Accurate determination of the Ca2+ activity in milk-based systems by Ca-ISE: Effects of ionic composition on the single Ca2+ activity coefficient and liquid junction potentials
| Autor: | H.P. van Leeuwen, R. Gao, M.A.J.S. van Boekel, H.J.F. van Valenberg |
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| Rok vydání: | 2011 |
| Předmět: |
Systematic error
Activity coefficient food.ingredient Laboratorium voor Fysische chemie en Kolloïdkunde calcium-ion Liquid junction potential Analytical chemistry Ionic bonding selective electrode Ionic composition Compositional difference Analytical Chemistry Ion food Skimmed milk Physical Chemistry and Colloid Science VLAG WIMEK Chromatography Chemistry Leerstoelgroep Productontwerpen en kwaliteitskunde food and beverages General Medicine Product Design and Quality Management Group ultrafiltrate Food Science |
| Zdroj: | Food Chemistry 129 (2011) 2 Food Chemistry, 129(2), 619-623 |
| ISSN: | 0308-8146 |
| DOI: | 10.1016/j.foodchem.2011.04.076 |
| Popis: | 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. |
| Databáze: | OpenAIRE |
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