THC-COOH Detected!  ∆-8 or ∆-9?

Urine testing for cannabis metabolites is a routine analysis for drug testing labs, but what metabolite is actually being observed when a positive result is detected? Cannabis is a very complex matrix composed of many different constituents, some illegal and some legal in the United States. Delta-9-THC is the main psychoactive component in cannabis, but this compound has over 30 different isomeric forms! Some of which are discussed in more detail in the following blog: Analyzing THC Concentrates? Look for Isomers!

For the purpose of this blog, I’ll only be talking about delta-9-THC and delta-8-THC. Delta-9-THC is illegal for recreational use in most states but the legality of it is growing. Delta-8-THC, which has some diluted psychoactive effects, is legal on a federal level but has been banned in a few states.

So what happens when delta-8-THC is ingested and a urine screen for delta-9-THC is performed? The metabolites for delta-8-THC and delta-9-THC are structurally similar isobars and are only differentiated by the location of a singular double bond. Both compounds will produce a carboxylated metabolite requiring chromatographic separation in order to differentiate between the two isomers which may not occur in most routine testing methods.

Here, a method has been developed to detect delta-9-THC-COOH (11-nor-9-carboxy-9-THC) and delta-8-THC-COOH (11-nor-9-carboxy-8-THC) in 3.5 mins by LC-MS/MS. This method utilizes isocratic mobile phase conditions for high throughput, has simple mobile phase additives, and produces baseline resolution.

Column	Raptor FluoroPhenyl (cat.# 9319A12)
Dimensions:	100 mm x 2.1 mm ID
Particle Size:	2.7 µm
Pore Size:	90 Å
Guard Column:	Raptor FluoroPhenyl EXP Guard Column Cartridge 5 mm, 2.1 mm ID, 2.7 µm (cat.# 9319A0252)
Temp.:	30 °C
Sample	(±)11-Nor-9-carboxy-D9-THC (cat.# 34068), other compound obtained separately
Diluent:	30/70 Water/Methanol, 0.1% formic acid
Conc.:	2.5 ng/mL
Inj. Vol.:	2 µL
Mobile Phase
A:	Water, 0.1% formic acid
B:	Methanol, 0.1% formic acid
	Time (min) Flow (mL/min) %A %B 0.00 0.4 30 70 3.5 0.4 30 70
Detector	MS/MS
Ion Source:	Electrospray
Ion Mode:	ESI+
Instrument	UHPLC

Peaks	tR (min)	Conc. (ng/mL)	Precursor Ion	Product Ion 1	Product Ion 2
Δ-8-THC-COOH	2.842	2.5	345.2	299.3	327.2
Δ-9-THC-COOH	3.237	2.5	345.1	327.1	299.2

By using this method of analysis, drug testing labs are able to resolve the two metabolite isomers with a 3.5 minute cycle time, allowing for rapid differentiation between the two compounds. Is your lab currently running or interested in this analysis? Let us know about it in the comments below!