Restek at SOFT 2023
29 October – 3 November, Denver, CO, U.S.
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The Evolving Landscape of THC Drug Testing: Delta-8 vs. Delta-9
Wednesday, November 1
Dr. Jamie York (presenter), Haley Berkland
For THC drug testing, the carboxy metabolite is historically the analyte used to determine cannabis usage. This compound has a long half-life and can be detected in urine or blood for several weeks in heavy consumers. This can pose a challenge when determining if a user is intoxicated at the time of testing. Today, labs are interested in the addition of the hydroxy metabolite, the intermediate between THC and the carboxy metabolite. The intermediate is short lived, but it is useful in the determination of chronic usage and when determining if a user is under the influence. Delta-8-THC is a common isomer of delta-9-THC that also demonstrates psychoactive effects and is of analytical interest to drug testing laboratories. The chromatographic separation of delta-9-THC and delta-8-THC and their respective metabolites are required due to their shared masses.
Several column chemistries were scouted, and a method was developed to separate delta-9-THC and delta-8-THC as well as their carboxy and hydroxy metabolites. Biphenyl, ARC-18, and FluoroPhenyl stationary phases were tested on a 100 x 2.1 mm column dimension using water and methanol as mobile phases, both modified with 0.1% formic acid.
The Biphenyl stationary phase did not display selectivity for the three pairs of isomers under the scouting conditions tested. The ARC-18 phase showed selectivity for both the delta-9/8-THC isomers and their carboxy metabolites, but not the hydroxy metabolites. When the strength of the solvent is reduced to attempt to resolve the hydroxy metabolites, the THC isomers become excessively retained, and the hydroxy metabolites are still not resolved. The FluoroPhenyl column showed great selectivity for the target analytes and resolved all three pairs of isomers. A method to fully resolve them was developed on a 100 x 3 mm column with great resolution and retention along with a 12-minute total cycle time.
Using a Virtual Liquid Chromatography Tool to Develop Methods for Novel Psychoactive Substances
Wednesday, November 1
Haley Berkland (presenter), Melinda Urich, Justin Steimling, Dr. Jamie York, Chris Nelson, Tim Yosca, John Garrett
Novel psychoactive substances (NPS) have created a challenge for toxicology laboratories. New NPS are constantly disappearing as fast as they emerge, making it difficult to stay on top of which compounds are necessary to add to laboratory testing scopes.
The development and optimization of liquid chromatography (LC) separations is time-consuming and costly, often requiring several steps, including literature research, column selection, method scouting, method development, and method optimization. To alleviate the burden of sacrificing instrument-uptime, labor, and materials, an instrument-free software modeling tool was developed to include a comprehensive drugs of abuse (DoA) library.
Methods for NPS compounds were successfully developed in under ten minutes per method using this online chromatogram modeling tool. To verify the ability of the modeler to develop methods for NPS, three methods were developed and optimized using the chromatogram modeler for the following NPS subclasses: 1) synthetic opioids and toxic adulterants, 2) designer benzodiazepines, and 3) stimulants and synthetic cannabinoids. All methods utilized a Raptor Biphenyl 100 x 2.1, 2.7 μm column with a MPA of water and MPB of methanol, both acidified with 0.1% formic acid. The flow rate was 0.6 mL/min, and the column temperature was 40°C. The developed methods were transferred to an LC-MS/MS system and the experimental results were compared with the modeler.
The acceptance criteria for retention time agreement between experimental and modeled values was set at +/-15 seconds, chosen to represent a typical MRM window. All analytes in all three methods fell within this window, as well as maintaining elution order and resolution.
This online chromatogram modeling tool helps users obtain optimized separations while maintaining critical pair resolution by adjusting parameters, such as column dimension, mobile phase, gradient programs, and more, for almost 300 compounds, including the 38 newly added NPS drugs.
The Benefits of 2.1 mm Internal Diameter Analytical Columns for the Analysis of Drugs of Abuse by LC-MS/MS
Wednesday, November 1
Samantha Herbick (presenter), Dr. Jamie York
The biphenyl phase offers advantageous selectivity compared to a C18 column for drugs of abuse (DoA) panels but choosing the right column dimension is paramount to obtain robust and accurate data. Every column dimension can be advantageous in different scenarios, but generally clinical labs are all working towards the same goals: high throughput, low sample volume, good sensitivity, and low cost. In this work, the advantage of 2.1 mm internal diameter (ID) columns is discussed and demonstrated for the analysis of drugs of abuse.
Two methods were developed to analyze common isobars in drugs of abuse panels on Raptor Biphenyl columns using methanol and water modified with 0.1% formic acid and column oven set to 45 ⁰C. One method used a 50 x 2.1 mm column with a flow rate of 0.6 mL/min, and the other used a 50 x 4.6 mm column with a flowrate of 0.9 mL/min. Both methods used gradient conditions with a total cycle time of 9 minutes. A lifetime study was conducted by performing 1000 total injections of samples prepared through a common dilute-and-shoot approach on the 50 x 2.1 mm column dimension.
Both methods were compared for efficiency, sensitivity, resolution (Rs), consumption of mobile phase, and robustness, and the 2.1 mm ID column was able to demonstrate superior sensitivity while consuming less resources and minimizing impact to the MS while still providing adequate resolution of isobars and excellent column robustness.