Scientific applications Oxygen sensor

a dissolved oxygen meter laboratory use

the clark-type electrode used oxygen sensor measuring oxygen dissolved in liquid. basic principle there cathode , anode submersed in electrolyte. oxygen enters sensor through permeable membrane diffusion, , reduced @ cathode, creating measurable electric current.

there linear relationship between oxygen concentration , electric current. two-point calibration (0% , 100% air saturation), possible measure oxygen in sample.

one drawback approach oxygen consumed during measurement rate equal diffusion in sensor. means sensor must stirred in order correct measurement , avoid stagnant water. increasing sensor size, oxygen consumption increases , stirring sensitivity. in large sensors there tend drift in signal on time due consumption of electrolyte. however, clark-type sensors can made small tip size of 10 µm. oxygen consumption of such microsensor small practically insensitive stirring , can used in stagnant media such sediments or inside plant tissue.

optodes

an oxygen optode sensor based on optical measurement of oxygen concentration. chemical film glued tip of optical cable , fluorescence properties of film depend on oxygen concentration. fluorescence @ maximum when there no oxygen present. when o2 molecule comes along collides film , quenches photoluminescence. in given oxygen concentration there specific number of o2 molecules colliding film @ given time, , fluorescence properties stable.

the signal (fluorescence) oxygen ratio not linear, , optode sensitive @ low oxygen concentration. is, sensitivity decreases oxygen concentration increases following stern–volmer relationship. optode sensors can, however, work in whole region 0% 100% oxygen saturation in water, , calibration done same way clark type sensor. no oxygen consumed , hence sensor insensitive stirring, signal stabilize more if sensor stirred after being put in sample. these type of electrode sensors can used insitu , realtime monitoring of oxygen production in water splitting reactions. platinized electrodes can accomplish real time monitoring of hydrogen production in water splitting device.