University of Michigan

Richard D Sacks

Christine L Rankin

Anita J Peters

Megan Ellen McGuigan

Mark A Klemp

Tincuta Maria Veriotti

Kensall D Wise

Joseph A Potkay

Masoud Agah

Suzanne L Tanguay

Michael L Akard

Katharine T Beach

Joshua Jonathan Mark Whiting

A high-sensitivity, separation microcolumn assembly for a microgas chromatograph and the like is provided. The assembly has an ultra-low mass complete with integrated heaters. The assembly uses multiple zones for temperature control, and microstructures that permit very rapid heating and cooling of the microcolumn.

Separation microcolumn assembly for a microgas chromatograph and the like

A gas chromatography system having a computer-controlled pressure controller that delivers pressurized pulses to a column junction point of two series-coupled columns having different stationary-phase chemistries and a method of using the same. Each pressurized pulse causes a differential change in the carrier gas velocities in the two columns, which lasts for the duration of the pressurized pulse. Whereby, the pressurized pulse selectively increases the separation of a component pair that exhibits separation at the exit of the first column, but otherwise co-elutes from the column ensemble.

Pulsed carrier gas flow modulation for selectivity enhancements with gas chroma tography using series-coupled ensembles

A gas chromatography system having a computer-controlled venting valve system that delivers pressurized pulses to a column junction point of two series-coupled columns having different stationary-phase chemistries and a method of using the same. Each pressurized pulse causes a differential change in the carrier gas velocities in the two columns, which lasts for the duration of the pressurized pulse. Whereby, the pressurized pulse selectively increases the separation of a component pair that exhibits separation at the exit of the first column, but otherwise co-elutes from the column ensemble.

Pulsed carrier gas flow modulation for selectivity enhancements with gas chromatography using series-coupled column ensembles

A gas chromatography system in which prefocusing of a sample analyte is provided through the use of an adsorbent coated porous layer open tubular trap tube. Through the use of an adsorbent coated collection device low boiling point components can be successfully trapped for preconcentration and injection at temperatures well above that necessary when employing conventional cryo-focusing.

Adsorbent trap for gas chromatography

A gas chromatography system featuring column bifurcation and pressure tuning. The system of this invention incorporates a bifurcated system in which samples eluting from a first separation column are directed selectively through one of two or more additional separation columns. Flow directing is achieved through the use of valves which switch carrier gas which are outside of the path of the analyte mixture. Effective tuning of the system is provided by adjusting the intermediate pressure which controls the effective lengths of the initial separation column and the additional final separation columns.

Gas chromatography system with column bifurcation and tunable selectivity

Several embodiments of gas chromatography systems are disclosed incorporating mechanical sample injection valves. The injection valves incorporate a delivery tube having an outlet which is swept past the inlet of a separation column to provide a short duration inlet plug into the separation column. Carrier gas and sample gas flow is managed through the valve to prevent inadvertent injection after an injection is desired and to assure that the sample is not contaminated by past sample flow. Embodiments of injections valve are described for providing inputs into several gas chromatography columns. In addition, a gas chromatography system is described in which multiple columns are used which are time multiplexed with a single detector to produce a complex combined chromatogram from the plural columns. By appropriate selection of column characteristics and injection sequence, the resulting chromatogram can provide an overlay of chromatograms which provide good resolution of all the constituents of the mixture of interest within a short analysis time.

Mechanical gas chromatography injection valves and column multiplexing

A gas chromatography system of the type incorporating a thermal focusing chamber for introducing a sample into a column for separation and analysis. The system of the present invention provides benefits in terms of reducing memory effect of one analysis being influenced by prior experiments, a reduction in system dead volume which leads to broadening of peaks produced on the chromatogram and artifacts caused by sample decomposition. These advantages are achieved principally through a novel fluid circuit in which the sample is trapped onto the column by trapping it at the end of the thermal focusing chamber closest to the column. This feature has the effect of eliminating the necessity of the sample residing in the heated focusing chamber for a period giving rise to sample decomposition. This system further avoids the necessity of passing the inlet flow through mechanical valves which also contributes to memory effect. This system further has the benefit of enabling sampling of sources at various pressures including ambient pressure as an air quality sensing probe. An alternative embodiment is a simplified system for enabling ambient pressure source monitoring without mechanical valves in the sample flow path.

Sample collection and inlet systems for gas chromatography apparatus

A gas chromatography system which incorporates a simplified sample injection system in which replaces conventional mechanical injection systems with one based strictly upon thermal trapping of a continuously supplied carrier gas and sample stream. The carrier gas and sample stream pass continuously through the device which incorporates a thermal focusing chamber which communicates with the inlet end of a gas chromatography separation column. By causing the focusing chamber temperature of a sample tube passing through the focusing chamber to be dropped, incoming components comprising the sample stream are condensed and trapped. Injection into the column occurs rapidly heating the sample in the thermal focusing chamber causing a narrow sample plug to be introduced into the column. Various embodiments of this invention are intended for operation for evaluating carrier gas and sample stream provided at a above atmospheric pressure, or which are drawn through the system by vacuum source at the outlet end of the column. In addition, vacuum backflushing features are also described.

Thermal modulation inlet for gas chromatography system

Gas chromatography apparatus and procedures are described which enables gas chromatography to be carried out more rapidly than in accordance with prior art techniques and further enables chromatogram peaks caused by materials of interest from being obscured due to their super imposition upon high peak long durations produced by another component of peaks in an organic mixture. Reductions in chromatography evaluation time are achieved through employing a vacuum pump which caused backflushing of a very short column after materials of interest have been eluted but before higher boiling points components of the mixture have eluted. Backflushing is carried out using a vacuum pressure source which when used with a short column, permits rapid and complete backflushing. The chromatography system according to this invention allows simultaneous column backflushing while a new sample is being collected in a cooling chamber for cryofocussing for a subsequent injection. Another aspect of the invention is to cause a reversal in the flow direction through the column to occur at or just after a high intensity long duration peak causing component the mixture has eluted causing the remaining components to be drawn back into a thermal focusing chamber for subsequent injection. By stopping the process at this point the concentration of high long duration peak forming materials which have been eluted can be reduced so that subsequent reinjection will reveal features of interest in the chromatogram which would have otherwise been obscured.

Gas chromatography system and methods

A magnetron glow discharge plasma device is utilized as a furnace for vaporization, atomization and excitation of analytical solution samples of trace elements for atomic emission spectroscopy. The apparatus includes a sample deposited on the glow discharge lamp, a spectrometer optically coupled to the lamp through a transparent wall portion of the furnace, a photoelectric detector connected to the spectrometer for sensing the light and converting the light to an electrical signal and a computer for digitally storing and processing the sent signal.

Growing community of inventors

Ann Arbor, MI, United States of America

Richard D Sacks