Defu Cai

In this paper, multiwalled‐carbon‐nanotube‐based matrix solid‐phase dispersion coupled to HPLC with diode array detection was used to extract and determine honokiol and magnolol from Magnoliae Cortex. The extraction efficiency of the multiwalled‐carbon‐nanotube‐based matrix solid‐phase dispersion was studied and optimized as a function of the amount of dispersing sorbent, volume of elution solvent, and flow rate of elution solvent, with the aid of response surface methodology. An amount of 0.06 g of carboxyl‐modified multiwalled carbon nanotubes and 1.5 mL of methanol at a flow rate of 1.1 mL/min were selected. The method obtained good linearity (r² > 0.9992) and precision (RSD < 4.7%) for honokiol and magnolol, with limits of detection of 0.045 and 0.087 μg/mL, respectively. The recoveries obtained from analyzing in triplicate spiked samples were determined to be from 90.23 to 101.10% and the RSDs from 3.5 to 4.8%. The proposed method that required less samples and reagents was simpler and faster than Soxhlet and maceration extraction methods. The optimized method was applied for analyzing five real samples collected from different cultivated areas.

A stability‐indicating HPLC method was developed and validated for the determination of berberine hydrochloride and trimethoprim in pharmaceutical dosage form in the presence of degradation products. The proposed RP‐HPLC method utilizes an Agilent TC‐C18, 4.6 mm × 250 mm, 5 μm, column using a mobile phase consisting of acetonitrile‐50 mM potassium dihydrogen phosphate (30 : 70, v/v, pH adjusted to 3 with orthophosphoric acid) at a flow rate of 1.0 mL/min and UV detection at 271 nm. The linearity of berberine hydrochloride and trimethoprim was in the range of 2 to 60 μg/mL (r= 0.9996) and 1 to 30 μg/mL (r= 0.9995), respectively. Repeatability and intermediate precisions were also determined with percentage relative standard deviation (% RSD) less than 2.0%. The limits of detection were found to be 9.8 ng/mL for berberine hydrochloride and 2.5 ng/mL for trimethoprim. The mean recoveries for berberine hydrochloride and trimethoprim were 99.8 and 98.8%, respectively. The stability of the two drugs was determined under different conditions and the proposed method has shown effective separation for their degradation products. And the proposed assays method can thus be considered stability‐indicating.

A simple and low‐cost method based on matrix solid‐phase dispersion (MSPD) extraction, HPLC separation, and diode array detection has been developed for the determination of indigo and indirubin in Folium isatidis. The experimental parameters that may affect the MSPD method, including dispersing sorbent, ratio of dispersing sorbent to sample, elution solvent, and volume of the elution solvent were examined and optimized. The optimized conditions were determined to be that C18 was used as dispersing sorbent, the ratio of C18 to sample mass was selected to be 4:1, and 10 mL of N,N‐dimethyl formamide was used as elution solvent. The highest extraction yields of the two compounds were obtained under the optimized conditions. The method showed good linearity (r > 0.9995) and precision (RSD < 3.0%) for indigo and indirubin, with the limits of detection of 18 and 22.5 ng/mL, respectively. The recoveries were in the range of 90.33–100.74% with RSDvalues ranging from 1.7 to 3.6%. Comparing to ultrasonic and Soxhlet methods, the proposed MSPD procedure was more convenient and less time‐consuming with reduced requirements on sample and solvent amounts. The proposed procedure was applied to analyzed three real samples that were collected from different localities.

—Matrix solid-phase dispersion (MSPD) extraction and HPLC have been used for determination of paeonol and ferulic acid in “Su-Xiao-Xin-Tong Dropping Pills” (SXDP). For extraction of these compounds, the type of sorbent, the type and volume of elution solvent were studied. The highest yields were obtained with a ratio 4:1 of C₁₈ to sample and 10 mL methanol-water-glacial acetic acid (80:20:0.5, v/v). The chromatographic separation was achieved with methanol:water:glacial acetic acid (50:50:0.5, v/v) as mobile phase at a flow rate of 1.0 mL/min, a Dikma Diamonsi-C₁₈ column (250 mm × 4.6 mm, 5 µm), and UV detection at 315 nm. Linearity (R² > 0.999), intra- and inter-day (RSD < 2.0%) precision were determined. The linearities of paeonol and ferulic acid were in the range of 25–250 µg/mL and 2.5–25 µg/mL, respectively. The limit of detection was found to be 0.080 µg/mL for paeonol and 0.030 µg/mL for ferulic acid. The mean recoveries for paeonol and ferulic acid were 94.5 and 93.3%, respectively. It is a simple and sensitive analytical method with good accuracy and reproducibility.