Apparatus for Improved Immunosuppressant Drug Monitoring

Abstract

A liquid chromatography / mass spectrometry system includes: a source of a first mobile phase solvent consisting essentially of water plus 10 mM ammonium formate plus 0.05% formic acid; a source of a second mobile phase solvent consisting essentially of methanol plus 10 mM ammonium formate plus 0.05% formic acid; a chromatography column comprising a length of 30 mm or less of a stationary phase comprising an 8-carbon alkyl chain material bonded to 2.6 μm diameter particles having solid silica cores surrounded by porous silica outer layers; an electrospray ion source of a mass spectrometer fluidically coupled to the chromatography column so as to generate ions therefrom; a mass analyzer of the mass spectrometer operable to quantitatively detect the ions; and a programmable processor electronically coupled to the mass analyzer and comprising instructions operable to determine, based on the ion detection, a concentration of everolimus, sirolimus, tacrolimus, or cyclosporin A.

Description

CROSS REFERENCE TO RELATED APPLICATION[0001]This application is a Divisional of and claims the benefit, under 35 U.S.C. 120, of co-pending and co-owned U.S. application Ser. No. 13 / 830,103, now U.S. Pat. No. ______, filed on Mar. 14, 2013, the contents of which are incorporated by reference herein in their entirety.FIELD OF THE INVENTION[0002]This invention relates to assays of drugs in biological samples and, more particularly, to assays of immunosuppressant drugs in whole blood by liquid chromatography coupled to mass spectrometry.BACKGROUND OF THE INVENTION[0003]In certain circumstances, the immune system must be controlled in order to either augment a deficient response or suppress an excessive response. For example, when organs such as kidney, heart, lung, bone marrow, and liver are transplanted in humans, the body will sometimes reject the transplanted tissue by a process referred to as allograft rejection. In treating allograft rejection, the immune system is frequently suppr...

AI Technical Summary

Benefits of technology

[0012]The inventors have discovered that the phospholipids are so strongly partitioned onto the stationary phase of reverse-phase analytical columns that the conventional cleaning or washing steps that are generally included between chromatographic runs are insufficient to totally remove all bound phospholipids from the column. The residual phospholipids, being thus dispersed through the column prior to another chromatographic separation, cause carryover effects resulting in broad elution of these interfering compounds over a range of retention times. The inventors have further discovered that, somewhat surprisingly, using an analytical column of a relatively short length can give adequate separation of the phospholipids from the ISDs, with elimination of ion suppression, since the short columns may be adequately purged of residual phosphipids between runs.

Problems solved by technology

The inventors have discovered that the phospholipids are so strongly partitioned onto the stationary phase of reverse-phase analytical columns that the conventional cleaning or washing steps that are generally included between chromatographic runs are insufficient to totally remove all bound phospholipids from the column.

Images