Total Determination of Nine Uremic Toxins and Choline in Blood Serum by High-Performance Liquid Chromatography with Tandem Mass Spectrometry Detection

A procedure for the simultaneous determination of nine uremic toxins and choline in blood serum is presented. Target substances are selected based on the published data as promising biomarkers for establishing the severity and nature of the progression of immunoglobulin A nephropathy, a kidney disease leading to disability, and in the absence of timely treatment, to the death of young and middle-aged people. Using ultrafiltration, separate determination of free and protein-bound indole uremic toxins was achieved. The use of high-performance liquid chromatography in combination with high-resolution tandem mass spectrometry provides satisfactory analytical accuracy in the absence of the complete chromatographic separation of analytes under standard reversed-phase HPLC conditions. In calibration a solution of albumin in a phosphate buffer solution was used as a surrogate blood serum. Protein concentration of 45 mg/mL and pH 7.4 correspond to these characteristics of native blood serum. The pilot experiment showed the promise of determining the most important indicators of the state of the intestinal microbiome—choline and trimethylamine oxide in dried blood spots.