Determination of iohexol and iothalamate in serum and urine by capillary electrophoresis

Estimation of glomerular filtration rate (eGFR) is essential to assess kidney function. Iodine-containing contrast agents detection by HPLC has been proposed as a safe alternative for inulin or radioactive compounds. However, HPLC is a time-consuming and labor-intensive method. The aim of this study was to develop an assay for iohexol and iothalamate using capillary electrophoresis. Iohexol and iothalamate were directly analyzed by CE in serum and urine, using photometric detection (246 nm). Serum peak height was proportional to iohexol and iothalamate concentrations. Detection limits for iohexol and iothalamate were 10 and 5 mg/L. Limits of quantification were 13.0 and 15.0 mg/L. Within-run CVs were 4.9 and 6.5%; between-run CVs 3.1-9.9% and 3.8-13.7%. A good correlation was observed between CE and HPLC: y = 1.1703x + 5.017 (iohexol) and y = 0.7807x + 11.01 (iothalamate; (y = concentration obtained by CE [mg/L], x = concentration obtained by HPLC [mg/L]). In addition, CE allowed to determine urinary iohexol concentration. Although the detection limit for CE was higher than for HPLC, CE can still be used for eGFR determination. Advantages of this high-throughput method are the absence of sample pretreatment and a minimal sample volume requirement.