Implementation of a design of experiments to study the influence of the background electrolyte on separation and detection in non‐aqueous capillary electrophoresis–mass spectrometry

Abstract

Non-aqueous capillary electrophoresis (NACE) background electrolytes are most often composed of a mixture of methanol and acetonitrile (ACN) with soluble ammonium salts added as electrolyte. In this study on NACE-MS, we used a mixture of glacial acetic acid and ACN giving rise to an acidic background electrolyte (BGE) with a very low dielectric constant. Impressive changes in selectivity and resolution were observed for structurally closely related indole alkaloids including diastereomers upon addition of ammonium formate as electrolyte and upon variation of the solvent ratio. In order to obtain best separation and MS detection conditions and to reveal the influence of the parameters of the BGE on separation and detection and vice versa of the MS parameters on separation, an optimization strategy was employed using a design of experiments in a central composite design with response surface methodology. It was proven that at high electroosmotic flow conditions capillary electrophoretic separations and thus optimization can be realized without interference from the coupling to an MS system. Several significantly interacting parameters were revealed, which are not accessible with classical univariate optimization approaches. With this optimization, alkaloid mixtures from a plant extract of Mitragyna speciosa, containing a large number of diastereomeric compounds were successfully separated.

Nonaqueous capillary electrophoresis–mass spectrometry: A versatile, straightforward tool for the analysis of alkaloids from psychoactive plant extracts

“…These requirements are perfectly matched by capillary electrophoresis coupled to mass spectrometry []. In this study, we present the versatility, high separation power, and matrix tolerance of a previously developed and optimized nonaqueous capillary electrophoresis–mass spectrometry method for the analysis of Kratom ( Mitragyna speciosa ) [], now for the analysis of different biogenic drug samples. The drugs samples were chosen according to different properties of their alkaloid composition: Banisteriopsis caapi and Peganum harmala as different sources for harmala alkaloids that are structurally closely related substances; M. speciosa and Kratom preparations as samples with a high number of diastereomeric compounds; Voacanga africana as a representative sample containing iboga alkaloids with a high number of different of alkaloids; Datura stramonium as source for tropane alkaloids and Mimosa tenuiflora as tryptamine source.…”

“…Tropane alkaloids have a direct impact on the central nervous system, leading to shortness of breath and death, but they are widely used as medicine under controlled dosage []. We will show that the method developed lately can be used for the analysis of all those different alkaloids without any modification of the procedure [].…”

Nonaqueous CE ESI‐IT‐MS analysis of Amaryllidaceae alkaloids

“…The organic solvents influence electrophoretic migration by changing solute–solvent, solute–additive, and ion–ion interactions. Moreover, p K a values of analytes in organic solvents are significantly different from those in water . So proper ratio of methanol to ACN served as solvent in which analytes could be well separated.…”

Screening and Identification of Mitragynine and 7-Hydroxymitragynine in Human Urine by LC-MS/MS

“…Lower doses tend to yield a dopaminergic-dominant result or stimulation, while higher doses result in a mu-opioid receptor-dominant effect, which eclipses the dopaminergic expression or physical and emotional hedonia and pain relief [12,24,35,36]. Many analytical approaches have been reported for the separation and identification of kratom, including GC and GC-MS [2,3,[37][38][39], LC and LC-MS [38,[40][41][42][43][44] and CE and CE-MS [43,45,46]. In this study, we report a rapid and effective method for quantification mitragynine and 7-hydroxymitragynine compounds in human urine matrix.…”