Simple Determination of p-Cresol in Plasma Samples Using Fluorescence Spectroscopy Technique.

The development of simple, fast, cheap and reliable analytical methods for tracing biological indicators is demanded through clinical investigations. Herein, we developed, for the first time, a cheap and specific method for the extraction and quantification of p-cresol (pC) in real plasma samples of chronic kidney disease (CKD). Plasma samples were prepared by hydrolyzing in an acidic medium to convert pCS (p-cresol sulfate) and p-Cresol glucuronide (pCG) to pC. Next, proteins of plasma samples were precipitated and then pC was extracted by acetonitrile (ACN) and saturated NaCl (as salting-out agent). Finally, fluorescence emissions were measured at λex/λem = 280/310 nm. The specificity of the method was checked by testing various possible interfering agents. The obtained results revealed a specific determination of pC. Under optimal conditions, a linear range was detected from 0.5 to 30 µg/mL of pC with a lower limit of detection (LLOQ) of 0.5 µg/mL. The reliability of the method was checked by calculating the repeatability, selectivity, and accuracy of the developed method for pC determination in plasma samples. The application of the developed method was investigated for the detection of pC in a number of CKD patients. Due to the simplicity and selectivity, the developed method could be applied for routine analysis of pC concentrations in the plasma samples of CKD patients. In addition, the developed method showed great potential for developing a point-of-care testing (POCT) device.