About the size of a paperback, a new flow-injection immuno-assay configuration offers new levels of sensitivity. Capable of measuring compounds in parts per billion, the system is said to be more sensitive than existing field assay techniques and even the equal of some current laboratory tests. The miniature device is intended to make quick, quantitative detection of a variety of organic and inorganic substances in connection with health, food, quality, illicit drugs, environmental contamination, and biological or chemical weapons. The developer, Saddleback Aerospace Inc., Los Alamitos, Calif., is implementing a concept patented by the National Institute of Standards and Technology, Gaithersburg, Md. The device uses dye-filled liposomes that selectively bind to the particular substance being measured. The process involves mixing a liquid sample with the liposomes and injecting the mix into the device. An internal micro-pump will meter the precise amount of sample necessary for an analysis. Dye released from the liposomes indicates how much of a particular substance is present. NIST says the time to produce test results typically ranges from less than a minute to a few minutes. The design will include a keypad for entering sample information and a display for reading test results. The device, when it reaches the market in 1999, is expected to sell for $2,000 to $3,000 and each test is expected to cost between $1 and $3.