Apparatus, system, and method using immiscible-fluid-discrete-volumes

A method comprising:

• contacting a stream of aqueous sample fluid flowing in a first conduit with a stream of non-aqueous spacing fluid that is immiscible with the aqueous sample fluid to form discrete volumes of the aqueous sample fluid separated from one another by the non-aqueous spacing fluid, wherein the aqueous sample fluid comprises target nucleic acid, and wherein a first plurality of the discrete volumes contains at least one molecule comprising the target nucleic acid and a second plurality of the discrete volumes contains no molecules comprising the target nucleic acid;
• amplifying the target nucleic acid in one or more of the first plurality of the discrete volumes to form an amplicon;
• in a second conduit, detecting a fluorescence signal from the amplicon in the one or more of the first plurality of the discrete volumes;
• and
• based on the detecting, discriminating between the one or more of the first plurality of the discrete volumes and the second plurality of the discrete volumes.