Field‐amplified sample injection in capillary electrophoresis with amperometric detection for the ultratrace analysis of diastereomeric ephedrine alkaloids

Abstract

A coupling method of field-amplified sample injection (FASI) CE with amperometric detection is developed for ultratrace analysis of ephedrine alkaloids stereoisomers. FASI was introduced by injecting electrokinetically the sample solution for 10 s into the capillary filled with highly conductive background electrolyte (BGE). The diastereomeric selectivity and the detection sensitivity were improved by using borate buffer of high ionic strength as BGE. Parameters affecting FASI and CE separation were investigated to achieve the optimal conditions. Four analytes were separated within 15 min using 200 mmol/L borate buffer (pH 9.5) and separation voltage of +18 kV, with detection potential at +1.0 V (vs. Ag/AgCl) and carbon disc electrode as working electrode. Excellent linearity was observed between peak current and concentration of analytes in the range of 0.1-100 ng/mL. The LODs (S/N = 3) for (-)-ephedrine, (+)-pseudoephedrine, (-)-N-methylephedrine and (+)-N-methylpseudoephedrine were 39.3, 54.9, 30.8, and 44.1 pg/mL, respectively. The proposed method was successfully applied to the determination of alkaloids in Ephedra sinica, with results agreed well with HPLC method. Mean recoveries of 102.1-109.7% and RSDs less than 6% were found. And the merits of high sensitivity and selectivity, as well as a simple and stable operation, have been demonstrated.

Capillary electrophoresis in phytochemical analysis (2014–2017)

“…Quantitative determination of five alkaloids (camptothecin, 9‐methoxycamptothecin, 9‐aminocamptothecin, 10‐hydroxy‐camptothecin and 7‐ethyl‐10‐hydroxycamptothecin) in camptotheca fruit and bark with 4.8 to 15.0‐fold enhancement by LVSS . Field‐amplified sample injection (FASI) was used for on‐line pre‐concentration (about 1,000‐fold improvement in sensitivity) of alkaloids including ephedrine and pseudoephedrine in Ephedra herbs , and diastereomeric ephedrine alkaloids (very low concentration with 0.03‐0.05 ppb) including (‐)‐ephedrine, (+)‐pseudoephedrine, (‐)‐N‐methylephedrine and (+)‐N‐methylpseudoephedrine in Ephedra sinica . Dynamic pH junction and CE‐quadrupole time‐of‐flight mass spectrometry (Q‐TOF‐MS) method was developed for online enrichment and sensitive determination of trace systemins in plants, with enrichment factors ranged from 90‐ to 127‐fold for six target systemins .…”

“…On the other hand, a multi-criteria optimization, using the Doehlert matrix design and Derringer's desirability function, was used to optimize the separation of 17 phenolic compounds from extra-virgin olive oil by CZE [41]. A large number of experimental responses (37) including peak resolution (18), stability (18) and runtime (1) were simultaneously evaluated. The optimized method, which realized separating 17 analytes within 19 min, was applied to 15 commercial extra-virgin olive oil samples from Brazil supermarkets.…”

Rapid and cost-effective method for the simultaneous quantification of seven alkaloids in Corydalis decumbens by microwave-assisted extraction and capillary electrophoresis

“…CE is one of the most promising tools for alkaloid analysis with high separation efficiency, low solvent consumption, and short analysis time. CE methods have been successfully applied to determine the main alkaloids in some Chinese herbal medicines .…”

Analyses of Total Alkaloid Extract ofCorydalis yanhusuoby Comprehensive RP × RP Liquid Chromatography with pH Difference

“…Various analytical methods have been used for the determination of alkaloid extracts of medicinal plants like gas chromatography [ 18 ], gas chromatography mass spectrometry [ 19 ], electrophoresis [ 20 ], liquid chromatography, and liquid chromatography with mass detection, along with other techniques [ 21 – 23 ]. However, the seeking of novel analytical methods is necessary for the diversity of alkaloids and the complexity of samples, especially for the discovery of low abundant alkaloids and structurally similar alkaloids.…”