Screening of drugs in equine plasma using automated on-line solid-phase extraction coupled with liquid chromatography-tandem mass spectrometry.

The research article presents a quick method to screen for multiple types of drugs in horse blood plasma using liquid chromatography-tandem mass spectrometry (LC-MS-MS). This method is used for testing pre-race horse plasma samples for drug presence.

Methodology and Procedure

• The first step in this method involved protein precipitation from horse plasma samples by using acetonitrile.
• The samples then underwent centrifugation where the supernatant was injected into an automated on-line solid-phase extraction (SPE) system.
• This system was coupled to a triple quadrupole LC-MS-MS — a powerful tool used often in drug detection — which was placed in positive electrospray ionisation (+ESI) mode.
• The selected reaction monitoring (SRM) scan was then used to analyse the extracted compounds.
• For extraction and chromatographic separation of drug components, a polymeric extraction column and a reversed-phase C18 LC column were used respectively. Modified settings such as gradient elution aided in quicker analysis time.

Results and Validation

• The turnaround time for the entire process, inclusive of post-run and equilibration, was found to be a speedy 9.5 minutes.
• The procedure proved successful in detecting plasma samples fortified with 19 groups of drugs, including narcotic analgesics, local anesthetics, antipsychotics, bronchodilators, mucolytics, corticosteroids, sedatives, and tranquillizers. These drugs could be detected even at extremely low concentrations of sub-parts per billion (ppb) to low parts per trillion (ppt).
• No significant matrix interference was observed at expected retention times of the targeted ion transitions, indicating the method’s specificity and accuracy.
• A notable feature of the study was that over 70% of the drugs being tested had detection limits at or below 100 picograms per milliliter (pg/mL), with some reaching detection limits as low as 19 pg/mL, showing the method’s remarkable sensitivity.
• The method was adequately validated for extraction recovery, precision, and sensitivity, and a blockage study was also conducted before its implementation.
• The research concluded that this quick and efficient method is suitable for regular screening of horse plasma samples for drug presence prior to races.