Sweat testing for cystic fibrosis: errors associated with the in-situ sweat test using chloride ion selective electrodes.

The in-situ sweat test is prone to errors from various sources. This 
paper examines errors due to evaporation, absorption of water into the 
skin, and pressure of the electrode on the skin. Only evaporation 
caused serious errors. The accuracy and precision when measuring small chloride/sweat 
samples on the skin are not significantly worse than when measuring 
bulk solutions. 