Halogen bonding between iodine and ciprofloxacin (I⋯N XB) induces I–I cleavage with fluorescence enhancement.

A new method for the determination of baicalin in Scutellariae Radix extract and its preparations by high performance liquid chromatography (HPLC) coupling with flow injection chemiluminescence detection (FIA-CL) has been developed. The method was based on the chemiluminescence reaction of potassium permanganate with baicalin in nitric acid medium; the CL intensity can be enhanced by formaldehyde. In this study, the conditions of chemiluminescence and chromatography were examined, and the schematic diagram of the HPLC-FIA-CL analyzer was optimized. The analytes were separated on Hypersil RP-C18 columns (100 4.6 mm, I.D., 5 mm) by equality elution with 47:53 (v/v) methanol-0.3% phosphoric acid as a mobile phase at a flow rate of 0.8 mL·min -1 and a column temperature of 40°C. Under the optimum condition, the CL intensity was proportional to the concentration of baicalin over the range of 4.10´10 -7~6 .15´10 -5 mol·L -1 . The limit of detection (S/N = 3) was 2.79´10 -7 mol·L -1 with the relative standard deviation 2.5% (Cs = 6.15´10 -6 mol·L -1 , n = 5). The method has been applied to the determination of baicalin in Scutellariae Radix extract and its preparations, and satisfactory results were obtained.