Na Guo

Shenyang Pharmaceutical University, Feng-t’ien, Liaoning, China

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Publications (3)4.78 Total impact

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    ABSTRACT: A simple, specific, and accurate high-performance liquid chromatographic method, using UV detection for the determination of penciclovir in human plasma, is described. Chromatographic separation is performed on a BDS-C(18) column using a mixture of phosphate buffer (20mM, pH adjusted to 7.5 with phosphoric acid), methanol, and acetonitrile (94:3:3, v/v/v) as mobile phase. The wavelength of the UV detector is set at 254 nm. The flow-rate is 1.0 mL/min. The assay is linear over the concentration range of 0.1-5.0 microg/mL for penciclovir (r > 0.9996). The limit of quantitation for penciclovir in human plasma is 0.1 microg/mL. The relative standard deviation is less than 7.0% for all the analytes. The method is successfully applied to a randomized crossover bioequivalence study of two different famciclovir capsules in 20 healthy volunteers.
    Journal of chromatographic science 11/2008; 46(9):819-22. · 0.79 Impact Factor
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    ABSTRACT: A simple and effective method for the separation of oxybutynin enantiomers was developed using high performance liquid chromatography with hydroxypropyl-beta-cyclodextrin (HP-beta-CD) as the chiral mobile phase additive and a C18 reversed-phase column as the stationary phase. beta-CD and HP-beta-CD were investigated as chiral mobile phase additives separately. The results showed that oxybutynin enantiomers could not be separated when adding beta-CD in the mobile phase, but optimal resolution was obtained when using HP-beta-CD as the chiral mobile phase additive. Excellent enantioseparation was achieved with the mobile phase composed of 30 mmol/L KH2PO4-acetonitrile(80:20, v/v) mixed with 60 mmol/L HP-beta-CD at pH 4.0. The detection wavelength was set at 223 nm and the column temperature was set at 28 degrees C with a flow rate of 0.8 mL/min. Under the optimized conditions, the resolution of enantiomers was 1.54 and the limit of quantitation was 1.0 ng. Comparing with chiral stationary phase chromatography, the method was simple, economic and considerably reproducible.
    Se pu = Chinese journal of chromatography / Zhongguo hua xue hui 04/2008; 26(2):259-61.
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    ABSTRACT: A sensitive atmospheric pressure chemical ionization liquid chromatographic-mass spectrometric (APCI-LC-MS) assay with positive ion mode has been developed for the determination of nifedipine in human plasma. In this method, nifedipine was extracted from human plasma using diethyl ether with dimethoxanate as the internal standard. Analysis was achieved on a BDS C(18) column with methanol-H(2)O (66:34, v/v) as the mobile phase. Sustained-release nifedipine tablets from DiSha (test, Weihai, China) and from GuoFeng (reference, Qingdao, China) were evaluated following a single 20mg oral dose to 20 healthy volunteers. Bioequivalence between the products was determined by calculating 90% confidence intervals (90% CI) for the ratio of C(max), AUC(0-t) and AUC(0-infinity) values for the test and reference products, using logarithmic transformed data. The 90% confidence intervals for the ratio of C(max) (86.6-105.2%), AUC(0-t) (97.8-110.9%) and AUC(0-infinity) (96.5-110.4%) values for the test and reference products are within the interval (80.0-125.0% for AUC, and 70-143% for C(max)), proposed by State of Food and Drug Administration [SFDA, 2005. Guidance for Bioavailability and Bioequivalence Studies for Chemical Drug Products in Human Being. China, p. 19]. It was concluded that the two sustained-release nifedipine tablets are bioequivalent in their rate and extent of absorption and, thus, may be used interchangeably.
    International Journal of Pharmaceutics 09/2007; 341(1-2):91-6. · 3.99 Impact Factor