Simultaneous determination of four immunosuppressants by means of high speed and robust on-line solid phase extraction–high performance liquid chromatography–tandem mass spectrometry

In this study immunosuppressants, i.e. cyclosporin A (CyA), tacrolimus (TRL), sirolimus (SRL) and everolimus (RAD) were quantified in whole blood samples from immunosuppressant treated transplant recipients by an integrated on-line solid phase extraction–high performance liquid chromatography–tandem mass spectrometry (SPE–HPLC–MS/MS) system. This method has been developed to improve the following characteristics: speed, robust analysis, simultaneous determination and low cost. This can be achieved by the use of a perfusion column as an extraction cartridge in combination with a short HPLC column and highly selective and sensitive atmospheric pressure ionisation tandem mass spectrometry (API–MS/MS) in the multiple reaction monitoring (MRM) detection mode. This high throughput technique is perfectly appropriate for routine therapeutic drug monitoring (TDM) of organ transplanted patients.