Determination of citric acid based on inhibition of the crystal growth of calcium fluoride.
Inhibition of the growth of calcium fluoride crystals in the presence of citrate was followed using a kinetic-potentiometric technique and a calcium ion-selective electrode, and as a consequence, a method for the determination of citrate in the range 0.5-2.4 micrograms ml-1 has been developed. The method was successfully applied to the determination of citrate contained in pharmaceutical products and urine. Urine analysis requires prior separation of phosphate, sulphate and magnesium(II). Elimination of these interferences was studied and accomplished using precipitation processes. Magnesium and phosphate were jointly eliminated in basic media by the addition of ammonium ions. Phosphate and sulphate were eliminated with barium(II). Phosphate was also eliminated as a lithium salt.
Grases
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Department of Chemistry, University of Balearic Islands, Palma de Mallorca, Spain.
Costa-Bauzá
A
A
March
J G
JG
D002124:Calcium Fluoride; D002951:Citrates / Q000032:analysis* / Q000652:urine; D019343:Citric Acid; D003460:Crystallization; D006801:Humans; D011199:Potentiometry
D002951:Citrates; D019343:Citric Acid; D002124:Calcium Fluoride