Structural analysis of monoterpene glycosides extracted from Paeonia lactiflora Pall. using electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry and high-performance liquid chromatography/electrospray ionization tandem mass spectrometry

Paeoniflorin standard was first investigated by electrospray ionization Fourier transform ion cyclotron resonance tandem mass spectrometry (ESI-FTICR-MS/MS) using a sustained off-resonance irradiation (SORI) collision-induced dissociation (CID) method at high mass resolution. The experimental results demonstrated that the unambiguous elemental composition of product ions can be obtained at high mass resolution. Comparing MS/MS spectra and the experimental methods of hydrogen and deuterium exchange, the logical fragmentation pathways of paeoniflorin have been proposed. Then, the extracts of the traditional Chinese medicine Paeonia lactiflora Pall. were analyzed by high-performance liquid chromatography/electrospray ionization tandem mass spectrometry (HPLC/ESI-MS/MS). By comparison with the ESI-FTICR-MS/MS data of paeoniflorin, the isomers paeoniflorin and albiflorin in Paeonia lactiflora Pall. have been identified using HPLC/MS with CID in an ion trap and in-source CID. Furthermore, using the characteristic fragmentation pathways, the retention times (t(R)) in HPLC and MS/MS spectra, the structures of three other kinds of monoterpene glycoside compounds have been identified on-line without time-consuming isolation.

Studies on lignan constituents from Schisandra chinensis (Turcz.) Baill. fruits using high-performance liquid chromatography/electrospray ionization multiple-stage tandem mass spectrometry

A reversed-phase high-performance liquid chromatography-diode array detector-electrospray ionization multiple-stage tandem mass spectrometry (RP-HPLC-DAD-ESl-MSn) method has been developed for the detection and analysis of lignan constituents in the methanol extract from the fruits of Schisandra chinensis (Turcz.) Baill. RP-HPLC-DAD-ESI-MSn and electrospray ionization Fourier transform ion cyclotron resonance multiple-stage tandem mass spectrometry (ESI-FT-TCR-MSn) have been applied to investigate the characteristic product ions of four lignan reference compounds. Then, the logical fragmentation pathways of the lignans have been proposed. By comparing the retention time (t(R)) of HPLC, the ESI-MSn data and the structures of analyzed compounds with the data of reference compounds and in the literature, 11 peaks in HPLC have been unambiguously identified and another 5 peaks have been tentatively identified or deduced. Also, in the present paper, the extracted ion chromatograms (EIC) have been used to analyze the lignan isomers. The experimental results demonstrate that RP-HPLC-DAD-ESI-MSn is a specific and useful method for the identification of the lignan constituents and their isomers.

Study on the variation of chemical constituents during combination of ginseng with trogopteroum feces and semen raphani by high performance liquid chromatography-mass spectrometry

A high performance liquid chroatography-electrospray ionization-mass spectrometric method was developed for analysis and identification of ginsenosides from the decoction of ginseng, ginseng with trogopteroum feces and ginseng with semen raphani. Ten ginsenosides were separated and detected. The content variation of these ginsenosides was researched. The experimental results showed, that ginsenosides were less in compatible decoction than in separate one expect Ro. the stripping of ginsenosides were restrained by semen raphani and during combination of ginseng with trogopteroum feces, the precipitates were produced by ginsenosides.

Studies on the flavones using liquid chromatography-electrospray ionization tandem mass spectrometry

Fragmentation pathways of nine flavone compounds have been studied by using electrospray ionization multi-stage tandem mass spectrometry (ESI-MSn). Analyzing the product ion spectra of flavonoids and aglycones, we observed some diagnostic neutral losses, such as *CH3, H2O, residue of glucose and gluconic acid, which are very useful for the identification of the functional groups in the structures. Furthermore, specific retro Diels-Alder (RDA) fragments for flavones with different hydroxyl substitution have also been discussed. The information is helpful for the rapid identification of the location site of hydroxyl substitution on flavones. Fragmentation pathways of C-glycosidic flavonoid have also been discussed using ESI-MSn, demonstrating ions [M-H-60](-), [M-H-90](-), [M-H-120](-) are characteristic ions of C-glycosidic flavonoid. According to the fragmentation mechanism of mass spectrometry and HPLC-MS data, the structures of seven flavones in Scutellaria baicalensis Georgi have been identified on-line without time-consuming isolation. The HPLC-ESI-MSn method for analyzing constituents in the Scutellaria baicalensis Georgi has been established.

Rapid identification of saponins in plant extracts by electrospray ionization multi-stage tandem mass spectrometry and liquid chromatography/tandem mass spectrometry

Electrospray ionization multi-stage tandem mass spectrometry (ESI-MSn) and liquid chromatography coupled with on-line mass spectrometry (LC/MS/MS) were applied to characterize saponins in crude extracts from Panax ginseng. The MSn data of the [M - H](-) ions of saponins can provide structural information on the sugar sequences of the saccharide chains and on the sapogins of saponins. By ESI-MSn, non-isomeric saponins and isomeric saponins with different aglycones can be determined rapidly in plant extracts. LC/MS/MS is a good complementary analytical tool for determination of isomeric saponins. These approaches constitute powerful analytical tools far rapid screening and structural assignment of saponins in plant extracts. Copyright (C) 2000 John Wiley & Sons, Ltd.

The research of cellulose derivatives as chiral stationary phases and high performance liquid chromatography with polarimeter as on-line detector

Three cellulose derivatives were synthesized and used as chiral stationary phases based on silica gel. The effects of adsorbances on the column numbers and stabilities have been investigated. These stationary phases exhibited high chiral recognition for various racemates. At the same time, the on-line curves of polarimeter were obtained by high performance liquid chromatography with polarimeter as on-line detector.

An amperometric detector with a tubular electrode deposited on the capillary for capillary liquid chromatography

A procedure is described for the preparation of a tubular electrode by chemical deposition of platinum at the end of a fused-silica capillary. The properties of the electrode were tested under liquid chromatographic conditions, demonstrating that both the static and the dynamic behaviour of the detection system satisfy the requirements of capillary chromatographic separations and compare well with a wall-jet amperometric system and with UV photometric detection. The detection system described is easy to prepare and does not require any time-consuming positioning of the electrode system as it is integrated into the separation part of the apparatus. (C) 1998 Elsevier Science B.V.

Liquid chromatography amperometric detection of nitrite using a polypyrrole modified glassy carbon electrode doped with tungstodiphosphate anion

Chromatography-amperometric detection of nitrite with a polypyrrole modified glassy carbon electrode doped with tungstodiphosphate anion (Dawson-type P2W18O626-/PPy/GC electrode) based on its electrocatalytic reduction of nitrite is described. The cyclic and hydrodynamic voltammetry of nitrite at the P2W18O626-/PPy/GC electrode was studied. The factors affecting the detection of nitrite and the analytical performance of the modified electrode in flowing stream were investigated. The results show that the modified electrode has a good sensitivity (the limit of detection is 1 mu mol dm(-3)) and a satisfactory reproducibility (RSD = 3.78%, N = 21). The modified electrode was used in the chromatographic detection of nitrite spiked in the liquid from a tin of mushrooms and the mineralized spring water. It was found that the modified electrode exhibited good selectivity for nitrite.

Detection of menadione sodium bisulfite (vitamin K-3) by reversed-phase high performance liquid chromatography with series dual-electrode amperometric detector

A reversed-phase high-performance liquid chromatography with series dual glassy carbon electrodes for the amperometric detection of water-soluble menadione is described. The complex post-column derivatization reaction and the high background currents were avoided. The menadione sodium bisulfite was reduced at -0.3 V vs. SCE at the upstream (generator) electrode and oxidized at +0.2V vs. SCE at the downstream (collector) electrode. The mobile phase was 0.2moll(-1) HAc-NaAc aqueous buffer (pH 5.50) and 40% (v/v) methanol. The linear response was in the range of 35 ng to 15 mu g, with a detection Limit of 15 ng (S/N=3). The correlation coefficient was 0.9997 (n=6). The electrochemical detection with series dual electrodes has a higher selectivity for menadione (vitamin K-3) compound than with UV detection.

Improvements in the selectivity of electrochemical detectors for liquid chromatography and flow injection analysis using the self-assembled n-alkanethiol monolayer-modified au electrode

4-Aminophenol (4-AP), paracetamol (PRCT), norepinephrine (NE), and dopamine (DA) (all somewhat hydrophobic compounds) were HPLC electrochemically detected while the signals from uric acid (UA) and ascorbic acid (AA) (both hydrophilic compounds at the pH studied) were minimized, taking advantage of the permselectivity of the self-assembled n-alkanethiol monolayer (C-10-SAM)-modified Au electrodes based on solute polarity, The effects of various factors, such as the chain length of the n-alkanethiol modifier, modifying time, and pH value, on the permeability of C-10-SAM coatings were examined, The calibration curves, linear response ranges, detection limits, and reproducibilities of the EC detector for 4-AP, PRCT, NE, and DA were obtained, The result shows that the EC detector can be applied in the chromatographic detection of 4-AP, PRCT, NE, and DA in urine, effectively removing the influence of UA and AA in high concentrations existing in biological samples. As a result, a great improvement in the selectivity of EC detectors has been achieved by using Au electrodes coated with neutral n-alkanethiol monolayer.

SIMULTANEOUS DETERMINATION OF GUANINE, URIC-ACID, HYPOXANTHINE AND XANTHINE IN HUMAN PLASMA BY REVERSED-PHASE HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY WITH AMPEROMETRIC DETECTION

A reversed-phase high-performance liquid chromatographic method with amperometric detection is described for the separation and quantification of uric acid, guanine, hypoxanthine and xanthine. The isocratic separation of a standard mixture of the compounds was achieved in 5 min on a Spherisorb 5 C-18 reversed-phase column, with a mobile phase of NaH2PO4 (300 mmol dm(-3) pH 3.0)-methanol-acetonitrile-tetrahydrofuran (97.8 + 0.5 + 1.5 + 0.2). Uric acid, guanine, hypoxanthine and xanthine were completely separated, with detection limits in the range 2-20 pmol per injection. The effect of pH and the composition of the mobile phase on the separation are described. The hydrodynamic voltammograms of these compounds were recorded at a glassy carbon electrode. The linear range of the calibration graph for each compound was: uric acid; 1-5000 mu mol dm(-3); guanine, 0.5-2000 mu mol dm(-3); hypoxanthine, 0.1-500 mu mol dm(-3) and xanthine, 0.5-5000 mu mol dm(-3). The within- and between-day precision was good. The uric acid and hypoxanthine content in human plasma was measured using the proposed method. Good recoveries of uric acid (97.9-103%), hypoxanthine (98.0-99.2%), guanine (96.0-98.3%) and xanthine (96.0-102%) were obtained from human plasma. The results of electrochemical detection were in good agreement with those of UV detection.

DETERMINATION OF CYSTEINE AND REDUCED GLUTATHIONE IN HUMAN PLASMA BY LIQUID-CHROMATOGRAPHY WITH PULSED AMPEROMETRIC ELECTROCHEMICAL DETECTION USING A PLATINUM-PARTICLES MODIFIED GLASSY-CARBON ELECTRODE

An assay procedure utilizing pulsed amperometric detection at a platinum-particles modified electrode has been developed for the determination of cysteine and glutathione in blood samples following preliminary separation by reversed-phase liquid chromatography. A chemically modified electrode (CME) constructed by unique electroreduction from a platinum-salt solution to produce dispersed Pt particles on a glassy carbon surface was demonstrated to catalyze the electo-oxidation of sulfhydryl-containing compounds: DL-cysteine (CYS), reduced glutathione (GSH). When used as the sensing electrode in flow-system pulsed-amperometric detection (PAD), electrode fouling could be avoided using a waveform in which the cathodic reactivation process occurred at a potential of - 1.0 V vs. Ag/AgCl to achieve a cathodic desorption of atomic sulfur. A superior detection limit for these free thiols was obtained at a Pt particle-based GC electrode compared with other methods; this novel dispersed Pt particles CME exhibited high electrocatalytic stability and activity when it was employed as an electrochemical detector in FIA and HPLC for the determination of those organo-sulfur compounds.

DETERMINATION OF AMINOPYRINE AND ITS METABOLITE IN BIOLOGICAL FLUID BY LIQUID-CHROMATOGRAPHY ELECTROCHEMISTRY WITH A GLASSY-CARBON ELECTRODE DISPERSED WITH ALPHA-ALUMINA PARTICLES

A sensitive high-performance liquid chromatographic method has been developed for the quantitative determination of aminopyrine (AM) and its metabolite 4-aminoantipyrine (AAN). The method utilizes reverse-phase chromatography/amperometric detection with a glassy carbon electrode dispersed with alpha-arumina particles as the working electrode, on which the oxidation of AM and AAN was greatly improved compared with that on a bare glassy carbon electrode. As a result, the detection limit was as low as 1.4 ng for AM and 0.8 ng for AAN, and the calibration plots for the above compounds have wide linear ranges from 100 ng/mL to 100 mu g/mL and 60 ng/mL to 80 mu g/mL (for AM and AAN, respectively). The above method was applied for the detection of these materials in human urine with satisfactory results.

DIRECT-INJECTION OF URINE AND DETERMINATION OF ACETAMINOPHEN BY MICELLAR LIQUID-CHROMATOGRAPHY WITH A WALL-JET CELL CARBON-FIBER MICROELECTRODE

A wall-jet cell/carbon fibre microelectrode detector was designed and used for the micellar liquid chromatographic assay of acetaminophen. The separations were carried out in an analytical column packed with C-18 stationary phase and the mobile phase was

AMPEROMETRIC DETECTION OF CATECHOLAMINES WITH LIQUID-CHROMATOGRAPHY AT A POLYPYRROLE-PHOSPHOMOLYBDIC ANION-MODIFIED ELECTRODE

A conducting polypyrrole film immobilized with PMo12O403- anion on a glassy carbon electrode was prepared by an electrochemical method. This kind of chemically modified electrode (CME) was prepared successfully by doping the polypyrrole film electrode wit