Not all those have been scientifically tested. Research using vaporizers found the delivery efficiency highest at around 226 °C (439 °F), falling to about half efficiency at 150 °C (302 °F) to 180 °C (356 °F) degrees depending on material.[41] The purest preparations produced the highest efficiencies, about 56% for pure THC versus 29% for plant material (female flower tops) with 12% THCA content. Besides THC, several other cannabinoids as well as a range of other plant components including terpenoids were detected in the plant material. Using pure THC in the vaporizer, no degradation products (delta-8-THC (D8-THC), cannabinol (CBN), or unknown compounds) were detected by HPLC analysis.[41] The longer vapor is stored, the more THC is lost as it condenses on the surface of the vaporizer or the balloon. This loss may be negligible over a few minutes but may exceed 50% after 90 minutes.[41] The Leiden University study found that as much as 30–40% of inhaled THC was not absorbed by the lungs but simply exhaled. However, they did not find large individual differences in the amounts exhaled.[41]