Partition number

The elution order depends on the increasing partition number (PN) defined as... 

RP-HPLC with nonaqueous solvents and UVD at 246 nm was developed for the determination of low level POVs of vegetable oils. These measurements are specific for conjugated diene peroxides derived from vegetable oils with relatively high linoleic acid content. These measurements may be supplemented by nonspecific UVD at 210 nm and ELSD for detection of all eluted species. The elution sequence of the triglycerides in a nonaqueous RP-HPLC is linearly dependent on the partition number of each species, Vp, which is defined as = Nq — 2Ni, where Nq is the carbon number and is the double bond number. In the case of hydroperoxides = Nq — 2Nd — Vhpo, where Vhpo is the number of hydroperoxyl groups in the molecule (usually 1 for incipient POV). For... 

Particle emissions, diesel fuel additive, 624 Partition number, conjugated dienes, 671 Pasteurization, lactoperoxidase, 612, 631, 634 Paterno-Buchi triplet 1,4-diradical, 290-1 PCPO see Bis(pentachlorophenyl) oxalate Pentacoordinate silyl peroxides, 808-10 Pentacosane, thermal oxidation, 685 O -Pentafluorobenzylhydroxyamine, aldehyde determination, 670... 

The IUPAC Commission on Oils, Fats and Derivatives undertook the development of a method and collaborative study for the determination of triglycerides in vegetable oils by liquid chromatography. Three collaborative studies were conducted from 1985 to 1987. Refinements were made in the method after the first collaborative study, and the second and third collaborative studies demonstrated that the method produces acceptable results. Materials studied were soybean oil, almond oil, sunflower oil, olive oil, rapeseed oil, and blends of palm and sunflower oils and almond and sunflower oils. Six test samples were analyzed by 18 laboratories from 11 countries in the second study 4 test samples were analyzed by 16 laboratories from 12 countries in the third study. The method for the determination of triglycerides (by partition numbers) in vegetable oils by liquid chromatography was the first action adopted by AOAC INTERNATIONAL as an IUPAC-AOC-AOAC method (103). 

Fatty acids have so far been analysed by CEC either as the free acids or as phenacyl- or methyl esters. Aqueous acetonitrile (50 mM) at pH 6 (9 1 v/v) was shown to be the optimal mobile phase [191]. It is generally known that in reversed-phase chromatography free fatty acids and fatty acid methyl esters separate according to the partition number, which is defined as the carbon number minus twice the number of double bonds. A double bond reduces the retention time by the equivalent... 

Firestone, D. (1994) Liquid chromatographic method for determination of triglycerides in vegetable oils in terms of their partition numbers summary of collaborative study. J. AOAC Int., 77, 954—957. 

The N-alkylation reaction represents a bifurcation of the normal alkene epoxidation reaction cycle and, therefore, N-alkylation is a suicide event that leads to catalytic inhibition in the native system. With synthetic tetraarylporphyrins that mimic the N-alkylation reaction, the use of halogen-substituted catalysts that are stable toward oxidative degradation (26, 27) provide the most useful model systems because the heme model remains intact for a significantly greater number of turnovers than the partition number. The partition number is the ratio of epoxidation cycles to N-alkylation cycles, i.e., N-alkyl porphyrins are formed before the heme is oxidatively destroyed. 

Reversed-phase (RP) TLC is less popular and has been applied so far only for the resolution of fatty acids and triacylglycerols. It is based on the distribution of lipid molecules between a nonpolar stationary phase and a relatively polar mobile phase. Lipids are, therefore, separated according to their overall polarity, expressed by the partition number (PN). PN relates the migration of a component to the total number of carbon atoms, CN (in the acyl residues only), and the total number of double bonds, n, so that PN = CN - In. The higher the PN, the stronger is the component retained in the nonpolar layer (the lower the Rf value). 

The relative retention time of a given component has been defined in terms of an "equivalent carbon number" (ECN) or "partition number" value, defined as the actual number of carbon atoms in the aliphatic residues (CN) less twice the number of double bonds (n) per molecule (the carbons of the glycerol moiety are not counted for this purpose), i.e. 

Partition number" (PN), given by the number of carbon atoms in the... 

Figure 41. A schematic representation of the SOPHE partition scheme (a) SOPHE partition grid in which the three sets of curves are described hy Eq. (8) SOPHE partition number N equals 10 (b) subpartitioning into smaller triangles ean be performed by using either Eq. (8) or alternatively the points along the edge of the triangle are interpolated by the eubie spline interpolation method and each point inside the triangle is linearly interpolated three times and an average is taken.

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