FTIR and SUVF spectroscopy applied to reservoir compartmentalization: a comparative study with gas chromatography fingerprints results

The purpose of this study was to evaluate reservoir continuities and geochemical evolution of oils from individual reservoirs by using gas chromatography (GC) fingerprints method and to compare the results with those obtained from Fourier transform infra red (FTIR) and synchronous ultra violet fluorescence (SUVF) spectroscopy techniques. Six crude oils which belong to different levels of exploitation were selected from Alam El Bueib (AEB) oil field (Western Desert, Egypt). The samples studied belong to three different reservoir units in different wells.The results show that the all-independent techniques provide results in good agreement and that the oils characteristics and their evolution in the reservoir can be described similarly by fingerprints GC, FTIR and SUVF spectroscopy. The FTIR and SUVF spectroscopy techniques therefore constitute a rapid and non-expensive alternative for reservoir organic geochemistry studies.     

FTIR and SUVF spectroscopy as an alternative method in reservoir studies. Application to Western Mediterranean oils

Reservoir geochemistry assessment has traditionally used the gas chromatogram fingerprint method and star diagrams. Recently we tested alternative techniques, such as Fourier transform infra red (FTIR) and synchronous ultra violet fluorescence (SUVF) spectroscopy to optimise the evaluation of reservoir continuities, and to characterize the geochemical evolution of oils from individual reservoirs. We used some Western Mediterranean oils to demonstrate that these independent techniques provide results that are in good agreement with each other. GC fingerprints, FTIR and SUVF spectroscopy can describe the oil characteristics and its evolution in the reservoir. We also show that some FTIR parameters can be closely related to the API degree.     

Use of 13C nuclear magnetic resonance distortionless enhancement by polarization transfer pulse sequence and multivariate analysis to discriminate olive oil cultivars

Distortionless enhancement by polarization transfer (DEPT) pulse sequence was used to set up a quantitative high-resolution ¹³C nuclear magnetic resonance (NMR) method to discriminate olive oils by cultivars and geographical origin. DEPT pulse sequence enhances the intensity of NMR signals from nuclei of low magnetogyric ratio. The nuclear spin polarization is transferred from spins with large Boltzmann population differences (usually protons) to nuclear species characterized by low Boltzmann factors, e.g., ¹³C. The signal enhancement of ¹³C spectra ensures the accuracy of resonance integration, which is a major task when the resonance intensities of different spectra must be compared. The resonances of triglyceride acyl chains C _n:0, C_18:1, C_18:2, and C_18:3, were also assigned. Multivariate analysis was carried out on the 35 carbon signals obtained. By using variable reduction techniques, coupled with standard statistical methods—partial least squares and principal components analysis—it was largely possible to separate the samples according to their variety and region of origin. With one problem variety removed, 100% prediction of the three remaining varieties was achieved. Similarly, by using the three regions with greatest representation in the data, all but one of a test set of 34 samples were correctly predicted. Thus, the composition of olive oils from different cultivars and of different geographical origin were compared and successfully studied by multivariate analysis. These considerations in conjunction with the structural elucidations of triglyceride molecules demonstrated that ¹³C NMR is among the most powerful techniques yet described for analysis of olive oils.     

Estimation of cetane index for esters of fatty acids

Cetane indexes have been calculated for the esters of the individual saturated fatty acids in the C₈-C₂₄ range plus palmitoleic, oleic, linoleic, and linolenic acids. Two methods were used for these calculations: ASTM 976 and a method involving simultaneous equations relating the experimentally determined cetane numbers for several transesterified oils and the fatty acid compositions of the oils. Cetane indexes calculated according to ASTM 976 produced values which were too low for ester mixtures high in saturated acids and low in polyunsaturated acids, and were somewhat high for ester mixtures high in polyunsaturated acids. When cetane indexes calculated according to the simultaneous equation method were applied to the fatty acid mixtures, the agreement with those experimentally determined was approximately the error of determination of the cetane number.     

Characterization of Volatile Compounds of Virgin Olive Oil Originating from the USA

The volatile profiles of virgin olive oils originating from the USA were first studied: 71 volatile compounds were identified in 21 monovarietal virgin olive oils using solid‐phase microextraction–gas chromatography/mass spectrometry, representing 100 % of the headspace composition. Principal component analysis (PCA) allowed for the grouping of olive oils based on geographical origin, and also the distinguishing of olive oil varieties by their relative positions in the group; 17 distinguishable volatile compounds that significantly contributed to the olive oil classification were found to be distributed on a PCA plot according to their sensory attributes. Moreover, the major volatile components were compared among varieties and origins to clarify the genetic and geographic influences. Our results indicate the significant effects of both origin and cultivar on the volatile composition of olive oil as well as the dominant role of the geographic effect compared to the genetic effect on applied samples.     

Comparison of fatty acid profiles and mid‐infrared spectral data for classification of olive oils

The composition of olive oils may vary depending on environmental and technological factors. Fatty acid profiles and Fourier‐transform infrared (FT‐IR) spectroscopy data in combination with chemometric methods were used to classify extra‐virgin olive oils according to geographical origin and harvest year. Oils were obtained from 30 different areas of northern and southern parts of the Aegean Region of Turkey for two consecutive harvest years. Fatty acid composition data analyzed with principal component analysis was more successful in distinguishing northern olive oil samples from southern samples compared to spectral data. Both methods have the ability to differentiate olive oil samples with respect to harvest year. Partial least squares (PLS) analysis was also applied to detect a correlation between fatty acid profile and spectral data. Correlation coefficients (R²) of a calibration set for stearic, oleic, linoleic, arachidic and linolenic acids were determined as 0.83, 0.97, 0.97, 0.83 and 0.69, respectively. Fatty acid profiles were very effective in classification of oils with respect to geographic origin and harvest year. On the other hand, FT‐IR spectra in combination with PLS could be a useful and rapid tool for the determination of some of the fatty acids of olive oils.     

Raman Spectroscopic Barcode Use for Differentiation of Vegetable Oils and Determination of Their Major Fatty Acid Composition

In this study, differentiation of vegetable oils and determination of their major fatty acid (FA) composition were performed using Raman spectral barcoding approach. Samples from seven different sources (sunflower, corn, olive, canola, mustard, soybean and palm) were analyzed using Raman spectroscopy. Second derivative of the spectral data was utilized to generate unique barcodes of oils. Chemometric analyses, namely, principal component analysis (PCA) and partial least square (PLS) methods were used for data analysis. PCA was applied for classification of the samples according to the differences in their levels arising from their barcode data. A successful differentiation based on second derivative barcodes of Raman spectra (2D‐BRS) of vegetable oils was obtained. In addition, PLS method was applied on 2D‐BRS in order to determine the major FA composition of these samples. Coefficient of determination values for palmitic, stearic, oleic, linoleic, α‐linolenic, cis‐11 eicosenoic, erucic and nervonic acids were in the range of 0.970–0.989. Limit of detection and limit of quantification values were found to be satisfactory (0.09–8.09 and 0.30–26.95 % in oil) for these fatty acids . Advantages of both chemometric analysis and spectral barcoding approach have been utilized in the present study. Taking the second derivative of the Raman spectra has minimized background variability and sensitivity to intensity fluctuations. Spectral conversion to the barcodes has further increased the quality of information obtained from Raman spectra and also made it possible to improve the visualization of the data. Converting Raman spectra of oils into barcodes enables simpler presentation of the valuable information, and still allows further analysis such as classification of vegetable oils and prediction of their major fatty acids with high accuracy.     

Zur Bestimmung,zum Vorkommen und zur Zusammensetzung von polycyclischen aromatischen Kohlenwasserstoffen in Ölen und Fetten

On the Occurrence, Determination and Composition of Polycyclic Aromatic Hydrocarbons in Crude Oils and Fats Various methods have been published regarding analytical determination of polycyclic aromatic hydrocarbons (PAH). In principle, all methods are composed of following steps: Enrichment, clean-up and quantitation. The authors prefer the caffein-complexation technique. They have been using this since many years for the routine PAH-analysis of fats and oils. This report contains the results of PAH determination in the most common crude oils used in Europe as well as the statistical trend of their contamination with “light” and “heavy” PAH's. Moreover, the PAH contamination of different oils according to their geographical origin is shown and possible sources of contamination are discussed. The role of Benzo[a]pyrene as the “reference PAH” and its correlation with “heavy” PAH is subjected to a critical evaluation.     

N.m.r. study of US Eastern and Western shale oils produced by pyrolysis and hydropyrolysis

Shale oils produced from US Eastern and Western oil shales by pyrolysis and hydropyrolysis processes have been investigated by both ¹H and ¹³C high-resolution n.m.r. techniques. Eastern shale oils produced by hydropyrolysis, and subsequently hydrotreated, were also included. From the n.m.r. data of the shale oils, the average molecular structure parameters were calculated. These parameters quantitatively represent the differences observed in the n.m.r. spectra of the various shale oils because of changes in the chemical composition. Mol percentages of aromatics, olefins, and alkanes were also determined for the shale oils, and show that the composition of the shale oil is dependent upon the geographic origin of the oil shale, the pyrolysis method, and the hydrogenation process. In addition to the study of shale oils, solid-state ¹³C n.m.r. spectra of Eastern and Western oil shales before and after pyrolysis and hydropyrolysis were obtained. The spectral data show that the carbon aromaticities for the Eastern oil shales and shale oils are higher than for the Western oil shale and shale oils. The data also show that hydropyrolysis relative to pyrolysis reduces the amount of residual organic carbon remaining on the spent shales. Carbon aromaticity data for both oil shale and shale oil suggest that the organic moieties present in kerogen may be retained in the shale oils to a greater extent after hydropyrolysis than after pyrolysis.     

Gas-liquid chromatographic analysis of cyclopropene fatty acids

A gas-liquid chromatographic method is described for the quantitative estimation of cyclopropene fatty acids as their methyl mercaptan derivatives. This method estimates individual cyclopropene acids as well as normal and cyclopropane acids. Nine seed oils were analyzed for their cyclopropene fatty acid content. Evidence was obtained for the presence of a cyclopropene fatty acid of shorter chain length than malvalic inAlthaea rosea cav and one with a higher chain length than sterculic inBombacopsis glabra seed oil. This method is less accurate for cottonseed oil than for the other oils tested because of the appearance of some unsymmetrical peaks of unknown origin. The mercaptan derivatives of the cyclopropene acids may be isolated by silver ion thin-layer chromatography. Small amounts of cyclopropane fatty acids were found in a number of the oils analyzed for cyclopropene fatty acids. Presented at the AOCS meeting, Chicago, October 1964.     

Sunflower oil diesel fuel: Engine wear implications

Diesel lubricating oil contaminated with sunflower oil fuel was degraded under conditions simulating an engine crankcase environment for metal wear testing. Wear analyses were performed using a fourball apparatus according to ASTM D 4172. Lubricity of oils was characterized by ball scar dimensions. Contaminated lubricating oils exhibited lower metal wear indexes than pure lube oil control samples, even when the former were severely degraded as measured by thickening and loss of alkaline reserve.     

Regional and cultivar comparison of Italian single cultivar olive oils according to flavor profiling

Geographical origin, cultivar, and olive ripening stage are important factors which affect the typical flavor profile of extra virgin olive oils. Aromatic compounds and sensorial profiles of “Casaliva”, “Frantoio”, and “Leccino” olive oils from three different Italian production regions Abruzzo (eastern‐central Italy), Lombardy (northern Italy), and Tuscany (western‐central Italy) were assessed in two cropping years and at three olive ripening stages (green, veraison, and ripe). The chemical aromatic compounds were more effective in discriminating the oils than their sensorial attributes. Oils showed peculiar aromatic and sensorial profiles according to their region of origin. Genetically similar “Casaliva” and “Frantoio” showed also analogous profiles, but distinct from “Leccino”. The interaction between regions of cultivation and cultivars significantly affected the flavor profiling. Practical applications: This research provides a sound proof that geographical origin, cultivar, and fruit ripening stage, could play an important interactive role in shaping the flavor profiling of extra virgin olive oils. This represents a scientific basis of the “typicality” concept, which should address the marketing strategies for exploiting of the PDO products.     

Nachweis von verestertem Olivenöl

Detection of Esterified Olive Oil Ester oils, prepared by esterification of olive oil fatty acids with glycerol, can be detected on the basis of increased level of palmitic acid in 2-position of triglycerides after selective enzymatic hydrolysis of the fatty acids in 1 and 3 position. The sensitivity of this method is, however, limited, because the fatty acid composition of the individual oils varies to a great extent, depending on their origin and processing. The sensitivity of detection is improved, if the monoene fraction of the triglycerides separated by silver nitrate thin-layer chromatography, instead of total triglycerides, is subjected to enzymatic hydrolysis. Natural tolerances of olive oils from different origin, quality, processing and composition are given on the basis of analysis of numerous samples. The oils were analyzed by both methods. In order to evaluate the sensitivity of detection, two ester oils having different levels of palmitic acid were analyzed either alone or in admixture with various concentrations of other selected olive oils.     

Use of high-resolution 13C nuclear magnetic resonance spectroscopy for the screening of virgin olive oils

¹³C Nuclear magnetic resonance (NMR) spectra of 104 oil samples were obtained and analyzed in order to study the use of this technique for routine screening of virgin olive oils. The oils studied included the following: virgin olive oils from different cultivars and regions of Europe and north Africa, and refined olive, “lampante” olive, refined olive pomace, high-oleic sunflower, hazelnut, sunflower, corn, soybean, rapeseed, grapeseed, and peanut oils, as well as mixtures of virgin olive oils from different geographical origins and mixtures of 5–50% hazelnut oil in virgin olive oil. The analysis of the spectra allowed us to distinguish among virgin olive oils, oils with a high content of oleic acid, and oils with a high content of linoleic acid, by using stepwise discriminant analysis. This parametric method gave 97.1% correct validated classifications for the oils. In addition, it classified correctly all the hazelnut oil samples and the mixtures of hazelnut oil in virgin olive oil assayed. All of these results suggested that ¹³C NMR may be used satisfactorily for discriminating some specific groups of oils, but to obtain 100% correct classifications for the different oils and mixtures, more information than that obtained from the direct spectra of the oils is needed.     

A Systematic Chemometric Approach to Identify the Geographical Origin of Olive Oils

The verification of the geographical origin of olive oils by analytical techniques is still a challenge. The goal of this work is to explore the application and accuracy of different chemometric tools combined with near infrared spectroscopy (NIR) based analytical methods in the field of geographical authenticity of olive oils. As olive oils associated with different geographical origins are mainly characterized by different fatty acid (FA) and triacylglycerol (TAG) compositions, NIR methods for the fast and reliable determination of these parameters are developed. Next, these NIR methods are used to characterize a comprehensive set of olive oils (n > 5000) derived from 19 different countries. This set of data is used to build a statistical workflow, which allows the determination of the geographical origin of unknown olive oil samples. First of all, the untreated data set is pretreated by k‐means clustering and the selection of the relevant analytical variables by principal component analysis (PCA) and linear discriminant analysis (LDA) and min/max normalization of all parameters. Subsequently, classification is performed with a reduced sample set of the 200 most similar samples identified by k‐nearest neighbor tool (kNN). For classification purpose kNN, LDA, naïve Bayes classifier, and logit regression are applied. Practical Applications: The established statistical workflow can be used to verify the geographical origin of olive oils. The application and usage of up to four different statistical models for classification purpose results in a superior probability of the predicted origin in comparison to the application of only one single statistical classification test. As standardized methods are used as reference methods for building the NIR methods, the FA and TAG composition and the iodine value can be either determined by the standard methods or by the described NIR method. The presented statistical approach will help to build up a system for the verification of the geographical origin of olive oils.     

滇产植物油理化指标测定

研究滇产食用植物油的理化特征与储藏期品质变化规律。以两种特色植物油为对照,对云南出产的五种植物油脂的理化指标进行评价和对比。同时使用过氧化值和酸价,对所研究的油脂的储藏期品质变化进行初步探索。结果表明:云南产植物油质量均满足国标要求。但由于其加工工艺原因,植物油级别较低。含有不饱和脂肪酸的植物油在光照情况下过氧化值和酸价明显改变,可作为质量变化的主要指标。云南出产的四种特色植物油脂不饱和脂肪酸含量较高,是良好的食用油产品;但仍需改善加工工艺以提高其级别。葡萄籽油、红花籽油需添加额外抗氧化剂稳定其品质;过氧化值是最适于进行日常油品质量控制的指标。     

Reliable Classification of Olive Oil Origin Based on Minor Component Profile Using 1H‐NMR and Multivariate Analysis

Mislabeling of olive oil with respect to its geographical origin is a frequently encountered fraud. Although according to European Regulation (EU) No 29/2012 it is mandatory to declare the geographical origin of an olive oil on the label, no generally accepted analytical method exists to verify this labeling. As Italy, Greece, and Spain are the main producing countries in the Mediterranean Area, the aim is to develop an analytical method that allows classification of these three origins and which can be reliably applied to routine samples. A protocol for the extraction and subsequent ¹H‐NMR measurement of the polar fraction of olive oil is developed and applied to a large number of authentic reference samples. A classification model is developed which obtains 96% of correct classification during cross‐validation. The method is being routinely applied for testing commercial off‐the‐shelf olive oils, and its accuracy is continuously verified. Practical Applications: In addition to checking the geographical origin of an olive oil, the developed protocol allows to analyze the polar constituents of an olive oil in great detail with little effort, which should prove useful also for other applications, for example, quantitation of phenols or detection of admixtures with other vegetable oils.     

Comparative analysis of triacylglycerols from Olea europaea L. fruits using HPLC and MALDI‐TOFMS

MALDI‐TOFMS and HPLC are two analytical methods that were used to characterize triacylglycerols (TAG) of the Meski, Sayali, and Picholine Tunisian olive varieties. The HPLC chromatograms of the oils showed the presence of 15 TAG species, among which triolein (OOO) was the most abundant (21–48%). In the Sayali cultivar, OOO was the predominant TAG species followed by POO and LOO. However, the minor TAG molecules were represented by LnLO and LnLP. MALDI mass spectra produced sodiated ([M + Na]⁺) and potassiated ([M + K]⁺) TAG molecules; only the major TAG were potassiated [OOO + K] ([OOO + K]⁺, [POO + K]⁺, and [LOO + K]⁺). In contrast to the HPLC chromatograms, the MALDI mass spectra showed 13 peaks of TAG. The major peak was detected at m/z 907, which corresponds to OOO with an Na⁺ adduct. The results from both HPLC and MALDI techniques predict the fatty acid composition and their percentages for each olive variety. Practical applications: TAG are the main components in vegetable oils. These biomolecules determine the physical, chemical, and nutritional properties of the oils. The nutritional benefits of TAG are related to DAG (moderate plasma lipid level) and esterified FA, which are intermediate biosynthetic molecules of TAG. TAG analysis is necessary to discriminate between oils of different origin, since some oils have similar FA profiles. Olive products, oils, and table olives, are the main diet sources of TAG in the Mediterranean countries. In this work, chromatographic and spectrometric methods were used for TAG analysis and characterization of Tunisian olive varieties.     

Manoeuvring the physicochemical and nutritional properties of vegetable oils through blending

Modification of vegetable oils is carried out to make them suitable according to their specific end use as most of the vegetable oils in original forms do not meet the recommended dietary allowance of saturated (SFA), monounsaturated (MUFA) and polyunsaturated (PUFA) fatty acids. Vegetable oils are modified using a variety of techniques including hydrogenation, interesterification, fractionation, and blending. However, blending is the most widely accepted method for improving the physicochemical properties, nutritive value and oxidative stability of vegetable oils because it is simple, cost-effective, non-destructive, and does not involve chemical treatments. Blending vegetable oils with contrasting fatty acid compositions or blending omega 3 fatty acids and antioxidants rich minor oils with major oils are two common strategies to formulate blends. Blended oil with balanced fatty acids could play substantial role in improving the consumers' health. However, while designing vegetable oil blends, it is important to keep in mind the intended application of the formulated blend, consumer's demands and also food laws. This review paper covers the literature related to blending of vegetable oils with a focus on effect of vegetable oils blending on their physicochemical and nutritional properties, health benefits and utility in food industries.     

Determination of rare earth elements in Niger Delta crude oils by inductively coupled plasma-mass spectrometry

A profile for rare earth elements (REE) of crude oils from the offshore – shallow water and onshore fields in the Niger Delta, analyzed by inductively coupled plasma-mass spectrometry (ICP-MS) is reported. The oil samples were prepared for ICP-MS measurement by acid digestion into colourless aqueous solution. The analysis method was validated using standard reference materials SLRS-4 and NIST-1640. Results showed percentage recovery values that ranged from 81.8% to 115.4% for Co, Cu, Fe, Mn, Ni, Sb and U and from 98.8% to 104.7% for Co, Cu, Fe, Mn, Ni and Sb. The magnitude of deviation recorded in SLRS-4 for Co and Fe suggests that it may not be a suitable standard for these elements using the ICP-MS method outlined in this study. The concentrations of the detected REE; La, Ce, Pr, Nd, Sm, Eu, Gd, Dy, Er and Yb ranged from 0.01 to 1.58 ppb with an average of 0.98 ppb (%RSD < 5) for the oil samples analyzed. Light REEs (LREE) were identified in all the oil samples while heavy rare earth elements (HREE) were identified in offshore oil samples only. LREE patterns constructed from chondrite-normalized values for the oils show some similarities among the oils, which suggest common origin of the oils and that the REE got into the oils from similar source. While those with different chondrite-normalized REE patterns suggest different source input of the REE. This indicates that REE will be a useful tool in oil–oil correlation. Statistical evaluation of these oils by cluster analysis using the REE as variables clearly discriminated according to their geographic sources. Biodegradation has pronounced effect on the concentration of REE in oils. Therefore, REE contents of oils will be useful in oil classification. ICP-MS proved to be a versatile method for the determination of rare earth elements in Niger Delta oils.