I shouldn’t have any Delta-9-THC in my product. How did it end up there?

Conversion of acids to neutrals?

Decarboxylation of THCA to Delta-9-THC occurs slowly at room temperature and at a much higher rate at high temperatures. If your original sample contained THCA and no detectable Delta-9-THC, decarboxylation of the THCA will occur and eventually the amount of Delta-9-THC in the sample will become detectable. Since the detection limit varies between laboratories and methods, a sample may contain detectable D-THC when tested in one laboratory or by one method but not in another laboratory or another method.

Acidic condition converting CBD to Delta-9-THC?

Weak acids catalyze the isomerization of CBD to Delta-9-THC whereas stronger acids catalyze the isomerization of CBD to Delta-8-THC. Therefore, the presence of acids in the formulated CBD product can catalyze the isomerization of CBD to Delta-9-THC. Weak acids such as ascorbic acid and citric acid that are often found in food products are sufficiently acidic to produce Delta-9-THC from CBD in formulated products.

Misidentification of Delta-9-THC peak

The acid catalyzed isomerization of CBD to Delta-8-THC that is commonly used to prepare it also produces varying amounts of side products depending on reaction conditions and the specific acid catalyst that was used. One of these side-products, D4(8)-iso-THC is often present in Delta-8-THC. When analyzed by reversed-phase HPLC, Delta-9-THC and D4(8)-iso-THC are not chromatographically resolved and they have the same absorption spectra so a sample containing no Delta-9-THC could be reported to contain Delta-9-THC if the sample contains D4(8)-iso-THC that is misidentified as Delta-9-THC. GCMS analysis of these samples resolves Delta-8-THC, Delta-9-THC, and the side products so that all can be determined without interference or misidentification.