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1.
Chemical characteristic fragment filtering in MSn chromatograms was proposed to detect and identify the components in rhubarb rapidly using high‐performance liquid chromatography coupled with linear ion trap–Orbitrap mass spectrometry. Characteristic fragments consist of diagnostic ions and neutral loss fragments. Characteristic fragment filtering is a postacquisition data mining method for the targeted screening of groups with specific structures, including three steps: first, in order to comprehensively summarize characteristic fragments for global identification of the ingredients in rhubarb, representative authentic standards of dominant chemical categories contained in rhubarb were chosen, from which fragmentation rules and a characteristic fragments schedule were proposed; second, characteristic fragment filtering was used to rapidly recognize analogous skeletons; finally, combined with retention time, accurate mass, characteristic fragments, and previous literature, the structures of the filtered compounds were identified or tentatively characterized. As a result, a total of 271 compounds were detected and identified in rhubarb, including 34 anthraquinones, 83 anthrones, 46 tannins, 17 stilbenes, 24 phenylbutanones, 26 acylglucosides, 26 chromones, and 15 other compounds, 69 of which are potentially new compounds. The proposed characteristic fragment filtering strategy would be a reference for the large‐scale detection and identification of the ingredients of herbal medicines.  相似文献   

2.
Yu L  Li SF 《Journal of chromatography. A》2007,1161(1-2):308-313
Capillary electrophoresis has been utilized for the rapid analysis of bacteria under specific experimental conditions. In this work, a method of large-volume sample stacking with polarity switching was evaluated for the analysis of bacteria by capillary electrophoresis with laser-induced fluorescence detection in order to enhance the detection sensitivity. The results indicated that the proposed method is not only effective for the focusing of bacterial cells, but also for the separation of mixtures of bacteria. With the optimized conditions, an enhancement factor of around 60-fold was obtained when long sample plug (up to 39.6% of capillary volume) was injected. Moreover, with the help of such stacking method, single, sharp, intense peak with high efficiency was observed without multiple peaks attributable to irregular clusters and aggregates of bacterial cells. This simple stacking approach appears to be promising as a rapid sterility test in various fields of applications.  相似文献   

3.
4.
A sequential online extraction, clean‐up and separation system for the determination of betaine, l ‐carnitine and choline in human urine using column‐switching ion chromatography with nonsuppressed conductivity detection was developed in this work. A self‐packed pretreatment column (50 × 4.6 mm, i.d.) was used for the extraction and clean‐up of betaine, l ‐carnitine and choline. The separation was achieved using self‐packed cationic exchange column (150 × 4.6 mm, i.d.), followed by nonsuppressed conductivity detection. Under optimized experimental conditions, the developed method presented good analytical performance, with excellent linearity in the range of 0.60–100 μg mL−1 for betaine, 0.75–100 μg mL−1 for l ‐carnitine and 0.50–100 μg mL−1 for choline, with all correlation coefficients (R2) >0.99 in urine. The limits of detection were 0.15 μg mL−1 for betaine, 0.20 μg mL−1 for l ‐carnitine and 0.09 μg mL−1 for choline. The intra‐ and inter‐day accuracy and precision for all quality controls were within ±10.32 and ±9.05%, respectively. Satisfactory recovery was observed between 92.8 and 102.0%. The validated method was successfully applied to the detection of urinary samples from 10 healthy people. The values detected in human urine using the proposed method showed good agreement with the measurement reported previously.  相似文献   

5.
6.
Stable isotope labels are routinely introduced into proteomes for quantification purposes. Full labeling of cells in varying biological states, followed by sample mixing, fractionation and intensive data acquisition, is used to obtain accurate large‐scale quantification of total protein levels. However, biological processes often affect only a small group of proteins for a short time, resulting in changes that are difficult to detect against the total proteome background. An alternative approach could be the targeted analysis of the proteins synthesized in response to a given biological stimulus. Such proteins can be pulse‐labeled with a stable isotope by metabolic incorporation of ‘heavy’ amino acids. In this study we investigated the specific detection and identification of labeled proteins using acquisition methods based on Precursor Ion Scans (PIS) on a triple‐quadrupole ion trap mass spectrometer. PIS‐based methods were set to detect unique immonium ions originating from labeled peptides. Different labels and methods were tested in standard mixtures to optimize performance. We showed that, in comparison with an untargeted analysis on the same instrument, the approach allowed a several‐fold increase in the specificity of detection of labeled proteins over unlabeled ones. The technique was applied to the identification of proteins secreted by human cells into growth media containing bovine serum proteins, allowing the preferential detection of labeled cellular proteins over unlabeled bovine ones. However, compared with untargeted acquisitions on two different instruments, the PIS‐based strategy showed some limitations in sensitivity. We discuss possible perspectives of the technique. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

7.
A simple method for the determination of betaine, l ‐carnitine, and choline in human urine was developed based on column‐switching ion chromatography coupled with nonsuppressed conductivity detection by using a self‐packed column. A pretreatment column (50 mm × 4.6 mm, id) packed with poly(glycidyl methacrylate‐divinylbenzene) microspheres was used for the extraction and cleanup of analytes. Chromatographic separation was achieved within 10 min on a cationic exchange column (150 mm × 4.6 mm, id) using maleic anhydride modified poly(glycidyl methacrylate‐divinylbenzene) as the particles for packing. The detection was performed by ion chromatography with nonsuppressed conductivity detection. Parameters including column‐switching time, eluent type, flow rates of eluent, and interfering effects were optimized. Linearity (r 2 ≥ 0.99) was obtained for the concentration range of 0.50–100, 0.75–100, and 0.25–100 μg/mL for betaine, l ‐carnitine, and choline, respectively. Detection limits were 0.12, 0.20, and 0.05 μg/mL for betaine, l ‐carnitine, and choline, respectively. The intra‐ and interday accuracy and precision for all quality controls were within ±10.11%. Satisfactory recovery was observed between 92.5 and 105.0%. The validated method was successfully applied for the determination of betaine, l ‐carnitine, and choline in urine samples from healthy people.  相似文献   

8.
A new MEKC method with large‐volume sample stacking and polarity switching was developed for on‐line preconcentration and detection of sulfonylurea herbicide (SUH) residues in cereals, including nicosulfuron (NS), thifensulfuon (methyl) (TFM), tribenuron‐methly (TBM), sulfometuron‐methyl (SMM), pyrazosulfuron‐ethyl (PSE), and chlorimuron‐ethyl (CME). In order to achieve a high resolution and enrichment factor, several parameters were optimized, such as the pH of the running buffer, the concentration of the BGE and the SDS, the separate voltage, the sample size, the pH, and the electrolyte concentration of the sample. The optimal running buffer was composed of 30 mM borate and 80 mM SDS at pH 7.0. The borate concentration in the sample was 30 mM and the pH value of the sample was the same as that of the running buffer. The concentrating voltage and the separating voltage were –15 kV and 15 kV, respectively. The sample size was 1.455 kPa × 780 s (33.11 cm). Under the optimum conditions, for NS, TFM, TBM, SMM, PSE, and CME, the enrichment factors were 613, 642, 835, 570, 709, and 599; the LODs were 0.29–0.50 ng/g, 0.22–0.36 ng/g, 0.60–0.89 ng/g, 0.39–0.72 ng/g, 0.28–0.56 ng/g, and 0.31–0.57 ng/g; the LOQs of six SUHs were all 5 ng/g; the average recoveries of the spiked sample were 86.68–92.99%, 80.73–93.65%, 81.49–94.40%, 82.97–95.1%, 82.96–98.84%, and 80.41–92.94%, respectively.  相似文献   

9.
In this study, in‐column fiber‐optic (ICFO) laser‐induced fluorescence (LIF) detection technique is coupled with capillary electrophoresis (CE) for the rapid separation of neodymium for the first time. The effects of buffer concentration, buffer pH, and separation voltage on the CE behaviors, including electrophoretic efficiency and detection sensitivity, are investigated in detail. Under the optimal condition determined in this study (15 mM borate buffer, pH 10.50, separation voltage 24 kV), neodymium could be separated effectively from the neighboring lanthanides (praseodymium and samarium) within several minutes, and the limit of detection for neodymium is estimated to be at the ppt level. The ICFO‐LIF‐CE system assembled in this study exhibits unique performance characteristics such as low cost and flexibility. Meanwhile, the separation efficiency and detection sensitivity of the assembled CE system are comparable to or somewhat better than those obtained in the previous traditional CE systems, indicating the potential of the assembled CE system for practical applications in the fields of spent nuclear fuel analysis, nuclear waste disposal/treatment, and nuclear forensics.  相似文献   

10.
The application of ion chromatography with the column‐switching technique for the simultaneous analysis of peroxydisulfate and conventional inorganic anions in a single run is described. With this method, conventional inorganic anions were separated by consecutive elution through both the guard column and separation column, but peroxydisulfate that only passed through the guard column had a good peak shape and short retention time. A series of standard solutions consisting of target anions of various concentrations from 0.01 to 75 mg/L were analyzed, with a correlation coefficient (r) ≥ 0.9990. The limits of detection were in the range of 0.49–9.84 μg/L based on the S/N of 3 and a 25 μL injection volume. RSDs for retention time, peak area, and peak height were all <1.77%. A spiking study was performed with satisfactory recoveries between 97.6 and 103.4% for all anions. The quantitative determination of peroxydisulfate and conventional inorganic anions in surface waters was accomplished within 18 min by this column‐switching technique.  相似文献   

11.
A novel coumarin-based compound 1 featuring thiosemicarbazone as binding unit, was reported as a colorimetric and fluorescent probe for the detection of fluoride anion. The addition of F? to a solution of probe 1 in tetrahydrofuran resulted in evident naked-eye color change from green-yellow to orange-red under daylight and obvious fluorescence quenching within 3 s. And the detection limit toward F? was calculated to be as low as 2.16 × 10?7 mol/L. 1H NMR titrations proved that the interaction between 1 and fluoride ion: hydrogen bond at low fluoride ion concentration, deprotonation at high fluoride ion concentration. Besides, it exhibited highly sensitivity and selectivity for F? over other examined ions (Cl?, Br?, I?, AcO?, NO3?, HSO4?, H2PO4?) in tetrahydrofuran solution.  相似文献   

12.
A sensitive and selective method for simultaneous quantitation of 15 benzodiazepines in human whole blood using rapid GC with negative‐ion chemical ionization MS is proposed. A mixed‐mode cation‐exchange polymeric sorbent was used for SPE. Different extraction solvents or mixtures of solvents of different compositions for elution of the adsorbed analytes, and washing steps for eliminating interferences in the column were tested. Analytes were eluted from the column using 5% v/v NH4OH in methanol. A derivatization step using different silylation reagents, time, and temperature was tested. Extracts from SPE were silylated by a mixture of N‐(tert‐butyldimethylsilyl)‐N‐methyltrifluoroacetamide, acetonitrile, ethyl acetate, and subjected to gas chromatographic analysis. The LODs of 15 benzodiazepines in whole blood samples ranged from 0.24–0.62 ng mL?1. The RSDs of samples used for three different quality control concentration levels were lower than 7.0%, and the accuracy ranged from 89.5 to 110.5%. The results show that the developed method is accurate, sensitive, selective, and very fast. Finally, the applicability of this method for determination of trace concentrations of several benzodiazepines in real blood samples has been demonstrated.  相似文献   

13.
A new rapid switching near‐IR electrochromic conjugated propeller‐shape polymer (PBTPAFL) with lower oxidation potential containing a di‐triarylamine group was synthesized via Suzuki coupling approach. The observed UV‐vis‐NIR absorption changes in the PBTPAFL film at various potentials are fully reversible and associated with strong color changes from the original light green to dark green and then to a Prussian blue. Excellent continuous cyclic stability of the electrochromic characteristics with a rapid color switching time 2.58 s and bleaching time 1.76 s was found as well. Compared with P1 and P2, the introduction of more electron‐donating propyl phenyl group in the para position of PBTPAFL lowered the oxidative potential and prevented coupling reaction during the electrochromic procedure. The high molecular weight conjugated polymer having high thermal stability with Td10 more than 450 °C has excellent solubility in common organic solvents such as NMP, THF, chloroform, toluene, xylene, and benzene at room temperature (25 °C) due to the propeller‐shape structure and long alkyl chain on fluorene. Herein, from the combination of the experimental and computational study, we proposed a mechanism on the basis of the molecular orbital theory to explain the electrochromic oxidation behavior. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3913–3923, 2010.  相似文献   

14.
A simple CE method for simultaneous determination of glyphosate and its metabolites (i.e. aminomethylphosphonic acid, glyoxylate, sarcosine and formaldehyde) in plants is reported here. A BGE of pH 7.5, 10% ACN, 7.5 mM phthalate, containing 0.75 mM hexadecyltrimethylammonium bromide as an electro‐osmotic flow modifier, an applied voltage of –20 kV and absorptiometric monitoring at 220 nm were the optimal chemical and instrumental parameters. The method, with development time 20 min, shows linear calibrations within the range 5–500 μg/mL (for all target analytes) with correlation coefficients between 0.999 and 0.998. It has been validated by application to samples of Lolium spp. The electroinjection mode hinders most interferents to enter the capillary, thus providing a clean electropherogram and making unnecessary long sample‐preparation steps.  相似文献   

15.
This paper describes approaches for stacking large volumes of sample solutions containing a mixture of chlorophenols and chlorophenoxyacetic acids as their anions in capillary zone electrophoresis, and compares results to standard capillary electrophoresis (CE) and normal stacking modes. In order to increase the amount of sample injected beyond the optimal conditions and maintain high resolution, the sample introduction buffer must be removed after the stacking process is completed. This is achieved by pumping the sample buffer out of the column using polarity switching. Large sample volumes are loaded by hydrodynamic injection, then stacked at the injection buffer/run electrolyte interface, followed by the removal of the large plug of low-conductivity sample matrix from the capillary column using polarity switching and finally the separation of the stacked anions in a basic buffer (pH 8.65). Around 10- and 40-fold improvement of sensitivity was achieved by normal stacking and large-volume stacking with polarity switching, respectively, when compared to the standard CE analysis. Sweeping-micellar electrokinetic capillary chromatography (MEKC) was also investigated for the purpose of comparison to the stacking technique. The method should be suitable for the analysis of these chemical compound classes in industrial chlorophenoxyacetic acid manufacture.  相似文献   

16.
Pheophytins and pyropheophytin are degradation products of chlorophyll pigments, and their ratios can be used as a sensitive indicator of stress during the manufacturing and storage of olive oil. They increase over time depending on the storage condition and if the oil is exposed to heat treatments during the refining process. The traditional analysis method includes solvent‐ and time‐consuming steps of solid‐phase extraction followed by analysis by high‐performance liquid chromatography with ultraviolet detection. We developed an improved dilute/fluorescence method where multi‐step sample preparation was replaced by a simple isopropanol dilution before the high‐performance liquid chromatography injection. A quaternary solvent gradient method was used to include a fourth strong solvent wash on a quaternary gradient pump, which avoided the need to premix any solvents and greatly reduced the oil residues on the column from previous analysis. This new method not only reduces analysis cost and time but shows reliability, repeatability, and improved sensitivity, especially important for low‐level samples.  相似文献   

17.
A relatively simple procedure is described for the selective and highly sensitive determination of amitrole (3-amino-1,2,4-triazole) by ionpair HPLC with amperometric detection. The separation was achieved on a polar CN-column using hexane, propanol, water (62:36:2) with LiClO4 (2.5 g·l–1) and trichloroacetic acid (2 g·l–1) as electrolytes. The determination range lies between 500 pg and 500 ng and the limit of detection was found to be 200 pg (s.d.: 11%; N=9). The minimum detectability for the alternative UV-monitoring was 2.5 ng. The developed method may be helpful in production and quality control and for the selective determination of amitrole in commercial formulations.  相似文献   

18.
Nucleotide pyrophosphatase/phosphodiesterase 1 (NPP1) is a membrane glycoprotein involved in the hydrolysis of extracellular nucleotides. Its main substrate is ATP yielding AMP and pyrophosphate. NPP1 has been proposed as a novel drug target, for diabetes type 2 and the treatment of calcium pyrophosphate dihydrate deposition disease leading to inflammatory arthritis. The monitoring of NPP1 reactions is difficult because its velocity is very slow requiring highly sensitive analytical procedures. In this study, a method of large‐volume sample stacking with polarity switching was developed, and separations were optimized. Large sample volumes were loaded by hydrodynamic injection (5 psi, 13 s) followed by removal of a large plug of sample matrix from the capillary using polarity switching (?10 kV). The stacked analytes were subsequently separated in phosphate buffer (100 mM, pH 9.2) at 20 kV. The validated method was found to be linear (R2 = 0.9927) in the concentration range of 0.05–50 μM of AMP, with high accuracy and precision. The determined LOD and LOQ of AMP were 18 nM and 60 nM, respectively. Compared to a previously reported CE procedure using sweeping technique, a fivefold improvement of sensitivity was achieved. Moreover, the new technique was faster, and reproducibility of migration times was improved (RSD value = 1.2%). Importantly, adenine nucleotide analogs and derivatives tested as NPP1 inhibitors could be completely separated from the substrate ATP and the enzymatic product AMP. The method was applied to NPP1 inhibition assays investigating nucleotide‐derived inhibitors in the presence of ATP.  相似文献   

19.
A one-step lateral flow test was developed for the quantitative determination of total type B fumonisins in maize with a test range up to 4,000 μg/kg and a limit of detection of 199 μg/kg. The test presented gives a result within 4 min, including 1 min strip drying, and does not require any sample cleanup steps after a previous 3-min sample extraction. Quantitative readout with a compact photometric strip reader will also indicate the best suited measurement range when needed. The test is based on a competitive immunoassay format where a ready-to-use antibody–colloidal gold particle complex is mixed with 50 μL sample extract in a microwell and used as a signal reagent. The test strip is inserted into the well and the mixed content migrates onto the strip, which contains a test zone and a control zone. Mycotoxin–protein conjugate coated on the test zone captures free signal reagent, and colored particles concentrate, forming a visible line. The intensity of the test line is dependent on the total fumonisin concentration in the sample. Naturally contaminated quality-control maize material was used for matrix-matched calibration of photometric readout. The test presented is both quantitative and rapid, with no cross-reactivity to other mycotoxins. The applicability of the lateral flow test was shown by the screening of 23 naturally contaminated maize samples. Relative standard deviations ranged from 1.7 to 32.9%.  相似文献   

20.
The application of ion chromatography with the single pump cycling‐column‐switching technique was described for the analysis of trace inorganic anions in weak acid salts within a single run. Due to the hydrogen ions provided by an anion suppressor electrolyzing water, weak acid anions could be transformed into weak acids, existing as molecules, after passing through the suppressor. Therefore, an anion suppressor and ion‐exclusion column were adopted to achieve on‐line matrix elimination of weak acid anions with high concentration for the analysis of trace inorganic anions in weak acid salts. A series of standard solutions consisting of target anions of various concentrations from 0.005 to 10 mg/L were analyzed, with correlation coefficients r ≥ 0.9990. The limits of detection were in the range of 0.67 to 1.51 μg/L, based on the signal‐to‐noise ratio of 3 and a 25 μL injection volume. Relative standard deviations for retention time, peak area, and peak height were all less than 2.01%. A spiking study was performed with satisfactory recoveries between 90.3 and 104.4% for all anions. The chromatographic system was successfully applied to the analysis of trace inorganic anions in five weak acid salts.  相似文献   

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