Attogram detection limit for aqueous dye samples by laser-induced fluorescence

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Science  18 Feb 1983:
Vol. 219, Issue 4586, pp. 845-847
DOI: 10.1126/science.6823553


A modified flow cytometer has been used to detect attogram quantities of aqueous rhodamine 6G by laser-induced fluorescence analysis. A detection limit of 28 attograms (35,000 molecules) was obtained, nearly two orders of magnitude better than earlier measurements. The detection limit in concentration units was 1.4 x 10(-13) mole per liter. During the 1-second measurement period, the total volume sampled was 0.42 microliter. On average, only half a rhodamine 6G molecule was present in the 6-picoliter probed volume.