A simple approach to compensate the suction caused by the electrospray ionization source in capillary electrophoresis‐mass spectrometry systems

Abstract

ESI sources continuously consume the liquid at the tip of the capillary, which causes the dragging of the BGE. The laminar nature of this flow causes the broadening of the peaks and loss of separation efficiency. The usual solution for this problem is to compensate this phenomenon by reducing the pressure at the inlet vial by either leveling of this vial or pumping off the air that is over it. However, one must know the pressure to be applied in order to prevent under- or over-compensation. The procedure herein introduced allows the easy calculation of this pressure by obtaining two electropherograms at two different values of separation voltage. The migration times of the peaks allow the calculation of the apparent mobilities even in the presence of the laminar flow. Therefore, one can calculate the contributions from both electrophoresis and hydrodynamic flow, and finally the pressure associated with the undesirable flow. This pressure is then applied as a negative pressure at the inlet vial in the following experiments. Increase of up to 192% in the number of plates was obtained in a simple experiment. In addition, the bubble forming caused by the ESI suction during injection was prevented by turning off the nebulizer gas during the changes of inlet vials.

Low Flow Voltage Free Interface for Capillary Electrophoresis and Mass Spectrometry Driven by Vibrating Sharp-Edge Spray Ionization

“…If flow is superimposed to stabilize the electrospray and speed the separation, the efficiency of the electrophoresis will be reduced. In other instances, it has also been noted that the process of electrospray itself may superimpose laminar flow in capillary electrophoresis. , …”

A capillary electrophoresis/tandem mass spectrometry approach for the determination of monoalkyl carbonates

“…4 Calibration curve for MEC using TCA as internal standard. Both linear and logarithm (inset) graphs show good linearity and no significant difference among the sets prepared with different levels of ethanol (1,5,10,20, and 40% v/v) and bicarbonate. The values for intercept and slope and standard errors were, respectively, 0.003 AE 0.027 and (4.202 AE 0.024) L mmol À1 .…”

“…4 shows a calibration curve for MEC using TCA as internal standard. Solutions were prepared with 7 initial concentrations of NaHCO 3 (0.25, 0.5, 1, 2, 4, 8, 16 mmol L À1 ) and 5 concentrations of ethanol (1,5,10,20, and 40% v/v) resulting in 35 samples, which were analysed in triplicates. These concentrations cover the expected levels of ethanol and bicarbonate in common samples such as fermentation processes, blood of a drunken person, and alcoholic beverages.…”

Analysis of Glycans by Electrophoretic Approaches

“…Furthermore, suction effects caused by the sheath-liquid flow can cause a laminar flow inside the CE capillary which results in band broadening if the pressure is not compensated through the inlet vial. 79 On the other hand, non-volatile BGE additives that provide effective separation but are in principle not compatible with MS can be used in low amounts without causing too much ion-suppression. Non-volatile buffers were applied in the BGE for protein analysis with CE-ESI-MS. 80 Sodium phosphate strongly suppressed ionization, but 25 mM ammonium borate could be used without compromising signal intensities.…”