Jose R. Valentin

Gas chromatography in space

Gas chromatography has proven to be a very useful analytical technique for in situ analysis of extraterrestrial environments as demonstrated by its successful operation on spacecraft missions to Mars and Venus. The technique is also one of the six scientific instruments aboard the Huygens probe to explore Titans atmosphere and surface. A review of gas chromatography in previous space missions and some recent developments in the current environment of fiscal constraints and payload size limitations are presented.

Continuous monitoring of a changing sample by multiplex gas chromatography

Multiplex gas chromatography (MGC) is a technique in which multiple samples may be introduced into a chromatographic system regardless of the elution time of the individual components. Although the output obtained from a MGC experiment is not directly interpretable, computational techniques can be used to obtain the chromatogram from the detector output data. This is done by calculating the impulse response function from the multiplexed output data.

Maximum entropy chromatogram reconstruction

Maximum entropy has been successfully applied to problems of optical images and NMR spectroscopy. In this paper, we present the results of maximum entropy deconvolution applied to simulated and real chromatographic data. A brief theoretical discussion is given. The technique is tested both qualitatively and quantitatively using simulated data. Peak resolution can be dramatically improved but quantitative accuracy is limited. The technique is applied to a re-analysis of Pioneer Venus chromatographic data and to storage column data.

Gas chromatographic column for the storage of sample profiles

The concept of a sample retention column that preserves the true time profile of an analyte of interest is studied. This storage system allows for the detection to be done at convenient times, as opposed to the nearly continuous monitoring that is required by other systems to preserve a sample time profile. The sample storage column is essentially a gas chromatography column, although its use is not the separation of sample components. The functions of the storage column are the selective isolation of the component of interest from the rest of the components present in the sample and the storage of this component as a function of time. Using octane as a test substance, the sample storage system was optimized with respect to such parameters as storage and readout temperature, flow rate through the storage column, column efficiency and storage time. A 3-h sample profile was collected and stored at 30 degrees C for 20 h. The profile was then retrieved, essentially intact, in 5 min at 130 degrees C.

Advanced instrumentation for exobiology

Advanced microdevices for the exploration of the solar system have become increasingly important in the current environment of fiscal constraints and payload size limitations. The Discovery-class missions being proposed for future exploration, while being clearly responsive to this environment, will require highly miniaturized and efficient instruments based on these advanced devices. Several instrument concept developments are continuing at Ames Research Center in support of specific exobiology science goals in future solar system studies on candidate Discovery and other missions. Developments include highly miniaturized metastable ionization detectors for gas chromatography that weight as little as 1 - 2 grams with sensitivities of 10-14 mol/second and an advanced ion mobility spectrometer that has near-universal sensitivity and weighs as little as 200 grams. New chemical sensors based on solid-state pyroelectric devices are being studied and developed that weigh a few milligrams and, for example, have a sensitivity of 0.1 ppm for H2O2. Advanced X- ray diffraction and fluorescence instruments for crystallographic and geochemical measurements on unprepared soil and rock samples are under test. A stable isotope laser diode spectrometer for determination of 12C/13C and 18O/16O isotope ratios on Mars at fractional percent accuracies has been breadboarded. Finally, advanced computational methods are being applied to new instrument concepts allowing new, less complex, and thus, smaller instruments.