Determination of four forms of plasma thiol amino acids in individuals with chronic kidney disease by UPLC-MS/MS.

The study introduces a robust analytical method based on UPLC-MS/MS for quantifying thiol amino acids, including cysteine (Cys), cysteinylglycine (CG), homocysteine (Hcy), and glutathione (GSH), in their total and total free forms within human plasma. An optimized blank matrix was employed for accurate quantification of endogenous compounds. The method exhibited excellent linearity, precision, accuracy, recovery, and stability, making it highly suitable for plasma analysis.

Preparation of thiol-free amino acid plasma matrix for quantification of thiol amino acids and their oxidized forms in human plasma by UPLC-MS/MS.

Thiol amino acids, with great physiological significance, are unstable, and have small molecular weights, as well as very low endogenous concentrations. Therefore, to quantitatively and directly analyze them using liquid chromatography-tandem mass spectrometry is difficult. To overcome these problems, we aimed to prepare a thiol-free amino acid plasm matrix as blank sample to reduce the background for the first time.