Investigation of Imidazolium-Based Ionic Liquids as Additives for the Separation of Urinary Biogenic Amines via Capillary Electrophoresis

Abstract

Ionic liquids (ILs), such as imidazoles, can be used to prevent the sorption of analytes onto the walls of the capillary. Prior works have confirmed that coating the capillary wall with a cationic layer can increase its surface stability, thereby improving the repeatability of the separation process. In this study, micellar electrokinetic chromatography (MEKC) is employed to evaluate how two ILs with different anions—namely, 1-hexyl-3-methylimidazolium chloride [HMIM+Cl−] and 1-hexyl-3-methylimidazolium tetrafluoroborate [HMIM+BF4−]—affect the separation efficiency for biogenic amines (BAs) such as metanephrine (M), normetanephrine (NM), vanilmandelic acid (VMA), and homovanillic acid (HVA) in urine samples. To this end, solid-phase extraction (SPE) is employed using different sample pH values, with the results demonstrating that HVA and VMA is easily extracted at a sample pH of 5.5, while a sample pH of 9.0 facilitated the extraction of M and NM. In the applied SPE protocol, selected analytes were isolated from urine samples using hydrophilic–lipophilic-balanced (HLB) columns and eluted with methanol (MeOH). The validation data confirmed the method’s linearity (R2 > 0.996) for all analytes within the range of 0.25–10 µg/mL. The applicability of the optimized SPE-MEKC-UV method was confirmed by employing it to quantify clinically relevant BAs in real urine samples from pediatric neuroblastoma (NBL) patients.

Development of a capillary electrophoresis method based on magnetic solid‐phase extraction for simultaneous and sensitive detection of eight biogenic amines in foods

“…The developed MSPE‐CE method and previously reported methods for the determination of BAs are compared in Table S5. This work achieved significantly lower LODs compared with the findings of previous studies 36‐40 . More importantly, the approach was environmentally friendly due to low organic regent consumption and reusable adsorbents.…”

“…This work achieved significantly lower LODs compared with the findings of previous studies. [36][37][38][39][40] More importantly, the approach was environmentally friendly due to low organic regent consumption and reusable adsorbents. Thus, the established MSPE-CE method in this study indicates tremendous potential for detecting BAs from food samples.…”

Capillary Electrophoresis: A Three-Year Literature Review

“…Baseline separation of all five proteins investigated was obtained, and the separation mechanism was illustrated by the changes in the capillary surface and the interactions of ILs with proteins. Two other imidazole ILs, 1-hexyl-3-methylimidazolium chloride and 1-hexyl-3-methylimidazolium tetrafluoroborate, were used in MEKC to enhance the separation efficiency of biogenic amines, and the method was validated using urine samples from pediatric neuroblastoma patients …”

“…Two other imidazole ILs, 1-hexyl-3-methylimidazolium chloride and 1hexyl-3-methylimidazolium tetrafluoroborate, were used in MEKC to enhance the separation efficiency of biogenic amines, and the method was validated using urine samples from pediatric neuroblastoma patients. 72 Xie et al synthesized a CD-based IL, [N-methylimidazole-β-CD][bromide], for the separation of five chlorogenic acid isomers. 73 In comparison with the IL precursor (native β-CD), the solubility of the IL in aqueous solutions was significantly increased and thus can be used in higher concentrations.…”