An online accumulation/mobilization preconcentration technique based on a dynamic pH junction technique and electrokinetic injection was employed for analysis of phenolic acids (sinapic, ferulic, coumarinic, caffeic, syringic, vanillic, and 4-hydroxybenzoic acid) in extracts from Majorana hortensis leaves. Samples were extracted by pressurized solvent extraction with acetone at 150 degrees C and 15 MPa. The capillary electrophoretic method employed 50 mmol.L (-1) sodium borate, pH 9.5, as the sample electrolyte, 50 mmol.L (-1) sodium phosphate, pH 2.5, as the background electrolyte, and 50 mmol.L (-1) sodium phosphate, pH 2.5, with 60 mmol.L (-1) sodium dodecyl sulfate as the mobilization electrolyte. The method allowed 720-fold to 5560-fold preconcentration of the phenolic acids during 30 min of electrokinetic accumulation with detection limits from 0.38 to 4.22 ng.mL (-1).
A new method for the determination of anti-diabetic drugs metformin and rosiglitazone based on the use of capillary electrophoresis with electrospray mass spectrometry was developed. The proposed method allowed their separation within 11 min by using 50 mM formic acid at +20 kV. Positive electrospray ionization and selected ion monitoring [M+H](+) of metformin (m/z=130) and rosiglitazone (m/z=358) were performed. Several important experimental parameters influencing electrospray ionization of metformin and rosiglitazone were studied. The final composition of sheath liquid was water/methanol/formic acid (50:49.5:0.5, v/v/v), at a flow rate of 2 μL/min. The developed method was applied for the determination of metformin and rosiglitazone simultaneously in human serum after protein precipitation with acetonitrile. The limits of detection of developed method were 4.42 and 2.14 ng/mL for rosiglitazone and for metformin, respectively, which is sufficient for therapeutic serum concentration levels monitoring for both studied drugs.
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