Microsecond time-resolved mass spectrometry

Abstract

A microsecond time-resolved mass spectrometry device and method of using desorption electrospray ionization ( 10 ) was described for the kinetic study of fast reactions. The device includes a liquid jet generator ( 64 ) that is configured to emit a continuous liquid jet ( 50 ) having a length. An ambient ionization source ( 10 ) is directed toward a selected variable location along the continuous liquid jet ( 50 ) to desorb at least a portion of the continuous liquid jet ( 50 ). A mass analyzer ( 30 ) analyzes a mass-to-charge ratio of an ionized sample that is within the desorbed portion of the continuous liquid jet ( 50 ). The acquired mass spectra reflect the reaction progress in different reaction times and, therefore, may be used to derive the reaction rate.

What is claimed is: 
     
         1 . A microsecond time-resolved mass spectrometry device comprising:
 a liquid jet generator configured to emit a continuous liquid jet having a length;   an ambient ionization source directed toward a selected variable location along the length of the continuous liquid jet to desorb at least a portion of the continuous liquid jet; and   a mass analyzer configured to analyze a mass-to-charge ratio of an ionized sample within the desorbed portion of the continuous liquid jet.   
     
     
         2 . The microsecond time-resolved mass spectrometry device of  claim 1 , wherein the liquid jet generator further comprises:
 first and second sample sources containing first and second reactants, respectively; and   a mixer fluidically coupling the first and second sample, the mixer having an outlet configured to eject the continuous liquid jet comprised of the first and second reactants.   
     
     
         3 . The microsecond time-resolved mass spectrometry device of  claim 2 , wherein the mixer is a Tee-mixer. 
     
     
         4 . The microsecond time-resolved mass spectrometry device of  claim 2 , wherein the mixer is moveable relative to the ambient ionization source for selecting the variable length of the continuous liquid jet. 
     
     
         5 . The microsecond time-resolved mass spectrometry device of  claim 2 , wherein the first and second sample sources are syringes. 
     
     
         6 . The microsecond time-resolved mass spectrometry device of  claim 5 , wherein each syringe includes a capillary fluidically coupling the syringe to the mixer. 
     
     
         7 . The microsecond time-resolved mass spectrometry device of  claim 5 , wherein each of the syringes is driven by a syringe pump or an HPLC pump. 
     
     
         8 . The microsecond time-resolved mass spectrometry device of  claim 2 , wherein the first and second sample sources are first and second HPLC systems. 
     
     
         9 . The microsecond time-resolved mass spectrometry device of  claim 1 , wherein the ambient ionization source includes a source of charged solvent and a source of nebulizing gas. 
     
     
         10 . The microsecond time-resolved mass spectrometry device of  claim 1 , wherein the ambient ionization source includes a charged needle, a laser beam, excited atoms, energetic ions, plasma, or high energy particles. 
     
     
         11 . The microsecond time-resolved mass spectrometry device of  claim 1 , wherein a capillary extends from an outlet of the liquid jet generator. 
     
     
         12 . The microsecond time-resolved mass spectrometry device of  claim 11 , wherein the capillary is constructed from deactivated fused silica. 
     
     
         13 . A mass spectrometer system for kinetic study, the system comprising:
 (i) an ion source comprising:
 (a) first and second sample sources containing first and second reactants, respectively; 
 (b) a mixer fluidically coupling the first and second sample sources, the mixer having an outlet configured to eject a continuous liquid jet comprised of a mixture of the first and second reactants; and 
 (c) a nebulizing ionizer configured to generate a charged, nebulized solvent and to direct the nebulized solvent onto the continuous liquid jet to desorb at least a portion of the continuous liquid jet as an ionized sample, wherein the mixer is moveable relative to the nebulizing ionizer; 
   (ii) a mass analyzer connected to the ion source and configured to analyze a mass-to-charge ratio of the ionized sample; and   (iii) a controller configured to operate the ion source or the mass analyzer or both.   
     
     
         14 . The system of  claim 13 , wherein the first and second sample sources are syringes. 
     
     
         15 . The system of  claim 14 , wherein each syringe includes a capillary fluidically coupling the syringe to the mixer. 
     
     
         16 . The system of  claim 14 , wherein each syringe is driven by a syringe pump or an HPLC pump. 
     
     
         17 . The system of  claim 13 , wherein the first and second sample sources are first and second HPLC systems. 
     
     
         18 . A method of measuring a rate constant of a reaction using mass spectrometry in microsecond time resolution, the method comprising:
 supplying at least two reactants to a mixer;   ejecting a continuous liquid jet comprised of a mixture of the at least two reactants from the mixer;   positioning a nebulizing ionizer at a first distance along the continuous liquid jet and desorbing at least a portion of the continuous liquid jet as a first ionized sample;   directing the first ionized liquid sample to a mass analyzer;   measuring a relative abundance of the first ionized liquid sample;   positioning the nebulizing ionizer at a second distance along the continuous liquid jet and desorbing at least a portion of the continuous liquid jet as a second ionized sample, wherein the second distance is greater than the first distance;   directing the second ionized liquid sample to the mass analyzer;   measuring a relative abundance of the second ionized liquid sample; and   relating the relative abundances of the first and second ionized liquid samples.   
     
     
         19 . The method of  claim 18 , wherein positioning the nebulizing ionizer includes moving the mixer relative to the nebulizing ionizer. 
     
     
         20 . The method of  claim 18 , wherein supplying the at least two reactants further comprises:
 directing a first reactant from a first syringe to a first inlet of the mixer; and   directing a second reactant from a second syringe to a second inlet of the mixer.   
     
     
         21 . The method of  claim 18 , wherein directing the first and second reactants is driven by separate syringe pumps or separate HPLC pumps. 
     
     
         22 . The method of  claim 18 , wherein the mixer is a Tee-mixer. 
     
     
         23 . A method of measuring the rate constant of a reaction using mass spectrometry in microsecond time resolution, the method comprising:
 supplying at least two reactants to a mixer at a first flow rate;   ejecting a first continuous liquid jet comprised of a mixture of the at least two reactants from the mixer at a first speed;   positioning a nebulizing ionizer along the first continuous liquid jet so as to desorb at least a portion of the first continuous liquid jet as a first ionized sample and into a mass analyzer;   measuring a relative abundance of the first ionized liquid sample with the mass analyzer;   adjusting the supplying of at least one of the at least two reactants to a second flow rate such that a second continuous liquid jet is ejected from the mixer at a second speed;   desorbing at least a portion of the second continuous liquid jet with the nebulizing ionizer and into the mass analyzer;   measuring a relative abundance of the second ionized liquid sample; and   relating the relative abundances of the first and second ionized liquid sample.   
     
     
         24 . The method of  claim 23 , wherein the at least two reactants are supplied by first and second syringes, respectively, or first and second HPLC systems, respectively. 
     
     
         25 . The method of  claim 23  further comprising:
 controlling the supplying of the at least two reactants with a controller to provide the first flow and second flow rates.