Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

    We have a manual that explains all the features 

Record number 407617
Title Accurate determination of the Ca2+ activity in milk-based systems by Ca-ISE: Effects of ionic composition on the single Ca2+ activitiy coefficient and liquid junction potentials
Author(s) Gao, R.; Leeuwen, H.P. van; Valenberg, H.J.F. van; Boekel, M.A.J.S. van
Source Food Chemistry 129 (2011)2. - ISSN 0308-8146 - p. 619 - 623.
Department(s) Product Design and Quality Management Group
Physical Chemistry and Colloid Science
Publication type Refereed Article in a scientific journal
Publication year 2011
Keyword(s) selective electrode - calcium-ion - ultrafiltrate
Abstract Calcium ion selective electrode (Ca-ISE) was found to underestimate the actual Ca2+ ion activity in simulated milk ultrafiltrate (SMUF) and milk. It is shown that the ionic compositional difference between conventional calibration solutions and milk type samples had a significant effect on the single Ca2+ activity coefficient, which generates the erroneous estimate of Ca2+ activities in SMUF and milk. This study tests new standards with ionic profiles similar to SMUF, aiming at the reduction of the errors generated by the compositional difference between conventional standards and milk samples. As a result, the new standards showed a significant improvement in the accuracy of Ca2+ activity and Ca2+ activity coefficient over the conventional standards. The systematic error is reduced from 20% to 5% for SMUF and from 44% to 15% for milk. In addition, the new standards generate liquid junction potentials that are practically insignificant
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