LC-MS/MS method for simultaneous determination of serum p-cresyl sulfate and indoxyl sulfate in patients undergoing peritoneal dialysis.

Abstract

p-Cresol sulfate (pCS) and indoxyl sulfate (IS) are protein-bound uremic toxins that accumulate in patients with chronic kidney disease (CKD). They are closely associated with the mortality rate of CKD and morbidity of cardiovascular disease. In the present study, we established a rapid method for determination of pCS and IS by HPLC-MS/MS in serum samples from 205 CKD patients undergoing peritoneal dialysis. In brief, serum was extracted by acetonitrile and spiked with hydrochlorothiazide. The prepared sample was eluted through HPLC column (Agilent Zorbax SB-C18 , 3.5 μm, 2.1 × 100 mm) with a mobile phase of acetonitrile and 10 mm ammonium acetate solution (10:90, v/v) for subsequent detection of pCS and IS by MS/MS. The linearity ranged from 50 to 10,000 ng/mL for pCS (r >0.99), and from 500 to 10,000 ng/mL for IS (r >0.99). The lower limit of quantification was 50 ng/mL for pCS, and 500 ng/mL for IS. Relative standard deviation (RSD) of intra- and inter-day precision was within ±15%. The results showed that pCS and IS levels were partially correlated with renal function in CKD patients, and IS was directly related to serum creatinine and estimated glomerular filtration rate.