High pressure selected ion chemical ionization interface for connecting a sample source to an analysis device
AssigneeGeorgia Tech Research Corporation
InventorsFred L. Eisele, Harald Berresheim
Life of this patent
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Abstract
A high pressure interface device for connecting a gas chromatograph to a mass spectrometer having a high pressure laminar flow, flow tube ion reactor cell containing an isolated ionization source and an axial sample injection port in which specific ion species formed by radioactive bombardment of gas mixture are reacted with gaseous samples to result in an ionized gaseous sample. When coupled to a multistage pumped mass spectrometer, this invention makes possible detection sensitivities of trace sample species in the subparts per trillion range and under proper condition does not need calibration.
Claims28
An apparatus for connecting a gaseous medium source located upstream from the apparatus to a mass analysis device located downstream from the apparatus, the apparatus comprising a flow tube ion reactor cell, an isolated ionization source, at least one sample injection means, and a buffer gas inlet means,
- said flow tube comprises proximal and distal ends and inner and outer surfaces, said proximal end being connected to said buffer gas inlet means and said distal end being connected to said mass analysis device;
- said at least one sample injection means being located coaxially with said flow tube and comprising a hollow shaft terminating in a sample outlet port;
- said isolated ionization source being located within said flow tube in an ion source region upstream and isolated from said sample outlet port;
- said buffer gas injection port being located upstream from said isolated ionization source and from said sample outlet port and configured so as to allow the introduction of a buffer gas coaxially about said sample outlet port;
- means for creating a laminar flow of said buffer gas within said flow tube;
- and
- an ion-molecule reaction region within said flow tube and located downstream from said sample outlet port.
A method for introducing a gaseous sample to a mass analysis device comprising the steps of:
- (a) providing a sample gas;
- (b) providing a buffer gas comprising a carrier gas and one or more trace gas neutral species;
- (c) providing a buffer gas ionization mechanism;
- (d) providing a flow tube ion reactor cell;
- (e) introducing said buffer gas into said flow tube ion reactor cell as a buffer gas flow;
- (f) providing a means for uniformly diffusing said buffer gas within said flow tube ion reactor cell and for causing said buffer gas to have a laminar flow in an axial direction along said flow tube ion reactor cell;
- (g) ionizing said buffer gas by said buffer gas ionization mechanism within an ion source region, producing an ionized buffer gas flow;
- (h) introducing said sample gas within said flow tube ion reactor cell generally along the central axis of said ionized buffer gas flow;
- (i) reacting said sample gas with said ionized buffer gas by a sample ionization mechanism within an ion/molecule reaction region resulting in the ionization of said sample gas by ion/molecule reactions;
- and
- (j) introducing said ionized sample gas and ionized buffer gas into said mass analysis device.
A measurement system used to calculate sample species concentration from measured instrumental parameters and a single physical constant, comprising:
- (a) a buffer gas including a carrier gas and at least one trace gas parent neutral species;
- (b) a flow tube reaction cell comprising a laminar buffer gas flow region, an ion source region, and a separate ion/molecule reaction region;
- (c) a means for ionizing said buffer gas to create reactant ions;
- and
- (d) a means for ionizing said sample gas by reaction with said reactant ions to create product ions, wherein the ratio of said product ions to said reactant ions remaining after reaction with said sample gas, together with the reaction rate coefficient and reaction time, is used to calculate the concentration of said sample species in said sample gas.
A measurement method which used the concentration ratio of at least two ions to calculate the concentration of one of at least one parent neutral species contained in a sample gas comprising the steps of:
- (a) providing a buffer gas including a carrier gas and at least one trace gas neutral reactant species;
- (b) creating a laminar flow of said buffer gas;
- (c) ionizing said buffer gas within an ion source region so as to create buffer gas species reactant ions;
- (d) reacting said sample gas with said buffer gas reactant species ions within an ion/molecule reaction region separate from said ion source region to create sample gas ion species;
- (e) introducing said sample gas ion species and said buffer gas species reactant ions to a detection means;
- and
- (f) using the concentration ratio of said sample gas ion species to said buffer gas species reactant ion remaining after reaction with said sample gas and the reaction rate and reaction time to determine the concentration of said at least one parent neutral species.
Dependencies are inferred from the claim text.