Mass analysis system with low pressure differential mobility spectrometer

Abstract

A mass analysis system including a low pressure dissociation region and a differential mobility spectrometer. The differential mobility spectrometer including at least one pair of filter electrodes defining an ion flow path where the filter electrodes generate an electric field for passing through a selected portion of the sample ions based on the mobility characteristics of the sample ions. The differential mobility spectrometer also includes a voltage source that provides DC and RF voltages to at least one of the filter electrodes to generate the electric field, an ion inlet that receives sample ions that have passed through the low pressure dissociation region, and an ion outlet that outputs the selected portion of the sample ions. A mass spectrometer receives some or all of the selected portion of the sample ions.

1 . A mass analysis system comprising:
 a low pressure dissociation region,   a differential mobility spectrometer including:
 at least a pair of filter electrodes defining an ion flow path therebetween, the filter electrodes generating an electric field for passing through a selected portion of the sample ions based on the mobility characteristics of the sample ions, 
 a voltage source for providing RF and DC voltages to at least one of the filter electrodes to generate the electric field, 
 an ion inlet for receiving sample ions that have passed through the low pressure dissociation region, and 
 an ion outlet for outputting the selected portion of the sample ions, and 
   a mass spectrometer for receiving some or all of the selected portion of the sample ions.   
     
     
         2 . The system of  claim 1 , wherein the dissociation region includes at least one of a collision region, desolvation region, and declustering region. 
     
     
         3 . The system of  claim 2 , wherein the low pressure dissociation region is configured to accelerate the sample ions. 
     
     
         4 . The system of  claim 3 , wherein the low pressure dissociation region is configured to perform at least one of declustering and fragmenting the sample ions. 
     
     
         5 . The system of  claim 1 , wherein the pressure of the differential mobility spectrometer and a portion of the low pressure dissociation region is less than about atmospheric pressure. 
     
     
         6 . The system of  claim 5 , wherein the pressure of the differential mobility spectrometer and a portion of the low pressure dissociation region is less than about 100 torr. 
     
     
         7 . The system of  claim 1 , wherein the pressure of the ion flow path is substantially the same as the pressure of a portion of the low pressure dissociation region. 
     
     
         8 . The system of  claim 1  comprising at least one ion guide located in at least one of the low pressure dissociation region and an intermediate region between the differential mobility spectrometer and the low pressure dissociation region. 
     
     
         9 . The system of  claim 7 , wherein the at least one ion guide includes at least one ion focusing element. 
     
     
         10 . The system of  claim 8 , wherein the ion focusing element includes at least one of an RF rod, RF ring, RF lens, DC lens, DC ring, deflector plate, and grid. 
     
     
         11 . The system of  claim 1 , wherein the low pressure dissociation region is configured to receive a flow of the sample ions from an ion source. 
     
     
         12 . The system of  claim 11 , wherein the flow is formed by a vacuum drag from the dissociation region. 
     
     
         13 . The system of  claim 10 , wherein the ion source includes a second differential mobility spectrometer. 
     
     
         14 . The system of  claim 11 , wherein the second differential mobility spectrometer operates at substantially atmospheric pressure or above. 
     
     
         15 . The system of  claim 10 , wherein the low pressure dissociation region is configured to accelerate ions within a free jet expansion. 
     
     
         16 . The system of  claim 1  comprising a housing, the housing substantially enclosing the differential mobility spectrometer. 
     
     
         17 . The system of  claim 16 , wherein the housing substantially encloses the low pressure dissociation region. 
     
     
         18 . The system of  claim 17 , wherein the housing includes a housing inlet for receiving the sample ions. 
     
     
         19 . The system of  claim 16 , wherein the housing includes a housing outlet, in communication with the ion outlet, for outputting the portion of selected sample ions into the mass spectrometer. 
     
     
         20 . The system of  claim 19 , wherein the mass spectrometer includes at least one ion optics element for receiving the selected portion of the sample ions via the housing outlet. 
     
     
         21 . The system of  claim 20 , wherein the mass spectrometer includes a mass analyzer in communication with the at least one ion optics element. 
     
     
         22 . The system of  claim 1  comprising an insulating material in communication with at least one of the filter electrodes. 
     
     
         23 . The system of  claim 1  comprising at least one heated region configured to perform at least one of i) declustering ions, ii) desolvating ions, iii) accelerating the reclustering of ions with reagents, and iv) shifting the clustering equilibrium for ions with dopant or reagents. 
     
     
         24 . The system of  claim 1 , wherein the pressure of the differential mobility spectrometer and a portion of the low pressure dissociation region is about 50 to about 760 torr. 
     
     
         25 . The system of  claim 1 , wherein the differential mobility spectrometer comprises four electrodes. 
     
     
         26 . A method for analyzing a sample comprising:
 passing sample ions through a low pressure dissociation region,   applying RF and DC voltages to at least one of at least one pair of filter electrodes,   generating an electric field in a flow path between the at least one pair of filter electrodes,   passing through the electric field a selected portion of the sample ions based on the mobility characteristics of the sample ions, and   receiving some or all of the selected portion of the sample ions at a mass spectrometer.   
     
     
         27 . The method of  claim 26  comprising accelerating the sample ions in the low pressure dissociation region. 
     
     
         28 . The method of  claim 27  comprising performing at least one of declustering and fragmenting the sample ions in the low pressure dissociation region. 
     
     
         29 . The method of  claim 26 , wherein the pressure of the flow path and a portion of the low pressure dissociation region is less than about 760 torr. 
     
     
         30 . The method of  claim 29 , wherein the pressure of the flow path and a portion of the low pressure dissociation region is less than about 100 torr. 
     
     
         31 . The method of  claim 26 , wherein the pressure of the ion flow path is substantially the same as a portion of the pressure of the low pressure dissociation region. 
     
     
         32 . The method of  claim 26  comprising guiding the sample ions through at least one of the low pressure dissociation region and an intermediate region. 
     
     
         33 . The method of  claim 32 , wherein the guiding is performed by an ion guide including at least one ion focusing element. 
     
     
         34 . The method of  claim 33 , wherein the ion focusing element includes at least one of an RF rod, RF ring, RF lens, DC ring, DC lens, deflector plate, and grid. 
     
     
         35 . The method of  claim 26  comprising receiving a flow of the sample ions at the low pressure dissociation region from an ion source. 
     
     
         36 . The method of  claim 26  comprising providing at least one heated region configured to perform at least one of i) declustering ions, ii) desolvating ions, iii) accelerating the reclustering of ions with reagents, and iv) shifting the clustering equilibrium for ions with a dopant or reagent. 
     
     
         37 . The method of  claim 26 , wherein the at least one pair of filter electrodes comprises four electrodes. 
     
     
         38 . A sample analysis system comprising:
 a first pressure region operating at a pressure of about atmospheric pressure or greater including:
 a first DMS filter for receiving sample ions from an ion source and passing through a first set of selected sample ions, and 
   a second pressure region, in communication with the first pressure region, operating at less than about atmospheric pressure including:
 a dissociation region for accelerating the first set of selected sample ions, and 
 a second DMS filter for passing through a second set of selected sample ions. 
   
     
     
         39 . The system of  claim 38  comprising:
 a third pressure region, in communication with the second pressure region, operating at less than about 1 torr including:
 an ion optics element for receiving the second set of selected sample ions. 
 
 
     
     
         40 . The system of  claim 39  comprising:
 a fourth pressure region, in communication with the third pressure region, operating at less than about 10 −4  torr including:
 a mass analyzer. 
 
 
     
     
         41 . The system of  claim 38  comprising a dopant inlet, in communication with the first pressure region, for introducing at least one reagent. 
     
     
         42 . The system of  claim 38  comprising a gas inlet, in communication with first pressure region, for introducing at least one of a curtain gas and a transport gas. 
     
     
         43 . The system of  claim 38  comprising at least one heated region configured to perform at least one of i) declustering ions, ii) desolvating ions, iii) accelerating the reclustering of ions with reagents, and iv) shifting the clustering equilibrium for ions with dopant or reagents. 
     
     
         44 . The system of  claim 43  comprising at least one adjustable heating element for controlling the temperature in the at least one heated region. 
     
     
         45 . The system of  claim 41  comprising a heated region located within the first or second pressure region, wherein the heated region is configured to perform at least one of remove unwanted clusters of the sample ions and accelerate reclustering of the sample ions with the at least one reagent. 
     
     
         46 . The system of  claim 41  comprising a reaction region in the first pressure region for clustering a portion of the sample ions using the at least one reagent. 
     
     
         47 . An ion analyzer comprising:
 a ion source,   a flow of ions from the ion source,   a reaction region for introducing at least one modifier to the flow of ions,   a first DMS, operating substantially at atmospheric pressure, for receiving the flow of ions from the reaction region, the first DMS performing a first mobility based filter operation on the flow of ions,   a declustering region, operating at less than atmospheric pressure, for receiving the flow of ions from the first DMS, and   a second DMS, operating at less than atmospheric pressure, for receiving the flow of ions from the declustering region and performing a second mobility based filter operation on the flow of ions.   
     
     
         48 . The analyzer of  claim 47  comprising a mass spectrometer for receiving the flow of ions from the second DMS. 
     
     
         49 . The analyzer of  claim 48 , wherein the mass spectrometer includes a mass analyzer. 
     
     
         50 . The analyzer of  claim 47  comprising at least one heated region configured to perform at least one of i) declustering ions, ii) desolvating ions, iii) accelerating the reclustering of ions with reagents, and iv) shifting the clustering equilibrium for ions with dopant or reagents. 
     
     
         51 . The analyzer of  claim 47 , wherein the first DMS performs separations based on a clustering model mechanism. 
     
     
         52 . The analyzer of  claim 51 , wherein the second DMS performs separations based on a rigid sphere collision model mechanism. 
     
     
         53 . The analyzer of  claim 47  comprising an ion guide upstream of the second DMS for providing the flow of ions to the second DMS. 
     
     
         54 . An ion analysis system comprising:
 an ion source,   a flow of ions from the ion source,   a first means for modifying a first portion of ions from the flow of ions to alter the α function associated with the first portion of ions,   a first DMS configured to receive the first portion of ions, conduct a differential mobility separation, and output a second portion of ions,   a second means for modifying the second portion of ions to alter the α function associated with the second portion of ions, and   a second DMS configured to receive the second portion of ions, conduct a differential mobility separation, and output a third portion of ions.   
     
     
         55 . The system of  claim 54 , wherein the means for modifying includes at least one of a reaction region, clustering region, dissociation region, and declustering region.