Capillary electrophoresis coupled with end‐column electrochemiluminescence for the determination of ephedrine in human urine, and a study of its interactions with three proteins

Abstract

A tris(2,2-bipyridyl)ruthenium(II) (Ru(bpy)₃²⁺)-based electrochemiluminescence (ECL) detection coupled with capillary electrophoresis (CE) method has been established for the sensitive determination of ephedrine for the first time. Under the optimized conditions [ECL detection at 1.15 V, 25 mmol/L phosphate buffer solution (PBS), pH 8.0, as running buffer, separation voltage 12.5 kV, 5 mmol/L Ru(bpy)₃²⁺ with 60 mmol/L PBS, pH 8.5, in the detection cell] linear correlation (r = 0.9987) between ECL intensity and ephedrine concentration was obtained in the range 6.0 × 10⁻⁸-6.0 × 10⁻⁶ g/mL. The detection limit was 4.5 × 10⁻⁹ g/mL (S:N = 3). The developed method was successfully applied to the analysis of ephedrine in human urine and the investigation of its interactions with three proteins, including bovine serum albumin (BSA), cytochrome C (Cyt-C) and myoglobin (Mb). The number of binding sites and the binding constants between ephedrine and BSA, Cyt-C and Mb were 8.52, 12.60, 10.66 and 1.55 × 10⁴ mol/L, 6.58 × 10³ mol/L and 1.59 × 10⁴ mol/L, respectively.

Capillary electrophoresis of natural products: 2011–2012

“…When the appropriate derivatizing chemistry is attained, the sensitivity of ELCL detection in CE is on par with that of fluorescence. Tris(2,2′‐bipyridyl)ruthenium(II) (Ru(bpy) 3 2+ ) is the most common luminophore for ELCL . There were five articles pertaining to the use of ELCL as the detection method in CE and the two papers that caught our attention are discussed below.…”

“…There were two reports of the use of CE to monitor toxicity. The toxicity of the alkaloid ephedrine was assessed by monitoring its level in urine . This alkaloid is strictly monitored by the medical commission of the international Olympic committee as one of the prohibited substances in the doping list because of its properties as a stimulant of the central nervous system.…”

The advances of electromigration techniques applied for alkaloid analysis

“…Additional fluorescence detection for derivatized amino acids in tobacco, and electrochemical detection in the microchip device for sensitivity improvement of dopamine detection, have stemmed from the catalytic properties of Ru(bpy) 3 3+ ions, generated on the ECL electrode (Chang et al ., ; Qiu et al ., ). Alongside analyzing plant extracts and biological fluids, electrochemiluminescence detection has also been applied in studies of drug–protein interactions (Yang et al ., ).…”

“…The enrichment step not only enables the detection of concentration of the desired analytes, but also plays a clean‐up role, which appears crucial in the case of such complex matrices as blood and cell culture medium. Yet, direct analysis after dilution or derivatization of the analyzed samples has also been reported, employed with more selective detectors such as electrochemiluminescence (Liu et al ., , , ; Yang et al ., ) or fluorescence (Belder et al ., ). Determination of codeine and paclitaxel in cancer patients' urine, with simple sample preparation and UV detection has been presented by Rodriguez et al .…”

Interactions of indole alkaloids with myoglobin: A mass spectrometry based spectrometric and computational method

“…Myoglobin (Mb) is a member of the heme protein family and a well‐established protein . Mb is one of the most studied proteins and serves as a paradigm for the characterization of ligand–protein complexes .…”