With the use of a coincidence technique the contributions of the L shell to the total electron ejection cross section of argon by 350 keV proton bombardment has been measured. The results were compared with predictions of the plane-wave Born approximation calculated with both hydrogen-like and self-consistent Hartree-Fock/Hartree-Slater atomic wavefunctions for the target atom. Observed discrepancies between theory and experiment may possibly be ascribed to electron capture from the target to continuum states of the projectile (electron capture to the continuum, ECC). The role of multiple Coulomb ionisation and the sensitivity to the choice of the atomic wavefunctions are discussed.