Methanol and LC-MS-grade water were obtained from Fisher Scientific GmbH (Schwerte, Germany). Ammonium acetate, formic acid, and hydrochloric acid were purchased from Sigma-Aldrich (Deisenhofen, Germany). Dabigatran (the active form of Dabigatran etexilate), [13C6]-Dabigatran, rivaroxaban, and [13C6]-rivaroxaban were purchased from Alsachim (Strasbourg, France).
Primary stock solution of Dabigatran, [13C6]-Dabigatran, rivaroxaban, and [13C6]-rivaroxaban, each at a concentration of 10 mg/L, were prepared separately in Methanol/water (50:50) and stored at -20°C. Using drug-free citrate plasma, we prepared several calibrators (0.8, 1.6, 3.1, 6.3, 12.5, 25.0, 50.0, 100, 200, 400 and 800 μg/L of both Dabigatran and rivaroxaban) for the assay. Commercially available quality-control samples for Dabigatran and rivaroxaban purchased from Technoclone GmbH (Vienna, Austria) were used.
An internal standard solution including 20 μg/L [13C6]-Dabigatran, as well as 20 μg/L [13C6]-rivaroxaban, was prepared by mixing 1 ml [13C6]-Dabigatran stock solution, 1 ml [13C6]-rivaroxaban stock solution and 498 ml Methanol/water (90:10) containing 10 mmol/L hydrochloric acid.
Primary stock solution of Dabigatran, [13C6]-Dabigatran, rivaroxaban, and [13C6]-rivaroxaban, each at a concentration of 10 mg/L, were prepared separately in Methanol/water (50:50) and stored at -20°C. Using drug-free citrate plasma, we prepared several calibrators (0.8, 1.6, 3.1, 6.3, 12.5, 25.0, 50.0, 100, 200, 400 and 800 μg/L of both Dabigatran and rivaroxaban) for the assay. Commercially available quality-control samples for Dabigatran and rivaroxaban purchased from Technoclone GmbH (Vienna, Austria) were used.
An internal standard solution including 20 μg/L [13C6]-Dabigatran, as well as 20 μg/L [13C6]-rivaroxaban, was prepared by mixing 1 ml [13C6]-Dabigatran stock solution, 1 ml [13C6]-rivaroxaban stock solution and 498 ml Methanol/water (90:10) containing 10 mmol/L hydrochloric acid.