Collaborative test of determination of iodine value in fish oils. 1. Reaction time and carbon tetrachloride or cyclohexane as solvents |
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Authors: | Stuart M Barlow Anthony P Bimbo Eric L Miller Snorri Thorisson D E Walters |
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Affiliation: | 1. International Fishmeal and Oil Manufacturers Association, AL3 4PA, St. Albans, United Kingdom 2. Zapata Protein (USA) Inc., 22539, Reedville, Virginia 4. Department of Clinical Veterinary Medicine, University of Cambridge, CB3 0ES, Cambridge, United Kingdom 5. Icelandic Fisheries Laboratory, 121, Reykjavik, Iceland 7. The Babraham Institute and Churchill College, University of Cambridge, CB3 0DS, Cambridge, United Kingdom
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Abstract: | Twenty-two laboratories participated in a collaborative test to determine the iodine value (IV) of eight samples of fish oil
(four with IV<150, four with IV>150) with either carbon tetrachloride (AOCS Official Method Cd 1–25) or cyclohexane (AOCS
Recommended Practice Cd 1b-87) as solvent and either 1 or 2 h of reaction time. Laboratories received coded duplicate samples
(hidden duplicates) and carried out duplicate determinations on each oil by each solvent-time combination (open duplicates).
Replacing carbon tetrachloride with cyclohexane resulted in a lower IV (P<0.001). The decrease averaged 1.6 IV units for low-IV oils and 3.8 IV units for high-IV oils; this difference in response
of 2.2 IV units between low- and high-IV oils was significant (P<0.001). Increasing the reaction time had a relatively small effect (0.34±0.18). There was no interaction of reaction time
with solvent or oil type. Cyclohexane caused emulsions, which made it difficult to titrate residual iodine and thus increased
the variability of the determination. The repeatability standard deviations (s
r
), based on hidden duplicates, for 1-h reaction time with carbon tetrachloride and cyclohexane were 2.17 and 3.35, respectively.
The corresponding reproducibility standard deviations were 2.73 and 4.53. |
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Keywords: | Carbon tetrachloride collaborative test cyclohexane fish oil iodine value |
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