Chemical oxygen demand sensor employing a thin layer electrochemical cell

Chemical Oxygen Demand (COD) Sensor Using a Stopped-Flow Thin Layer Electrochemical Cell

“…In other words, if L ( 2Dt 1a2 Y L becomes the dominant factor in the term expÀpt expÀp 2 DtaL 2 ) of the above equations. In our former work [12], however, the results obtained were obviously in¯uenced by diffusion. The lower edge of the thin layer compartment was in direct contact with the bulk solution and the cell layer thickness, L, was not small enough to be neglected for diffusion.…”

“…60 mm) and the electrode area (from 3.0 to 0.75 cm 2 ). We performed electrolyses of D-glucose, one of the most reactive among the standard analytes used in our former work [12], and compared the times taken for the observed currents to reach half their initial values with those obtained using the old cell (each experiment was repeated three times). The values obtained using the new cell were 0.65, 0.65, 0.65, 0.65, and 0.70 s for solutions of 1, 5, 10, 30, and 50 ppm theoretical COD, while those with the old cell were 4.1, 4.8, 5.7, 9.5, and 15.5 s respectively and linearly proportional to the concentration (r 0X994).…”

“…In our former work [12], a COD sensor was constructed which comprised a sandwich-type thin layer electrochemical cell with a copper electrode in an alkaline medium. The protocol was based on exhaustive electrolysis, whereby the net faradaic charge, corresponding to the number of electrons consumed in electrolyzing (oxidizing) the organic species, was correlated to the COD as evaluated by the conventional methods using dichromate or permanganate.…”

“…By decreasing the sample volume, a large electrode area to sample volume ratio is obtained and thus only a short time is required to exhaustively electrolyze the sample. The electrode used in the former work [12] was constructed by attaching face to face glass and copper plates separated by Te¯on spacers, creating an extremely shallow cell. Upon immersing the working electrode in the sample solution, the thin layer compartment was ®lled by capillary action and the measurements were performed.…”

Electrochemical and microfabrication strategies for remotely operated heavy metal sensor networks for water analysis : the dual challenges of calibration-less measurement and sample pretreatment.

“…Once again, the class of analytes that causes electrode fouling are the humic acids [58]. One of the advantages of coulometric analysis is that in the event of partial electrode fouling, it simply takes longer for analyte molecules to reach the electrode surface.…”