The utility of silica hydride‐based stationary phases for dual‐mode ultra high performance liquid chromatography separation of synthetic cathinone positional isomers

Abstract

Emerging drugs usually mimic the effects of traditional drugs, but are not always controlled due to the chemically altered structures. Positional isomers of emerging drugs are difficult to analyze because they challenge the separation and detection techniques commonly employed by forensic laboratories. The utility of silica hydride stationary phases for the ultra‐high performance liquid chromatography separation of synthetic cathinone positional isomers was studied in this manuscript. SiH phases are operable under both reversed phase and aqueous normal phase chromatographic conditions without the need to change solvent reservoirs. The separation of eight positional isomers of the synthetic cathinone, pentedrone, was investigated using five silica hydride phases, and compared to a classical dual column reversed phase, hydrophilic interaction chromatography system, and to a bimodal pentaflurophenyl column. Significant selectivity differences were observed using either a combination of a classical reversed phase C18 and NP Silica columns or the various bimodal columns. The silica hydride silica‐C column, which contains no derivatized ligands attached to the silica hydride backbone, not only gave the most orthogonal separation of the bimodal columns, but provided a unique separation of all eight positional isomers (resolution ≥ 1) using the combination of reverse phase and aqueous normal phase chromatographic conditions.

The separation and identification of synthetic cathinones by portable low microflow liquid chromatography with dual capillary columns in series and dual wavelength ultraviolet detection

“…For RP, the use of an unconventional pentaflurophenyl (PFP) column, which exhibits unique interactions due to presence of fluorene groups on the phenyl ring, would be an interesting choice [47]. The use of silica hydride stationary phases, which exhibit unique selectivity compared to conventional silica columns, could provide enhanced orthogonality [49]. The use of different stationary phases in the hydrophilic interaction chromatography (HILIC) or aqueous normal phase mode, would be interesting to explore [49,50].…”

“…The use of silica hydride stationary phases, which exhibit unique selectivity compared to conventional silica columns, could provide enhanced orthogonality [49]. The use of different stationary phases in the hydrophilic interaction chromatography (HILIC) or aqueous normal phase mode, would be interesting to explore [49,50]. It would appear that the use of absorbance ratios, which exhibited a relatively high degree of specificity, would qualify at least as a Category C technique.…”

Recent forensic applications of enhanced chromatographic separation methods

“…The second column or the same column employed with different mobile phase conditions Article Related Abbreviations: ASTM, American Society for Testing and Materials; FID, flame ionization detection; HILIC, hydrophilic interaction liquid chromatography; HR, high resolution; IL, ignitable liquids; IMS, ion mobility spectrometry; IR, infrared; KI, Kovats index; LI, Lee index; PFP, pentafluorophenyl; SAMHSA, Substance Abuse and Mental Health Services Administration; SFC, supercritical fluid chromatography; TOF, time of flight; UHP, ultra-high performance; VOC, volatile organic compounds; WPCA, weighted principal component analysis have different chromatographic properties that hopefully lead to uncorrelated separations. By changing the separation method peaks that coelute may be de-coupled [1,2,[5][6][7]. The addition of a second chromatographic system can provide an additional retention time for use in compound identification [5].…”

“…The addition of a second chromatographic system can provide an additional retention time for use in compound identification [5]. The ability of the chromatographic techniques to be paired with a variety of detectors is not changed by the addition of additional dimensions [1][2][3][4]6,7].…”

“…The enhanced separation methods applicable to LC, GC, and SFC are shown in Figure 1. The term multimodal describes a method that varies the mobile phase conditions using the same stationary phase [6,7]. Comprehensive chromatography describes a method of sending distinct fractions of set intervals for every peak from the first column (one at a time) to a second column [1,2].…”