The oxygen and carbon concentrations on metal surfaces were determined by two methods. The first method was based on the detection
of the emitted particles in the12C(d,p)13C and16O(d, p)17O reactions, the second one on the measurement of the induced radioactivities in the12C(d,n)13N and16O(t,n)18F reactions, respectively. The results, obtained by the two different methods for high purity metals, were in agreement. A
type of error which exists in the determination of trace amounts of carbon and oxygen in pure metals by combustion and reductive
fusion was quantitatively demonstrated. This error exists also in the determination of oxygen by 14 MeV neutron bombardment.