The University of North Carolina is offering a technology license for modifications to conventional electrospray ionization equipment as well as for nano-electrospray ionization (ESI) that allows multiple ionic samples to be injected at once into a mass spectrometry device. This invention keeps the samples from mixing in the liquid phase before ionization, which has been known to cause undesired interactions that affect the mass spectrum. The equipment is well-suited to the calibration of mass spectrometers using two separate solutions, but can also be used in many experimental scenarios incorporating multiple samples. It is relatively easy to fabricate, set up, and maintain when compared to other multiple-ESI systems.
Electrospray ionization (ESI) is one method used to generate ions from a liquid sample for mass spectrometry, and, as such, is especially useful as an ion source for liquid chromatography-mass spectrometry. In a typical ESI device, a liquid sample from a previous step (e.g., a chromatography column) is pushed through a narrow-diameter electrospray needle with an electrode near its tip. The needle is aimed at the opening of a sampling device, such as a capillary tube, which has a counter-electrode and the other end of which interfaces with the mass spectrometer. A high voltage is applied between the electrodes, such that the sample emerges from the needle as a fine mist and is charged en route to the sampling device. From there, it may enter the mass spectrometer in the required ionic form.
Researchers Gary L. Glish and Ryan M. Danell in UNC's Department of Chemistry created a simple “zero-adjustment” multiple electrospray configuration with the aim to resolve some of the difficulties in mass spectrometry. Their technology can be retrofitted to most mass spectrometers accepting input from ESI, or custom built for a particular device. The small entrance to the ion sampling capillary was widened into a funnel shape to provide a larger “target” for two or more electrospray plumes. This entrance was covered in a fine wire mesh to serve as a counter-electrode. The capillary entrance was large enough so that precise aiming of the electrospray needles was not necessary (hence the “zero-adjustment”). Two glass capillary tubes were pulled into electrospray needles small enough for nano-ESI. A thin metal wire inserted into the tip of each needle served as its ionization electrode. In use, needles were filled with solution and mounted on a movable stage positioned in front of the capillary sampling device.
Benefits of the modifications include:
• Eliminates adverse effects of mixing samples before ionization
• Facilitates accurate calibration of mass spectrometers
• Less complex and labor-intensive than other approaches
• Could conceivably reduce the frequency of electrospray needle changes and realignments in between mass spectrometry experiments
The technology can be used for:
• Internal mass calibration of mass spectrometers
• Input of multiple simultaneous samples to mass spectrometers which accept ESI as an ion source
UNC's Office of Technology Development seeks to stimulate development and commercial use of UNC-developed technologies. The ion-trap technology is available on a non-exclusive basis only. For this technology, the following intellectual property has been published: U.S. Patent No. 6,703,611 granted in 2004.
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