Device and method for making discrete volumes of a first fluid in contact with a second fluid, which are immiscible with each other

A system comprising:

• a fluidic network comprising:
• a first conduit,
• a second conduit,
• a third conduit,
• a fourth conduit,
• a first junction coupling the first conduit to the second conduit,
• a second junction coupling the second conduit to the third conduit, and
• a third junction coupling the third conduit to the fourth conduit;
• a pressure differential source operably coupled to the fluidic network;
• a fluorescence detector arranged external to a location along the third conduit and to detect fluorescence transmitted along an optical path from an interior of the third conduit to the fluorescence detector;
• and
• a flow control system operably coupled to the fluidic network and the pressure differential source, wherein in an operational state the flow control system is configured to control flow of liquid through the fluidic network such that:
• the first conduit receives discrete volumes of an aqueous liquid and a spacing liquid into the first conduit such that the discrete volumes of the aqueous liquid are separated from each other by the spacing liquid, the spacing liquid being immiscible with the discrete volumes of the aqueous liquid,
• the second conduit receives a plurality of the discrete volumes from the first conduit through the first junction,
• the third conduit receives a first batch of the plurality of the discrete volumes of the aqueous liquid from the second conduit through the second junction and the discrete volumes of the aqueous liquid of the first batch individually flow through the optical path of the fluorescence detector while the second conduit holds a second batch of the plurality of the discrete volumes of the aqueous liquid, and
• the fourth conduit supplies spacing liquid to the third conduit through the third junction to adjust spacing between the discrete volumes of the first batch in the third conduit.