Use of benchtop exactive high resolution and high mass accuracy orbitrap mass spectrometer for screening in horse doping control.

Liquid chromatography-mass spectrometry (LC-MS) has been widely used in doping control laboratories over the last two decades. Currently, simple quadrupole, triple quadrupole and ion trap are the most commonly employed analyzers in toxicological analysis. Nevertheless, the main lack of these technologies is the restricted number of target compounds simultaneously screened without loss of sensitivity. In this article we present an innovative screening approach routinely applied in the French horse doping control laboratory based on high resolution (50000) and high mass accuracy (<5 ppm) in full scan MS mode for more than 235 target analytes screened from an initial volume of 5 mL of urine. The sample preparation was classically founded on solid phase extraction by means of reverse phase C18 cartridges. LC-MS analyses were carried out on a Shimadzu binary HPLC pumps linked to a C18 Sunfire column associated with the high resolution exactive benchtop orbitrap mass spectrometer. This screening was performed alternatively in positive-negative ionization mode during the same run. Thus, the identification of compounds of interest was made using their exact mass in positive-negative ionization mode at their expected retention time. All data obtained were processed by ToxID software (ThermoFisherScientific) which is able to identify a molecule by theoretical mass and retention time. In order to illustrate this innovative technology applied in our laboratory, sample preparation, validation data performed on 20 target compounds from 16 different horse urine samples, chromatograms and spectra will be discussed in this paper.