Application of 1-alkylamines to a liquid chromatographic/turbo ionspray tandem mass spectrometric method for quantifying metabolites of a new bone anabolic agent, TAK-778, in human serum

• Published in: Journal of mass spectrometry. 2002-06, Vol.37 (6), p.631-638
• Main Authors: Teshima, Koichiro, Kondo, Takahiro, Maeda, Chie, Oda, Tsuneo, Hagimoto, Toshiaki, Tsukuda, Ryoichi, Yoshimura, Yoshinobu
• Format: Article
• Language: English
• Subjects: 1-alkylamines; adduct ion; Alkylation; Amines - chemistry; Analysis; Benzothiepins - administration & dosage; Benzothiepins - blood; Benzothiepins - pharmacokinetics; Biological and medical sciences; Biotransformation; Blood Chemical Analysis - instrumentation; Blood Chemical Analysis - methods; Calibration; Chromatography, High Pressure Liquid - methods; General pharmacology; Humans; Hydrogen-Ion Concentration; Injections, Intramuscular; liquid chromatography/turbo ionspray tandem mass spectrometry; Mass Spectrometry - methods; Medical sciences; metabolite; Pharmacology. Drug treatments; quantification; Reference Standards; Sensitivity and Specificity; TAK-778
• ISSN: 1076-5174; 1096-9888
• DOI: 10.1002/jms.324

We investigated the application of alkylamines, as additives to the mobile phase, to a quantification method for the metabolites, M‐III and M‐IV, of TAK‐778, which is a new bone anabolic agent, in human serum using liquid chromatography/tandem mass spectrometry (LC/MS/MS). Prior to setting up the analytical method, we found that 1‐alkylamines co‐existing with M‐III and M‐IV in the turbo ionsprayed solution formed 1‐alkylammonium adduct molecules of these metabolites during the ionization process, and the abundance of the adduct ions was considerably higher than that of protonated molecules ([M + H]+s) of these metabolites. Based on these findings, we investigated a variety of 1‐alkylamines and their spiked concentrations in the mobile phase for LC/MS/MS analysis to obtain higher sensitivities for the quantification of these metabolites. After these examinations, we found that 1‐hexylamine at a final concentration of 0.05 mmol l−1 was the most suitable additive for the mobile phase, and set the selected reaction monitoring (SRM) ions for the 1‐hexylammonium adduct molecule and [M + H]+, allowing about a fivefold gain in the SRM chromatographic peak compared with that without 1‐hexylamine. The adduct ion was considered to be formed by interaction between the amino group of 1‐hexylamine and the phosphoryl group of M‐III and M‐IV. The internal standard (I.S.) used was deuterated M‐III for each metabolite. The analytes and I.S. were extracted with diethyl ether from serum samples at neutral pH and injected into the LC/MS/MS system with a turbo ionspray interface. The limit of quantification for both analytes was 0.5 ng ml−1 when 0.1 ml of serum was used, and the calibration curves were linear in the range 0.5–100 ng ml−1. The method was precise; the intra‐ and inter‐day precisions of the method were not more than 5.6%. The accuracy of the method was good, with deviations between added and calculated concentrations of M‐III and M‐IV being typically within 16.6%. This method provided reliable pharmacokinetic data for M‐III and M‐IV after the intramuscular administration of TAK‐778 sustained‐release formulation in humans. Copyright © 2002 John Wiley & Sons, Ltd.