Micro coulometric titration in a liquid drop.
Miniaturized coulometric titration in a liquid drop has been investigated. Assays of ascorbic acid and thiosulfate with iodine titration were chosen as models. Constant volumes of falling liquid drops containing sample or reagent are manipulated via gravimetrical force to move along a slope hydrophobic path and directed to stop or to move out from an electrode. Such manipulation is useful for delivery of sample and reagents, in a way of flow without tubing. Electrochemical generation of titrant, in this case, iodine, is started at the electrode and micro coulometric titration can be performed in a drop by applying constant current. Timing in the titration can be made via naked eye with a stopwatch or via recording with a webcam camera connecting to a computer to detect the change due to the blue color complex of the excess iodine and starch.
Department of Chemistry, Faculty of Science, Chiang Mai University, Chiang Mai 50200, Thailand; Center of Excellence for Innovation in Analytical Science and Technology, Chiang Mai University, Chiang Mai 50200, Thailand. Electronic address: tkanyanee@gmail.com.
Tinakorn
T
Kanyanee
Pongwasin
P
Fuekhad
Kate
K
Grudpan
D001205:Ascorbic Acid / Q000032:analysis*; D004560:Electricity; D004566:Electrodes; D057927:Hydrophobic and Hydrophilic Interactions; D007455:Iodine / Q000737:chemistry*; D013213:Starch / Q000737:chemistry*; D013885:Thiosulfates / Q000032:analysis*; D017186:Titrimetry / Q000379:methods*; D014741:Video Recording
D013885:Thiosulfates; D013213:Starch; D007455:Iodine; D001205:Ascorbic Acid
Ascorbic acid; Flow without tubing; Iodometry; Liquid drop; Miniaturized coulometric titration; Thiosulfate