Reversed-phase liquid chromatography-mass spectrometry of some organic tellurium compounds

The chromatographic behavior of some organic tellurium compounds (OTCs) was studied under the conditions of high-performance liquid chromatography with mass spectrometric detection. The retention characteristics (retention factor, relative retention, and differential molar Gibbs energy difference) of the compounds were obtained under the conditions of gradient elution reversed-phase liquid chromatography. The chemical ionization mass spectra of OTCs at atmospheric pressure were considered. It was shown that there was a relation between the structure of the compounds studied and their chromatographic retention.     

Thermospray liquid chromatography-mass spectrometry of corticosteroids.

A high-performance liquid chromatographic method was developed for thermospray mass spectrometric analysis of steroidal hormones. Using a Nova-Pak C18 reversed-phase column and isocratic elution with a solvent comprised of 25 mM ammonium formate in 30% acetonitrile, corticosteroids were separated within 10 min. This solvent also permitted ultraviolet absorbance detection down to 220 nm with low-nanogram sensitivity. The use of acetonitrile was favourable for thermospray mass spectrometric analysis because mass spectra were obtained with a pseudomolecular ion as the base peak. A combination of liquid chromatography, ultraviolet absorbance detection and thermospray mass spectrometry provided a sensitive and reliable method for unequivocal confirmation of the presence of steroidal drugs in equine urine.     

Liquid chromatography-electrospray mass spectrometric identification of ginsenosides in Panax ginseng roots.

A high-performance liquid chromatographic method was developed for electrospray mass spectrometric analysis of ginsenosides in Panax ginseng roots. The analyses were performed on a reversed-phase C18 column using a binary eluent (aqueous 8 mM NH4OAc, buffered to pH 7 with NH4OH-acetonitrile) under gradient conditions. Twenty-five ginsenosides could be separated and detected. The mass spectra obtained provided information on their molecular masses. A MS-MS experiment was undertaken in order to determine the sugar unit sequences and the aglycone moieties.     

Use of particle beam liquid chromatography-electron impact mass spectrometry for structure elucidation of oxodipine and three of its metabolites

In order to test the analytical capabilities of the particle beam liquid chromatograph-mass spectrometer interface in structural identification in drug metabolism, a liquid chromatographic-mass spectrometric (LC MS) method using this new technique was developed for oxodipine and some of its expected metabolites. After two extraction steps at pH 9 and 1.5, the separation of the compounds, which have a wide polarity range, was carried out by an isocratic high-performance liquid chromatographic method with a 25-cm cyano-bonded column. The compounds were eluted with hexane-methanol-methylene chloride (76:12:12). Mass spectra were recorded after electron impact ionization (75 eV) with a source temperature of 150 degrees C. Under these conditions, comparison of the spectra with those obtained after gas chromatography or with a direct introduction probe showed identical fragmentation patterns when a sufficient amount of product was injected for LC-MS analysis.     

Liquid chromatographic and mass spectral analysis of N-substituted analogues of 3,4-methylenedioxyamphetamine

The C1 to C3 N-alkyl, N,N-dimethyl, and N-hydroxy analogues of 3,4-methylenedioxyamphetamine (MDA) are identified by high performance liquid chromatographic (HPLC) and spectrometric techniques. The compounds are separated using reversed-phase procedures on C18 stationary phase with an acidic (pH 3) aqueous methanol mobile phase. The mass spectra of the compounds are distinctive and reference spectra are provided. The N-hydroxy derivative is unstable at high temperatures and decomposes to MDA and the oxime of 3,4-methylenedioxyphenyl-2-propanone.     

High pressure mass spectrometry of some liquid chromatographic mass spectrometric reagents

Pressure dependence of several reversed phase liquid chromatographic solvents, including methanol, acetonitrile and mixtures of methanol: water and acetonitrile: water has been investigated. Typical ions, [MH]⁺, [2M+H]⁺ and [3M+H]⁺, were recorded as function of source pressure and as a function of the amount of water in the mixture. Ion formation processes in methanol: water and acetonitrile: water are discussed. The influence of liquid chromatographic mass spectrometric solvent pressure on the mass spectra of samples has been demonstrated on an amino acid sample.     

Liquid chromatography-mass spectrometry of trace compounds with a moving-belt interface and multi-dimensional chromatography

A high-performance liquid chromatographic method with on-line mass spectrometric detection is described for the structural analysis of a number of synthetic impurities, present at trace levels in almitrine. To obtain mass spectra with various ionization methods and high-resolution mass measurements, a moving-belt liquid chromatograph-mass spectrometer interface is used. A two-column switching system allows the injection of large amounts of almitrine, from which the trace compounds are trapped on a second column, while discarding the major component. This permits the introduction of the impurities into the mass spectrometer by elution of the second column, without the risk of introducing too large an amount of the major compound into the mass spectrometer. The mass spectra thus obtained are of sufficient quality to permit a correct structural assignment of the impurities.     

Highly sensitive determination and characterization of intact cellular ester-linked phospholipids using liquid chromatography-plasma spray mass spectrometry

Liquid chromatographic class separations of common cellular phospholipids combined with plasma spray ionization of the effluents were investigated. Comparison with true thermospray ionization involving ammonium acetate buffering revealed a gain in total ionization in the plasma spray of a factor of approximately 10 using a cation-exchange column and a solvent mixture consisting of acetonitrile-methanol-water (400:100:15, v/v). Plasma spray ionization studies of bovine brain polyphosphoinositides interrelated by the phosphate content in the inositol moiety showed almost identical monoglyceride and diglyceride ion clusters, indicating possibilities of studying the biochemical turnover of such phospholipids. Plasma spray ionization liquid chromatography-mass spectrometry of bacterial membrane phospholipids (Pseudomonas fluorescens) revealed possibilities of obtaining indications of individual fatty acid compositions from the spectra of the phosphatidylinositol and phosphatidylethanolamine fractions present. Conventional gas chromatographic fatty acid analysis agreed with the direct mass spectrometric structure elucidations. Interestingly, the two phospholipid classes had different relative fatty acid compositions with a significantly higher degree of cyclic fatty acids in the phosphatidyl ethanolamines. Plasma spray ionization yielded linear dose-response curves for both the monoglyceride and diglyceride fragment signals in the selected-ion monitoring mode. The detection limit for the monoglyceride and diglyceride species of phosphatidylcholine under the chromatographic and mass spectrometric conditions used was found to be in the picogram range.     

Operational variables in high-performance liquid chromatography-electrospray ionization mass spectrometry of peptides and proteins using poly(styrene-divinylbenzene) monoliths

Capillary reversed-phase high-performance liquid chromatography (RP-HPLC) utilizing monolithic poly(styrene-divinylbenzene) columns was optimized for the coupling to electrospray ionization mass spectrometry (ESI-MS) by the application of various temperatures and mobile phase additives during peptide and protein analysis. Peak widths at half height improved significantly upon increasing the temperature and ranged from 2.0 to 5.4 s for peptide and protein separations at 70 degrees. Selectivity of peptide elution was significantly modulated by temperature, whereas the effect on proteins was only minor. A comparison of 0.10% formic acid (FA), 0.050% trifluoroacetic acid (TFA), and 0.050% heptafluorobutyric acid (HFBA) as mobile phase additives revealed that highest chromatographic efficiency but poorest mass spectrometric detectabilities were achieved with HFBA. Clusters of HFBA, water, and acetonitrile were observed in the mass spectra at m/z values >500. Although the signal-to-noise ratios for the individual peptides diverged considerably both in the selected ion chromatograms and extracted mass spectra, the average mass spectrometric detectabilities varied only by a factor of less than 1.7 measured with the different additives. Limits of detection for peptides with 500 nl sample volumes injected onto a 60 mm x 0.20 mm monolithic column were in the 0.2-13 fmol range. In the analysis of hydrophobic membrane proteins, HFBA enabled highest separation selectivity at the cost of lower mass spectral quality. The use of 0.050% TFA as mobile phase additive turned out to be the best compromise between chromatographic and mass spectrometric performance in the analysis of peptides and proteins by RP-HPLC-ESI-MS using monolithic separation columns.     

LC-PDA and LC-ESI-MS separation and determination of process-related substances arising from stilbene-type fluorescent whitening agents. Application to monitoring of their photodegradation products in industrial effluents and aqueous environmental systems

A simple and rapid gradient elution high-performance liquid chromatographic method using photodiode array and electrospray ionization mass spectrometric detectors was developed for separation and determination of the process-related substances and photodegradation products of stilbenesulfonic acids, viz. 4,4'-dinitrostilbene-2,2'-disulfonic acid (DNSDA), 4-amino-4'-nitrostilbene-2,2'-disulfonic acid (ANSDA), and 4,4'-diaminostilbene-2,2'-disulfonic acid (DASDA) in industrial waste waters. Gradient elution was carried out using ammonium acetate and acetonitrile as mobile phase and an Inertsil-ODS 3V column for separation. The negative-ion electrospray ionization mass spectra containing [M-H]- ions of sulfonic acids allowed molecular mass determination of unknowns and the structures were proposed on the basis of the fragment ions in the MS/MS spectra.     

Speciation of seleno compounds in yeast aqueous extracts by three-dimensional liquid chromatography with inductively coupled plasma mass spectrometric and electrospray mass spectrometric detection

A three-dimensional liquid chromatographic purification protocol based on sequential size-exclusion, anion-exchange and cation-exchange separation mechanisms was developed for the mapping of seleno compounds in aqueous yeast extracts. The method allowed the demonstration of the presence of more than 30 different seleno compounds. Semi-preparative size-exclusion and anion-exchange chromatography were optimized for maximum resolution using electrospray-compatible buffers in order to purify the compounds for mass spectrometric analysis. Molecular masses were attributed to many of the compounds on the basis of the selenium isotopic pattern in the electrospray mass spectra and of the collision-induced fragmentation patterns. Limitations preventing the ultimate identification of the selenium species detected are discussed.     

Reconstruction of mass spectra of components of unknown mixtures based on factor analysis

A method is described for the spectral resolution of combined gas chromatographic—mass spectrometric data. Factor analysis is applied to the identification of a second species in a single gas chromatographic peak. A plot can be constructed from the region of the non-negative values of spectral lines in the factor space. Feasible locations for the spectra of these constituents in the plot can be identified and give recognizable spectra of the separated constituents.     

Viscosalines B(1,2) and E(1,2): challenging new 3-alkyl pyridinium alkaloids from the marine sponge Haliclona viscosa

Four new 3-alkyl pyridinium alkaloids, the viscosalines?B(1) (1?a), B(2) (1?b), E(1) (2?a), and E(2) (2?b), were isolated from the Arctic sponge Haliclona viscosa. The structure elucidation of these isomeric compounds was challenging due to ambiguous fragments that derive during "standard" mass spectrometric fragmentation experiments. The final structure elucidation relied on the use of a combination of synthesis, liquid chromatography, and mass spectrometry. Three different mass spectrometers were used to differentiate between the synthetic structural isomers: a time-of-flight (TOF) mass spectrometer and two ion-trap mass spectrometers with different ion-transfer technologies (i.e., skimmer versus funnel optics). Although at first none of the spectrometers returned spectra that permitted structure elucidation, all three mass spectrometers provided analysis that successfully differentiated between the isomers after thorough method optimization. The use of in-source collision-induced dissociation (CID) with the ion trap and TOF instrument returned the most interesting results. The mode of fragmentation of the viscosalines under different experimental conditions is described herein. After successful optimization of the mass spectrometric method applied, the chromatographic method was improved to distinguish the previously inseparable isomers. Finally, both the liquid chromatography and mass spectrometric methods were applied to the natural products and the results compared to those from the synthetic compounds.     

Rapid LC–TOFMS Separation and Identification of Diarylheptanoids and Gingerol-Related Compounds in Dried Ginger

A tandem liquid chromatographic–time-of-flight mass spectrometric (LC–TOFMS) method has been developed for rapid separation and identification of diarylheptanoids and gingerol-related compounds in aqueous extracts of dried ginger. Total-ion-current chromatograms and mass spectra were acquired. A formula database of known compounds was established, against which components of dried ginger could be rapidly identified by matching their exact masses with theoretical masses of compounds calculated from their empirical formulae. Identification of 20 compounds was accomplished with error of 4 ppm, and further confirmation of elemental composition was obtained from the abundance of the isotope peaks. LC–TOFMS has been shown to be a useful tool for rapid identification of compounds in aqueous extracts of dried ginger.     

Applicability of high-performance liquid chromatography--continuous-flow fast atom bombardment mass spectrometry for simultaneous quantitation of multiple neurochemicals.

A method is described for the analysis of multiple neurochemically important compounds. The technique involves high-performance liquid chromatographic separation in combination with ultraviolet and continuous-flow fast atom bombardment mass spectrometric detection. High-performance liquid chromatographic elution behaviour and relative detection responsiveness as correlated with chemical structure are also presented.     

Identification of oxygenated polycyclic aromatic hydrocarbons in diesel particulate matter by capillary gas chromatography and capillary gas chromatography/mass spectrometry

Summary Using a two-step liquid chromatographic separation on normalphase cartridges, crude extracts of diesel particulate matter can be separated without time-consuming sample handling into special fractions which mainly contain slightly-polar oxygenated polycyclic aromatic hydrocarbons (oxy-PAH) and nitrated polycyclic aromatic hydrocarbons (nitro-PAH). Subsequent analysis was by fused-silica capillary gas chromatography on a SE54 column along with flame-ionisation (GC/FID) and positive-ion electron-impact mass spectrometric detection (GC/MS) respectively. A number of individual oxy-PAH belonging to four different chemical classes (ketones, quinones, anhydrides and aldehydes) and several individual nitro-PAH were characterized by their retention times and mass spectra. Presented at the 15th International Symposium on Chromatography, Nürnberg, October 1984     

局部麻醉药的反相色谱安培法检测

本文系统研究了普鲁卡因,利多卡因,丁卡因等3种局部麻醉药的液相色谱安培法检测行法,并与液相色谱光度法检测结果进行了比较。     

Determination of ethyl biscoumacetate and its metabolite 7-hydroxyethyl biscoumacetate in human serum by high-performance liquid chromatography and mass spectrometry.

An efficient reversed-phase high-performance liquid chromatographic method has been developed for the determination of ethyl biscoumacetate (EBA) and its metabolite in human serum, using the mu Bondapak C18 column and methanol-water-phosphoric acid (56:46.8:0.2, v/v/v) as the mobile phase. This method permitted the determination of both EBA and a metabolite in human serum. The latter has been mentioned by other authors only in urine samples, where significant concentrations were found. Identification of the metabolite as 7-hydroxyethyl biscoumacetate was based on its chromatographic separation, followed by isolation from the eluate and direct mass spectrometric identification. It has been found that the higher EBA concentrations in human serum described by Brodie et al. [J. Pharmacol. Exp. Ther., 106 (1952) 453] were caused by the insufficient resolving power of the spectrophotometric method used, leading to overlapping of the UV spectra of the parent drug and its metabolite.     

兴奋剂中利尿剂的检测方法

利尿剂是国际奥委会医学委员会禁止使用的一类兴奋剂。该文对兴奋剂中利尿剂的检测方法进行了综述,重点阐述了样品的处理方法,HPLC－GC－MS的检测方法及各种衍生化方法。     

Determination of three major triterpenoids in epicuticular wax of cabbage (Brassica oleracea L.) by high-performance liquid chromatography with UV and mass spectrometric detection

Lupeol, together with alpha- and beta-amyrins in smaller quantities, has been found for the first time in the epicuticular wax of white cabbage (Brassica oleracea L. convar. capitata (L.) Alef. var. alba DC) leaf surface extract. The three triterpenoids were identified by a new high-performance liquid chromatographic (HPLC) method with UV and mass spectrometric (MS) detection using atmospheric pressure chemical ionization (APCI). All three isomeric compounds gave a parent ion peak at m/z 409 [M+H-18](+) and the relative intensities of some characteristic fragment ion peaks in tandem mass spectrometric (MS-MS) spectra of this parent ion enabled differentiation between the isomers. An additional peak at m/z 439 [M+H](+), which could be oleanonic or ursonic aldehyde, was detected by HPLC-APCI-MS. Saponification of cabbage leaf surface extract with 20% NaOH in methanol at 65 degrees C for 2h had no influence on lupeol, or alpha- or beta-amyrins, but lead to the formation of three additional compounds, which were not identified.