Inert non-adsorbing crimpable capillaries and devices for adjusting gas flow in isotope ratio analysis

Abstract

A gas transfer system for transferring gas into an analytical instrument for isotope ratio analysis comprises a capillary for delivering sample and/or reference gas from a gas source, a first connector for connecting the capillary to the gas source, a second connector for connecting the capillary to the analytical instrument, a crimping device, wherein the internal surface of the capillary comprises a coating material to prevent or minimize adsorption of water to the surface. Also provided is a device for regulating gas flow in a gas inlet system of an analytical instrument, comprising a body member having an internal gas flow channel, and a clamping member for attachment to the body member such that when the clamping member is tightened onto the body member, the internal gas flow channel is adjustably and reversibly crimped, to adjust gas flow therethrough.

What is claimed is: 
     
         1 . A gas transfer system, for transferring gas from at least one gas source into a mass spectrometer for isotope ratio analysis that comprises scrambling-free measurement of clumped isotopes, comprising:
 at least one crimpable capillary, for delivering sample and/or reference gas from the at least one gas source into the mass spectrometer;   at least one first connector for connecting the at least one crimpable capillary to the at least one gas source;   at least one second connector, for connecting the at least one capillary to the mass spectrometer,   at least one crimping device, adapted to receive the at least one crimpable capillary and adjust gas flow into the mass spectrometer by crimping the at least one capillary,   wherein the internal surface of the crimpable capillary comprises a coating material to prevent or minimize adsorption of water to the surface and which is sufficiently free of other contaminants that could cause isotope scrambling of clumped isotopes.   
     
     
         2 . The gas transfer system of  claim 1 , wherein the crimpable capillary is a stainless steel, metal or alloy capillary coated on its internal surface with said coating. 
     
     
         3 . The gas transfer system of  claim 1 , wherein the capillary coating comprises at least one silicon-based coating. 
     
     
         4 . The gas transfer system of  claim 1 , wherein the coating is deposited on the internal surface by chemical vapor deposition (CVD). 
     
     
         5 . The gas transfer system of  claim 1 , wherein said at least one gas source is a gas source with adjustable volume. 
     
     
         6 . The gas transfer system of  claim 1 , further comprising two crimpable capillaries, for delivering respectively sample gas and reference gas from respective two gas sources into the mass spectrometer. 
     
     
         7 . The gas transfer system of  claim 1 , wherein said crimping device comprises:
 i. a first body member having at least one groove for seating at least one capillary;   ii. a second body member removably attachable to said first body member, the second body member holding a crimping member that is disposed so that when the second body member is attached to the first body member, the crimping member is adjustably forced onto a capillary in the groove so as to crimp the capillary and thereby reducing gas flow therethrough.   
     
     
         8 . A method of isotope ratio analysis of a gas from a sample that comprises clumped isotopes, comprising:
 transmitting the sample gas from at least one gas source through a first capillary into a mass spectrometer and performing a first isotopic measurement,   providing at least one reference gas from another reservoir,   transmitting the at least one reference gas through a second capillary into the mass spectrometer and performing a second isotopic measurement,   wherein gas flow into the isotope analytical instrument is adjusted by crimping the capillary, or an extension thereof, for the first and second isotopic measurements to obtain substantially equal gas flow during measurements of reference gas and sample gas.   
     
     
         9 . The method of  claim 8 , wherein the capillary is a crimpable stainless steel, metal or alloy capillary coated on its internal surface with a coating material to prevent or minimize adsorption of water to the surface. 
     
     
         10 . The method of  claim 8 , wherein the capillary is a non-crimpable glass, silica or ceramic capillary. 
     
     
         11 . The method of  claim 8 , wherein a gas flow rate into the analytical instrument is achieved by means of a device as set forth in  claim 8 . 
     
     
         12 . The method of  claim 8 , wherein said at least one gas source is a gas source with an adjustable volume. 
     
     
         13 . The method of  claim 8 , wherein said reference gas is selected from carbon monoxide, carbon dioxide, hydrogen, nitrogen, nitrogen oxides, and sulfur dioxide. 
     
     
         14 . The method of  claim 8 , wherein said at least one gas source is selected from a microvolume tube, an adjustable gas bellows system, a syringe and a gas bottle.