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Decreasing the uncertainty of peak assignments for the analysis of synthetic cathinones using multi-dimensional ultra-high performance liquid chromatography

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Abstract

Chromatographic techniques which are commonly employed in forensic analysis utilize retention time as an identification parameter. Conventional one-dimensional chromatographic techniques such as gas and liquid chromatography inherently lack the separation power required to resolve the multitude of combinations possible when analyzing emerging drugs. Multi-dimensional chromatography, which significantly increases resolving power, is a viable means to increase the utility of retention time measurements for compound identification. This study aims to demonstrate the utility of multi-dimensional ultra-high performance liquid chromatography (UHPLC) with at-column dilution for the screening and identification of synthetic cathinones with significantly decreased uncertainty. One-dimensional separations were conducted on mixtures of 16 controlled synthetic cathinones and 7 pentedrone positional isomers in order to determine the most orthogonal combination for multi-dimensional chromatography. The separations utilized several stationary phases for both reversed phase chromatography (RPC) and hydrophilic interaction chromatography (HILIC). Based on the separations performed, it was determined that a combination of a BEH C8 column (operated in RPC mode) and an HSS PFP column (operated in HILIC mode) as the first and second dimension columns, respectively, provided orthogonal separations with a decrease in peak assignment uncertainty of at least one order of magnitude. For at-column dilution, a HILIC trapping column was used with 0.025% formic acid in acetonitrile as the loading and diluting solvent. Multi-dimensional separations conducted on early, mid, and late eluting compounds showed excellent retention time repeatability, satisfactory recovery with excellent signal-to-noise, and good peak area repeatability for both the first and second dimensions. Ten simulated samples containing various adulterants and diluents were analyzed using multi-dimensional chromatography. All 10 samples showed excellent retention time matches between the sample and its corresponding standard. Thus, multi-dimensional UHPLC would significantly reduce peak assignment uncertainty leading to increased accuracy in the identification of seized drugs.

Graphical abstract: Decreasing the uncertainty of peak assignments for the analysis of synthetic cathinones using multi-dimensional ultra-high performance liquid chromatography

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Publication details

The article was received on 16 Mar 2018, accepted on 06 Jun 2018 and first published on 07 Jun 2018


Article type: Paper
DOI: 10.1039/C8AY00565F
Citation: Anal. Methods, 2018, Advance Article
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    Decreasing the uncertainty of peak assignments for the analysis of synthetic cathinones using multi-dimensional ultra-high performance liquid chromatography

    Cecilia M. Ochoa, P. Shoenmakers, C. R. Mallet and I. S. Lurie, Anal. Methods, 2018, Advance Article , DOI: 10.1039/C8AY00565F

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