The characteristic energy losses of inelastically backscattered electrons of 0.2-2 keV measured by low energy electron loss spectroscopy (LEELS) are shown to enable a destruction free determination of the sp(2)- and the sp(3)-coordinated fractions in BN-films. The specific loss structures from plasmon excitation in hBN and cBN, and from the pi --> pi* -transition in hBN are evaluated accordingly. In contrast to the commonly employed Fourier transform infrared spectroscopy (MR) the LEELS-method as surface sensitive technique is not influenced by contributions from the substrate or the commonly present hBN-baselayer for cBN-nucleation. Thus, the near surface region of properly deposited films could be shown to consist of pure cBN. When controlling the mean penetration depth of the primary electrons by changing their energy, phase sensitive depth profiling becomes possible. This is applied to determine the destruction depth of the cubic phase of BN under bombardment with Ar+-ions of 0.5-3 keV.