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Igarashi T, Aursand M, Sacchi R, Paolillo L, Nonaka M, Wada Y, Arata Y, Bildsoe H, Falcigno L, Fauhl C, Guillou C, Halvorsen J, Honma E, Ijuuin Y, Kushida K, Martin GJ, Miyake Y, Optum OI, Oshima Y, Remaud G, Retif M, Robins R, Satake M, Shimidzu N, Tsuchiya F, Watanabe K, Watanuki C. Determination of Docosahexaenoic Acid and n-3 Fatty Acids in Refined Fish Oils by H-NMR Spectroscopy: IUPAC Interlaboratory Study. J AOAC Int 2019. [DOI: 10.1093/jaoac/85.6.1341] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
Abstract
A high-resolution proton nuclear magnetic resonance (NMR) method for determining the concentration (mg/g) of docosahexaenoic acid (DHA), the molar proportion (mol%) of DHA, and the molar proportion of total n-3 fatty acids in fish oils was validated by an IUPAC interlaboratory study (the Commission VI-6 on Oils, Fats, and Derivatives WG 3/98). Thirteen laboratories from 5 countries tested 6 pairs of blind duplicate fish oils: a refined tuna oil, 2 extracted tuna oils, an extracted bonito oil, an extracted salmon oil, and an extracted sardine oil ranging from 9 to 30 mol% DHA and from 20 to 35 mol% n-3 fatty acids. Before 1D-proton NMR measurements with 300–500 MHz instruments, oil samples were weighed and diluted with deuterochloroform solution containing ethylene glycol dimethyl ether as internal standard. To achieve precise performance, a detailed procedure for signal area measurement was described in the protocol, and all participants were instructed about the critical importance of following the protocol. Statistical performances with invalid and outlier data removed were as follows: repeatability relative standard deviations (RSDr) ranged from 0.91 to 2.62% and reproducibility relative standard deviation (RSDR) ranged from 1.73 to 4.27% for DHA concentration (mg/g); RSDr ranged from 0.39 to 2.06%, and RSDR ranged from 0.59 to 3.46% for mol% DHA; RSDr ranged from 0.23 to 0.90% and RSDR ranged from 0.85 to 2.01% for mol% total n-3 fatty acids. The method is expected to be recommended by IUPAC.
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Affiliation(s)
- Tomoji Igarashi
- Japan Marine Oil Association, 32-7 Motoyoyogi-cho, Shibuya-ku, 151-0062, Tokyo, Japan; Japan Food Research Laboratories, Tama Laboratory, 6-11-10 Nagayama, Tama-shi, 206-0025, Tokyo, Japan
| | - Marit Aursand
- SINTEF, Division of Applied Chemistry, Fisheries and Aquaculture, N-7034, Trondheim, Norway
| | - Raffaele Sacchi
- University of Naples Federico II, Department of Food Science, Parco Gussone, 80055 Portici, Italy
| | - Livio Paolillo
- University of Naples Federico II, Department of Chemistry, via Mezzocannone 4, 80134 Naples, Italy
| | - Michio Nonaka
- Japan Marine Oil Association, 32-7 Motoyoyogi-cho, Shibuya-ku, 151-0062, Tokyo, Japan
| | - Y Wada
- Tokyo University of Fisheries, Department of Food Science and Technology, 4-5-7 Konan, Minato-ku, 108-8477, Tokyo, Japan
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Uehara H, Ijuuin Y, Morino Y, Kamidate T, Nakamura A, Imai H. Continuous ammonia monitor using a Stark microwave cavity resonator. Rev Sci Instrum 1980; 51:334. [PMID: 18647062 DOI: 10.1063/1.1136213] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
An ammonia monitor has been made by using a rectangular Stark microwave cavity tightly coupled through an iris to a Gunn oscillator. The Stark electrode installed inside the cavity is provided with a 100 kHz sinusoidal modulation voltage and a dc sweep voltage. The oscillation of the Gunn diode is tuned with the coupled Stark cavity to a frequency near a J,K=3,3 transition (23870.1 MHz) of ammonia. By fixing the Stark dc bias to a voltage which gives a peak intensity of the derivative output of the electric-resonance signal, ammonia is continuously monitored. An extremely good long-term stability is obtained. The noise level corresponds to 0.08 ppm of ammonia.
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Affiliation(s)
- H Uehara
- Sagami Chemical Research Center, Nishi-Ohnuma, Sagamihara-shi, Kanagawa 229, Japan
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