Evaluation of Stability of Thiopurine Metabolites Using a Validated LC-MS/MS Method.

Measurement of thiopurine metabolites is helpful to monitor adverse effects and assess compliance in patients on thiopurine treatment. The purpose of this study was to develop and validate an analytical method for measurement of thiopurine metabolites, thioguanine nucleotides (6-TGN) and 6-methylmercaptopurine nucleotide (6-MMPN), in RBCs. We developed and validated a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the quantification of 6-TGN and 6-MMPN and evaluated the stability of the thiopurine metabolites in RBC and whole blood states without any preprocessing at various storage conditions.

[Determination of urinary iodine concentration by inductively coupled plasma-mass spectrometry in thyroid cancer patients on low-iodine diet].

Background: Thyroid cancer patients should be on low-iodine diet (LID) before radioactive iodine therapy (RAIT) to maximize the effect of RAIT. Urinary iodine excretion is the most accurate marker of very recent dietary iodine intake. We developed and evaluated the analytical performance of inductively coupled plasma-mass spectrometry (ICP-MS) to determine urinary iodine concentration.