A method for the enrichment of phosphopeptides based on magnetic nanoparticles coated with polyoxometalate (POM) was developed. A layer-by-layer assembly technique was used to prepare magnetic nanoparticles (MNPs) coated with polyoxometalate and chitosan. The composites were used for phosphopeptide enrichment prior to analysis by matrix assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF MS). The composites exhibited advantages of rapid magnetic separation, hydrophilicity, positive electricity, and a high selectivity for enrichment of phosphopeptides. β-Casein was selected as a model phosphorylated protein to assess the performance of the enrichment technique. After the enrichment step, the limit of detection was determined to be 0.02 fmol. The prepared POM-based MNPs thus exhibit significant potential in the detection of low-abundance phosphoproteins.
A method based on the magnetic solid-phase extraction using magnetic carbon nitride composites coupled with high performance liquid chromatography-fluorescence detector (HPLC-FLD) was developed for the simultaneous determination of three hydroxyl polycyclic aromatic hydrocarbons (OH-PAHs) in urine. The synthesized sorbent was characterized by scanning electron microscope, X-ray diffractometer, vibrating sample magnetometer and surface area analyzer. The extraction parameters such as amount of sorbent, extraction time, eluting solvent and volume (single eluting volume×eluting times) were investigated in detail. Under the optimized conditions, the method showed a linear range of 0.25-250 μg/L (correlation coefficient=0.999). The limit of detection was 0.08 μg/L and the limit of quantification was 0.25 μg/L for each analyte. The proposed method gave a recovery of 90.1%-102%. The relative standard deviations for the intra-day and inter-day were 1.5%-7.7% and 2.2%-8.7%, respectively. The feasibility of the developed method was further demonstrated during the analysis of real samples. The results indicate that the magnetic carbon nitride composites can be used for the effective purification and enrichment of three OH-PAHs in urine. In addition, the method can be applied for analysis of urinary OH-PAHs in a simple, fast, and effective manner.
A magnetic particle with a trimethylstearylammonium-bromide-modified surface was prepared as an adsorbent by a sol-gel method. An on-line magnetic solid phase extraction (MSPE) device was established and used for extraction and preconcentration of two sulfonylurea herbicides (SUHs) (chlorsulfuron and bensulfuron-methyl) in water samples prior to high-performance liquid chromatography. On-line MSPE parameters were optimized, including desorption conditions, adsorbent dose, pH of the sample solution, and injection flow rate. Under the optimum conditions, satisfactory linearity was obtained (correlation coefficients ≥ 0.9997). The limits of detection (LODs) of chlorsulfuron and bensulfuron-methyl were 0.32 and 1.12 μg/L, respectively. The method was successfully applied to determine two sulfonylurea herbicides in three types of environmental water samples. The recoveries of sulfonylurea herbicides were in the range of 70.0%-113.4%. The results confirmed that this method is efficient and simple and has a wide application potential in separation and enrichment of sulfonylurea herbicides in environmental water samples.
Neurotransmitters (NTs) are endogenous chemical messengers that are involved in nerve signal transmission and play important roles in brain function. Changes in NT concentrations in the central nervous system are related to many mental and physiological illnesses. The determination of various NTs has become important in disease diagnosis, monitoring, and treatment interventions. Effective monitoring of NTs in vivo is essential for disease diagnosis and treatment as well as for the research and development of new drugs. This article provides a review of the methods used in NT detection in recent years, including instrumental and electrochemical techniques as well as some new detection methods, and summarizes the applications of the methods for NT detection in some diseases.
In this paper, the separation and purification of nattokinase have been reviewed by primarily focusing on solvent precipitation, adsorption column chromatography, magnetic microspheres, expanded bed, reverse micelle, and three-phase separation methods. The different methods for determination of the enzyme activity have been discussed and compared. Finally, the feasibility that the nucleic acid-based identification techniques can be used for nattokinase purification and enzyme activity assay has been proposed.
The application of boronic acid affinity chromatography to glycoprotein/glycopeptide enrichment is increasingly maturing. The enrichment selectivity, biocompatibility, and facile operation protocol are key aspects in efficient enrichment methods. In this work, a novel triazo-cyanide boronic acid functionalized material (TCNBA) was prepared using triazo-cyanide click chemistry. The TCNBA was proved to be successfully synthesized through infrared ray (IR) characterization. Subsequently, the glycopeptide/glycoprotein enrichment selectivity of the TCNBA was evaluated. Matrix-assisted laser desorption/ionization time-of-flight mass (MALDI-TOF MS) was employed for the glycopeptide enrichment selectivity evaluation. Taking the digestion of horseradish peroxidase (HRP) and immunoglobulin G (IgG) as samples, 13 and 11 glycopeptides could be characterized with improved signals after TCNBA enrichment, respectively. High abundance non-glycopeptides could be removed effectively from the eluting fraction. This result indicates the high glycopeptide enrichment selectivity of TCNBA. In addition, a mixture of HRP and bovine serum albumin (BSA) enzymatic solution (1:10, amount of substance ratio) was utilized as a sample, and five glycopeptide signals could be identified following enrichment. To evaluate the glycoprotein enrichment selectivity, sodium salt-polyacrylamide gel electrophoresis (SDS-PAGE) was adopted as an evaluation method. Mixtures of HRP, IgG, BSA, and ribonuclease B (RNaseB) proteins were employed as samples, and the results demonstrated that TCNBA had a high glycoprotein enrichment selectivity. The application of TCNBA to the analysis of a real biosample was also evaluated using human plasma. The results indicated the TCNBA could be utilized in large-scale glycoprotein analysis.
In this paper, molecularly imprinted photonic crystal hydrogels (MIPHs) were prepared by combining photonic crystals with molecular imprinting technology. The MIPHs were used as optical sensors for the rapid reorganization and detection of melamine in water samples. In this experiment, melamine was used as a template molecule, and the MIPHs were prepared by successive self-assembly, polymerization, and template removal. Morphological characterization by scanning electron microscopy (SEM) showed that the MIPHs possessed a highly ordered three-dimensional (3D) macroporous structure containing nanocavities. As optical sensors, the MIPHs were able to transform molecular recognition events into fluorescence signals for rapid and highly selective and sensitive recognition of the target molecule. Based on color changes of the MIPHs, the target analyte could be quickly identified by analysis with image software or even by observation with the naked eye. Under optimal conditions, the Bragg diffraction peak of the MIPHs shifted from 563 to 608 nm when exposed to melamine in mass concentrations of 10-11 to 10-6mol/L, whereas there were no obvious peak shifts when it was exposed to structural analogues of melamine.
Hydrophilic, magnetic molecularly imprinted resins (MMIRs) were fabricated inside Fe3O4@mSiO2 pores by the one-pot copolycondensation of chlorogenic acid (CGA), resorcinol, melamine, and formaldehyde. The final porous MMIRs with larger numbers of surface recognition sites were obtained by removing mSiO2. The successful preparation of MMIRs was confirmed using transmission electron microscopy, Fourier transform infrared spectroscopy, vibrating sample magnetometry, thermo-gravimetric analysis, and water contact angle analysis. The analyses suggest that the MMIRs have excellent hydrophilicity and magnetic solid-phase extraction efficiency. The MMIRs had a good adsorption capacity (50.87 mg/g), fast rate of adsorption (equilibrium was attained at 70 min), and specific recognition for CGA. The MMIRs, in combination with high performance liquid chromatography, were directly used for the selective extraction and determination of CGA in Duzhong brick tea. The limit of detection and recovery were 0.7 mg/L and 93.1%-109.4%, respectively, with relative standard deviations of less than 9.6%. The proposed strategy was extremely promising for the facile, rapid, and selective determination of CGA in real aqueous samples.
A novel and effective method was established for the qualitative analysis of impurities in auramine O samples of illegal food additives using high performance liquid chromatography-ion trap-time of flight mass spectrometry (HPLC-IT-TOF-MS). An impurity was identified in the auramine O sample using the optimized HPLC-IT-TOF-MS method. According to the exact mass of each fragment ion measured by multistage MS, the structure of the impurity was determined to be that of 4-(imino (4-(methylamino) phenyl) methyl)-N,N-dimethylaniline hydrochloride. The synthetic route of the auramine O and the source of the identified impurity were proposed. Simultaneously, a preparative high performance liquid chromatography (prep-HPLC) technique was successfully applied for the purification of the auramine O from complex samples. Prep-HPLC columns with particle sizes of 10 μm and 5 μm were used for the separation and purification with injection volumes of 1 mL and 500 μL, respectively. Finally an auramine O reference standard with 99.52% purity was obtained by secondarily purification and determined by the analytical HPLC area normalization method. Deducting the 0.34% moisture content and 0.13% ash content, the final purity of the sample was 99.05%, as determined by mass balance method. The chemical structure was examined using UV, IR, LC-MS, and NMR. The developed method is simple and efficient, and can be applied for the preparation of reference standard materials for other illegal food additives.
A method was established for determination of potential anti-osteoporosis ingredients from Liuwei Dihuang Decoction by osteoblast cell membrane chromatography/ultra-performance liquid chromatography/time-of-flight mass spectrometry (CMC/UPLC-TOF/MS). The osteoblasts were used as the source of cell membrane for the preparation of CMC stationary phase. An osteoblast CMC column (10 mm×2 mm) was prepared by coating silica gel (0.05 g) with cell membrane. The active ingredients in the aqueous extract of Liuwei Dihuang Decoction (90 g/L) were first screened by CMC. Water was used as the mobile phase, and the flow rate was 0.20 mL/min. Then, the eluates of the CMC were qualitatively analyzed by UPLC-TOF/MS using a WATERS ACQUITY UPLC BEH C18 column (10 mm×2 mm). Acetonitrile-water was used as the mobile phase at a flow rate of 0.40 mL/min. This method could quickly and selectively identify 16 potential anti-osteoporotic active ingredients from Liuwei Dihuang Decoction. Due to high catalpol content in Liuwei Dihuang Decoction and its good affinity with CMC column, catapol was selected for in vivo and in vitro pharmacological examinations. It was found that catalpol (1-10 μmol/L) could significantly promote the proliferation of osteoblasts in a dose-dependent manner. It also significantly increased the area of bone staining in osteoporosis zebrafish model. The osteoblast CMC/UPLC-TOF/MS method could quickly screen the anti-osteoporosis active ingredients in complex traditional Chinese medicine prescriptions, and had the advantages of simple operation, high efficiency and high sensitivity.
The analysis of veterinary drugs in organic fertilizers is crucial for an assessment of their potential risks to microbial communities in soils and to human health. A method has been developed for the simultaneous determination of ten fluoroquinolones in organic fertilizers by using the QuEChERS method coupled with high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). The sample was extracted with disodium ethylenediaminetetraacetic acid (Na2EDTA)-McIlvaine buffer (pH=4.0) and acetonitrile. The target compounds were separated on an Atlantis T3 C18 column (250 mm×4.6 mm, 5 μm) with a mobile phase of 0.2% (v/v) formic acid in acetonitrile and analyzed in the multiple reaction monitoring (MRM) mode via electrospray ionization (ESI). Ten fluoroquinolones were quantified by an internal standard method. The calibration curves of the ten fluoroquinolones exhibited good linearity over the range of 10-500 μg/kg, and the correlation coefficients were above 0.9930. The limits of detection were 0.5-2.5 μg/kg; the limits of quantification were 1.7-8.3 μg/kg. The analytical method was successfully applied in a survey of veterinary drug contamination in nine compost samples. The average recoveries were 82.5%-117.1%, with relative standard deviations of 3.4%-10.2%. The method is accurate, reliable, and sensitive and supports the simultaneous detection of various veterinary drug residues. Therefore, this method can provide a basis for the risk assessment of veterinary drugs in organic fertilizers.
Aloe polysaccharide was extracted by water extraction and ethanol precipitation. It was hydrolyzed by trifluoroacetic acid, eluted by a sodium hydroxide gradient on a Dionex CarboPac PA10 column, and detected using a pulsed amperometric detector. This method was used to determine the fucose, rhamnose, arabinose, galactose, glucose, mannose, and xylose in aloe polysaccharide. The results showed that the correlation coefficients (R2) of all the seven target compounds were more than 0.997 in the linear range, and the limits of detection were between 0.007 mg/L and 0.024 mg/L. The recoveries were in the range 97.5%-102.5% with the relative standard deviations in the range 0.1%-4.8%. The method is simple, rapid, sensitive, and accurate for the determination of the monosaccharide content and the constitution of aloe polysaccharides.
Two series of 41 Xinyang Maojian tea samples were investigated and the gas chromatography-mass spectrometry (GC-MS) fingerprints of their aroma components of seven different grades were established using headspace solid-phase micro extraction (HS-SPME) and GC-MS. Based on the 23 selected characteristic aroma components, the samples could be classified into seven different groups through discriminant analysis with four and three groups in two separate series. Six fingerprint similarity calculation methods that reflect the differences between grades of tea to different extents were employed, and the new improved extent similarity method was demonstrated to be the best among them. The results for the similarity evaluation displayed good correlation with the actual grades, especially for the series of tea of higher qualities, and the differences between the different grades of teas could be quantified.
A method was developed for the simultaneous determination of benzoic acid and its esters, parabens, phenoxyisopropanol, chlorphenesin, dehydroacetic acid, 2,6-di-tert-butyl-4-methylphenol, methylchloroisothiazolone, methylisothiazolone and other preservatives in cosmetics by gas chromatography-tandem mass spectrometry (GC-MS/MS). The samples were extracted ultrasonically with a 0.1 mg/mL L(+)-ascorbic acid menthol solution after being spiked with a mixture solution of 2-octanol, phenol and heptachlor as internal standards and anhydrous sodium sulfate as a dehydrating reagent. Finally, the extract was centrifuged, filtered, and then analyzed by GC-MS/MS. The analytes were separated using an HP-5MS capillary column (30 m×0.25 mm×0.25 μm) with a temperature-programming program. The inlet, transfer line and ion source temperatures were set to 260, 250 and 230℃, respectively. Helium (99.999%) was used as the carrier gas at a flow rate of 1 mL/min. The final extract (1 μL) was injected in split mode (10:1). Analysis was performed in the multiple reaction monitoring (MRM) mode. Three types of cosmetics, as well as water, milk and cream as samples were selected to verify the accuracy of the method at four levels. The average spiked recoveries ranged from 82.3% to 119.4% with relative standard deviations (n=6) of less than 14.3%. The limits of detection were lower than 0.99 μg/kg for all the preservatives. The method is sensitive, and reliable for the simultaneous determination of the 25 preservatives in cosmetics. Nonetheless, complementary methods need to be developed for the determination of some other preservatives that cannot be detected by GC-MS/MS.
byDalian Institute of Chemical
Physics,CASNational Chromatographic R. and A.
Copyright © 2010
Editorial Office of Chinese Journal of Chromatography, Dalian Institute of Chemical Physics, CAS 辽ICP备10003855号
457 Zhongshan Road,116023, Dalian,P.R.China
Tel: +86-411-84379021, Fax: +86-411-84379600 E-mail: firstname.lastname@example.org