An apparatus and method for measuring low or trace concentrations of compounds and mixture of gases. A method and apparatus of the invention permits separating ions of different mobilities by passing them through an abrupt change or step in electric field magnitude. By using the separation method, the compounds of interest may be measured with less interference from other compounds of the gas mixture, which reduces or eliminates the need for prior separation of the components of the gas mixture. Several embodiments of the invention are described including the use of current amplifiers on one, or more, parts of the apparatus. While a single screen can provide a chamber which is divided into two regions of different electric fields, it is within the scope of the invention to include multiple screens to provide several steps in the electric field permitting it to be possible to trap and measure ions with successively higher mobilities. The gases used include halogenated compounds, including fluorocarbons, and most preferable SF.sub.6.

A system and method for using an air collection device to collect a continuous air sample as the device descends through the atmosphere are provided. The air collection device may be one or more coils of thin-walled elongated hollow tubing having a small interior diameter. The thin-walled elongated hollow tubing may be of a substantially nonreactive and nonabsorptive material such as stainless steel. A valve or the like controls the flow of air into and out of the tubing with one of the ends of the tubing closed and the other of the ends open at the beginning or end of the ascent and closed substantially at the end of the descent to seal the continuous air sample in the air collection device. The air collection device may be insulated and have cushioning. Once the continuous air sample is collected in the air collection device, it is analyzed to determine the presence and mole fraction of trace gases at different altitudes in the atmosphere. A high resolution continuous vertical profile of the trace gas may be created. The air collection device may also be used to store a sample gas using a compressor which draws or pushes the gas into the air collection device over a selected period of time. The stored gas may be analyzed in the same manner as the atmospheric air to obtain a time history of the gas sample.

This invention relates to measuring the light that is scattered from particulates (aerosols) in a gas or liquid. The sample typically flows into the instrument and the particulates are measured in-situ. The intensity of the scattered light is measured at many different angles, which determines both the amount of particulates in the sample, and detailed information about the particles such as average size, shape and composition. The measurement can be applied to climate and air pollution research, and clean room monitoring.