The positron emitter 17F has been identified for the first time as a radioactive contaminant formed during 13N production. It was determined that 17F made up 18% of the short-lived radioactivity previously thought to be exclusively 15O. Mathematical deconvolution of decay curve data was employed as a complement to radioanalytical techniques. The nuclidic composition of the effluents from the proton bombardment of (a) water, (b) dilute ethanol and (c) 13C powder/water slurry was determined and compared with previous literature values.