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Determination of chloride, nitrate and calcium ions in sugar with ion selective‐electrodes
Author(s) -
KARIM M. T.,
NAJIB F. M.,
MOHAMMAD M. S.
Publication year - 1986
Publication title -
international journal of food science and technology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.831
H-Index - 96
eISSN - 1365-2621
pISSN - 0950-5423
DOI - 10.1111/j.1365-2621.1986.tb00394.x
Subject(s) - chemistry , ashing , chloride , ion , calcium , sugar , calcium nitrate , nitrate , inorganic chemistry , calibration curve , ion selective electrode , standard solution , analytical chemistry (journal) , chromatography , detection limit , selectivity , biochemistry , organic chemistry , physics , quantum mechanics , catalysis
Chloride, nitrate, and calcium ion‐selective electrodes were tested and found satisfactory for the determination of the corresponding ions in highly refined white sugar, molasses and other impure sugar samples at different stages of sugar manufacturing or refining. The interferences by Br − and I − ions in Cl − determination were eliminated by oxidation with 3 M HNO 3 and passing air to remove the free Br 2 and I 2 formed. The Cl − concentration was then determined with a chloride‐selective electrode against a calibration curve. Chloride should not be determined by ashing sugar, since this causes high losses of Cl − . It was found that NO 3 − and free Ca 2+ ions could be determined directly in the sugar solution against corresponding calibration curves. Total calcium was determined after ashing of sugar samples. The ash was dissolved in 0.1 M HCl and passed through an anion exchange resin to remove PO 3− 4 and SiO 2− 3 ions, and Ca 2+ was determined as before. Bound calcium was obtained by subtracting values of free from total calcium. Determination of bound calcium was useful to monitor the process of liming. For comparison, the three ions were also determined with acceptable precision without removing interfering ions using the method of standard addition and Gran's plot. The errors of determination for both direct and standard addition techniques were 3% for Cl − and NO − 3 and 1–5% for Ca 2+ .