The use of CE‐electrochemiluminescence with ionic liquid for the determination of bioactive constituents in Chinese traditional medicine

Abstract

CE / tris(2,2-bipyridyl) ruthenium(II) (Ru(bpy)(3) (2+)) electrochemiluminescence (ECL), CE-ECL, with an ionic liquid (IL) detection system was established for the determination of bioactive constituents in Chinese traditional medicine opium poppy which contain large amounts of coexistent substances. A minimal sample pretreatment which involves a one-step extraction approach avoids both sample loss and environmental pollution. As the nearby hydroxyl groups in some alkaloid such as morphine may react with borate to form complexes and IL, as a high-conductivity additive in running buffer, could cause an enhanced field-amplified effect of electrokinetic injection. Running buffer containing 25 mM borax-8 mM 1-ethyl-3-methylimidazolium tetrafluoroborate (EMImBF(4))IL (pH 9.18) was used which resulted in significant changes in separation selectivity and obvious enhancement in ECL intensities for those alkaloids with similar structures. Sensitive detection could be achieved when the distance between the Pt working electrode and the outlet of separation capillary was set at 150 microm and the stainless steel cannula was fixed approximately 1 cm away from the outlet of the capillary. Quantitative analysis of four alkaloids was achieved at a detection voltage of 1.2 V and a separation voltage of 15 kV in less than 7 min. Detection limits of thebaine, codeine, morphine, and narcotine were 2.5 x 10(-7), 2.5 x 10(-7), 1 x 10(-9) and 1 x 10(-6) M(S/N = 3), respectively. The method was successfully applied to determine the amounts of opium alkaloids in real poppy samples.

Quality control of herbal medicines by capillary electrophoresis: Potential, requirements and applications

“…The buffer comprised a commercially available CE electrolyte (CElixir reagent B, pH 2.5) and a combination of two CD derivatives (25 mM HP-X-CD and 75 mM DM-X-CD). Most recently, the use of an IL (1-ethyl-3-methylimidazolium tetrafluoroborate) added to the background electrolyte (BGE) (25 mM borax solution) was described [28]. Adding the IL did not cause any improvements in peak resolution, but it enhanced sensitivity in electrochemiluminescence detection remarkably.…”

CE‐electrochemiluminescence with ionic liquid for the facile separation and determination of diester‐diterpenoid aconitum alkaloids in traditional Chinese herbal medicine

“…In addition, the concentration of IL (EMImBF 4 ) could partly affect the field-amplified sample stacking effect. Thus, the effect of viscosity of IL should also be considered [13]. However, longer migration time and broader peaks could be observed when the concentration of IL additive was too high.…”

“…However, CE is getting more frequently used owing to its inherent high separation efficiency and simplicity of instruments. Recently, a sensitive detection technique, tris (2,2 0 -bipyridyl) ruthenium (II) ½RuðbpyÞ was developed for the determination of trace analytes due to the potential of greatly enhanced sensitivity and selectivity [13]. Consequently, CE-ECL has been critically reviewed due to high separation efficiency, sensitivity and selectivity [14][15][16].…”

Advances and analytical applications in chemiluminescence coupled to capillary electrophoresis

“…A relevant application consisted on the determination of proline produced from enzymatic reaction and its application to assay prolidase activity in nonpretreated serum of diabetic patients to evaluate collagen degradation in diabetes mellitus [55] or to study drug-enzyme interactions, such as non-steroidal anti-inflammatory drugs on prolidase activity in erythrocytes [56]. Other innovative contributions carried out with this commercial device include the application of ECL detection for the chiral separation of a racemic mixture of disopyramide in plasma, in which the buffers used in the capillary inlet and outlet differed from each other in terms of buffer pH, ionic strength, type of BGE as well as buffer composition [57], or the use of ionic liquid as an additive of the running buffer for the separation of main opium alkaloids in Chinese traditional medicine, providing high sensitivity and good reproducibility [58].…”