Validation by image analysis of a turbidimetric method to study calcium oxalate crystallization.

Numerous studies of calcium oxalate crystal formation have been carried out in the past two decades. In the present study, experiments were carried out to validate a turbidimetric method allowing to assess the calcium oxalate crystallization process. This method is quick and reproducible and can be used to quantify the inhibition of calcium oxalate crystal growth by various compounds. An experimental method of validation has been developed, which consisted in filtering solutions pure or containing modifiers at given crystallization times, photographing the filters used on scanning electron microscopy and analyzing the images using mathematical methodology. The results obtained through image analysis, namely crystal density (mean particle number per unit volume) and mean area, were correlated with the turbidimetric parameters. This finding was consistent with the qualitative examination of the photographs. Moreover, the morphological differences in crystals observed on the photographs were confirmed by the calculated length/width ratio. One can therefore assume that inhibition of calcium oxalate crystal growth is at least, partly explained by surface adsorption phenomena, which may add to complex formation.