Processing Contaminants in Edible Oils by Shaun Macmahon;Jessica K. Beekman; & Jessica K. Beekman

Author:Shaun Macmahon;Jessica K. Beekman; & Jessica K. Beekman [Неизв.]
Language: eng
Format: epub
ISBN: 9780128200681
Publisher: Elsevier Ltd.
Published: 2022-01-28T03:08:36+00:00

Granvogl and Schieberle

Considering the impact of using the appropriate standard in direct analysis, Granvogl and Schieberle developed a stable isotope dilution analysis (SIDA) for the determination of seven glycidyl esters (esters of lauric, myristic, palmitic, stearic, oleic, linoleic, and linolenic acid) by LC-MS including the synthesized corresponding [2H]- or [13C]-labeled isotopologues as internal standards [5].

Sample preparation was based on fractionation on silica gel 60 containing 7% of water and stepwise elution of the analytes with n-pentane/diethyl ether (95/5, v/v). The fraction containing the glycidyl esters was collected, evaporated to dryness, and reconstituted in acetonitrile. For LC separation, an HPLC surveyor chromatography system equipped with a pentafluorophenylpropyl stationary phase (Luna 3u PFP, 150mm×2.0mm I.D., 3 μ[mu]m, 100Å; connected to a 4mm×2.0mm I.D. pre-column; both Phenomenex) and a water/acetonitrile (with 0.1% of formic acid) mobile phase gradient was chosen. MS detection was performed by APCI+ in SIM mode using a triple quadrupole tandem mass spectrometer (TSQ Quantum Discovery, Thermo Scientific, Dreieich, Germany).

In a further development, sample clean-up via column chromatography, which required large volumes of solvent, was replaced by preparative HPLC using a C8 Ascentis column (250mm×4.6mm I.D., 5 μ[mu]m; Supelco, Sigma-Aldrich, Bellefonte, PA) and isocratic elution with methanol/2-propanol (95/5, v/v; 5 mL/min) [6]. Finally, Granvogl and Schieberle included two further glycidyl esters into their approach, namely glycidyl caprylate and glycidyl caprinate, which are potentially important for palm kernel oil and coconut oil, again in combination with their corresponding labeled isotopologues used as internal standards, resulting in an analytical approach including nine individual glycidyl esters for quantitation [7].

First, this direct method developed by Granvogl and Schieberle was applied to the quantitation of glycidyl esters in several avocado oil and refined olive oil samples (Table 5.8), as well as to a wide variety of edible oils (Table 5.9).

Furthermore, the improved method by Granvogl and Schieberle [6] was compared to two indirect quantitation methods (Table 5.10): the SGS 3-in-1 method [18,19] and the method of the German Society for Fat Science (DGF C-III 18 (09)) [20]. The SGS 3-in-1 method is based on alkaline catalyzed release of glycidol, transformation of glycidol to 3-monobromo-1,2-propanediol, derivatization with phenylboronic acid, and analysis by GC-MS. Analysis of seven samples of different types of oil (two avocado oils, one safflower oil, one palm oil, one triacylglycerol-rich oil, and two diacylglycerol-rich oils) showed good correlation for all samples for the developed direct method and the indirect SGS 3-in-1 method [18,19].

Table 5.8

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