Huwei Liu

Online Coupling of In-Tube Solid-Phase Microextraction with Direct Analysis in Real Time Mass Spectrometry for Rapid Determination of Triazine Herbicides in Water Using Carbon-Nanotubes-Incorporated Polymer Monolith

Online coupling of in-tube solid phase microextraction (IT-SPME) with direct analysis in real time mass spectrometry (DART-MS) was realized for the first time and applied in the analysis of triazine herbicides in lake water and orange juice. We incorporated single-wall carbon nanotubes (SWNTs) into a polymer monolith containing methacrylic acid (MAA) and ethylene dimethacrylate (EDMA) to form a novel poly(methacrylic acid-co-ethylene dimethacrylate-co-single wall carbon nanotubes) (poly(MAA-EDMA-SWNT)) monolith, which was then used in IT-SPME for enrichment of six triazine herbicides from water samples. With the online combination of IT-SPME with DART-MS, the analytes desorbed from the monolith were directly ionized by DART and transferred into MS for detection, thus rapid determination was achieved. Compared with regular DART-MS method, this online IT-SPME-DART-MS method was more sensitive and reproducible, because of the IT-SPME procedures and the isotope-labeled internal standard used in the experiment. Six triazine herbicides were determined simultaneously using this method with good linearity (R(2) > 0.998). The limit of quantification (signal-to-noise ratio of S/N = 10) of the six herbicides were only 0.06-0.46 ng/mL. The proposed method has been applied to determine triazine herbicides in lake water and orange juice, showing satisfactory recovery (85%-106%) and reproducibility (relative standard deviation of RSD = 3.1%-10.9%).

Analytical Methods in Lipidomics and Their Applications

■ CONTENTS Analytical Methods of Lipidomics 162 Extraction Methods of Lipids 163 Direct-Infusion MS-Based Lipidomics Analysis 163 Electrospray Ionization (ESI) MS 163 Matrix-Assisted Laser Desorption Ionization (MALDI) MS 164 Other Ionization Techniques Used in Lipidomics Analysis 164 Mass Spectrometry Imaging (MSI) in Lipidomics 165 Chromatography-Based Lipidomics Analysis 165 TLC 166 GC 166 HPLC 166 SFC 167 CE 167 Spectroscopy 167 Nuclear Magnetic Resonance (NMR) 167 Raman Spectroscopy 168 Applications of Lipidomics Analysis in Life Science 168 Lipidomics of Cancers 168 Lipidomics of Alzheimer’s Disease (AD) 168 Cellular Lipidomics 168 Plants 168 Conclusions 170 Author Information 170 Corresponding Author 170 Notes 170 Biographies 170 Acknowledgments 171 References 171

Applications of ambient mass spectrometry in high-throughput screening

The development of rapid screening and identification techniques is of great importance for drug discovery, doping control, forensic identification, food safety and quality control. Ambient mass spectrometry (AMS) allows rapid and direct analysis of various samples in open air with little sample preparation. Recently, its applications in high-throughput screening have been in rapid progress. During the past decade, various ambient ionization techniques have been developed and applied in high-throughput screening. This review discusses typical applications of AMS, including DESI (desorption electrospray ionization), DART (direct analysis in real time), EESI (extractive electrospray ionization), etc., in high-throughput screening (HTS).

Monolithic Superhydrophobic Polymer Layer with Photopatterned Virtual Channel for the Separation of Peptides Using Two-Dimensional Thin Layer Chromatography-Desorption Electrospray Ionization Mass Spectrometry

Superhydrophobic monolithic porous polymer layers with a photopatterned hydrophilic channel have been prepared. These layers were used for two-dimensional thin layer chromatography of peptides. The 50 microm thin poly(butyl methacrylate-co-ethylene dimethacrylate) layers supported onto 4.0 x 3.3 cm glass plates were prepared using UV-initiated polymerization in a simple glass mold. Photografting of a mixture of 2-acrylamido-2-methyl-1-propanesulfonic acid and 2-hydroxyethyl methacrylate carried out through a mask afforded a 600 microm wide virtual channel along one side of the layer. This channel, which contains ionizable functionalities, enabled the first dimension separation in ion exchange mode. The aqueous mobile phase migrates only through the channel due to the large difference in surface tension at the interface of the hydrophilic channel and the superhydrophobic monolith. The unmodified part of the layer featuring hydrophobic chemistry was then used for the reversed phase separation in the orthogonal second dimension. Practical application of our technique was demonstrated with a rapid 2D separation of a mixture of model peptides differing in hydrophobicity and isoelectric point using a combination of ion-exchange and reversed phase modes. In the former mode, the peptides migrated 11 mm in less than 1 min. Detection of fluorescently labeled peptides was achieved through UV light visualization. Separation of the native peptides was monitored directly using a desorption electrospray ionization (DESI) source coupled to a mass spectrometer. Unidirectional surface scanning with the DESI source was found suitable to determine both the location of each separated peptide and its molecular mass.

Lipid profiling of rat peritoneal surface layers by online normal- and reversed-phase 2D LC QToF-MS

An online, two-dimensional (2D) liquid chromatography (LC) quadrupole time-of-flight mass spectrometry (QToF-MS) method was developed for lipid profiling of rat peritoneal surface layers, in which the lipid classes and species could be simultaneously separated in one injection with a significantly increased sensitivity. Different lipid classes were separated on a normal-phase column in the first dimension and lipid molecular species were separated on a reversed-phase column in the second dimension, so that the ion suppression effects were reduced while the detection sensitivity was improved. Identified were 721 endogenous lipid species from 12 lipid classes, in which 415 structures were confirmed using tandem mass spectra, and the other 306 lipid molecular species were identified by accurate masses. The linearity, limit of detection, and repeatability were all satisfactory. The method was applied to the investigation of the lipid changes in rat peritoneal surface layer after peritoneal dialysis, and 32 potential lipid biomarkers were identified, as their concentrations in the dosed group were 2.2–12.5 times of those in the control group. The results revealed that this 2D LC-MS system was a promising tool for lipid profiling of complex biological samples.

Determination of synthetic colourant food additives by capillary zone electrophoresis

Abstract A capillary zone electrophoresis method for the separation of six synthetic food colourants is proposed. A background electrolyte solution consisting of 20 m M borate buffer adjusted to pH 7–9 and electromigration injection at 4 kV for 14 s were utilized. A baseline separation of six synthetic colourants commonly used as food additives can be achieved within 10 min, and a linear relationship between the concentration and peak area for each of these pigments was obtained in the concentration range 2–50 ppm, with a correlation coefficient greater than 0.995. The selection of the analytical conditions and the experimental reproducibility are discussed.

Recent advances of chromatography and mass spectrometry in lipidomics

Lipidomics, as a novel branch of metabolomics, which is aimed at comprehensive analysis of lipids and their biological roles with respect to health and diseases, has attracted increased attention from biological and analytical scientists. As a result of the complexity and diversity of lipids, accurate identification and efficient separation are required for lipidomics analysis. Mass spectrometry (MS) and chromatography have been extensively developed in the past few decades and hold a distinguished position in qualification and separation science. They are powerful and indispensable tools for lipidomics. Herein, we present the recent advancement of MS, chromatography, and their hyphenation technologies in lipidomics.

Determination of flavonoids in Semen Cuscutae by RP-HPLC.

Flavonoids contents in 40 samples of Semen Cuscutae collected from areas all around China were investigated. Five principal flavonoids, quercetin 3-O-beta-D-galactoside-7-O-beta-D-glucoside, quercetin 3-O-beta-D-apiofuranosyl-(1-->2)-beta-D-galactoside, hyperoside, quercetin and kaempferol were analyzed simultaneously by using a reversed phase liquid chromatograph system with 0.025 M phosphoric acid-methanol as mobile phase. The recovery of the method was 97.0-102.9%, and all the flavonoids showed good linearity (r > or = 0.9990) in a relatively wide concentration range. The results indicated that contents of flavonoids in S. Cuscutae varied significantly from species to species, locality to locality, and parasiting host to host. Cuscuta australis contained a much higher content of kaempferol than C. chinensis, and few flavonoids were detected in C. japonica. The quality of S. Cuscutae can be evaluated according to the contents of flavonoids.

Optimized separation of pharmacologically active anthraquinones in Rhubarb by capillary electrochromatography

A capillary electrochromatography (CEC) method with diode‐array detection has been developed for the separation of the therapeutically important anthraquinones from Rhubarb extract and commercial traditional Chinese drugs containing Rhubarb. The separation of four major anthraquinones (aloe‐emodin, emodin, chrysophanol, and physcion) was optimized with respect to pH and concentration of buffers, addition of acetonitrile, applied voltage, and column temperature. Baseline separation was achieved for the four anthraquinones in less than 12 min using a background electrolyte consisting of 5 mM acetic acid (pH 4.5) with 80% acetonitrile. The possibility of CEC for the analysis of traditional Chinese medicines was discussed.

Analytical methods for tracing plant hormones

Plant hormones play important roles in regulating numerous aspects of plant growth, development, and response to stress. In the past decade, more analytical methods for the accurate identification and quantitative determination of trace plant hormones have been developed to better our understanding of the molecular mechanisms of plant hormones. As sample preparation is often the bottleneck in analysis of plant hormones in biological samples, this review firstly discusses sample preparation techniques after a brief introduction to the classes, roles, and methods used in the analysis of plant hormones. The analytical methods, especially chromatographic techniques and immuno-based methods, are reviewed in detail, and their corresponding advantages, limitations, applications, and prospects are also discussed. This review mainly covers reports published from 2000 to the present on methods for the analysis of plant hormones.