Precision null-point potentiometry direct microdetermination of iodide in solutions with high chloride concentrations
✍ Scribed by H.V. Malmstadt; J.D. Winefordner
- Book ID
- 102980863
- Publisher
- Elsevier Science
- Year
- 1961
- Tongue
- English
- Weight
- 517 KB
- Volume
- 24
- Category
- Article
- ISSN
- 0003-2670
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✦ Synopsis
Recently precision null-point potentiometric
techniques were developed which pro-vi&d high sensitivity, speed, simplicity and accuracy for the micro determination of chloride in water samplesl, blood serum2 , and solutions obtained by decomposing organic fractions containing chlorinated compound@; and the general principles of the measurement method were presentcd%e. The same general technique is now described for the direct determination of iodide in the presence of large amounts of chloride, as found in brines or iodized salt. In iodized salt the sodium chloride weight usually exceeds the iodide by a factor of TO,OOO to zoo,ooo, and in brines the chloride weight exceccls the iodide by hundreds to thousands of times.
The determination of iodide in brines, iodized salt or similar samples is generally performed by separation of the iodid,e after oxidation and subsequent measurement by titration+8.
The separation is often ncccssary because the high ratio of chloride to iodide invalidates the measurement method. However, it is shown that a separation of iodide from chloride is not necessary by the precision null-point potentiometric technique. Since the measurement is also rapid it is possible to perform a complete analysis in about 3 min, including weighing the sample, addition of reagents, measurement, and calculation of results. THE IODIDE MEASUREMENT METHOD H. V. MALMSTADT, J. I). WINEFORDNER null-point potcntiomctric m&hod. The complctc analysis time is about 3 min. Iodized salt samples containing 5-100 p.p.m. iodide were dctcrmincd with an average deviation IL& than 0.3 p.p.m. and with rclativc errors of about o.5(y0 at IOO p.p.m. and about 5% at 10p.p.m. iodide. The mcasured samples contained I--20 c(g of iodide in zo ml of solution, and thcsodium chloride to iodide weight ratio was as hi@ as 200.00r~ to I. Similar precision and accuracy were ohtaincd for prepared brines containing 10-200 p.p.m. iodide and a wide range of chloride to iodide ratios. %USAMMENFASSUNG Bcschrcibung ciner potcntiomctrischcn Bcstimmung von schr kleinen ivlcnr;cn Jod in Gcgcnwart von grossen Mengcn Chloritl.