Biomedical subjects

Changxiao Liu

Publications and source records attributed to Changxiao Liu.

5 recordsLinked to original sources

PubMed2006

Determination of metolazone in human blood by liquid chromatography with electrospray ionization tandem mass spectrometry.

A rapid, sensitive and accurate liquid chromatographic-tandem mass spectrometric method is described for the determination of metolazone in human blood. Metolazone was extracted from blood using ethyl acetate and separated on a C18 column interfaced with a triple quadrupole tandem mass spectrometer. The mobile phase consisting of a mixture of acetonitrile, 10 mmol/l ammonium acetate and formic acid (60:40:0.1, v/v/v) was delivered at a flow rate of 0.5 ml/min. Electrospray ionization (ESI) source was operated in positive ion mode. Selected reaction monitoring (SRM) mode using the transitions of m/z 366-->m/z 259 and m/z 321-->m/z 275 were used to quantify metolazone and the lorazepam (internal standard), respectively. The linearity was obtained over the concentration range of 0.5-500 ng/ml for metolazone and the lower limit of quantitation (LLOQ) was 0.5 ng/ml. For each level of QC samples, inter- and intra-run precision was less than 8.07 and 3.56% (relative standard deviation (RSD)), respectively, and the bias was within +/-4.0%. This method was successfully applied to the pharmacokinetic study of metolazone formulation after oral administration to humans.

Chromatography, Liquid↗

PubMed2006

Screening for in vivo metabolites of isovalertatin family oligosaccharides in rats by liquid chromatography coupled to electrospray ionization tandem mass spectrometry.

Liquid chromatography/electrospray ionization tandem mass spectrometry (LC/MS(n)) was used to identify trace levels of in vivo metabolites after the administration of isovalertatin M23 or isovalertatin D23 to rats. The biosamples of urine, feces, and ileum incubation were pre-treated by solid-phase extraction (SPE), and then chromatographed with a reversed-phase C8 column with acetonitrile/1.5 mM aqueous ammonia (18:82, v/v) as the mobile solvent. The parent drug and the possible metabolites were identified by two independent qualitative parameters, retention time and collision-induced dissociation product ions. Nine and seven metabolites were successfully characterized from biosamples after administration of isovalertatins M23 and D23, respectively, to rats. The metabolism seemed to take place in the rat intestinal tract, and metabolic pathways were identified including isovaleryl de-esterification and hydrolysis of alpha-glucose units located either at the reducing or the non-reducing terminus.

Amines↗

PubMed2005

Simultaneous determination of ZT-1 and its metabolite Huperzine A in plasma by high-performance liquid chromatography with ultraviolet detection.

ZT-1 is a novel acetylcholinesterase (AChE) inhibitor. It is rapidly transformed to Huperzine A (Hup A) in vitro. A simple and rapid HPLC-UV method for the simultaneous determination of ZT-1 and its metabolite Hup A in plasma is described. The chromatographic separations were achieved on a C(18) ODS column (250 mm x 4.6 mm ID) using methanol-1 mmol/L ammonium acetate (70:30,v/v) as mobile phase. The flow rate was 0.7 mL/min, the detection wavelength was 313 nm and the column temperature was kept at 35 degrees C. Plasma samples were prepared as rapidly as possible and extracted immediately with 5 mL of chloroform:iso-propyl alcohol mixture (v/v, 9:1). The retention times of ZT-1 and Huperzine A (Hup A) were 18.7 and 14.4 min, respectively. The mean absolute recoveries of two analytes were >90%. Quantification limits were all 0.02 nmol/mL for ZT-1 and Hup A. This analytical method was reliable and convenient procedure that meets the criteria for the pharmacokinetic evaluation of ZT-1 on experimental animals.

Alkaloids↗

PubMed2005

Validated liquid chromatography-tandem mass spectrometric method for the quantitative determination of daidzein and its main metabolite daidzein glucuronide in rat plasma.

A highly selective and sensitive liquid chromatographic-tandem mass spectrometric (LC-MS-MS) method was developed and validated to determine daidzein and its main metabolite daidzein glucuronide in rat plasma. The analytes and internal standard genistein were extracted from plasma samples by n-hexane-diethyl ether (1:4, v/v), and separated on a C18 column. The mobile phase consisted of acetonitrile-water-formic acid (80 : 20: 1, v/v/v). Detection was performed on a triple quadrupole tandem mass spectrometer by selected reaction monitoring (SRM) mode via atmospheric pressure chemical ionization (APCI) source. The method has a limit of quantification of 0.24 ng/ml. The linear calibration curves were obtained in the concentration range of 0.24-1000 ng/ml. The intra- and inter-day precisions were lower than 13.2% in terms of % RSD. The accuracy ranged from -0.5% to 2.4% in terms of % RE (relative error). This method was successfully applied to the determination of plasma concentration of daidzein and its main metabolite daidzein glucuronide in rats after an oral administration of 20 mg/kg daidzein.

Animals↗

PubMed2003

Determination of vertilmicin in rat serum by high-performance liquid chromatography using 1-fluoro-2,4-dinitrobenzene derivatization.

A procedure for the high-performance liquid chromatographic determination of vertilmicin in rat serum was described using pre-column derivatization. The serum proteins were precipitated with acetonitrile and vertilmicin in the supernatant was derivatized with 1-fluoro-2,4-dinitrobenzene. Etimicin was selected as the internal standard. The mobile phase consisted of methanol--20mM ammonium acetate (80:20, v/v), and flow-rate was 0.9 ml/min. Ultraviolet detection was set at 365 nm. The reaction products were chromatographed on a C(18) column kept at 40 degrees C. A good linearity was found in the range of 0.5-250 microg/ml. Both intra- and inter-day precisions of vertilmicin, expressed as the relative standard deviation, were less than 7.4%. Accuracy, expressed as the relative error, ranged from -0.1 to 3.6%. The mean absolute recovery of vertilmicin at three different concentrations was 92.5%. Serum volumes of 50 microl were sufficient for the determination of vertilmicin. The method was proved suitable for the pharmacokinetic study of vertilmicin in rats.

Aminoglycosides↗