Thin-layer chromatography on silver nitrate-impregnated silica gel for analysis of homemade tetrahydrocannabinol mixtures

Forensic Toxicol. 2022 Jan;40(1):125-131. doi: 10.1007/s11419-021-00592-9. Epub 2021 Jul 26.


Purpose: Various forms of cannabidiol (CBD)-containing products are sold in Japan. CBD is easily converted to mixtures of ∆9-tetrahydrocannabinol (∆9-THC) and its isomer, ∆8-THC, using household chemicals like diluted hydrochloric acid. This ease of production increases concerns regarding production of homemade THC mixtures. It is difficult to separate ∆9-THC, ∆8-THC, and CBD using thin-layer chromatography (TLC) on conventional silica gel. The selectivity of TLC on silver nitrate-impregnated silica gel (AgNO3-silica gel) differs from that of conventional silica gel. This study thus aimed to evaluate the separation ability of AgNO3-silica gel TLC.

Methods: To evaluate potential separation ability, standards of five THC isomers (∆9-THC, ∆8-THC, a pair of diastereomers of ∆10-THC, and ∆6a,10a-THC), CBD, CBN, and ∆9-THCA were analyzed by 10% AgNO3-silica gel TLC (developed using toluene, system A) and silica gel TLC [developed using n-hexane/diethyl ether (8:2, v/v), system B]. Then, mock homemade THC mixtures, prepared by heating crystalline CBD in acidic ethanol, were analyzed using systems A and B.

Results: System A showed clear separation between the five THC isomers and between ∆9-THC, ∆8-THC, CBD, and their by-products in the mock homemade THC mixture. However, system B did not separate some combinations of THC isomers and gave a single group-like spot to the THC mixture.

Conclusion: AgNO3-silica gel TLC shows high separation ability between THC isomers and among ∆9-THC, ∆8-THC, and CBD. It will thus be useful for analyzing homemade THC mixtures.

Keywords: Homemade tetrahydrocannabinol (THC) mixture; Silver nitrate-impregnated silica gel (AgNO3-silica gel); Thin-layer chromatography (TLC); ∆8-Tetrahydrocannabinol (∆8-THC); ∆9-Tetrahydrocannabinol (∆9-THC).

MeSH terms

  • Cannabidiol*
  • Chromatography, Thin Layer
  • Coloring Agents
  • Dronabinol*
  • Silica Gel
  • Silver Nitrate


  • Silica Gel
  • Dronabinol
  • Silver Nitrate
  • Cannabidiol
  • Coloring Agents