Calibrant delivery for mass spectrometry

Abstract

This article describes a means of sampling ions that are created at a location remote from the primary ion source used for mass spectral analysis. Such a source can be used for delivery of calibrant ions on demand. Calibrant ions are sprayed into an atmospheric pressure chamber, at a position substantially removed from the sampling inlet. A gas flow sweeps the calibrants towards the sampling inlet, and a new means for toggling the second ion beam into the instrument can be achieved with the use of a repelling field established by an electrode in front of the sampling inlet. The physical separation of two or more sources of ions eliminates detrimental interactions due to gas flows or fields. When using a nanoflow electrospray tip as the primary ion source, the potential applied to the tip completely repels calibrant ions and there is no compromise in terms of electrospray performance. When calibrant ions are desired, the potential applied to the nanoflow electrospray tip is lowered for a short period of time to allow calibrant ions to be sampled into the instrument, thus providing a means for external calibration that avoids the typical complications and compromises associated with dual spray sources. It is also possible to simultaneously sample ions from multiple ion beams if necessary for internal mass calibration purposes. This method of transporting additional ion beams to a sampling inlet can also be used with different types of atmospheric pressure sources such as AP MALDI, as well as sources configured to deliver ions of different polarity.

Microfluidic Dual Emitter Electrospray Ionization Source for Accurate Mass Measurements

“…Numerous methods have been reported for sequential introduction of analyte and reference solutions into a single mass spectrometer inlet using two different capillary ESI emitters. They include repositioning of the emitters at the inlet, ,− the use of a mechanical baffle to temporarily block the electrospray from one emitter at a time, , dynamic control of the ESI voltage, , and modification of external electric fields to gate ions in the gas phase. − Both mechanically based and electrically based strategies for sequentially operated, dual ESI systems are capable of accurate mass measurements (<5 ppm error) with switching times between tens to hundreds of milliseconds. Some dual-emitter systems for sequential sample introduction have also been used for gas-phase ion/ion reactions where both populations of ions must be rapidly generated. − …”

Ion/Ion Reactions of MALDI-Derived Peptide Ions: Increased Sequence Coverage via Covalent and Electrostatic Modification upon Charge Inversion

“…Experiments were performed on a 4000 AB Sciex QTRAP (Concord, ON, Canada), which has been modified to perform ion/ion reactions . The ion source is equipped with an AP-MALDI source (MassTech, Columbia, MD) and with a microionspray emitter (New Objective Inc., Waburn, MA) orthogonal to the sample inlet (Figure ). , The microionspray emitter, remote to the MS inlet and MALDI stage plate, allows for the introduction of opposite polarity ions into the MS. Briefly, the AP-MALDI source has a circular opening, where a conductive transfer tube penetrates into the ion source and attaches to the curtain plate.…”

“…In this work, we demonstrate the gas phase modification of peptide ions generated by atmospheric pressure MALDI (AP-MALDI) 42 using a dual source interface developed by Schneider et al 43 attached to a hybrid triple quadrupole/linear ion trap tandem mass spectrometer and the structural characterization of the modified and unmodified versions of the ions via ion trap CID. The formation of imine bonds (i.e.…”

“…In this work, we demonstrate the gas-phase modification of peptide ions generated by atmospheric pressure MALDI (AP-MALDI) using a dual-source interface developed by Schneider and Covey attached to a hybrid triple-quadrupole/linear ion trap tandem mass spectrometer and the structural characterization of the modified and unmodified versions of the ions via ion trap collision-induced dissociation (CID). The formation of imine bonds (i.e., Schiff base formation) using an aldehyde-containing dianion, 4-formyl-1,3-benzenedisulfonic acid (FBDSA) , has been demonstrated with peptide ions generated via ESI.…”

Multi-channel microfluidic chip coupling with mass spectrometry for simultaneous electro-sprays and extraction

“…Besides, another similar microfluidic chip structure with high DC powers applying on the dual channels implemented to spray two samples simultaneously, which successfully prevented the ion suppression to some extent. These advantages simplified the operation of microfluidic chip-based ionization coupling with MS because optimizing the angle of EESI 25 , positioning the dual emitters at the MS inlet 28 , and dynamic controlling the ESI voltages for dual sprays were necessary 12 , 31 . Moreover, dual extraction (dual EESI) was realized based on the multi-spray configuration with high DC powers, which can improve the extracted signal intensity and sensitivity.…”