Copper-coated microsprayer interface for on-line sheathless capillary electrophoresis electrospray mass spectrometry of carbohydrates

Abstract

A sturdy home-built sheathless CE/ESI-QTOF-MS system was developed and optimized for carbohydrate analysis. The interface and employed methodology provided a simple analytical solution to laborious CE/MS interfacing methods and to problems in characterization of complex carbohydrate mixtures that require high-resolution separation of the components. The CE/ESI interface, feasible in any MS laboratory, consists of a one-piece CE column having the CE terminus in-laboratory shaped as a microsprayer and coated with copper. The CE microsprayer was inserted into an in-house made stainless steel clenching device and the whole assembly was mounted onto a quadrupole TOF mass spectrometer. The analytical potential of the interface in terms of suitability, microsprayer performance, copper coat durability, ionization efficiency, spray stability, and sensitivity was tested first on a simple mixture of standard saccharides, which were separated, resolved, and detected with high separation efficiency. The approach was next assessed for the screening of a biological sample, a complex mixture of O-glycosylated sialylated amino acids from urine of a patient suffering from Schindler disease. Preliminary data allow this method to be considered as one of general applicability in structural glycobiology and glycomics and easy to be implemented for proteomic surveys as well.

Comparing and Combining Capillary Electrophoresis Electrospray Ionization Mass Spectrometry and Nano–Liquid Chromatography Electrospray Ionization Mass Spectrometry for the Characterization of Post-translationally Modified Histones

“…However, they have not been used frequently because of their limited robustness and lack of well-established interfaces and routine analysis protocols. The most widely used method for establishing the terminating electrical contact is coating the outer surface of the CE capillary tip with a conductive material (35)(36)(37). Unfortunately, the lifetimes of such coatings are generally very limited, as they suffer from deterioration under the influence of the high voltages applied.…”

Glycosylation analysis of glycoproteins and proteoglycans using capillary electrophoresis‐mass spectrometry strategies

“…The most effective sheathless configurations are based on coating the sprayer tip with a conductive layer to provide the electrical contact needed for both CE and ESI. Very popular sheathless interfaces are those based on applying either gold [45], copper [46], or carbon [47] on the spraying tip which may be either the CE capillary itself, etched as a microsprayer, or a spraying needle butted to the CE column [48]. The lowest LOD reported for glycan analysis by using a sheathless interface and the capillary end etched as microsprayer was 0.5 pmol [46].…”

“…Under sheathless conditions, the BGE composition has to be adapted to the requirements of the ionization. In this instance the authors used alkaline BGEs when working with negative ionization [46].…”

“…Very popular sheathless interfaces are those based on applying either gold [45], copper [46], or carbon [47] on the spraying tip which may be either the CE capillary itself, etched as a microsprayer, or a spraying needle butted to the CE column [48]. The lowest LOD reported for glycan analysis by using a sheathless interface and the capillary end etched as microsprayer was 0.5 pmol [46]. The minute amount of glycans resulting after usual sample extraction/preparation protocols, and the high ionization efficiency necessary for proper ionization of some carbohydrate categories, required the development of sheathless nanospray configurations.…”

“…separation [70] or (ii) sheathless interfaces with metallic coatings (e.g., copper) were utilized [46,[61][62][63]. Discontinuous interfacing (by fraction collecting) with subsequent nano-ESI-MS was used as off-line alternative, either employing nanospray-needles [59] or a nozzle-array chip (Nanomate, Advion) in combination with an automated sample application device [60].…”