Two Lipoxidase Methods for Measuring cis,cis-Methylene Interrupted Polyunsaturated Fatty Acids in Fats and Oils : Collaborative Study

Abstract

Two methods for measuring the cis, cis methylene interrupted polyunsaturated fatty acids (cis, cis-PUFA) content of fats and oils were compared collaboratively. The methods evaluated were one proposed by the Food and Drug Administration (Method I) and one used by industry (Method II). Analyses of variance between methods and samples and between laboratories and methods showed similar select differences significant at the 95% level (P < 0.05) for both methods. The reproducibility standard deviations were lower with Method II for 3 of the 5 samples, but equally higher than with Method I for 2 other samples. The repeatability standard deviation for one of the oils was significantly higher for Method II but were significantly higher for Method I for 2 other oils. Over all of the samples, the 2 methods gave similar results and there was no overall statistical difference in the performance.

Lipid Geometrical Isomerism: From Chemistry to Biology and Diagnostics

“…UV spectroscopy is also used to detect the formation of conjugated systems during chemical or enzymatic isomerization of fatty acid double bonds. , Conjugated double bonds in fatty acids give rise to a series of broad bands at successively higher wavelengths (Table ). Different geometrical isomers have slightly different spectra, where the greater is the number of trans -double bonds, the higher is the extinction coefficient and the shorter are the wavelengths of the band maxima . The differences in the absorption maxima for the geometric isomers are so subtle that they would not likely be discernible in biologically or chemically produced fatty acid isomer mixtures.…”

“…Different geometrical isomers have slightly different spectra, where the greater is the number of trans-double bonds, the higher is the extinction coefficient and the shorter are the wavelengths of the band maxima. 119 The differences in the absorption maxima for the geometric isomers are so subtle 116 that they would not likely be discernible in biologically or chemically produced fatty acid isomer mixtures.…”

Youden Two-Sample Method

“…Collaborative test on the count of Escherichia coli [35] Proficiency test for the determination of heavy metals in mineral feed. The importance of correctly selecting the certified reference materials during method validation [36] Evaluation tools to understand statistical methods related to the z-score for use in proficiency testing by interlaboratory comparisons [37] Evaluation of learning outcomes in quantitative analysis lab using Youden plots [38] State of the art with respect to the selection and use of proficiency testing schemes and the interpretation of results and evaluations given in proficiency testing schemes [39] Performances of analytical methods for atmospheric deposition and soil analysis assessed through intercomparison exercises [40] HIV external quality assessment (EQA) results by the KCDC from the 17 HIV testing laboratories that also performed HIV-1 western blot testing of the 585 laboratories [41] Second interlaboratory exercise on non-steroidal anti-inflammatory drug analysis in environmental aqueous samples [42] Statics and chemometrics for analytical chemistry [7] A proficiency testing scheme was developed for a limited number of analytical laboratories participating in the analysis of natural water in Israel [43] Proficiency test for heavy metals in feed and food in Europe [44] A multilaboratory proficiency testing programme was conducted by the National Accreditation Board for Testing and Calibration Laboratories (India) and coordinated by the Institute of Pesticide Formulation Technology.…”

“…The experimental systems selected first for gaining experience and training in the application of the method have been the determination of polyunsaturated fatty acids in fats and oils [35], total blood cholesterol [36] and aspirin in pharmaceutical preparations [37], i.e. food and clinical and pharmaceutical applications, respectively.…”

“…Again, the data from laboratory 1 were rejected because of a mistake; those from laboratories 11 and 12 are listed but were not used (10.3 and 10.5 g/100 g, respectively, for sample X and 29.6 and 10.1 g/100 g, respectively, for sample Y), as they lie beyond the set limit [35] in the calculations.…”