[Show abstract][Hide abstract] ABSTRACT: A high-performance liquid chromatographic method coupled with electrospray mass spectrometry was developed for the simultaneous determination of dolasetron and its major metabolite, hydrodolasetron, in human plasma. A new sample pretreatment method, i.e., salt induced phase separation extraction (SIPSE), was proposed and compared with four other methods, i.e., albumin precipitation, liquid-liquid extraction, hydrophobic solvent-induced phase separation extraction and subzero-temperature induced phase separation extraction. Among these methods, SIPSE showed the highest extraction efficiency and the lowest matrix interferences. The extraction recoveries obtained from the SIPSE method were all more than 96% for dolasetron, hydrodolasetron and ondansetron (internal standard). The SIPSE method is also very fast and easy because protein precipitation, analyte extraction and sample cleanup are combined into one simple process by mixing acetonitrile with plasma and partitioning with 2 mol/L sodium carbonate aqueous solution. The correlation coefficients of the calibration curves were all more than 0.997, in the range of 7.9-4750.0 ng/mL and 4.8-2855.1 ng/mL for dolasetron and hydrodolasetron, respectively. The limits of quantification were 7.9 and 4.8 ng/mL for dolasetron and hydrodolasetron, respectively. The intra-day and inter-day repeatability were all less than 10%. The method was successfully applied to the pharmacokinetic study of dolasetron.
Preview · Article · May 2012 · Journal of chromatographic science
[Show abstract][Hide abstract] ABSTRACT: A simple and accurate method has been developed to simultaneously separate and determine 10 bioactive compounds in citrus fruits by high-performance liquid chromatography coupled with diode array detection and electrospray ionisation mass spectrometry (HPLC-DAD-ESI/MS). This HPLC assay was performed on a reversed-phase C18 column with acetonitrile and 0.1% (v/v) aqueous formic acid as mobile phase. DAD has been performed at 273, 283 and 324nm for quantification of the alkaloids, flavanones and hydroxycinnamic acids. MS was also employed to identify the each analyte. Ten analytes (naringin, hesperidin, neohesperidin, ferulic acid, p-coumaric acid, chlorogenic acid, caffeic acid, octopamine, synephrine and tyramine) demonstrated good linearity (r⩾0.9990) in a relatively wide concentration range. The method revealed high average recovery (range, 92.1-97.9%) and good precision with interday and intraday variations with less than 4.71%. The limits of detection (LODs) ranged from 0.02 to 0.11μg/ml, while the limits of quantification (LOQs) were defined in the range of 0.08-0.39μg/ml. The proposed method has been successfully applied to analyse three types of bioactive constituents in eight citrus hybrids pulps and eight citrus hybrids peels, which has been successfully cultivated in China.
[Show abstract][Hide abstract] ABSTRACT: A multiresidue method was developed based on extraction of 10 g sample with 10 mL acetonitrile and subsequent liquid-liquid partitioning formed by adding 4 g MgSO₄ plus 1 mL chloroform. During the partitioning process, the extraction recoveries of polar analytes were found to be essentially determined by the acetonitrile content in the aqueous phase. The use of MgSO₄ gave the least acetonitrile left in the aqueous phase (lower than 5%) and thus promoting complete partitioning of analytes into the organic phase. At the same time, removal of water from the acetonitrile phase was achieved by adding only a small amount of chloroform with no influence on the acetonitrile content in the aqueous phase, thus leading to decreasing the co-extraction of polar matrix components. The most complete mutual separation of acetonitrile and water was achieved by the joint use of MgSO₄ and chloroform and thus the optimal extraction recovery and analytical selectivity were obtained simultaneously. The new method, with higher recoveries of polar analytes, better analytical selectivity and simpler manipulation, is a claimed improvement to the original QuEChERS method. The proposed method was finally validated by the determination of 20 pesticides in a mixed food matrix by using liquid chromatography tandem mass spectrum (LC-MS/MS). Acceptable linearity, sensitivity, recovery, precision and selectivity results were obtained.
No preview · Article · Mar 2011 · Journal of Chromatography A
[Show abstract][Hide abstract] ABSTRACT: Scutellaria baicalensis Georgi (S. baicalensis), a perennial herb of the Labiatae family, is a well-known traditional Chinese medicine. In the present study, a comprehensive qualitative analysis of flavonoids in the stems and leaves of S. baicalensis was performed. Under the optimized experimental conditions, 21 flavonoids were clearly detected. 17 of them were successfully identified based on the on-line UV and MS(n) data and were sequentially confirmed by the literature search. The rest 4 flavonones, which were not on-line identified, were successfully isolated and were identified by 1D and 2D NMR. One of them, 5,6,7,3',4'-pentahydroxy flavanone-7-O-glucuronide (2) is a new compound.
No preview · Article · Mar 2011 · Journal of chromatography. B, Analytical technologies in the biomedical and life sciences
[Show abstract][Hide abstract] ABSTRACT: Based on the phenomenon that hydrophilic acetonitrile can be separated from water by adding a hydrophobic solvent, a phase transition extraction (PTE) method for isolation of phytochemical compositions was developed. The isolation efficiency of the proposed method was assessed in complete grouping of the constituents in three important traditional Chinese medicine plants. Further study of the PTE for Scutellaria bacalensis Georgi found that the constituents in the organic phase are all flavonoid aglycones while the ones in the aqueous phase are all flavonoid glycosides, revealing the property of high structure selectivity for the proposed PTE process. The effect of using different modifiers on the isolation efficiency was investigated. The results obtained by using non-oxygenated hydrophobic solvents are perfect while those by inorganic salts are acceptable, but those by oxygenated hydrophobic solvents are bad. Subsequent GC analysis revealed that the solvent composition difference between the two separated phases among PTE processes using different types of modifier is responsible for the different isolation results obtained. Finally, the proposed method was proved to be insensitive to both the acetonitrile concentration and the added amount of modifier.
No preview · Article · Feb 2011 · Journal of Separation Science
[Show abstract][Hide abstract] ABSTRACT: Desorption electrospray ionization mass spectrometry (DESI MS) is rapidly becoming a powerful analysis tool for a wide variety of samples in the open air. By combining DESI MS and derivatization, acetone in human blood samples, one of the diabetes mellitus (DM) biomarkers, was rapidly analyzed. Prior to DESI, the plasma sample was first exposed to hydroxylamine hydrochloride and acetone in plasma was derived into fixed oxime. The reactive products were validated by DESI/MS/MS. Quantification was performed in the positive-ion electrospray ionization mode by monitoring of the product ions at m/z 74 for acetone oxime and m/z 116 for 4-methyl-2-pentanone oxime as the internal standard. The limit of detection was of the order of magnitude of 0.10 ppbv and the linear range comprised two decades of concentration, covering the relevant concentration range of acetone in plasma samples. The method has achieved fast, high-throughput analysis of acetone in human plasma with little beforehand preparation and an experiment time of only a few seconds.
[Show abstract][Hide abstract] ABSTRACT: Novel sample preparation approaches for HPLC bioanalysis based on the phenomenon that acetonitrile can be separated from water by adding salts or cooling at subzero temperatures have been reported. These two methods are superior to conventional liquid-liquid extraction since the separated acetonitrile phase can be directly injected to the RP-LC system. However, the salting-out method suffers from a potential problem that the remained salt in the acetonitrile phase may harm the MS detector, while the subzero-temperature method is troublesome to operate. Here, we have reported a similar phase separation phenomenon that the acetonitrile aqueous mixture can be separated by adding a hydrophobic solvent; and capitalising on this phase transition phenomenon, we have proposed an alternative approach, named solvent induced phase transition extraction (SIPTE), to extract drug from plasma for HPLC-MS analysis. The proposed SIPTE method is much simpler and avoids contaminating the MS detector. Three structurally diverse drugs were selected as test compounds to design the SIPTE method and to validate the efficiency of this method. The four goals of plasma sample pretreatment for HPLC-MS analysis, i.e. removal of proteins, removal of other low-molecular interferences, preconcentration of the analytes of interest, and matching the sample solvent with the HPLC-MS system, can be rapidly performed in a very simple step by using the SIPTE method.
Full-text · Article · Nov 2009 · Journal of Chromatography A
[Show abstract][Hide abstract] ABSTRACT: In this text we present a series of LC-MS/UV-based strategies for on-line structure identification of unknown flavone glycosides in Dracocephalum tanguticum. The aglycone portion, the glycosylation position, the order of sugars and the identity of sugars of each glycoside were unambiguously identified. The new strategy--identifying the partial structure of a molecule by comparison with a different compound possessing the same assumed partial structure--is quite effective for structure identification of the aglycone of 1-4; the unusual non-radical [Y(0)-H-CH(2)](-) ion observed for the methoxylated flavonoid glycoside 8 is quite useful for structure elucidation of the aglycone of 5-8; the UV data obtained on-line with post-column addition of UV-shift reagents are powerful for determination of the glycosylation and methoxylation positions for each flavone glycoside. Finally, isolation and subsequent individual analysis by NMR were performed to provide complementary information for the configurations of each sugar and the linkage types of each disaccharide. Thus, the structures of the eight detected flavone glycosides, which all have never been reported in D. tanguticum before, were positively identified.
No preview · Article · Sep 2009 · Journal of chromatography. B, Analytical technologies in the biomedical and life sciences
[Show abstract][Hide abstract] ABSTRACT: Scutellaria baicalensis Georgi is a well-known medicinal plant widely used in China and other East Asian countries. High performance liquid chromatography combined with diode array detection and electrospray ion trap mass spectrometry was used to determine the flavonoid profile of S. baicalensis. Under the optimized experiment conditions, 32 flavonoids were clearly detected. Eighteen main ones were doubtless identified by comparing their retention time, UV and MS (MS(n)) data with isolated or commercial standards. The UV characteristics of these 18 known standards were studied in detail. The rules summarized provided valuable indications for the subsequent on-line identification processes. By interpreting both the MS and the UV data in detail, other 13 minor flavonoids in S. baicalensis were on-line identified successfully.
Preview · Article · Jul 2009 · Journal of Chromatography A