High-efficiency molecular counting in solution: Single-molecule detection in electrodynamically focused microdroplet streams
- Oak Ridge National Lab., TN (United States)
We report fluorescence detection of individual rhodamine 6G molecules using a linear quadrupole to focus streams of microdroplets through the waist of a counterpropagating cw Ar{sup +} laser. Since the terminal velocity scales as the square of the droplet diameter, the droplet-laser interaction time was `tunable` between 5 and 200 ms by using water samples spiked with a small, variable (2-5% v/v) amount of glycerol. Fluorescence bursts from droplets containing single molecules were clearly distinguished from the blanks in real time with an average signal-to-noise ratio of about 10, limited primarily by photobleaching and droplet size fluctuations (<1%). The volume throughput rates associated with this approach (approx. 10 pL/s) are roughly 10{sup 3} higher than those associated with particle levitation techniques, with minimal sacrifice in sensitivity. Total molecular detection efficiencies of about 80% (at >99% confidence) were obtained for 100 and 15 fM rhodamine 6G solutions, in good agreement with detailed theoretical calculations and statistical limitations. 39 refs., 7 figs., 1 tab.
- DOE Contract Number:
- AC05-96OR22464
- OSTI ID:
- 512891
- Journal Information:
- Analytical Chemistry (Washington), Vol. 69, Issue 11; Other Information: PBD: 1 Jun 1997
- Country of Publication:
- United States
- Language:
- English
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