Analysis of indoxyl sulfate in biological fluids with emphasis on sample preparation techniques: A comprehensive analytical review

The uremic toxin indoxyl sulfate (IS) has been related to the development of various medical conditions notably chronic kidney disease (CKD). Hence, quantification of this biomarker in biological fluids may be a diagnostic tool to evaluate renal system functionality. Numerous analytical methods including liquid chromatography, gas chromatography, spectroscopy, and electrochemical techniques have since been used to analyze IS in different biological fluids. The current review highlights the relevant studies that assessed IS with a special focus on sample preparation, which is essential to reduce or eliminate the effect of endogenous components from the matrix in bioanalysis.