High-efficiency molecular counting in solution: Single-molecule detection in electrodynamically focused microdroplet streams

Journal Article · Sun Jun 01 04:00:00 EDT 1997 · Analytical Chemistry (Washington)

DOI:https://doi.org/10.1021/ac970093b· OSTI ID:512891

Lermer, N; Barnes, M D; Kung, C Y; Whitten, W B; Ramsey, J M ^[1]

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1. 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), Journal Name: Analytical Chemistry (Washington) Journal Issue: 11 Vol. 69; ISSN ANCHAM; ISSN 0003-2700
• Country of Publication: United States
• Language: English

Related Subjects

42 ENGINEERING
66 PHYSICS
ARGON
COUNTING TECHNIQUES
DETECTION
DROPLETS
EFFICIENCY
ELECTRODYNAMICS
FLUORESCENCE
GAS LASERS
LIQUIDS
MOLECULES
NUMERICAL DATA
PHOTONS
RHODAMINES
SIGNAL-TO-NOISE RATIO