Facile separation and determination ofAconitine alkaloids in traditional Chinese medicines by CE with tris(2,2'-bipyridyl) ruthenium(II)-based electrochemiluminescence detection

Electrodeposition immobilized molybdenum disulfide quantum dots and their electrochemiluminescence application in the detection of melamine residues in milk powder

In this paper, one-step hydrothermal and electrodeposition methods were used to prepare a MoS2 quantum dot (QD) solid-phase electrochemiluminescent (ECL) electrode for the detection of melamine residues in milk powder. With the assistance of chitosan, MoS2 QDs fixed by the one-step electrodeposition method show better ECL performance than those by traditional deposition methods due to better dispersibility and stability. Based on the quenching of the MoS2 QDs ECL signal by melamine, quantitative detection of melamine in the sample was performed. The structure and morphology of a MoS2-CHIT/indium tin oxide (ITO) solid-phase ECL electrode were characterized by TEM and XPS, and melamine was detected by the ECL method using a three-electrode system. The proposed sensor exhibited good linearity in the range of 1.00 × 10-11 to 1.00 × 10-7 mol L-1 (ΔI = 12 100.62 + 1009.93 lg c (mol L-1), R2 = 0.997), and the method shows the advantages of simplicity and sensitivity compared to traditional detection methods. The interference of common ions in milk powder on the modified electrode was within 5%, and the recovery rate of real sample detection was within 97-98%. As a result, the proposed method is suitable for detecting melamine residues in milk powder.

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

A CE-electrochemiluminescence(CE-ECL) detection system, CE/tris(2,2'-bipyridyl) ruthenium(II)ECL with ionic liquid, was established for the determination of diester-diterpenoid aconitum alkaloids (aconitine (AC), mesaconitine (MA) and hypaconitine (HA)) in traditional Chinese herbal medicine. Running buffer containing 25 mM borax-20 mM 1-ethyl-3-methylimidazolium tetrafluoroborate at pH 9.15 was used, which resulted in significant changes in separation and obvious enhancement in ECL intensity for AC, MA and HA with similar structures. End-column detection was achieved in 50 mM phosphate buffer with 5 mM Ru(bpy)₃²⁺ (pH 9.15) at applied detection voltage of 1.20 V when the distance between the Pt working electrode and outlet of capillary (50 cm × 25 μm id) was set at 150 μm. One single quantitative analysis of three alkaloids was achieved at a separation voltage of 15 kV within 10 min. Moreover, two extraction processes (ethanol extraction and ethyl ether extraction after basification) were investigated. The result showed that ethanol extraction process has higher extraction efficiency than ethyl ether extraction process. Under the optimized conditions, the detection limits of AC, MA and HA were 5.62 × 10(-8) , 2.78 × 10(-8) and 3.50 × 10(-9) mol/L (S/N=3), respectively. The method was successfully applied to determine the amounts of AC, MA and HA in the aconitum herbal samples.