Pressurized Hot Water Extraction and Capillary Electrophoresis for Green and Fast Analysis of Useful Metabolites in Plants

Capillary electrokinetic chromatography for chiral separation of potential SARS-CoV-2 3CL protease inhibitors

In this work, a capillary electrophoresis method was developed as a quality control tool to determine the enantiomeric purity of a series of five chiral compounds evaluated as potential severe acute respiratory syndrome coronavirus 2 3CL protease inhibitors. The first cyclodextrin tested, that is, highly sulfated-β-cyclodextrin, at 6% (m/v) in a 25 mM phosphate buffer, using a capillary dynamically coated with polyethylene oxide, at an applied voltage of 15 kV and a temperature of 25°C, was found to successfully separate the five derivatives. The limits of detection and quantification were calculated together with the greenness score of the method in order to evaluate the method in terms of analytical and environmental performance. In addition, it is noteworthy that simultaneously high-performance liquid chromatography separation of the enantiomers of the same compounds with two different columns, the amylose tris(3,5-dimethylphenylcarbamate)-coated and the cellulose tris(3,5-dichlorophenylcarbamate)-immobilized on silica stationary phases, was studied. Neither the former stationary phase nor the latter was able to separate all derivatives in a mobile phase consisting of n-heptane/propan-2-ol 80/20 (v/v).

Evaluation of greenness and analytical performances of separative methods for chiral separation of novel lactam-based P2RX7-antagonists

In this work, a preparative supercritical fluid chromatography (SFC) method was first developed to separate a series of chiral compounds evaluated as lactam-based P2RX7 antagonists. Subsequently, high-performance liquid chromatography, SFC, and capillary electrophoresis (CE) were comparatively investigated as QC tools to determine the enantiomeric purity of the separated isomers, including analytical performance and greenness. The screening of the best conditions was carried out in liquid and SFC on the nine derivatives and the amylose tris(3,5-dimethylphenylcarbamate)-based chiral stationary phase was found to be highly efficient. The same screening was carried out in CE and very different conditions, either in acidic or basic background electrolyte and different cyclodextrins used as chiral selectors, allowed the separation of six of the nine derivatives. 1-((3,4-Dichlorophenyl)carbamoyl)-5-oxopyrrolidine-2-carboxylic acid (compound 1) was chosen as a probe, and its semi-preparative separation by SFC and enantiomeric verification using the three techniques are presented. Its limit of detection and limit of quantification are calculated for each method. Finally, the greenness of each quality control method was evaluated.

Sweeping-micellar electrokinetic chromatography versus reversed phase liquid chromatography for the determination of coumarin in curry

Coumarin is a phytotoxin found in the popular spice cinnamon, which is used to flavor many Asian curry dishes. In this work, we developed and compared the analytical performance of reversed-phase liquid chromatography (RP-LC) and sweeping-micellar electrokinetic chromatography (MEKC) methods for the determination of coumarin in complex curry (gravy) samples. Using a matrix matched sample (curry after solvent extraction with methanol and diluted with 100 mM phosphoric acid), the intra-day and inter-day repeatability of retention/migration time and (corrected) peak area for both methods were acceptable (%RSD (n=6) ≤ 5%). The linear range and limit of quantitation (LOQ) were an order of magnitude better in RP-LC (RP-LC linear range = 0.11-108 mg/kg, LOQ = 0.11 mg/kg) (Sweeping-MEKC linear range = 2.16-216 mg/kg, LOQ = 2.16 mg/kg). However, the limit of detection (S/N=3) and LOQ in sweeping-MEKC was 0.65 mg/kg and 2.16 mg/kg, which were sufficient to report the levels of coumarin ≥ the European limit of 2 mg/kg in foods. During the analysis of 25 curry samples, relatively similar results for sweeping-MEKC and RP-LC were obtained for 6 samples that contained coumarin >LOQ of sweeping-MEKC. Interferences in RP-LC lead to significant overestimation of coumarin levels in 3 samples. Coumarin levels above the EU limit was found in 6 curry samples using the more selective sweeping-MEKC. This work should also raise public awareness on the presence of potentially high levels of coumarin in some foods.