Sapphire (α-Al ₂O ₃, transparent corundum) single crystals were analyzed with pulsed direct current glow discharge mass spectrometry. Combined hollow cathode was used as a discharge cell. To obtain stable sputtering of dielectric material, a formation of initial surface conductivity via preliminary vacuum deposition of thin metallic layer was proposed. Al and Ta film of different thickness (30–200 nm) were considered for this purpose. The approach was found to provide the effective sputtering of dielectrics. The formation of an oscillating system was shown during the sputtering of sapphire samples in a tantalum combined hollow cathode cell. For oriented sapphire single crystals, periodic oscillations of ²⁷Al ⁺ intensity were acquired. This phenomenon was observed only for dielectric single crystals and not for other dielectric samples, e.g. alumina ceramic or fused quartz. The linear dependence of oscillation period on the duration of discharge pulse was found. The origin of these oscillations seems to be attributed to periodic fluctuations of surface conductivity. Oscillation periods calculated for two different orientations of sapphire single crystals (001 and 012) were found to be proportional to the main period of sapphire lattice. Therefore, an assumption that the crystal internal structure of the sample might be the cause of the oscillations is discussed.