The design, fabrication, and demonstration of a hand-held microchip-based analytical instrument for detection and identification of proteins and other biomolecules are reported. The overall system, referred to as muChemLab, has a modular design that provides for reliability and flexibility and that facilitates rapid assembly, fluid and microchip replacement, troubleshooting, and sample analysis. Components include two independent separation modules that incorporate interchangeable fluid cartridges, a 2-cm-square fused-silica microfluidic chip, and a miniature laser-induced fluorescence detection module. A custom O-ring sealed manifold plate connects chip access ports to a fluids cartridge and a syringe injection port and provides sample introduction and world-to-chip interface. Other novel microfluidic connectors include capillary needle fittings for fluidic connection between septum-sealed fluid reservoirs and the manifold housing the chip, enabling rapid chip priming and fluids replacement. Programmable high-voltage power supplies provide bidirectional currents up to 100 microAlpha at 5000 V, enabling real-time current and voltage monitoring and facilitating troubleshooting and methods development. Laser-induced fluorescence detection allows picomolar (10(-11) M) detection sensitivity of fluorescent dyes and nanomolar sensitivity (10(-9) M) for fluorescamine-labeled proteins. Migration time reproducibility was significantly improved when separations were performed under constant current control (0.5-1%) as compared to constant voltage control (2-8%).

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We report the development of a hand-held instrument capable of performing two simultaneous microchip separations (gel and zone electrophoresis), and demonstrate this instrument for the detection of protein biotoxins. Two orthogonal analysis methods are chosen over a single method in order to improve the probability of positive identification of the biotoxin in an unknown mixture. Separations are performed on a single fused-silica wafer containing two separation channels. The chip is housed in a microfluidic manifold that utilizes o-ring sealed fittings to enable facile and reproducible fluidic connection to the chip. Sample is introduced by syringe injection into a septum-sealed port on the device exterior that connects to a sample loop etched onto the chip. Detection of low nanomolar concentrations of fluorescamine-labeled proteins is achieved using a miniaturized laser-induced fluorescence detection module employing two diode lasers, one per separation channel. Independently controlled miniature high-voltage power supplies enable fully programmable electrokinetic sample injection and analysis. As a demonstration of the portability of this instrument, we evaluated its performance in a laboratory field test at the Defence Science and Technology Laboratory with a series of biotoxin variants. The two separation methods cleanly distinguish between members of a biotoxin test set. Analysis of naturally occurring variants of ricin and two closely related staphylococcal enterotoxins indicates the two methods can be used to readily identify ricin in its different forms and can discriminate between two enterotoxin isoforms.

A detailed experimental study has been made of the adsorption of methane, nitrtheir binary mixtures, on a wet Fruitland coal at 115°F. Mixture measurements were typically made at nominal gas-phase compositions of 20, 40, 60, and 80 mole percent and pressues to approximatey 1,800 psia. These data elucidate clearly the competitive adsorption behavior of the individual components in these mixtures. The experimental information was used to test predictive methods for describing the adsorption behavior of the pure and mixed gases. Models included various two-dimensional equations of state, as well as more traditional methods, such as the Langmuir and loading ratio correlations and the ideal adsorbed solution (IAS) model. The relative merits of the various models are described. In general, all models perform well for pure-gas adsorption; however, results are less satisfactory for mixtures. The errors in mixture predictions increase as the individual components become more dissimilar in their adsorption behaviors. Greatest (percentage) errors occur for the less-adsorbed component and, in the worst case (nitrogen+carbon dioxide), the predictions for nitrogen show errors of more than 100% at some conditions. Overall, the two-dimensional equation-of-state and IAS models perform comparably, and they are more accurate than the Langmuir model. The data and modeling results should be of interest in coalbed methane production and, especially, in evaluating potential enhanced recovery operations based on nitrogen and/or carbon dioxide injection into coalbeds. INTRODUCTION Large quantities of naturul gas (methane) are stored in coal deposits. The amount of gas currently in coalbeds in the U.S. is estimated to be 400 Tcf(trillion cubic feet) of which about 95 Tcf is recoverable under current technology [1]*. For comparison, estimates put the U.S. domestic natural gas resources at less than 200 Tcf m. This conventional gas can supply our needs for only about 25 years at current consumption rates. Thus, coaled methane represents a valuable addition to the nation's energy reserve. Development of the coalbed resource is, however, in its infancy; coalbed methane acounted for 3% of domestic gas production in 1992 [3]. Further, the current state of scientific and engineering knowledge on coalbed methane is inadequate to develop optimum strategies for its recovery.