NMR Spectroscopy: Determination of Peroxide Value in Vegetable and Krill Oil by Using Triphenylphosphine as Tagging Reagent

Abstract

Hydroperoxides are formed as the primary product during lipid oxidation, being analyzed as the peroxide value to detect the degradation level of oils and fats. As an alternative to the classical titration method according to Wheeler, a 1 H-{ 31 P} decoupled NMR method is developed using triphenylphosphine (TPP) as a tagging agent. TPP reacts with peroxides to form TPP oxides. The quantification of the peroxide value is performed by comparing the amount of reacted TPP oxide and non-reacted TPP. This approach eliminates the requirement for an additional internal standard. Low-oxidized oils (peroxide value < 3 meq/kg) and high-oxidized oils with peroxide values of 150 meq/kg are precisely quantified with an relative standard deviation (RSD) of 4.90% and 0.16%, respectively. A total number of 108 oil samples are examined using the newly-developed 1 H-{ 31 P} decoupled NMR method, indicating the applicability for vegetable oils and krill oils. Practical Applications: The developed NMR method is applicable for the determination of the peroxide value in vegetable, marine and krill oils presenting a powerful alternative for the Wheeler titration method.

A Comprehensive Study for Determination of Free Fatty Acids in Selected Biological Materials: A Review

“…The FFA value of the VOs and fruit oil could be easily detectable in the range of 2.2–2.4 ppm in the form of triplets, and carboxyl content could be measurable from 11 to 12 ppm in the form of a multiplet [ 8 , 95 , 96 ], whereas a strong signal could cause overlapping in this method [ 8 , 14 ]. For the acidic property determination of the VO sample, the 1 H NMR method presents a spectral width of 24 ppm, number of scans of 32, relaxation delay of 1 s, and acquisition time of 5.45 s [ 97 ]. Schripsema et al [ 98 ] investigated aqueous extracts of butter and margarine samples at 25 °C, with a spectral width of 10 ppm and a relaxation delay of 4 s, and the results were precise and comparable with GC and HPLC [ 98 ].…”

“…Also, this method is effective for edible, waste, and recycled oil analysis [ 14 ]. For the analysis of VO, the 31 P NMR method is run with a spectral width of 100 ppm, number of scans of 512, relaxation delay of 10 s, and acquisition time of 6.50 s [ 97 ]. The FFA values of VOs could be visible at 134–136.5 ppm, glycerol contents at 146.5–148.5 ppm [ 14 , 100 ], and phospholipids could be visible at 0.4–(−1) ppm [ 99 , 101 ].…”

Simultaneous Determination of the Saponification Value, Acid Value, Ester Value, and Iodine Value in Commercially Available Red Fruit Oil (Pandanus conoideus, Lam.) Using 1H qNMR Spectroscopy

“…However, some of these methods still have weaknesses because they require chemical modification of the sample for analysis, as described by Guillen et al (2003). However, some qNMR methods have recently been reported for the characterization and quality assessment of lipids and oils (Guillén and Ruiz 2003a, b;Skiera et al 2014;Hafer et al 2020).…”

Assessment of &lt;i&gt;Balanites aegyptiaca&lt;/i&gt; and &lt;i&gt;Sesamum indicum&lt;/i&gt; Artisanal Oils Quality and Vitamin Contents

“…Oils and fats represent valuable products which are highly promoted for their nutrient content and contribution to human diet as well as in numerous industrial and pharmaceutical applications, therapeutic and cosmetic products [1]. Oils are products obtained from vegetal species consisting of approximately 95% triacylglycerols and 2-5% non-glyceride compounds (phospholipids, carbohydrate traces, methyl ketones, free fatty acids and their degradation products) [2].…”