Keywords: حلال نگهداری اورامیک; Ultra-performance liquid chromatography; Tandem mass spectrometry; Uremic retention solutes; p-Cresyl sulfate; Indoxyl sulfate; Trimethylamine-N-oxide; PhenylacetylglutamineCKD, chronic kidney disease; TMAO, trimethylamine-N-oxide; HPLC, high performance