Repeatability Assessment by ISO 11843-7 in Quantitative HPLC for Herbal Medicines

Development of a Quantitative NMR Method for Direct and Simultaneous Determination of Four Flavonoids in Scutellaria baicalensis georgi Extracts

Introduction:

Scutellaria Baicalensis Georgi (SBG), a Traditional Chinese Medicine (TCM) used for the treatment of antiviral therapy, contains many flavonoids.

Materials and Methods:

A simple, fast and accurate 1H quantitative nuclear magnetic resonance (1HqNMR) method was established for simultaneously determination of four flavonoids (Baicalin, Baicalein, Wogonin and Wogonoside) in SBG extract by using 3,4,5-trichloropyridine as an internal standard (IS). All the NMR determination work was performed at 308 K on an NMR sample tube inserted with a co-axial tube. The NMR sample tube was added with the sample (SBG extract and IS), the co-axial insert tube was added with D2O. Quantification of four flavonoids was carried out by calculating the relative peak area ratio of the selected proton signals from the target compounds and the IS.

Results:

The validated 1H-qNMR method was successfully used to determine the four flavonoids in 9 batches of SBG from different origins and the results were in good accordance with those obtained from HPLC.

Conclusion:

The established 1H-qNMR method could be used as a powerful tool for the quality control of SBG from different sources and had potential in the quantification of main components from other TCMs.

Theoretical repeatability assessment without repetitive measurements in gradient high-performance liquid chromatography

This paper puts forward a time and material-saving method for evaluating the repeatability of area measurements in gradient HPLC with UV detection (HPLC-UV), based on the function of mutual information (FUMI) theory which can theoretically provide the measurement standard deviation (SD) and detection limits through the stochastic properties of baseline noise with no recourse to repetitive measurements of real samples. The chromatographic determination of terbinafine hydrochloride and enalapril maleate is taken as an example. The best choice of the number of noise data points, inevitable for the theoretical evaluation, is shown to be 512 data points (10.24s at 50 point/s sampling rate of an A/D converter). Coupled with the relative SD (RSD) of sample injection variability in the instrument used, the theoretical evaluation is proved to give identical values of area measurement RSDs to those estimated by the usual repetitive method (n=6) over a wide concentration range of the analytes within the 95% confidence intervals of the latter RSD. The FUMI theory is not a statistical one, but the "statistical" reliability of its SD estimates (n=1) is observed to be as high as that attained by thirty-one measurements of the same samples (n=31).