Claude R. Mallet

Functionalization of divinylbenzene/N-vinylpyrrolidone copolymer particles: ion exchangers for solid phase extraction.

A series of four-mixed mode ion exchangers for SPE, consisting of either weak or strong cation or anion exchangers, have been synthesized by functionalization of spherical, porous particles made from a copolymer of N-vinylpyrrolidone and divinylbenzene. These materials are able to selectively retain and release acidic and basic solutes through the judicious choice of wash solvent pH, as shown through the use of SPE recovery tests.

Chapter 3 - Techniques for sample preparation using solid-phase extraction

This chapter describes techniques for sample preparation using solid-phase extraction (SPE). The 1-D reversed-phase sample clean-up method is a simple technique designed to remove major interferences such as plasma proteins or polar compounds. The 2-D reversed-phase solid-phase extraction method provides much cleaner backgrounds, but the development of the method is more complex. A range of useful methods for the sample preparation of samples of biologic origin (plasma and urine) prior to high-performance liquid chromatography (HPLC) or HPLC and mass spectrometry (MS) or MS analysis are discussed in the chapter, with an emphasis on the general principles of each method. Each method can carried out with multiple analytes and can be adapted to related sample preparation problems without difficulties. However, occasionally, the particular properties of a sample matrix, an analytical technique, or even simply the analytes require departures from the details of the approaches described in the chapter. Both offline and online SPE techniques have advantages depending upon the particular application, and additional progress in the future is anticipated with respect to the speed and efficiency of both approaches.

Analysis of ketamine and xylazine in complex matrices using two-dimensional liquid chromatography/tandem mass spectrometry

RATIONALE: Analyzing tissue samples is routinely performed when liquid biological samples are not available for replicate analysis. Preparing complex matrices, such as tissue, for analysis can be time-consuming. Traditional sample preparation methods typically begin with homogenization followed by a sample clean up step such as liquid-liquid or solid phase extraction. Samples are typically eluted, evaporated and reconstituted prior to instrumental analysis. The aim of this project was to evaluate multi-dimensional chromatography’s utility in reducing the amount of time from sample acquisition to analysis. METHODS: Tissue specimens were homogenized using a ceramic beads shaker. Homogenates were then diluted and loaded onto a mixed mode solid phase sorbent. The sorbent was washed, and the final eluate was transferred directly to vials without evaporation or reconstitution steps. Analysis was performed using a 2D UPLC configuration with an At-column dilution option coupled to a triple quadrupole mass spectrometer. The target analytes (xylazine and ketamine) were quantified under MRM using ESI in positive mode. RESULTS: The lowest limit of detection evaluated in this study was 0.01 ng/mL. The linear dynamic range utilized was 0.1 ng/mL to 10 ng/mL. The concentrations for xylazine in their respective tissues ranged from 0 to 0.316 ng/mL. Ketamine concentrations ranged from 0 to 0.905 ng/mL. The overall time for sample preparation was reduced to 30 minutes. The total run time was 10 minutes. CONCLUSIONS: The use of multidimensional chromatography with atcolumn-dilution allows for significant reduction in sample preparation time. The concentrations determined in these samples highlight the need

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

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.