Abstract: The present disclosure relates to a microfluidic flame ionization detector for use in small scale separations, such as, for example, microfluidic gas chromatography and microfluidic carbon dioxide based fluid chromatography. In some arrangements, the microfluidic counter-current flame ionization detector employs a non-parallel arrangement for the introduction of combustion gases into the combustion chamber. In other arrangements, the detector housing is configured to incorporate at least one of the detector electrodes within the housing using electrically isolating fittings.

Abstract: The present disclosure relates to flame based detection methods for compressed mobile phase chromatography. In particular, the present disclosure relates to the operation of a flame ionization detector for carbon dioxide based chromatography, such as supercritical fluid chromatography. The present disclosure includes a method of matching a chromatographic column with a flame ionization detector inner burner including providing a chromatographic column with an internal diameter, determining an optimal mobile phase flow rate for the chromatographic column, calculating an optimal inner diameter of the inner burner that combined with the internal diameter and flow rate of the column produces optimal detector performance, and providing a flame ionization detector inner burner having an inner diameter substantially equal to the calculated optimal inner diameter.

Abstract: Methods and apparatus for the modulation of flame gas stoichiometry to a flame-based detector for use in chromatographic separations are presented. As the total mass flow rate of mobile phase entering the flame-based detector changes (e.g., as a result of density programming in the separation), the mass flow rate of combustion gases to the detector are altered in proportion to the amount of mobile phase entering the detector. As a result, flame stability and sensitivity of the detector can be maintained by the methods and apparatus of the present disclosure.

Abstract: A system and method of reducing chromatographic band broadening within a separation column include passing a mobile phase through a length of a separation column, and generating a spatial thermal gradient external to and along the length of the separation column. The spatial thermal gradient is specifically configured to counteract a particular change in a property of the mobile phase as the mobile phase passes through the separation column. For example, the particular change counteracted may be a change in density or in temperature of the mobile phase. For analytical-scale columns, for example, the spatial thermal gradient may be configured to produce temperatures external to and along the length of the separation column that substantially matches temperatures predicted to form in the mobile phase along the column length as the mobile phase passes through the separation column, thereby substantially preventing formation of a radial thermal gradient in the mobile phase.

Abstract: Analytical-scale separation column assemblies include a tube with a bore packed with a stationary phase through which a mobile phase flows. In one embodiment, thermal elements are disposed remotely from and unattached to the tube. The thermal elements are in thermal communication with an external surface of the tube for producing a spatial thermal gradient outside of and along a length of the tube. In another embodiment, discrete, spatially separated strips of thermally conductive material are disposed on and wrapped around an external surface of the tube. Thermal elements are disposed remotely from the tube. Each thermal element is in thermal communication with one strip of thermally conductive material by a heat-transfer device. The thermal elements produce a spatial thermal gradient outside of and along a tube length by controlling temperature of each strip of thermally conductive material disposed on and wrapped around the external surface of the tube.

Abstract: A microfluidic device, for use in separation systems, includes a substrate having a fluidic channel. One or more heaters made of a thick film material are integrated with the substrate and in thermal communication with the fluidic channel of the substrate. The one or more heaters produce a thermal gradient within the fluidic channel in response to a current flowing through the one or more heaters. A plurality of electrically conductive taps can be in electrically conductive contact with the one or more heaters. The plurality of electrically conductive taps provides an electrically conductive path to the one or more heaters by which an electrical supply can produce the current flowing through the one or more heaters. Alternatively, the thick film material can be ferromagnetic, and the electrical supply can use induction to cause the current to flow through the one or more heaters.

Abstract: A chromatography system includes a separation column that separates a sample carried by a compressible mobile phase flow into analytes and a splitter in fluidic communication with the separation column to receive and divide the compressible mobile phase flow into first and second mobile phase streams in accordance with a split ratio. A thermally modulated variable restrictor is coupled between the splitter and a detector. The restrictor receives the first mobile phase stream from the splitter and has a temperature element in thermal communication with the first mobile phase stream to exchange heat therewith. A controller, in communication with the restrictor, dynamically adjusts a temperature setting of the temperature element of the restrictor to adjust the heat exchange between the thermally modulated variable restrictor and the first mobile phase stream in order to keep the split ratio constant throughout a chromatographic run.

Abstract: Thermally modulated variable restrictors used in chromatography systems enable independent control of system pressure and linear velocity of a compressible mobile phase passing through a chromatographic column. The restrictors include a restrictor body having a fluidic channel with an inlet that receives the mobile phase from the column and an outlet through which the mobile phase leaves the fluidic channel. A restrictor tip, disposed adjacent the outlet of the fluidic channel, has an egress opening that is smaller than an internal diameter of the fluidic channel. A heating element, thermally coupled to a subsection of the fluidic channel between its inlet and outlet, heats the mobile phase passing through that subsection of the fluidic channel. The restriction produced by the restrictor tip in response to the heating of the mobile phase enables independent control of system pressure and linear velocity of the mobile phase within the column.

Abstract: Thermally modulated variable restrictors used in chromatography systems enable independent control of system pressure and linear velocity of a compressible mobile phase passing through a chromatography column. A method for configuring a chromatography system with independent control of system pressure and mass flow rate of a compressible mobile phase includes determining a type of chromatography separation column to be used in the chromatography system, matching a thermally modulated variable restrictor to the type of chromatography separation column for use together during operation of the chromatography system, and bundling the chromatography column with its matching thermally modulated variable restrictor for distribution as a single package.

Abstract: The present disclosure relates to burner assemblies of flame-based detectors. These burner assemblies are configured to deliver decompressed mobile phase of supercritical fluid chromatography systems to the flame of a flame-based detector while providing for improved optimization of analyte response as well as enhanced flame stability during operation.

Abstract: The present disclosure relates to flame based detection methods for compressed mobile phase chromatography. In particular, the present disclosure relates to the operation of a flame ionization detector for carbon dioxide based chromatography, such as supercritical fluid chromatography. The present disclosure includes a method of matching a chromatographic column with a flame ionization detector inner burner including providing a chromatographic column with an internal diameter, determining an optimal mobile phase flow rate for the chromatographic column, calculating an optimal inner diameter of the inner burner that combined with the internal diameter and flow rate of the column produces optimal detector performance, and providing a flame ionization detector inner burner having an inner diameter substantially equal to the calculated optimal inner diameter.

Abstract: The invention provides interfaces between analytical instruments, e.g., between chromatography systems and mass spectrometers. In an exemplary embodiment, an ion source is provided for connecting a carbon dioxide-based chromatograph device to a mass spectrometer. The ion source includes a first conduit for receiving eluent from the chromatography device, a heater for heating at least a portion of said first conduit, a second conduit in fluid communication with the first conduit, an inlet for receiving eluent from said second conduit and introducing the eluent into an ion source region to form a plume of gas and/or liquid in the ion source region, and an ionization promoting inlet for injecting an ionization promoting fluid into the ion source region to interact with the plume to promote ionization of at least some of the plume.

Abstract: Methods and apparatus for the modulation of flame gas stoichiometry to a flame-based detector for use in chromatographic separations are presented. As the total mass flow rate of mobile phase entering the flame-based detector changes (e.g., as a result of density programming in the separation), the mass flow rate of combustion gases to the detector are altered in proportion to the amount of mobile phase entering the detector. As a result, flame stability and sensitivity of the detector can be maintained by the methods and apparatus of the present disclosure.

Abstract: The present disclosure relates to a microfluidic flame ionization detector for use in small scale separations, such as, for example, microfluidic gas chromatography and microfluidic carbon dioxide based fluid chromatography. In some arrangements, the microfluidic counter-current flame ionization detector employs a non-parallel arrangement for the introduction of combustion gases into the combustion chamber. In other arrangements, the detector housing is configured to incorporate at least one of the detector electrodes within the housing using electrically isolating fittings.

Abstract: The present disclosure relates to an oxidizer, and related methods, for oxidizing polar modifiers in chromatographic mobile phases. The oxidizer enables the use of flame-based detection in chromatographic separations, such as carbon dioxide based chromatography, which employ polar modifiers, such as methanol. Upon exiting a chromatographic column, the mobile phase containing the polar modifier is flowed through an oxidizer that contains a catalyst to oxidize at least a portion of the polar modifier to a species that does not interfere with the function of the flame-based detector. The oxidizer allows for flame-based detection, such as flame ionization detection, in applications in which a polar modifier with a reduced form of carbon is used.