Authors: Paul W Johns Steven R Dimler Julie J Watson Maryann Tigner Paul F Caskey
Publish Date: 2015/11/17
Volume: 9, Issue: 6, Pages: 1754-1762
Abstract
A method for the determination of soluble calcium and soluble phosphorus in commercial milled hydroxyapatite is described The Ca and P residing in the supernatant after highspeed centrifugation of a 100 w/w suspension in pH 68 HEPES buffer are quantified by cresolphthalein and phosphomolybdenum complex colorimetry respectively Method performance has been defined by assessments of linearity r 2 averages for Ca and P respectively were 0998 ± 0001 n = 15 and 1000 ± 0000 n = 15 intermediate precision soluble Ca rsd = 12 at 0500 mg/g to 05 at 804 mg/g soluble P rsd = 18 at 00526 mg/g to 05 at 35 mg/g soluble Ca/P molar ratio rsd = 18 at 63 to 05 at 188 n = 3 days and accuracy spike recovery average = 997 ± 36 for soluble Ca and 978 ± 06 for soluble P n = 4 A hydroxyapatite milled to successively smaller particle sizes exhibited increases in soluble Ca P and Ca/P as the particle size median decreased from 2339 to 1375 μm Application of the method to seven commercial lots of milled hydroxyapatite found soluble Ca from 0118 to 198 of theoretical Ca soluble P from 0386 to 180 of theoretical P and soluble Ca/P molar from 0258 to 354 The interaction of these lots with sodium caseinate in a simulated retort model was strongly correlated with their soluble Ca concentration r 2 09 The method provides a simple and inexpensive means for identifying potentially problematic lots of milled hydroxyapatite ie lots with soluble Ca and P levels sufficiently high to adversely affect the physical stability of retort sterilized milkbased liquid nutritional productsPaul W Johns declares that he has no conflict of interest Steven R Dimler declares that he has no conflict of interest Julie J Watson declares that she has no conflict of interest Maryann Tigner declares that she has no conflict of interest Paul F Caskey declares that he has no conflict of interest
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