[Preparation and application of mixed-mode capillary polymer monolithic column].

Based on the diversity of the retention mechanism, mixed-mode capillary monolithic columns have broad application prospect. In this work, a novel capillary polymer monolithic column was prepared with [2-(methacryloyloxy) ethyl] dimethyl-(3-sulfopropyl) ammonium hydroxide (SPE) as monomer, ethylene dimethacrylate (EDMA) as crosslinking agent, azobisisobutyronitrile (AIBN) as initiator and butylalcohol/1, 4-butanediol/water as ternary porogens. Under the optimized reaction conditions including the proportion of monomer and porogens, amount of initiator, reaction temperature and polymerization time, the monolithic column showed good mechanical strength up to 10 MPa, high permeability of 2. 17 x 10(-14) m2 and good repeatability. The peak area RSDs of column-to-column and batch-to-batch reproducibility were 1.0% and 4.6%, respectively. Finally, the capillary monolithic column was evaluated with polar and non-polar test mixtures. It showed hydrophilic interaction under high organic phase while hydrophobic interaction under low organic phase, indicating it a mixed-mode monolithic column.

A novel surface-confined glucaminium-based ionic liquid stationary phase for hydrophilic interaction/anion-exchange mixed-mode chromatography.

Glucaminium-based ionic liquids are a new class of recently developed ionic liquids and prepared by functionalizing the amine group of N-methyl-d-glucamine, which renders them good hydrophilicity due to the presence of the glucose structure and charged quaternary ammonium group. In the present study, a glucaminium-based ionic liquid N,N-diallyl-N-methyl-d-glucaminium bromide was synthesized and subsequently bonded to the surface of 3-mercaptopropyl modified silica materials through "thiol-ene" click chemistry. The obtained stationary phase was characterized by elemental analysis and infrared spectroscopy, and then packed as a HPLC column. A mixture of five nucleosides was used to characterize the separation performance of the obtained column under HILIC mode and the column efficiency was determined with cytidine as the test solute, reaching 80,000plates/m. Then, the retention behavior was evaluated by investigating the effect of various chromatographic factors on retention of different types of solutes, and the results revealed that the developed surface-confined glucaminium-based ionic liquid stationary phase exhibited a hydrophilic interaction/anion-exchange mixed-mode retention mechanism. Finally, two mixtures of nucleotides and flavonoids were separated on the glucaminium-based ionic liquid column, respectively under hydrophilic interaction and hydrophilic interaction/anion-exchange mixed-mode chromatography. In conclusion, the multimodal retention capabilities of the glucaminium-based ionic liquid column could offer a wider range of retention behavior and flexible selectivity toward polar and hydrophilic compounds.

Facile synthesis of boronate-decorated polyethyleneimine-grafted hybrid magnetic nanoparticles for the highly selective enrichment of modified nucleosides and ribosylated metabolites.

Ribosylated metabolites, especially modified nucleosides, have been extensively evaluated as cancer-related biomarkers. Boronate adsorbents are considered to be promising materials for extracting them from complex matrices. However, the enrichment of ribosylated metabolites in low abundance is still a challenge due to the limited capacity and selectivity of the existing boronate adsorbents. In this study, a novel type of magnetic nanoparticles named Fe3O4@SiO2@PEI-FPBA was synthesized by grafting polyethyleneimine (PEI) onto the surface of Fe3O4@SiO2 before modification by boronate groups. The high density of the amino groups on the PEI chains supplied a large number of binding sites for boronate groups. Thus, the adsorption capacity (1.34 ± 0.024 mg/g) of the nanoparticles, which is 6- to 7-fold higher than that of analogous materials, was greatly improved. The unreacted secondary amines and tertiary amines of the PEI enhanced the aqueous solubility of the nanoparticles, which could efficiently reduce nonspecific adsorption. The nanoparticles were able to capture 1,2 cis-diol nucleosides from 1000-fold interferences. Moreover, the flexible chains of PEI were favorable for effective enrichment and quick equilibration (<2 min). Finally, 60 ribose conjugates were enriched from human urine using the nanoparticles. Among them, 43 were identified to be nucleosides and other ribosylated metabolites. Nine low abundance modified nucleosides were detected for the first time. In conclusion, Fe3O4@SiO2@PEI-FPBA is an attractive candidate material for the highly selective enrichment of 1,2-cis-diol compounds.

Development and evaluation of new imidazolium-based zwitterionic stationary phases for hydrophilic interaction chromatography.

Hydrophilic interaction liquid chromatography (HILIC) has been widely used for separating polar compounds as a complement mode to reversed-phase liquid chromatography. The development of new stationary phases for HILIC is significant to improve the coverage of various polar and hydrophilic compounds. The present study described the preparation and application of novel imidazolium-based zwitterionic stationary phases. 1-Vinyl-3-(butyl-4-sulfonate) imidazolium was synthesized from 1-vinylimidazole and 1,4-butane sultone, then bonded to the surface of 3-mercaptopropyl modified silica particles (core-shell silica and totally porous silica) by "thiol-ene" click chemistry to obtain the resulting zwitterionic stationary phase with a positively charged imidazole ring and a negatively charged sulfonate group. The zwitterionic stationary phases exhibited good selectivity and favorable retention for a wide range of polar solutes (nucleosides, nucleic acid bases, benzoic organic acids, uric acid and its methyl derivatives, water-soluble vitamins) as compared to a bare silica column. The column efficiency could reach up to 100,000 theoretical plates/m with cytosine as the test solute. The retention changes of various types of test solutes were investigated under different chromatographic conditions including water content, pH, buffer salt concentration in mobile phase and column temperature. The results indicated that the retention of solutes on the stationary phase was the outcome of a mixed-mode retention mechanism (i.e. a combination of adsorptive and partitioning interactions). In conclusion, the new imidazolium-based zwitterionic stationary phases have shown excellent chromatographic behavior for a variety of polar solutes under HILIC mode, and have a great potential as a new type of stationary phases for HILIC.

[Triacyliglyeride profiling in serum by silver ion high performance liquid chromatography-atmospheric pressure chemical ionization mass spectrometry].

A simple and effective method was developed to investigate triacylglyceride (TAG) compounds in biological matrices using silver ion high performance liquid chromatography-mass spectrometry (Ag+ -HPLC-MS). The TAG compounds from mouse serum were extracted by a modified Folch method using the classical CHC13-MeOH solvent system. The extract was separated on a Varian ChromSpher 5 Lipids column with isocratic elution using acetonitrile-hexane (1: 99, v/v) as mobile phase at a flow rate of 0.75 mL/min, and detected by a mass spectrometer equipped with an atmospheric pressure chemical ionization (APCI) source in positive ion mode to acquire sufficient MS information of TAG compounds by enhanced mass spectrometry (EMS), enhanced product ion (EPI) and neutral loss (NL) scans. The identification of TAG compounds was based on their chromatographic behaviors and MS data. Besides, the NL scans of thirty fatty acids were performed to further validate the results. Finally, 66 TAG compounds as well as 5 cholesteryl ether (CE) compounds were obtained from the mouse serum extract. This method is simple, reproducible and also suitable for the analysis of TAG compounds in other samples.

A fully automated system with on-line micro solid-phase extraction combined with capillary liquid chromatography-tandem mass spectrometry for high throughput analysis of microcystins and nodularin-R in tap water and lake water.

Microcystins and nodularins are cyclic peptide hepatotoxins and tumour promoters from cyanobacteria. The present study describes the development, validation and practical application of a fully automated analytical method based on on-line micro solid-phase extraction-capillary liquid chromatography-tandem mass spectrometry for the simultaneous determination of seven microcystins and nodularin-R in tap water and lake water. Aliquots of just 100 µL of water samples are sufficient for the detection and quantification of all eight toxins. Selected reaction monitoring was used to obtain the highest sensitivity. Good linear calibrations were obtained for microcystins (50-2000ng/L) and nodularin-R (25-1000 ng/L) in spiked tap water and lake water samples. Excellent interday and intraday repeatability were achieved for eight toxins with relative standard deviation less than 15.7% in three different concentrations. Acceptable recoveries were achieved in the three concentrations with both tap water matrix and lake water matrix and no significant matrix effect was found in tap water and lake water except for microcystin-RR. The limits of detection (signal to noise ratio=3) of toxins were lower than 56.6 ng/L which is far below the 1 µg/L defined by the World Health Organization provisional guideline for microcystin-LR. Finally, this method was successfully applied to lake water samples from Tai lake and proved to be useful for water quality monitoring.

[Study of phospholipid profile of ovarian tumor by high performance liquid chromatography-mass spectrometry].

Ovarian tumor has been paid more and more attention since its influence on women's health and life quality is increasing. Ovarian cancer is one of the three gynecologic cancers, and its mortality is the highest one of them. Phospholipid metabolic profiling method based on high performance liquid chromatography-electrospray mass spectrometry (HPLC/ESI-MS) has been applied in the study of ovarian tumors including benign (B) and malignant (M) ovarian tumors. The data of phospholipid profile collected by HPLC/ESI-MS were transformed and the peak list was obtained with the commercial software automatically. The total differences of phospholipids among M, B and normal (N) groups were found with the orthogonal signal correction and partial least-squares (OSC-PLS). Further, the differential phospholipids were selected according to the S-plot, the variable importance value (VIP > 1) and p (p < 0.05). These phospholipids were plasmalogen phospatidylethanol, phosphatidylcholine, plasmalogen phosphatidylcholine, sphingomyelin and lysophosphatidylcholine. This research provides some new and useful information of what has happened in phospholipids of the women with ovarian tumors.

[Effect of menthol cigarette on rats for metabonomics by liquid chromatography-mass spectrometry].

A liquid chromatography-mass spectrometry (LC-MS) method was developed for the metabonomics study of menthol cigarette effect on rats. Urines from three groups of rats were analyzed, including control rats, rats treated with menthol cigarette and rats treated with normal cigarette, and the data were processed by the method of principal component analysis (PCA). The PCA score plot showed that the metabolic difference between the rats treated with menthol cigarette and the control rats was smaller than that between the rats treated with normal cigarette and the control rats. Based on the PCA score plot, eight important metabolites, for example, kynurenic acid, were found and identified. Their relative concentration changes among the three groups further indicated that menthol cigarette maybe decrease the metabolic effect on rats.