Search Results

You are looking at 1 - 6 of 6 items for

  • Author or Editor: D. Chehimi Ben Hassen x
Clear All Modify Search

Abstract  

The AgPO3−Pr(PO3)3 system has been studied for the first time by differential thermal analysis, X-ray diffraction and IR spectroscopy. The system shows one compound AgPr(PO3)4 which melts in a peritectic decomposition at 1069 K. An eutectic appears at 761 K. AgPr(PO3)4 belongs to the monoclinic system with space group P2t/c,Z=4. The parameters of the unit cell are:a=12.000(9),b=13.177(4),c=7.046(5) Å and β=123o,81(6),Z=4. Its IR absorption spectrum is typical of chain phosphates.

Restricted access

Abstract  

The thermodynamic exploitation of the solid–liquid equilibria in the MIPO3–Pb(PO3)2, MIPO3–Cu(PO3)2 and MIPO3–Ce(PO3)3 systems (with M I=Li, Na, K, Rb, Cs, Ag, Tl) is carried out using a semi-empirical equation of the liquidus curves already used with success for similar binary systems. The enthalpy of fusion is calculated for each pure polyphosphate on the assumption that the liquid solution is ideal and only formed by MIPO3 and M(PO3)q entities (q=2 for Pb and Cu, q=3 for M=Ce). In the most binary systems, a wide difference between the calculated values of the melting enthalpies of these polyphosphates and the measured ones determined from the DTA curves, was observed. This difference is probably due to the existence of some molecular associations in the liquid phase. The enthalpy of fusion of each terminal phase was then recalculated on the assumption that the liquid contains a molecular association of the type of MI pnMn(PO3)n(q+p) in the region of the diagram rich in MIPO3 or a molecular association of the type of MI nMnp(PO3)n(qp+1) in the region rich in M(PO3)q (q=2 for Pb and Cu, q=3 for M=Ce). In this case, the obtained values are in good agreement with experimental determinations.

Restricted access
Authors: F. Chehimi-Moumen, D. Ben Hassen-Chehimi, M. Ferid and M. Trabelsi-Ayadi

Abstract  

The preparation of a new acid lanthanide diphosphate is reported. The acid praseodymium diphosphate, obtained as a trihydrate salt, is investigated by chemical analysis, X-ray powder diffraction and IR spectroscopy. The study of the thermal behavior of HPrP2O7·3H2O shows that its dehydration begins at 367 K. A scheme of its decomposition is proposed.

Restricted access
Authors: F. Chehimi-Moumen, P. Llewellyn, F. Rouquerol, G. Vacquier, D. Ben Hassen-Chehimi, M. Ferid and M. Trabelsi-Ayadi

Summary  

The aim of this work is the optimization of the preparation of anhydrous gadolinium hydrogen phosphate with good fluorescence properties. The products obtained by dehydration of gadolinium hydrogen phosphate trihydrate depend on the conditions chosen for the thermal treatment. For this reason, the dehydration was followed by Constant Rate Thermal Analysis whilst strictly controlling the water vapour pressure above the sample. Intermediate samples, obtained during dehydration were characterised by IR spectroscopy and X-ray diffraction. It has thus been shown that the thermal pathway taken for the dehydration depends on the water vapour pressure above the sample in the region from 10-2to 5 mbar. Under the lowest water vapour pressure (510-3mbar), the elimination of the crystallization water is carried out in a continuous way and produces a quasi-amorphous intermediate. Under higher water vapour pressure (5 mbar), well crystallized intermediate products are obtained. The results obtained suggest that the trihydrate contains zeolitic water which confirms a prior structural study.

Restricted access
Authors: M. Férid, D. Ben Hassen-Chehimi, N. Kbir-Ariguib and M. Trabelsi-Ayedi

Abstract  

The NaPO3−Pr(PO3)3 system was studied by microdifferential thermal analysis (DTA), IR and X-ray diffraction spectroscopies. The only new compound observed in the system is NaPr(PO3)4, which melts incongruently at 1149 K. A eutectic appears at 5% Pr(PO3)3 at 901 K. The new compound NaPr(PO3)4 was characterized by means of powder X-ray diffraction and IR absorption spectroscopy. NaPr(PO3)4 is a NaLa(PO3)4 isotype; it crystallizes in the monoclinic system P21/c witha=12.328(7),b=13.130(5),c=7.231(5) Å, β=126°, 18(5),Z=4,V=945 Ȧ3.

Restricted access

An accurate, sensitive, and reproducible high-performance liquid chromatographic method with diode array detection has been developed for simultaneous determination of erythromycin, clarithromycin, and azithromycin residues in fish muscles. Analysis was carried out using a Shodex Asahipak high-performance liquid chromatography (HPLC) column, monitoring was at 210 nm and a mobile phase consisting of a mixture of acetonitrile and phosphate buffer (pH 11 ± 0.05) in the ratio of 60:40 (v/v). Solid-phase extraction method was used in samples extraction and purification. Recoveries were in the range 72.0–92.2% with relative standard deviation (RSD) from 2.3% to 8.3%. This method was validated for fish muscles in aquaculture following the commission decision 2002/657/EC criteria. It is demonstrated that the new method is robust for detection and quantification of the three macrolides residues. Decision limit (CCα) was from 214 to 228 μg/kg and capacity of detection (CCβ) was from 228 to 256 μg/kg.

Open access