Procedure for determination of immunosuppressive drugs in whole blood with liquid chromatography-isotope dilution mass spectrometry.

Background: Cyclosporin A, sirolimus, tacrolimus, and everolimus are immunosuppressive drugs used for therapy after organ transplantation. There are several analytical procedures for monitoring the drug level in blood, e.g.

Liquid chromatography-isotope dilution-mass spectrometry as a new basis for the reference measurement procedure for hemoglobin A1c determination.

Background: Standardization of hemoglobin (Hb)A(1c) measurements is a process of considerable interest for quality assurance in diabetes management. To contribute to continuous quality improvement and fulfillment of the requirements for reference measurement procedures according to the standards of the International Organization for Standardization, we developed a calibration system of highest metrological order using isotope dilution-mass spectrometry with a reference material.

Method: Samples were prepared by enzymatic cleavage based on the IFCC reference measurement procedure for LC-MS analysis.

Modified HPLC-electrospray ionization/mass spectrometry method for HbA1c based on IFCC reference measurement procedure.

Background: Monitoring of hemoglobin A(1c) (HbA(1c)) is important in the management of diabetes. The IFCC reference measurement procedure for HbA(1c) is based on the ratio of glycated to nonglycated N-terminal hexapeptides of the beta-chains of hemoglobin after digestion with Glu-C endoproteinase. We developed a modification of the original reference measurement procedure with HPLC-electrospray ionization/mass spectrometry (ESI/MS).

A novel LC-IDMS/MS method for the determination of the cardiac glycosides digoxin and digitoxin using caesium adducts.

This article describes an essential improvement of the published candidate reference measurement procedure for digoxin and digitoxin and compares it with the original method. The novelty of the method lies in the measurement of the caesium (Cs+) ion as product ion in the multiple reaction monitoring mode (MRM) with potentially improved analytical specificity whilst retaining a comparable accuracy and precision at therapeutic levels. The original measurement procedure used the single-ion mode (SIM).

Modification of the IFCC reference measurement procedure for determination of HbA 1c by HPLC-ESI-MS.

The reference measurement procedure for determination of HbA(1c) (glycated haemoglobin) using HPLC(high performance liquid chromatography)-ESI(electrospray ionisation)-MS(mass spectrometry) has been modified. Main modifications were a change in the buffer composition of the HPLC, a change in the gradient elution profile and the introduction of a post-column splitting system. The long-term stability of the HPLC-ESI-MS system proved to be of high importance to get reproducible results.

A new approach for the determination of immunosuppressive drugs using HPLC-MS/MS and Cs+ adducts.

In this study a new principle of measurement in LC-MS/MS (liquid chromatography mass spectrometry) for determination of the immunosuppressive drugs sirolimus, everolimus, tacrolimus, and cyclosporin A has been introduced by using the Cs(+) ion as the product ion in the multiple reaction monitoring mode (MRM). Separation of the immunosuppressive agents was achieved using a phenyl-hexyl-RP column together with a ternary gradient elution profile, consisting of water, methanol and acetonitrile combined with 0.1% v/v formic acid and 0.