (4 mg/ml urine) and storage below 0 degrees. The final derivatives are stable for weeks at room temperature. Low resolution mass spectra are reported. The fragmentation mechanisms are elucidated by analysis of O-trimethylsilyl-(TMS)-quinoxalinois, O-(TMS-d9)-quinoxalinois and O-TMS-6(7)-chloroquinoxalinois.     

Simultaneous GC-MS quantitation of phosphoric, aliphatic and aromatic carboxylic acids, proline and hydroxymethylfurfurol as their trimethylsilyl derivatives: In model solutions II

Summary Fragmentation patterns and quantitation possibilities of gas chromatography-mass spectrometry (GC-MS) with Ion Trap Detection (ITD) are reported for the trimethylsilyl (TMS) derivatives of selected aliphatic and aromatic/cyclohexanoic, mono-, di- and polyhydroxy/methoxy carboxylic acids,o-phosphoric acid, proline and 5-hydroxymethylfurfurol (HMF)— (common in natural matrices, such as fruits, honey etc.). In order to maintain stability of derivatives, their stock solutions were diluted with hexamethyldisilazane. Quantitation was carried out simultaneously on the basis both of the total ion current (TIC) and selective fragment ion (SFI) values. Data obtained proved that (i) the fragmentation of different TMS acids provided very informative, utilizable characteristics, that were also suitable for quantitation; (ii) the type of fragments do not differ in their m/z values compared to those obtained in the Mass Spectral Database; (iii) the advantages of ITD due to its ‘soft’ fragmentation feature resulted in higher abundance of characteristic ions , ([M−CH₃]⁺, [M+1]⁺, [M+TMS]⁺, [M+2TMS]⁺) compared to the non characteristic reagent ones (at m/z=73,147). Determination of oxalic, glycolic, pyruvic, levulinic, succinic, malic, pimelic, tartaric, citric, palmitic, oleic, stearic, arachidic, shikimic, quinic, chlorogenic acids, as well as those ofo-phosphoric acid, HMF and proline have been carried out in the concentration range of 1–20 ng of compounds. Reproducibility on the basis of TIC and SFI values, in the order listed, proved to be 0.8–8.6% and 1.3–16.0% (relative standard deviation percentages). Presented at: Balaton Symposium on High-Performance Separation Methods, Siófok, Hungary, September 3–5, 1997     

Examination of the diphenylpropanoids of nutmeg as their trimethylsilyl, triethylsilyl and tri-n-propylsilyl derivatives using combined gas chromatography and mass spectrometry.

Ethyl acetate extracts of thirteen samples of nutmeg and one sample of mace were examined as trimethylsilyl and tri-n-propylsilyl derivatives by gas chromatography and mass spectrometry. Eleven compounds derived from two types of diphenylpropanoid were identified; the relative proportions and quantities of these compounds varied considerably in the different samples. Single ion chromatograms were used to obtain the relative concentration of one series of compounds. Preparation of the triethylsilyl and tri-n-propylsilyl derivatives resulted in greatly increased separation of the diphenylpropanoids over trimethylsilyl derivatives, which tended to produce a group of compounds with many unresolved peaks.     

On-line, inlet-based trimethylsilyl derivatization for gas chromatography of mono- and dicarboxylic acids

An on-line, inlet-based trimethylsilyl (TMS) derivatization technique was optimized and evaluated for quantitative analysis of mono- and dicarboxylic acids. The technique involves co-injection of sample and reagent followed by gas-phase formation of TMS derivatives and analysis by gas chromatography with flame ionization detection. Derivatization efficiencies were determined by comparing measured and theoretical effective carbon numbers and used to optimize the technique with respect to experimental parameters. For analysis of C5-C17 monocarboxylic acids and C2-C10 dicarboxylic acids under optimized conditions, average derivatization efficiencies were > or = 94%, average measurement uncertainties were < or = 5%, and detection limits were approximately 2 ng. The technique was applied to the analysis of carboxylic acids generated from the ozonolysis of cyclic alkenes in a smog chamber.     

Determination of the structure of glycolaldehyde as their trimethylsilyl derivatives by gas chromatography-mass spectrometry

Summary The structure of glycolaldehyde and glyceraldehyde was determined using gas chromatography — mass spectrometry. Glycolaldehyde and glyceraldehyde, mixed with lactic acid, 2-furoic acid, furoin, xylose and ascorbic acid were separated on a capillary column coated with SE-52 as trimethylsilyl derivatives. The mass spectra show two dimeric forms for TMS-glycolaldehyde and one dimeric form for TMS-glyceraldehyde.     

Gas chromatography of bile acids as their hexafluoroisopropyl ester-trifluoroacetyl derivatives.

Bile acids, such as cholic, chenodeoxycholic, deoxycholic, lithocholic and ursodeoxycholic acids, were allowed to react with hexafluoroisopropanol and tri-fluoracetic anhydride at 37 for 30 min. The resulting derivatives were gas chromatographed on QF-1, with flame ionization detection, and were identified by gas chromatography-mass spectrometry. Separation was good. By using this method, these acids were detected in samples of human duodenal fluid; the ratios of each were 24.4, 41.5, 24.9, 2.3 and 6.9%, respectively.     

Gas chromatography of alpha-keto acids as their O-trimethyl silylquinoxalinol derivatives.

The O-trimethylsilyl (TMS) quinoxalinols are very useful derivatives for the gas chromatography of alpha-keto acids because of their high stability and the absence of stereoisomerism and because of the presence of specific, common and abundant fragments in electron impact mass spectra, which allows the low-level detection of whole groups of keto acids by single-ion detection. In this paper, the chromatographic properties of eleven O-TMS-quinoxalinols on OV-1, OV-17 and Dexsil 300 are reported in terms of methylene units. Also by use of methylene units, the chromatographic isotope effect is analyzed in detail for nine perdeutero-TMS derivatives. The effect is explained by the diminished interaction of the deuterated compounds with the unlabelled liquid phase.