Liquid-Liquid extraction and spectroscopic methods for distinguishing between hemp and marijuana


  • Brooke Underwood
  • Courtney LaPointe


Passage of the Farm Bill in December 2018 legalized cannabis containing less than 0.3% tetrahydrocannabinol (THC), otherwise known as hemp (1). This creates problems for law enforcement since current presumptive test kits either 1) don’t work at all or 2) work somewhat in differentiating
between legal and illegal hemp crops. This problem exists because most hemp crops and hemp products contain low levels of THC and the carboxylated form, THCA. Our approach involves the advancement of an efficient, mobile, liquid-liquid extraction (LLE) that provides presumptive, qualitative forensic evidence of the chemical extract of a bud or other plant material. This research is focused on developing a kit that functions in a similar manner to NIK kits, commonly used by law enforcement, where all components of the kit are contained within a bag. The current NIK kit for Marijuana provides a false positive when Hemp is placed in the bag, thus creating the need for a more reliable test (2). The evidence would later be sent to a crime lab for definitive analysis and quantitation of THC by ultraviolet- visible spectroscopy (UV-vis). This research has focused on the utilization of liquid-liquid extraction techniques and commercially available stains. The methods presented are rapid (requiring no more than five to six minutes to complete). The differentiation between two lots of commercially available hemp and seven lots of marijuana obtained from the Cookeville
City Police will be presented.