Po Chen

Bio: Po Chen is an academic researcher from Hunan University. The author has contributed to research in topics: Ion chromatography & Column chromatography. The author has an hindex of 8, co-authored 10 publications receiving 590 citations.

High-Performance Liquid Chromatography

Abstract: A high-performance liquid chromatographic (HPLC) method is developed for the determination of the pharmacologically active terpenoids Ginkgolide A, B, and C and bilobalide in Ginkgo biloba L. leaves extract (GBE). The extracts are dissolved in methanol-water (1:4) and extracted by ethyl acetate after evaporation of the organic solvent, the residue is dissolved in methanol, and the terpenoids in the resultant solution are determined by means of HPLC on a C 1 8 column with methanol-water (23:77) as an eluent. The recovery provided by the method is above 96.5%, and the minimum concentration that can be determined is 80 μg of terpenoid per gram of GBE. The method is suitable for GBE production process control.

Application of a Series Piezoelectric Sensor as a Detector in Ion Chromatography

Abstract: The application of a series piezoelectric sensor as a detector for ion chromatography (IC) is investigated. The device is used with sensitive response between the series piezoelectric quartz crystal oscillation frequency and specific conductivity of liquids for ion chromatographic detection. Two platinum wires are used as conductivity electrodes and inserted oppositely in the detection cell. The dead-volume of the detection is 15 microL, the noise is less than or equal to 1 Hz, the baseline drift is 5 Hz/h, and the detection limits of F- and Na+ are 5 and 25 ng, respectively. The effects of temperature, background conductivity, cell constant of the conductivity electrode, and dead volume on the sensitivity of the detector are discussed. The detector temperature should equal that of the column. An optimum sensitivity is obtained when the cell constant is approximately 3.5 cm. The optimum range of the background conductivity of the mobile phase is 150 to 1200 microseconds. When the solution conductivity is greater than 3000 microseconds, the detector does not work satisfactorily. The proposed IC cerebrospinal fluid detection method is applied to the determination of vitamin C in apple and Zn2+, Ca2+, Mg2+, and Cu2+ in human cerebrospinal fluid.

Analysis of Ginkgolides and Bilobalides in Ginkgo biloba L. Extract for Its Production Process Control by High-Performance Liquid Chromatography

Abstract: A high-performance liquid chromatographic (HPLC) method is developed for the determination of the pharmacologically active terpenoids Ginkgolide A, B, and C and bilobalide in Ginkgo biloba L. leaves extract (GBE). The extracts are dissolved in methanol-water (1:4) and extracted by ethyl acetate after evaporation of the organic solvent, the residue is dissolved in methanol, and the terpenoids in the resultant solution are determined by means of HPLC on a C 18 column with methanol-water (23:77) as an eluent. The recovery provided by the method is above 96.5%, and the minimum concentration that can be determined is 80 µg of terpenoid per gram of GBE. The method is suitable for GBE production process control.

Simultaneous Determination of Nitrate and Nitrite in Saliva and Foodstuffs by Non-suppressed Ion Chromatography with Bulk Acoustic Wave Detector.

Abstract: In the present paper, nitrate and nitrite in foodstuffs and saliva were simultaneously determined using a non-suppressed ion chromatography (IC) method with a bulk acoustic wave sensor (BAW) as detector, and 1.5 mmol/L potassium hydrogenphthalate (KHP) as mobile phase. The IC-BAW method is simple, rapid and accurate. The determination limits for nitrite and nitrate are 0.20 and 0.30 mg/L, respectively. The IC-BAW is comparable and agrees with the conventional spectrophotometric method for nitrite and nitrate determination.

Antiepileptic drugs—best practice guidelines for therapeutic drug monitoring: A position paper by the subcommission on therapeutic drug monitoring, ILAE Commission on Therapeutic Strategies

Abstract: Although no randomized studies have demonstrated a positive impact of therapeutic drug monitoring (TDM) on clinical outcome in epilepsy, evidence from nonrandomized studies and everyday clinical experience does indicate that measuring serum concentrations of old and new generation antiepileptic drugs (AEDs) can have a valuable role in guiding patient management provided that concentrations are measured with a clear indication and are interpreted critically, taking into account the whole clinical context. Situations in which AED measurements are most likely to be of benefit include (1) when a person has attained the desired clinical outcome, to establish an individual therapeutic concentration which can be used at subsequent times to assess potential causes for a change in drug response; (2) as an aid in the diagnosis of clinical toxicity; (3) to assess compliance, particularly in patients with uncontrolled seizures or breakthrough seizures; (4) to guide dosage adjustment in situations associated with increased pharmacokinetic variability (e.g., children, the elderly, patients with associated diseases, drug formulation changes); (5) when a potentially important pharmacokinetic change is anticipated (e.g., in pregnancy, or when an interacting drug is added or removed); (6) to guide dose adjustments for AEDs with dose-dependent pharmacokinetics, particularly phenytoin.