Sodium octanoate to reverse indoxyl sulfate and p-cresyl sulfate albumin binding in uremic and normal serum during sample preparation followed by fluorescence liquid chromatography

J Chromatogr A. 2009 May 29;1216(22):4684-8. doi: 10.1016/j.chroma.2009.04.015. Epub 2009 Apr 14.


Indoxyl sulfate and p-cresyl sulfate are protein-bound marker molecules in chronic kidney disease. Recent findings suggest that indoxyl sulfate and p-cresyl sulfate directly contribute to the uremic syndrome. A method for quantification of p-cresyl sulfate and indoxyl sulfate total serum concentrations was developed. We used sodium octanoate as competitor to replace non-covalent binding of p-cresyl sulfate and indoxyl sulfate to albumin. Total, within-run, between-run and between-day imprecision for indoxyl sulfate and p-cresyl sulfate were all below 6%. The limit of quantification was 3.2microM for both analytes. Recovery, tested in hemodialysis patients, was 102% for indoxyl sulfate and 105% for p-cresyl sulfate. Deming regression demonstrated good agreement for indoxyl sulfate between this new method and an external HPLC method. Method comparison for p-cresyl sulfate of the new method with our in-house GC-MS method demonstrated good agreement, whereas method comparison with an external HPLC method revealed a small proportional bias. Sodium octanoate binding competition is a novel sample preparation that allows for direct quantification of indoxyl sulfate and p-cresyl sulfate.

Publication types

  • Evaluation Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Albumins / metabolism*
  • Caprylates / chemistry*
  • Chromatography, Liquid / instrumentation
  • Chromatography, Liquid / methods*
  • Cresols / blood*
  • Fluorescence
  • Humans
  • Indican / blood*
  • Indican / urine*
  • Kidney Diseases / blood
  • Kidney Diseases / urine
  • Protein Binding
  • Sensitivity and Specificity
  • Sulfuric Acid Esters / blood*


  • Albumins
  • Caprylates
  • Cresols
  • Sulfuric Acid Esters
  • 4-cresol sulfate
  • Indican
  • octanoic acid