Effect of pH and (Ca/P, Mg/P) molar ratios on the crystalline structure of phosphates obtained from artificial urine


B. Zahraoui1, H. M. Djellouli2, S. Taleb2*, A. Cheriti1

1Phytochemistry & Organic Synthesis Laboratory- University of Bechar, 08000, Bechar, Algeria.

2 Materials & Catalysis Laboratory- Faculty of Pure Sciences - Djillali Liabès university- W22000- Sidi Bel-Abbès, Algeria.

* Corresponding author. E-mail: safiatal@yahoo.fr    

Received: 07 October 2012; revised version accepted: 04 March 2013



     The crystalline structure of the calcium phosphate precipitates which are formed in artificial urine depend on the physico-chemical conditions, particularly, pH and mineral composition. The objective of this study was to determine, using mineral solutions, the effects of pH and concentrations of phosphate, calcium and magnesium on the crystalline structure of phosphate precipitates. Experiments were carried out at 37°C with 34.27 mM of phosphate and five Ca/P and Mg/P molar ratios. The initial pH was kept constant during a reaction time of 3 h. After filtration of the suspensions, the mineral compositions of filtrates were characterized using infrared spectroscopy, and X-ray diffraction. At acidic pH (6.0 and 6.5), the precipitates consist mainly of Brushite (DCPD), but at basic pH (7.5 and 8.0), struvite (STR) is dominant, whereas at neutral pH, DCPD and STR precipitate simultaneously. The mineral analysis showed the formation of DCPD as the main crystalline phase for the Ca/P 0.08. But for molar ratios greater than or equal to 0.16, the FTIR analysis of the precipitates revealed the formation of octacalcium phosphate (OCP). Also, for Mg/P molar ratios greater than or equal to 0.16, the precipitate formed consists of a mixture of DCPD and STR.


Keywords: Solubility; Nucleation; Phosphates Crystalgrowth, Urinary crystals.


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