Retention behavior of 39 cannabinoids in reverse-phase liquid chromatography using C18 or phenyl hexyl columns.

Wilson W. · Journal of chromatography. A · 2026

**Background & Methods** This review evaluates the retention behavior of 39 cannabinoids using reverse-phase liquid chromatography with ultraviolet detection (LC-UV), comparing C18 and Phenyl Hexyl (pH) column stationary phases. The study was conducted by the National Institute of Standards and Technology (NIST) Chemical Sciences Division to address analytical challenges arising from synthetic cannabinoid production and chromatographic interferences in cannabis testing following the 2018 Agriculture Improvement Act. **Key Findings** - Both C18 and pH columns demonstrated predictable retention trends for THC homologs based on alkyl side-chain length, enabling systematic separation of cannabinoids with varying structural characteristics. - The Phenyl Hexyl column provided superior resolution by establishing a unique correlation between THC isomer elution and the specific position of the double bond within the cyclohexene ring, offering enhanced selectivity compared to the traditional C18 method. - The refined LC-UV methods developed by NIST CSD successfully minimized chromatographic interferences from synthetic by-products generated during the conversion of CBD into THC isomers and analogs, improving accuracy of Δ9-THC quantification below the federally mandated 0.3% dry weight threshold. **Dosage & Administration** Not reported. **Safety & Adverse Effects** Not reported. **Evidence Quality** This review is limited by its focus on analytical methodology rather than clinical outcomes, representing a technical comparison study rather than a randomized controlled trial or observational study. The evidence level is moderate, as it provides valuable analytical validation data but lacks human safety or efficacy data. Limitations include evaluation limited to cannabis plant and oil samples without assessment of finished consumer products, and results may not generalize to all synthetic cannabinoid variants. The study's strength lies in standardization efforts by a national reference laboratory addressing real-world regulatory compliance needs. Further validation across diverse cannabis cultivars and synthetic products would strengthen clinical applicability.

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