Determination Of Hydroperoxides Research Articles

Incomplete lipid extraction as a possible cause for underestimation of lipid oxidation in emulsions

AbstractLipid oxidation deteriorates the sensory and nutritional quality of food emulsions containing polyunsaturated fatty acids. Classically, different extraction solvents are used as a first step to measure lipid oxidation in emulsions. However, it is unclear how the applied extraction method influences the measured lipid oxidation values. In this work, we systematically examined the performance of common solvent mixtures such as chloroform, methanol, and hexane (or isooctane)–isopropanol on lipid extraction from emulsions stabilized with different emulsifiers (Tween 20 (T20), whey proteins, and pea proteins) and oxidation levels, and how this, in turn, affected the measured hydroperoxide concentrations. Chloroform–methanol was the most effective solvent (lipid yield >93 wt.%). When using hexane–isopropanol, extraction yields were consistently high for T20‐ and pea protein‐based emulsions (>60 wt.%), but in whey protein‐based emulsions, values as low as 26 wt.% were measured. In case of incomplete extraction, hydroperoxide concentrations measured by colorimetric methods need to be corrected for this effect. When using 1H NMR to assess lipid oxidation, the actual amount of extracted lipids is intrinsically taken into account. This highlights not only the importance of the extraction method in determining lipid oxidation in emulsions but also that of the actual analysis method.Practical application: This study highlights that the lipid extraction yield can vary depending not only on the emulsion composition (e.g., type of emulsifier) but also on the oxidative state of the emulsion and the extraction solvent used. If this is overlooked, errors can be made in the hydroperoxide determination. Although these effects can be corrected for, this is not standard procedure, which implies that awareness on this matter should be increased. It is also important to point out that depending on the solvent used, the different lipid classes (including various lipid oxidation products) may be extracted at different levels. Chloroform–methanol should be preferred for extraction of all lipid and lipid oxidation‐derived molecules, including aldehydes.

Elucidating the photodissociation fingerprint and quantifying the determination of organic hydroperoxides in gas-phase autoxidation

Hydroperoxides are formed in the atmospheric oxidation of volatile organic compounds, in the combustion autoxidation of fuel, in the cold environment of the interstellar medium, and also in some catalytic reactions. They play crucial roles in the formation and aging of secondary organic aerosols and in fuel autoignition. However, the concentration of organic hydroperoxides is seldom measured, and typical estimates have large uncertainties. In this work, we developed a mild and environmental-friendly method for the synthesis of alkyl hydroperoxides (ROOH) with various structures, and we systematically measured the absolute photoionization cross-sections (PICSs) of the ROOHs using synchrotron vacuum ultraviolet-photoionization mass spectrometry (SVUV-PIMS). A chemical titration method was combined with an SVUV-PIMS measurement to obtain the PICS of 4-hydroperoxy-2-pentanone, a typical molecule for combustion and atmospheric autoxidation ketohydroperoxides (KHPs). We found that organic hydroperoxide cations are largely dissociated by loss of OOH. This fingerprint was used for the identification and accurate quantification of the organic peroxides, and it can therefore be used to improve models for autoxidation chemistry. The synthesis method and photoionization dataset for organic hydroperoxides are useful for studying the chemistry of hydroperoxides and the reaction kinetics of the hydroperoxy radicals and for developing and evaluating kinetic models for the atmospheric autoxidation and combustion autoxidation of the organic compounds.

Elucidation of Olive Oil Oxidation Mechanisms by Analysis of Triacylglycerol Hydroperoxide Isomers Using LC-MS/MS.

Despite the importance of the insight about the oxidation mechanisms (i.e., radical and singlet oxygen (1O2) oxidation) in extra virgin olive oil (EVOO), the elucidation has been difficult due to its various triacylglycerol molecular species and complex matrix. This study tried to evaluate the mechanisms responsible for EVOO oxidation in our daily use by quantitative determination of triacylglycerol hydroperoxide (TGOOH) isomers using LC-MS/MS. The standards of dioleoyl-(hydroperoxy octadecadienoyl)-triacylglycerol and dioleoyl-(hydroperoxy octadecamonoenoyl)-triacylglycerol, which are the predominant TGOOHs contained in EVOO, were prepared. Subsequently, fresh, thermal-, and photo-oxidized EVOO were analyzed. The obtained results mostly agreed with the previously reported characteristics of the radical and 1O2 oxidation of linoleic acid and oleic acid. This suggests that the methods described in this paper should be valuable in understanding how different factors that determine the quality of EVOO (e.g., olive species, cultivation area, cultivation timing, and extraction methods) contribute to its oxidative stability.

Effect of processing conditions and catalyst type on the thermal oxidative degradation mechanisms and melt stability of metallocene and Ziegler‐catalyzed ethylene‐1‐hexene copolymers

AbstractPolyolefins have traditionally been polymerized via the heterogeneous Ziegler Natta (Z‐N) catalysts since their discovery in the 1950s, but the later developments of the homogeneous single site metallocene/methylaluminoxane (MAO) catalysts have opened the possibility for the synthesis of polyolefin polymers and copolymers (commercialized in the 1990s) with highly defined microstructure and great degree of control of their molecular architecture resulting in some unique beneficial properties compared to their Z‐N counterparts. The main aim of the work reported here was to examine critically the effects of the processing conditions during multipass extrusions on the molecular and rheological characteristics of metallocene‐catalyzed linear low density polyethylene and a Ziegler‐Natta‐based counterpart polymer and on the thermoxidative (in the melt) stability of their melts and their stabilization. Both polymers examined here were based on ethylene‐1‐hexene copolymers and produced by the same manufacturer with similar density and melt index (MI) values. The melt stability and rheological properties of the polymers were determined from melt flow and capillary rheometric measurements. The molecular characteristics were investigated using GPC for molecular weight determination, 13C‐NMR for short chain branching, 1H‐NMR and FTIR for the type and concentration of unsaturation groups, FTIR for carbonyl‐containing compounds and chemical analysis for hydroperoxide determination. The processibility of the two polymers was compared through examination of different processing conditions (die temperatures 210–285°C, screw speeds 50–200 rpm) used for a multipass extrusion process. Further, the effects of the processing conditions on the melt thermoxidation of the differently catalyzed LLDPE polymers were investigated. The results demonstrated that both the catalyst type and the processing conditions have a great effect on both the rheological and the themoxidative behavior of the polymers as well as on the balance between the competing oxidative reactions taking place in the polymer melt, for example, chain scission and crosslinking reactions. The results obtained for the different multipass extrusion conditions of the two polymers have illustrated clearly that the degradation mechanisms during their melt processing are substantially different. The melt degradation route of the Ziegler‐catalyzed polymer was shown to be dominated by chain scission reactions under all the processing conditions examined, and more so at the higher shear rates and temperatures. By contrast, the evidence clearly showed that the metallocene‐catalyzed polymer gave rise to crosslinking reactions that predominated even under the more severe processing conditions, that is, higher temperatures and shear rates.

Outcome of Tobacco Smoking Habit on Lipid Peroxidation and Antioxidant parameters in Anemic Individuals

Introduction: Globally tobacco smoking is considered as a foremost public health problem. Erythrocytes membrane lipids are rich in polyunsaturated fatty acids and the oxidative effects of oxygen on its membrane are greater than other tissues and the condition is heightened by tobacco smoke.Free radicals present in the tobacco increases peroxidation products in blood and vascular tissues are chiefly responsible for harmful effects.
 Objective: The present study was designed to investigate the impact of stress induced by tobacco smoke on lipid peroxidation and antioxidant parameters in patients with anemia.
 Methodology: A hospital-based case-control study was carried out in Kantipur Dental College Teaching Hospital, included 150 tobacco smoking anemic and 150 healthy volunteers. The stress parameter was assessed by the determination of malondialdehyde, lipid hydroperoxide and nitric oxide. The non-enzymatic antioxidants such as vitamins A, C and E and total antioxidant activity and enzymatic antioxidants were catalase, superoxide dismutase and glutathione peroxidase were also determined.
 Result: Hemoglobin level in anemic smokers showed raised level as compared to healthyindividualsbut there was diminished antioxidants status and elevated free radical parameters in anemic smokersdespite their raised hemoglobin status.We found statistically increased malondialdehyde, lipid hydroperoxide and nitric oxide levels and decreased enzymatic and non-enzymatic antioxidant status, thus increasing the oxidative stress.
 Conclusion: The present study showed high concentration of hemoglobin, low status of non-enzymatic antioxidants and high levels of oxidants as compared to controls reflecting the destructive and oxidative effects of tobacco smoke.

Quantification of Hydroperoxides by Gas Chromatography with Flame Ionisation Detection

Hydroperoxides are of great importance in the fields of atmospheric and biological chemistry. However, there are several analytical challenges in their analysis: unknown and usually low UV absorption coefficients, high reactivity, thermal instability, and a lack of available reference standards. To overcome these limitations, we propose a GC-FID approach involving pre-column silylation and quantification via the effective carbon number approach. Four hydroperoxides of α-pinene were synthesized in the liquid phase with singlet oxygen and identified using literature data on isomer yield distribution, MS spectra, estimated boiling temperatures of each isomer (retention time), their thermal stability and derivatisation rate. The developed procedure was used for the determination of hydroperoxides in bottled and autooxidised turpentine. We anticipate that this method could also be applied in atmospheric chemistry, where the reactivity of singlet oxygen could help explain the high formation rates of secondary organic aerosols.

Modification of the Ferrous Oxidation‐Xylenol Orange Method for Determination of Peroxide Value in Highly Pigmented Sea Cucumber Viscera Lipid

AbstractA ferrous oxidation‐xylenol orange (FOX) method was modified to measure the levels of hydroperoxides in highly pigmented sea cucumber (Cucumaria frondosa) viscera lipid. With the FOX method, oil hydroperoxides oxidize Fe(II) to Fe(III) ions, which in turn bind to xylenol orange (XO) to form a complex that has a maximum absorbance at 560 nm. When applied to lipid extracts containing high levels of carotenoid pigments, the carotenoids interfere in the absorbance measurement because the XO‐complex and carotenoids absorb at the same wavelength. To avoid this, an approach was developed where carotenoids were removed from the solution containing the XO‐complex before absorbance measurements were made. This was accomplished by aqueous extraction of the reaction solution, leaving an organic layer containing the carotenoid pigment. The absorbance of the aqueous layer was subsequently measured at 560 nm allowing for determination of the lipid hydroperoxide content (mmol kg−1) using a cumene hydroperoxide calibration curve. The method was validated using oxidized, unpigmented fish oils. The modified FOX method described herein was linear, accurate, and precise, and was validated over a hydroperoxide concentration range of 5–35 meq kg−1 lipid. This modified FOX method for hydroperoxide determination of highly pigmented lipids is a valuable alternative to the methods presently available for determination of peroxide values.

Main Methods and Approaches to the Determination of Markers of Oxidative Stress—Organic Peroxide Compounds and Hydrogen Peroxide

A review of publications, mainly for the last 15 years, characterizing the advantages, limitations, and prospects for the development of modern methods and approaches to the determination of organic hydroperoxides and hydrogen peroxide, which are the most important markers of the oxidative stress level in living organisms.

A two-dimensional non-comprehensive reversed/normal phase high-performance liquid chromatography/tandem mass spectrometry system for determination of limonene and linalool hydroperoxides

A two-dimensional non-comprehensive high-performance liquid chromatographic (HPLC) system coupled to electrospray ionization tandem mass spectrometry was developed for the determination of skin allergenic hydroperoxides of limonene and linalool. These compounds are some major components behind skin sensitization and contact (skin) allergy to fragrances.Fragrance hydroperoxides usually occur in complex compositions, often as constituents of the natural essential oils added to a large number of commercial products. Their similarities to interfering compounds, many with identical elemental composition, make the determination difficult even when using selective detection methods like mass spectrometry. In this work, a first-dimension chromatographic heart-cut isolation of the hydroperoxides on a reversed-phase HPLC system was combined with a second-dimension normal-phase HPLC system for separation of the hydroperoxides. The intersystem transfer was made by trapping the heart-cut fraction on a short graphitized carbon column, exchanging the mobile phase and back-flushing the hydroperoxides into the second dimension.Each analysis was performed within 60 min without any pretreatment, except dilution, prior to injection. The obtained instrumental limits of detection (LODs) at a signal-to-noise ratio of 3 were lower than 1.2 ng injected on column and method LODs were below 0.3 ppm. An after-shave product was shown to contain the highest concentrations of the measured hydroperoxides, with 445 ± 23 ppm of total linalool hydroperoxides. This level is likely able to elicit skin reactions in already sensitized individuals.

Iodometric Determination of Hydroperoxides in Hydrocarbon Autoxidation Reactions Using Triphenylphosphine Solution as a Titrant: A New Protocol

Hydroperoxides are important oxidants in epoxidation processes and play a central role in the industrial hydrocarbon autoxidation. This paper presents a new and water-free/low-water iodometric titration technique that can be utilized to quantify organic hydroperoxides. In this protocol, the aqueous thiosulfate titrant used in the conventional iodometric titration method was replaced with a new titrant (triphenylphosphine solution) in order to prevent the need for aqueous solutions. In addition, a comparison of two methods showed that titration time in this new method is shorter than that of thiosulfate titrant based one. It is predicted that a colorless charge-transfer complex is formed from interaction between triphenylphosphine and iodine. The proposed protocol can be utilized in the industrial processes that go through hydroperoxide intermediates.

Trefoil Factor 3 Deficiency Affects Liver Lipid Metabolism

Background/Aims: Tff3 protein plays a well recognized role in the protection of gastrointestinal mucosa. The role of Tff3 in the metabolism is a new aspect of its function. Tff3 is one of the most affected liver genes in early diabetes and fatty liver rodent models. The aim of this study was to investigate the effect of Tff3 deficiency on lipid and carbohydrate metabolism and on markers of oxidative stress that accompanies metabolic deregulation. Methods: Specific markers of health status were determined in sera of Tff3 deficient mice, including glucose level, functional glucose and insulin tolerance. Composition of fatty acids (FAs) was determined in liver and blood serum by using gas chromatography. Oxidative stress parameters were determined: lipid peroxidation level via determination of lipid hydroperoxide and thiobarbituric acid reactive substances (TBARS), antioxidative capacity (FRAP) and specific antioxidative enzyme activity. The expression of several genes and proteins related to the metabolism of lipids, carbohydrates and oxidative stress (CAT, GPx1, SOD2, PPARα, PPARγ, PPARδ, HNF4α and SIRT1) was determined. Results: Tff3 deficient mice showed better glucose utilization in the glucose and insulin test. Liver lipid metabolism is affected and increased formation of small lipid vesicles is noticed. Formation of lipid droplets is not accompanied by increased liver oxidative stress, although expression/activity of monitored enzymes is deregulated when compared with wild type mice. Tff3 deficient mice exhibit reduced expression of metabolism relevant SIRT1 and PPARγ genes. Conclusion: Tff3 deficiency affects the profile and accumulation of FAs in the liver, with no obvious oxidative stress increase, although expression/activity of monitored enzymes is changed as well as the level of SIRT1 and PPARγ protein. Considering the strong downregulation of liver Tff3 in diabetic/obese mice, presence in circulation and regulation by food/insulin, Tff3 is an interesting novel candidate in metabolism relevant conditions.

Hydroperoxides Formation in Jet Fuels Coming from Different Production Processes in Simulated Fuel System of Modern Aircraft

Abstract The paper presents issues related to the process of thermal degradation of jet fuel. This process is of a different nature depending on temperature and time, in which the fuel is subjected to thermal action. The standard method for testing the jet fuel thermal stability seems to be insufficient, therefore, the conduct of the research on a dedicated test rig was taken in this paper. The assessment of the fuel degradation process was carried out on the basis of determination of hydroperoxide and acid numbers as signs of the occurred process. The article has been prepared within the research project No. 2011/01/D/ST8/06567 funded by the National Science Centre in Poland.

Polyferrocenyl Polycyclosiloxane/Gold Nanoparticles: An Efficient Electrocatalytic Platform for Immobilization and Direct Electrochemistry of HRP

Sensitivity and enzyme stability are the main targets in the biosensors improvement. This work achieves both by means of the combination of two efficient electrocatalysts: ferrocene and gold nanoparticles (AuNPs). The AuNPs were electrodeposited onto a polyferrocenyl polycyclosiloxane polymer (FPP) in order to obtain an electrocatalytic framework for the covalent immobilization and direct electrochemistry of horseradish peroxidase (HRP). The developed surface is like that obtained with graphene modified electrodes, with very high specific area. The kinetic study of electrodes modified with and without HRP showed that the FPP/AuNPs system greatly improves other more complex systems based on the direct HRP electro-reduction by AuNPs, allowing the use of lower measuring potentials, with improved sensitivity, wider linear ranges and lower detection limits. The obtained apparent Michaelis-Menten constant, KM,app, was 0.32 mM, significantly lower than the intrinsic KM, revealing the very high enzymatic efficiency of the developed device. The HRP/AuNPs/FPP/Pt electrode was used as biosensor for hydrogen peroxide with two wide linear ranges of 0–200 μM and 200–6800 μM, and a high sensitivity of 685.71 μA mM−1 cm−2, a low detection limit of 50 nM and long-term stability. The new device has been successfully used too as for the determination of organic hydroperoxides.

Determination of Phosphatidylcholine Hydroperoxide (PCOOH) as a Marker of Membrane Lipid Peroxidation.

Increasing evidence for phosphatidylcholine hydroperoxide (PCOOH) as a marker of oxidative food deterioration and oxidative diseases has revealed the need for a pure PCOOH standard and a reliable quantification method. Recently, we synthesized the PCOOH isomers 1-palmitoyl-2-(9-hydroperoxyoctadecadienoyl)-sn-glycero-3-phosphocholine, (16:0/9-HpODE PC) and 1-palmitoyl-2-(13-hydroperoxyoctadecadienoyl)-sn-glycero-3-phosphocholine (16:0/13-HpODE PC). Using these standards along with liquid chromatography-tandem mass spectrometry, a reliable quantification method was developed. This mini-review describes these analytical techniques, with a particular emphasis on clinical sample analysis.

High chemiluminescence activity of an Fe(III)-TAML activator in aqueous-organic media and its use in the determination of organic peroxides.

High activity of Fe(III)-TAML, peroxidase mimic, upon the catalytic oxidation of luminol in aqueous-organic media (ethanol, isopropanol and acetonitrile) was determined. Using Fe(III)-TAML the sensitive chemiluminescence assays for the determination of benzoyl peroxide and tert-butyl hydroperoxide in the presence of organic solvents were performed.

High-throughput analysis of lipid hydroperoxides in edible oils and fats using the fluorescent reagent diphenyl-1-pyrenylphosphine

A fluorometric method for the determination of hydroperoxides (HP) in edible oils and fats using the reagent diphenyl-1-pyrenylphosphine (DPPP) was developed and validated. Two solvent media containing 100% butanol or a mixture of chloroform/methanol (2:1, v/v) can be used to solubilise lipid samples. Regardless of the solvent used to solubilise the sample, the DPPP method was precise, accurate, sensitive and easy to perform. The HP content of 43 oil and fat samples was determined and the results were compared with those obtained by means of the AOCS Official Method for the determination of peroxide value (PV) and the ferrous oxidation-xylenol orange (FOX) method. The proposed method not only correlates well with the PV and FOX methods, but also presents some advantages such as requiring low sample and solvent amounts and being suitable for high-throughput sample analysis.

LC‐MS/MS determination of phosphatidylcholine hydroperoxide and its truncated products in human blood plasma (1001.9)

Accumulation of phosphatidylcholine hydroperoxide (PCOOH), a primary oxidation product of phosphatidylcholine (PC), in the blood plasma has been observed in vascular pathological conditions, including inflammation and atherosclerosis. Here, we developed a method for quantification of PCOOH (1‐palmitoyl‐2‐hydroperoxyoctadecadienoyl‐sn‐glycero‐3‐phosphocholine, 16:0/HODE PC), especially isomers such as 16:0/13‐HODE PC and 16:0/9‐HODE PC that might be present in human plasma, together with their breakdown products (truncated PC such as 16:0/azelaoyl PC), by using LC‐MS/MS. Collision‐induced dissociation of sodiated PCOOH isomers ([M+Na]+, m/z 812) produced not only a fragment ion (m/z 147) but also characteristic neutral losses (88 Da for 16:0/13‐HODE PC and 169 Da for 16:0/9‐HODE PC). Three multiple reaction monitorings (MRMs) of sodiated PCOOH could be performed under optimum conditions. MRM (812/147) enabled determination of 16:0/HODE PC, and MRM (812/541 and 812/388) allowed measurement of 16:0/13‐HODE PC and 16:0/9‐HODE PC, respectively. By using the method, we could determine plasma PCOOH concentrations in healthy subjects (260nmol/L of total PCOOH, 50‐80nmol/L of truncated PC, 36nmol/L of 16:0/13‐HODE PC and 33nmol/L of 16:0/9‐HODE PC) and in patients with angiographically significant stenosis (45nmol/L of 16:0/13‐HODE PC, 51 nmol/L of 16:0/9‐HODE PC). The PCOOH detected is formed with lipoxygenase and free radical reaction. Oxidized PC with singlet molecular oxygen was not found. The newly developed LC‐MS/MS method appears to be a powerful tool for understanding in vivo membrane lipid peroxidation.

Determination of allergenic hydroperoxides in essential oils using gas chromatography with electron ionization mass spectrometry

Fragrance monoterpenes are widely used commercially due to their pleasant scent. In previous studies, we have shown that air-exposed monoterpenes form hydroperoxides that are strong skin sensitizers. Methods for detection and quantification of the hydroperoxides in essential oils and scented products are thus desirable. Due to thermolability and low UV absorbance, this is a complicated task. We have recently developed a sensitive LC-ESI-MS method, but with limited structural information and separation efficiency for positional isomers and stereoisomers. In the present study, we investigated derivatization with a trimethyl silyl reagent and subsequent GC with electron ionization MS for the determination of monoterpene hydroperoxides. All investigated monoterpene hydroperoxides could be chromatographed as thermostable trimethyl silyl derivatives and yielded the fragment m/z 89 ([OSi(CH3)3](+)) at a higher extent compared to corresponding alcohols. Limonene-2-hydroperoxide and four other hydroperoxide isomers of limonene were separated and detected in sweet orange oil autoxidized for two months. The concentration of limonene-2-hydroperoxide isomers was found to be 19 μg/mg in total. Also isomers of linalyl acetate hydroperoxide and linalool hydroperoxide were detected in autoxidized petitgrain oil (two months). The presented GC-MS method showed concentrations in the same order as previous LC-MS/MS analysis of the same type of oils.

A comparison of antioxidant capacity and some lipoprotein values in swimmers and sedentary subjects

Gokhan, I., Aktas,Y. & Arikan, G. (2014). A comparison of antioxidant capacity and some lipoprotein values in swimmers and sedentary subjects. J. Hum. Sport Exerc., 9(Proc1), pp.S490-S494. Increased oxygen consumption as a result of the exercise also increases the free radical production. These free radicals are neutralized by a defence mechanism consisting of enzymatic and non-enzymatic antioxidants. Training can have positive or negative effects on oxidative stress depending on the load and type of the training or the status of the individual prior to it. The purpose of this study is to search the capacity of lipoproteins, total oxidant and antioxidant in swimmers and sedentary subjects. The experimental group were 18 male children with mean age 15,16 ± 0,92 who have been swimming at least for 2 years and exercise regularly 3 days a week and 2 hours a day, as the control group, 18 male children with mean age 15,33 ±1,08 who do not regularly do any particular sports, participated voluntarily in our study. Oxidant-antioxidant measurements were conducted through venous blood samples collected in EDTA tubes on an empty stomach and at rest. Total Antioxidant Capacity (TAC) was determined through a method developed by Erel (2004) to measure the total antioxidant capacity of the body against the free radicals. Lipid Hydroperoxide (LOOH) determination was specified with a method in which xylenol orange and Fe++ are used (Arab and Steghens, 2004). Total Oxidant Status (TOS) was determined through a colorimetric method developed by Erel (2004). Oxidative Stress Index (OSI) was calculated with the formula Total Oxidative Stress (TOS) / (TAC). Plasma triglyceride, Total cholesterol, LDL, HDL, VLDL parameters were measured using Abbot and automatic chemistry analyser (Aeroset, Abbott, USA). For the comparison of the experiment and the control groups, Independent Samples T-Test was applied to compare the independent groups on the SPSS 16.00 statistical package. Statistically significant difference was determined to be p 0,05). Moreover, a statistically significant difference was observed between TAC, LOOH, TOS, OSI, TRIGLISERIT and HDL values of the experiment and the control groups (p 0,05). It was concluded that total antioxidant and antioxidant capacity of the swimmers’ group was higher compared to the sedentary group. The reason for this difference, we think, is that antioxidant defence mechanisms of the subjects who do swimming are more developed. Key words: SWIMMING, ANTIOXIDANT, LIPOPROTEIN, EXERCISE, OXIDATIVE STRESS.

Effect of Sample Solubilized Aliquot Volume and Concentration on Hydroperoxide Detection in PUFA-Rich Fish Oil

The objective of this work was to study the effect of sample oil concentration and volume on hydroperoxide determination in n-3 PUFA-rich sardine-anchovy oil. Oil samples were stored at −20°C, 6 d, air-free (T1); and 20°C, 2 d in air (T2). Significant differences between storage conditions were observed on hydroperoxide concentration. High reproducibility was obtained even in sample concentrations as low as 5 mg oil/mL of propan-1-ol. A high correlation was observed between the modified ferrous oxidation-xylenol orange method (FOX2) and AOAC peroxide value analysis methods, although FOX2 was faster, more sensitive, and precise when analyzing small hydroperoxide concentrations.