Application of Aerosol Nucleation Technique for Ultrasensitive Contaminant Detection
EMSL Project ID
1629
Abstract
The objective of this project is to develop a bench-scale instrument for detection of trace quantities of a variety of chemical signatures, including explosive, drug/narcotic, CW and other potentially hazardous substances. The technique applies an aerosol nucleation technique to obtain ultrahigh sensitivity of gas phase constituents. Selectivity to specific substances will be accomplished through selective ionization techniques and possible pre-separation with a gas chromatograph. Verification of authentic selection will be made using mass spectroscopic techniques. The prototype device for the detection of contaminant (target analyte) molecules is relatively simple and consists of a laminar flow tube reactor (LFTR) coupled to an ultrafine condensation particle counter (UCPC). The host substance is introduced into an inert carrier gas in the heated section of the LFTR as means to establish supersaturated conditions in the cooled section of the LFTR. The contaminant (in the same carrier gas) is injected into the host flow near the point where optimal supersaturation conditions occur and nucleation is then initiated. Nucleated particles, which are produced in the size range of 2 - 15 nm are detected at the exit of the LFTR by the UCPC. Because the device works with a gas-phase sample stream, it is possible to pre-separate the sample stream with a suitable particle filtration system followed by a fast gas chromatograph. Sensitivity to aerosol nucleation is enhanced by several orders of magnitude by exciting or ionizing the target analyte prior to its injection into the LFTR. This is most conveniently and accurately accomplished through a tunable laser system, either operating in the UV or capable of promoting a two- (or more) photon absorption in the analyte molecule. Authentic identification of the target analyte molecule in the nucleated particle is accomplished through injection of the particle stream from the LFTR into an appropriate mass spectrometer.
Project Details
Project type
Exploratory Research
Start Date
1999-12-31
End Date
2000-09-30
Status
Closed
Released Data Link
Team
Principal Investigator
Team Members