Improving MEKC–ESI–MS–MS Analysis of Synthetic Cathinones

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A team of scientists based in the Czech Republic has developed a micellular electrokinetic chromatography method coupled with tandem mass spectrometry (MEKC–ESI–MS–MS) that uses salts of perfluorocarboylic acid as the volatile background electrolyte (BGE). The method was applied to the determination of 12 drugs from the class of synthetic cathinones in urine samples. According to the paper published in the Journal of Chromatography A, the BGE used to form micelles did not affect the electron ionization efficiency of MS.¹

Screening of biological samples is normally performed using either liquid chromatography or gas chromatography coupled with mass spectrometry, but capillary electrophoresis is another powerful technique for drug screening that is often side-lined. Lead author Vítezslav Maier told The Column: “Capillary electrophoresis connected with mass spectrometry using the electrospray ionization interface has one important disadvantage. The non-volatile components of the running electrolyte, which are normally used in the CE, cannot be used in MS detection, and the optimization of the separation of structurally close and related compounds such as the synthetic cathinones is very difficult. But we observed that some perfluorocarboxylic acids and some perfluorocarboxylic acids and their salts can create volatile micelles which could be used for the separation of the structurally related compounds from the cathinone family without decreasing of the electrospray ionization efficiency. Thus, the detection limits are comparable with LC–MS.”

Blank urine samples and urine spiked with cathinones were analyzed using MEKC–ESI–MS–MS. Solid-phase extraction (SPE), used as clean-up step prior to analysis with ammonium salt of perfluorooctanoic acid, was used as the volatile BGE. According to the paper, the approach did not require sample derivatization and derived LOD values were comparable to GC–MS methods.

When asked about future work, Maier told The Column: “Currently, we are working on the separation of a second wide and new group of drugs — synthetic cannabinoids. We solved the separation of several synthetic cannabinoids and their metabolites by supercritical fluid chromatography and also by capillary electrophoresis with tandem mass spectrometry. Nowadays we make some pilot analyses of the real samples.”
 — B.D.
Reference
M. Svidrnoch, L. Lnenícková, I. Válka, P. Ondra, and V. Maier, Journal of Chromatography A1356, 258–265 (2014).

This story originally appeared in The Column. Click here to view that issue.