Field‐amplified sample injection combined with CE for the enantiodetermination of cathinones in urine samples

Abstract

This work presents a capillary electrophoresis methodology for the enantiodetermination of cathinones in urine employing a liquid–liquid extraction sample pretreatment. The cathinones were enantioseparated by adding a mixture of 8 mM 2‐hydroxypropyl β‐cyclodextrin and 5 mM β‐cyclodextrin to the background electrolyte, which consists of 70 mM of monosodium phosphate aqueous solution at pH 2.5. Field‐amplified sample injection was used as preconcentration strategy to improve the sensitivity. We studied various parameters that affect this stacking strategy, in particular, the sample solvent and its pH, the presence or absence of a low conductivity solvent plug introduced before the sample injection, the nature and volume of this plug, and the voltage and time of the electrokinetic injection of the sample. The optimum conditions were achieved by injecting a plug of isopropanol:H2O 50/50 at 50 mbar for 5 s prior to the electrokinetic injection of the sample prepared in an aqueous solution of HCl 10−6 M. The sensitivity enhancement factors were from 562 to 601 in terms of peak area and from 444 to 472 in terms of peak height. The method was validated by analyzing spiked urine samples, obtaining a linear range of 25 to 1000 ng/mL and limits of detection ranging from 15 to 45 ng/mL.

Recent Applications of Dynamic On-Line Sample Preconcentration Techniques in Capillary Electrophoresis

“…In the field-amplified stacking injection (FASI) technique, more efficient sample enrichments can be generally attained by electrokinetically injecting a low-conductivity sample solution. From the year 2019 to 2021, FASI has been applied to the analyses of macrocyclic antibiotics [22], diltiazem and metoprolol tartrate [23], cold medicine compounds [24], corticosteroids [25], α-blockers [26], 2,2'-azobis(2-amidinopropane) ion [27], sulfonamides [28], chlorophenols [29], cathinones [30], 9-hydroxyrisperidone [31], linear alkylbenzene sulfonates [32], quetiapine and its metabolites [33] as summarized in Table 2. Kowalski et al reported an FASI method for stacking macrocyclic antibiotics in hydrophobic interaction electrokinetic chromatography [22].…”

Determination of pepsin by capillary electrophoresis using mixed polymer coated capillary with switchable properties toward protein adsorption/desorption

“…Offline preconcentration requires pretreatment of the target analyte, which is characterized by large reagent consumption and a cumbersome operation process. On-line preconcentration techniques include ITP [23,24], field amplified sample stacking [25][26][27], large volume sample stacking [28][29][30], field amplified sample injection [31,32], sweeping techniques [33,34], pH junction techniques [35], and so on.…”

Development of a sensitive MEKC‐LIF method for synthetic cathinones analysis

“…In this context, several publications referenced CE for the enantiomeric separation of SC using cyclodextrines as chiral selector [10][11][12][13][14][15]. Recently, several preconcentration strategies were evaluated in order to reach high sensitivity for the enantiodetermination of cathinones in urine samples [16,17]. This research group also proposed an in-line SPE with CE-MS analysis for the enantiodetermination of R,S-3,4-methylenedioxypyrovalerone [18].…”