Harrison School of Pharmacy

Faculty and Staff Directory

 

Randall Clark Randall Clark
Professor

Department: Drug Discovery and Development
Auburn University
Harrison School of Pharmacy
3306 Walker Building
Auburn, AL 36849
Email: clarkcr@auburn.edu
Phone: 334-844-8326
Fax: 334-844-8331
 Bio

Our research in forensic drug chemistry involves studies to improve the differentiation of regioisomeric and isobaric compounds related to controlled drug substances. The experiments are designed to test and challenge the specificity of methods used in forensic drug sample evaluation and identification. The methylenedioxyphenethylamine group of compounds has been the focus of a significant amount of designer drug attention in recent years. Designer drugs have been described as molecular modifications of controlled substances to produce a drug species which exists just outside the scope of the current drug laws. Some countries have dealt with the legal issues surrounding these clandestine synthesized designer drugs by placing controls on individual molecular species. Other countries such as the United States have developed a controlled substance analog law attempting to proactively control many substances before they appear as clandestine drugs. In either case the forensic chemist is left with the need to specifically identify any new substance encountered in a drug sample.

Regioisomeric relationships are the result of different positions of attachment of functional groups in compounds that possess the same molecular formula (elemental composition). Isobaric substances are of the same nominal mass but different elemental compositions. Regioisomeric and isobaric substances are considered a significant challenge for the analytical techniques used to identify specific substances. This is extremely important when some of these molecules are legally controlled drugs of abuse or controlled precursor substances. Gas chromatography-mass spectrometry is the mandated method of confirming drug identity in a number of forensic and regulatory situations.

While the mass spectrum is often considered a specific "fingerprint" for an individual compound, there are other substances which may produce very similar or almost identical mass spectra. Such compounds having mass spectral equivalency and similar chromatographic elution properties, perhaps co-elution represent a serious analytical challenge. When the number of mass spectral equivalent isomeric substances is relatively small, chromatographic separation and reference standard availability is sufficient for differentiation. However, the continued designer exploration of some drug categories will likely produce even greater numbers of regioisomeric and isobaric substances especially among the phenethylamines. As the number of compounds having mass spectral equivalence increases so will the challenge of specific identification via chromatographic resolution and other analytical methods.

 Selected Publications

Karim M. Abdel-Hay, Jack DeRuiter, Forrest Smith, Amsha S. Alsegiani, Amber Thaxton-Weissenfluh and C. Randall Clark, “GC-MS Differentiation of the Six Regioisomeric Dimethoxybenzoyl-1-pentylindoles: Isomeric Cannabinoid Substances,” Journal of Pharmaceutical and Biomedical Analysis, 125, 360-368 (2016).

Younis F. Hamad Abiedalla, Jack DeRuiter and C. Randall Clark, “Product Ion MS-MS Differentiation of Regioisomeric Side-Chain Groups in Cathinone Derivatives,” Rapid Communications in Mass Spectrometry, 30, 1713-1721 (2016).

Younis F. Hamad Abiedalla, Karim Abdel-Hay, Jack DeRuiter and C. Randall Clark, “Differentiation of Cyclic Tertiary Amine Cathinone Derivatives by Product Ion Electron Ionization Mass Spectrometry,” Rapid Communications in Mass Spectrometry, 30, 763–772 (2016).

Karim M.Abdel-Hay, Jack DeRuiter, Forrest Smith, Tarek S. Belal and C. Randall Clark, “GC-MS Analysis of the Regioisomeric Methoxy- and Methyl-benzoyl-1-Pentylindoles: Isomeric Synthetic Cannabinoids,” Science and Justice, 55, 291-298 (2015).

Amber Thaxton, Tarek S. Belal, Forrest Smith, Jack DeRuiter, Karim M.Abdel-Hay and C. Randall Clark, “GC-MS Studies on the Six Naphthoyl-Substituted 1-Pentyl-Indoles: JWH-018 and Five Regioisomeric Equivalents,” Forensic Science International, 252, 107–113 (2015).

Amber Thaxton, Tarek S. Belal, Forrest Smith, Jack DeRuiter, Karim M. Abdel-Hay and C. Randall Clark, “Mass Spectral Studies on 1-n-pentyl-3-(1-naphthoyl)-indole (JWH-018), three Deuterium Labeled Analogues and the Inverse Isomer 1-naphthoyl-3-n-pentylindole,” Rapid Communications in Mass Spectrometry, 29, 871–877 (2015).

Karim M.Abdel-Hay, Jack DeRuiter and C. Randall Clark, “Differentiation of the 1-(methylenedioxyphenyl)-2-piperazinopropanes and 1-(methoxyphenyl)-2-piperazino-propanones By GC-IRD and GC-MS,” Forensic Science International, 235, 40–51 (2014).

Karim M. Abdel-Hay, Jack DeRuiter and C. Randall Clark, GC-MS and IR Studies on the Six Ring Regioisomeric Dimethoxyphenylpiperazines (DOMPPs), Journal of Forensic Sciences, 60, 285-294 (2015).

Senthikumar Karuppagounder, Dwipayan Bhattacharya, Manuj Ahuja, Vishnu Suppiramaniam, Jack DeRuiter, Randall Clark, and Murali Dhanasekaran, “Elucidating the neurotoxic effects of MDMA and its analogs,” Life Sciences, 101, 37-42 (2014).

Karim M.Abdel-Hay, Cameron M. Terrell, Jack DeRuiter and C. Randall Clark, “GC-MS and IR Studies on the Six Ring Regioisomeric Dimethoxybenzoyl-N-methylpiperazines (DMBzMPs),” Forensic Science International, 237, 53-61 (2014).

Jack DeRuiter, Karim M. Abdel-Hay, Forrest Smith and C. Randall Clark “Analytical Differentiation of 1-Alkyl-3-acylindoles and 1-Acyl-3-alkylindoles: Isomeric Synthetic Cannabinoids,” Analytical Chemistry, 86, 3801-3808 (2014).

Forrest T. Smith, Jack DeRuiter, Karim Abdel-Hay and C. Randall Clark “GC-MS Evaluation of the Six Benzoyl-Substituted-1-pentylindoles: Isomeric Synthetic Cannabinoids,” Talanta, The International Journal of Pure and Applied Analytical Chemistry, 129, 171-182 (2014).

Daniel P. Katz, Dwipayan Bhattacharya, Subhrajit Bhattacharya, Jack Deruiter, C. Randall Clark, Vishnu Suppiramaniam, Muralikrishnan Dhanasekaran “Synthetic Cathinones: "A Khat and Mouse Game," Toxicology Letters, 229,349-356 (2014).

Karim M.Abdel-Hay, Jack DeRuiter and C. Randall Clark, “Regioisomeric Bromodimethoxybenzylpiperazines Related to the Designer Substance 4-Bromo-2,5-dimethoxybenzylpiperazine: GC-MS and FTIR Analysis,” Forensic Science International, 240, 126-136 (2014).

 

Last Updated: March 7, 2017