Formation of Alternating Surfactant-Enriched and Surfactant-Depleted Phases in the Taylor Cone of a Nanoelectrospray.

The electrospray ionization of highly conductive solutions containing Triton X-100, a nonionic surfactant, is found to induce alternating periods of surfactant enrichment and depletion when the concentration of the surfactant is near the critical micelle concentration (CMC) and when the flow rate is on the order of 10 nL/min. Analyzing the surfactant-protein mixture shows that the protein is partially denatured during the surfactant enrichment. The measurement of the phospholipid and oligosaccharide mixture prepared in the surfactant solution shows that the ion signal of the lipid is in phase with, and the hydrophilic oligosaccharide is out of phase with the surfactant signal.

Feedback Control of Electrospray with and without an External Liquid Pump Using the Spray Current and the Apex Angle of a Taylor Cone for ESI-MS.

An electrospray operated in the steady cone-jet mode is highly stable but the operating state can shift to pulsation or multijet modes owing to changes in flow rate, surface tension, and electrostatic variables. Here, a simple feedback control system was developed using the spray current and the apex angle of a Taylor cone to determine the error signal for correcting the emitter voltage. The system was applied to lock the cone-jet mode operation against external perturbations.

Tuning oxidative modification by a strong electric field using nanoESI of highly conductive solutions near the minimum flow rate.

Oxidative modification is usually used in mass spectrometry (MS) for labeling and structural analysis. Here we report a highly tunable oxidation that can be performed in line with the nanoESI-MS analysis at the same ESI emitter without the use of oxidative reagents such as ozone and HO, and UV activation. The method is based on the high-pressure nanoESI of a highly conductive (conductivity >3.

Bipolar Electrospray from Electrodeless Emitters for ESI without Electrochemical Reactions in the Sprayer.

A bipolar ESI source is developed to generate a simultaneous emission of charged liquid jets of opposite polarity from an electrodeless sprayer. The sprayer consists of two emitters, and the electrosprays are initiated by applying a high potential difference (HV) across the counter electrodes facing each emitter. The sprayer and the liquid delivery system are made of all insulators without metal components, thus enabling the total elimination of electrochemical reactions taking place at the liquid-electrode interface in the typical electrosprayer.