Simultaneous Determination of Arsenic and Lead in Vegetable Oil by Atomic Fluorescence Spectrometry after Vortex-Assisted Extraction

Hydride generation atomic fluorescence spectrometry (HG-AFS) is used for the determination of hydride-forming elements due to its high sensitivity, simplicity, and low cost. A new HG-AFS method for the simultaneous determination of arsenic and lead in vegetable oil is reported. Vortex-assisted extraction with dilute nitric acid was used to isolate arsenic and lead from vegetable oil. The conditions influencing the fluorescence signal, including the carrier fluid, oxidizing agent, and reducing agent, were optimized. The interferences of coexisting ions were also evaluated. Under the optimized conditions, the limits of detection were 0.6 and 0.4?µg?kg^?1 for arsenic and lead. The recoveries were from 84.4 to 105% for both metals in vegetable oil. The optimized method was used for the determination of arsenic and lead in commercial vegetable oil. The analytical results by this approach were in good agreement with values obtained by inductively coupled plasma mass spectrometry with microwave digestion.     

常压火焰离子化质谱技术对食用植物油快速分析的初探

建立了常压火焰离子化质谱(Ambient flame ionization mass spectrometry,AFI-MS)快速分析食用植物油(橄榄油、芝麻油、花生油和葵花籽油)的方法。AFI-MS检出食用植物油(橄榄油、芝麻油、花生油和葵花籽油)中的26种甘油三酯和11种甘油二脂。AFI-MS分析显示,不同的食用植物油(橄榄油、芝麻油、花生油和葵花籽油)得到的质谱图轮廓信息不同。通过对不同食用植物油的甘油三酯相对峰强度进行分析,可初步归纳出食用植物油的类型。AFI-MS分析食用植物油的操作简单,普通的打火机就可以作为离子源用于食用植物油的分析。这种便捷的离子化技术可以用于食用植物油的快速分析。     

Discriminating olive and non-olive oils using HPLC-CAD and chemometrics

This work presents a method for an efficient differentiation of olive oil and several types of vegetable oils using chemometric tools. Triacylglycerides (TAGs) profiles of 126 samples of different categories and varieties of olive oils, and types of edible oils, including corn, sunflower, peanut, soybean, rapeseed, canola, seed, sesame, grape seed, and some mixed oils, have been analyzed. High-performance liquid chromatography coupled to a charged aerosol detector was used to characterize TAGs. The complete chromatograms were evaluated by PCA, PLS-DA, and MCR in combination with suitable preprocessing. The chromatographic data show two clusters; one for olive oil samples and another for the non-olive oils. Commercial oil blends are located between the groups, depending on the concentration of olive oil in the sample. As a result, a good classification among olive oils and non-olive oils and a chemical justification of such classification was achieved.     

Determination of twenty-five elements in lichens by sector field inductively coupled plasma mass spectrometry and microwave-assisted acid digestion

A simple and efficient digestion method for rapid sample preparation and quantification of 25 chemical elements in lichens by sector field inductively coupled plasma mass spectrometry is described. A microwave (MW)-assisted acid digestion was carried out at atmospheric pressure simultaneously handling up to 80 samples in screw-capped disposable polystyrene tubes. This digestion procedure was compared with the established MW digestion in closed vessels in order to examine its potential applicability in routine analysis for environmental monitoring. Three certified reference materials, i.e. BCR 482 (lichens), BCR 62 (olive leaves) and BCR 100 (beech leaves), as well as a small set of real samples were analyzed. Limits of quantification, accuracy and precision of the method were assessed. The majority of the elements were totally recovered from the lichens and from the other vegetable matrices. Low contamination risk, simplicity, time-saving, and applicability in routine analyses make this method very suitable for use in extensive screening campaigns.     

Determination of residues of endosulfan and five pyrethroid insecticides in virgin olive oil using gas chromatography with electron-capture detection

A simple, fast and economical method has been developed for the determination of endosulfan and five pyrethroid insecticides, cypermethrin, deltamethrin, fenvalerate, lambda-cyhalothrin and permethrin, in virgin olive oil. The method uses a Sep-Pak alumina-N column cleanup after a liquid-liquid extraction or low-temperature precipitation step, and gas chromatography (GC) with electron-capture detection. The matrix effect was assessed for the GC systems used. Recoveries were 71-91% with RSD values of 6-17%. The method was applied to 338 virgin olive oil samples for monitoring of residues of these pesticides. Cypermethrin and lambda-cyhalothrin were detected at the limit of quantification in one sample each, while 22% of samples contained endosulfan residues, mostly at very low levels ranging from 0.02 to 0.57 mg/kg.     

Usefulness of the direct coupling headspace-mass spectrometry for sensory quality characterization of virgin olive oil samples

The applicability of the headspace coupled to mass spectrometry for evaluation of the sensory quality of virgin olive oil samples is presented. The volatiles of the oil are directly transferred from the sample vial to the detector without chromatographic separation. The mass spectrum obtained can be considered as a fingerprint of the oil sample and can be used for classification purposes. After a training step with samples previously qualified following the official method, a classification model was created using the supervised technique soft independent modeling of class analogy (SIMCA). Eight negative (rancid, winey-vinegary, muddy sediment, hay-wood, vegetable water, earthy, fusty and musty-humidity) and three principal positive attributes (fruity, bitter and pungent) have been included in this study. With them, a classification model consisting of two main classes (extra- and lampante-virgin olive oil) was constructed. In addition, the unsupervised technique cluster analysis permited the discrimination among oils with different negative attributes. The proposed procedure has been applied to the classification of commercial samples (as extra- or lampante-virgin olive oils) and the results were compared with those provided by the expert's panel with acceptable correlation.     

Direct olive oil authentication: detection of adulteration of olive oil with hazelnut oil by direct coupling of headspace and mass spectrometry, and multivariate regression techniques

Control of adulteration of olive oil, together with authentication and contamination, is one of the main aspects in the quality control of olive oil. Adulteration with hazelnut oil is one of the most difficult to detect due to the similar composition of hazelnut and olive oils; both virgin olive oil and olive oil are subjected to that kind of adulteration. The main objective of this work was to develop an analytical method able to detect adulteration of virgin olive oils and olive oils with hazelnut oil by means of its analysis by a headspace autosampler directly coupled to a mass spectrometer used as detector (ChemSensor). As no chromatographic separation of the individual components of the samples exists, a global signal of the sample is obtained and employed for its characterization by means of chemometric techniques. Four different crude hazelnut oils from Turkey were employed for the development of the method. Multivariate regression techniques (partial least squares and principal components analysis) were applied to generate adequate regression models. Good values were obtained in both techniques for the parameters employed (standard errors of prediction (SEP) and prediction residual error sum of squares (PRESS)) to evaluate its goodness. With the proposed method, minimum adulteration levels of 7 and 15% can be detected in refined and virgin olive oils, respectively. Once validated, the method was applied to the detection of such adulteration in commercial olive oil and virgin olive oil samples.     

Sequential (step-by-step) detection,identification and quantitation of extra virgin olive oil adulteration by chemometric treatment of chromatographic profiles

An analytical method for the sequential detection, identification and quantitation of extra virgin olive oil adulteration with four edible vegetable oils--sunflower, corn, peanut and coconut oils--is proposed. The only data required for this method are the results obtained from an analysis of the lipid fraction by gas chromatography-mass spectrometry. A total number of 566 samples (pure oils and samples of adulterated olive oil) were used to develop the chemometric models, which were designed to accomplish, step-by-step, the three aims of the method: to detect whether an olive oil sample is adulterated, to identify the type of adulterant used in the fraud, and to determine how much aldulterant is in the sample. Qualitative analysis was carried out via two chemometric approaches--soft independent modelling of class analogy (SIMCA) and K nearest neighbours (KNN)--both approaches exhibited prediction abilities that were always higher than 91% for adulterant detection and 88% for type of adulterant identification. Quantitative analysis was based on partial least squares regression (PLSR), which yielded R2 values of >0.90 for calibration and validation sets and thus made it possible to determine adulteration with excellent precision according to the Shenk criteria.     

The comparison of solid phase microextraction-GC and static headspace-GC for determination of solvent residues in vegetable oils

The objective of these investigations has been the determination of volatile organic compounds including residue solvents present in vegetable oil samples. Some olive oil, rape oil, sunflower oil, soy-bean oil, pumpkin oil, grape oil, rice oil as well as hazel-nut oil samples were analysed. Among residue solvents the following compounds have been mentioned: acetone, n-hexane, benzene, and toluene. Some experiments for the solid phase microextraction (SPME)-GC-flame ionisation detection (FID) were performed to examine extraction conditions such as fiber exposure time, temperature of extraction, and temperature of desorption. Various SPME fibers such as polydimethylsiloxane, Carboxen/polydimethylsiloxane and polydimethylsiloxane/divinylbenzene coatings were used for the isolation of tested compounds from vegetable oil samples. After optimisation of SPME, real vegetable oil samples were examined using SPME-GC/MS. Based on preliminary experiments the qualitative and quantitative analyses for the determination of acetone, n-hexane, benzene and toluene were performed by SPME-GC-FID and static head-space (SHS)-GC-FID methods. The regression coefficients for calibration curves for the examined compounds were R(2) > or = 0.992. This shows that the used method is linear in the examined concentration range (0.005-0.119 mg/kg for SPME-GC-FID and 0.003-0.728 mg/kg for SHS-GC-FID). Chemical properties of analysed vegetable oils have been characterised by chemometric procedure (cluster analysis).     

Simple and fast determination of phenolic compounds from different varieties of olive oil by nonaqueous capillary electrophoresis with UV‐visible and fluorescence detection

In this article, we proposed very simple procedures to analyze important phenolic compounds in olive oil samples from different olive varieties. A nonaqueous CE method has been employed. The main phenolic alcohols in virgin olive oil (tyrosol and hydroxytyrosol) and some among the most abundant secoiridoid aglycone derivatives (dialdehydic form of decarboxymethyl elenoic acid linked to hydroxytyrosol, an isomer of oleuropein aglycone and the dialdehydic form of decarboxymethyl elenoic acid linked to tyrosol) were determined by a direct injection into the capillary of the olive oil dissolved in 1‐propanol 1:1 v/v. For the determination of compounds present at lower concentrations, a very simple liquid–liquid extraction method with ethanol has been proposed. The extraction was performed using a relationship 5:1 w/v olive oil/ethanol to achieve the necessary preconcentration of the analytes and the ethanolic extracts were directly injected into the capillary to obtain a very important time reduction. Good recoveries were obtained with both the procedures, using an internal standard. Finally, these procedures were applied to the analysis of these compounds in extra virgin olive oil samples from different varieties of olive.     

Analysis of oil used in late Roman oil lamps with different mass spectrometric techniques revealed the presence of predominantly olive oil together with traces of animal fat.

The lipid fraction of residues in ancient oil lamps found at the archaeological site of Sagalassos (south-west Turkey) was analysed by gas chromatography (GC) coupled to mass spectrometry (MS). The identification of plant sterols and long chain alcohols suggested that a vegetable oil was used in these lamps. The lipid sample was also analysed with reversed-phase liquid chromatography (LC) coupled to MS with atmospheric pressure chemical ionization (APCI). The identification of TAG's detected with LC-APCI-MS showed that predominantly olive oil was used as a fuel for the antique oil lamps. The presence of large quantities of multiply unsaturated triacylglycerol (TAG) and traces of saturated TAG indicated that also other oils and animal fat were added. Summarizing, the analysis of TAG's with LC-APCI-MS in lipid extracts of ancient ceramics proved to be a valuable method to reconstitute the original contents.     

A gas chromatographic determination of residues of eleven insecticides and two metabolites on olive tree leaves

A gas chromatographic (GC) method was developed and statistically validated for the simultaneous determination of residues of pyrethroid, endosulfan, and organophosphorus insecticides and some of their metabolites on olive tree leaves. Pesticide residues were extracted by static extraction with acetone-dichloromethane. After evaporation of the extract to dryness and redissolution in acetone, the organophosphorus insecticides were determined by GC with nitrogen-phosphorus detection. Another portion of the extract, after solvent change to acetonitrile, was cleaned up on an Alumina-N cartridge and analyzed for insecticides sensitive to electron-capture detection (ECD), i.e., pyrethroids and endosulfan and its metabolite. Recoveries of the organophosphorus insecticides ranged from 80.7 to 93.3% with relative standard deviations (RSDs) of < or = 7.2%; recoveries of the ECD-sensitive insecticides ranged from 71.6 to 89.5% with RSDs of < or = 11.6%. The method was used to analyze 26 samples of olive tree leaves from organic olive groves all over Greece, and the results confirmed the viability of the method for routine analysis. Residues of fenthion and fenthion sulfoxide were found in one and 3 samples, respectively, and their identities were confirmed by GC with mass spectrometry.     

A 2‐D‐HPLC‐CE platform coupled to ESI‐TOF‐MS to characterize the phenolic fraction in olive oil

A 2‐D‐HPLC/CE method was developed to separate and characterize more in depth the phenolic fraction of olive oil samples. The method involves the use of semi‐preparative HPLC (C18 column 250×10 mm, 5 μm) as a first dimension of separation to isolate phenolic fractions from commercial extra‐virgin olive oils and CE coupled to TOF‐MS (CE‐TOF‐MS) as a second dimension, to analyze the composition of the isolated fractions. Using this method, a large number of compounds were tentatively identified, some of them by first time, based on the information concerning high mass accuracy and the isotopic pattern provided by TOF‐MS analyzer together with the chemical knowledge and the behavior of the compounds in HPLC and CE. From these results it can be concluded that 2‐D‐HPLC‐CE‐MS provides enough resolving power to separate hundreds of compounds from highly complex samples, such as olive oil. Furthermore, in this paper, the isolated phenolic fractions have been used for two specific applications: quantification of some components of extra‐virgin olive oil samples in terms of pure fractions, and in vitro studies of its anti‐carcinogenic capacity.     

Radial basis neural network for the classification of fresh edible oils using an electronic nose

An electronic nose utilising an array of six-bulk acoustic wave polymer coated Piezoelectric Quartz (PZQ) sensors has been developed. The nose was presented with 346 samples of fresh edible oil headspace volatiles, generated at 45°C. Extra virgin olive (EVO), Non-virgin olive oil (OI) and Sunflower oil (SFO), were used over a period of 30 days. The sensor responses were then analysed producing an architecture for the Radial Basis Function Artificial Neural Network (RBF). It was found that the RBF results were excellent, giving classifications of above 99% for the vegetable oil test samples.This revised version was published online in November 2005 with corrections to the Cover Date.     

Trace elemental characterization of edible oils by ICP-AES and GFAAS

A method for the determination of the inorganic profile in edible oils is proposed. The quantification of selected metals in various oils (olive, pumpkin seed, sunflower, sesame seed, hazelnut, grape, soya, rice oil) was carried out using microwave assisted digestion followed by ICP-AES and GFAAS. The detection power of the ICP-AES technique was sufficient for the determination of Ca, Fe, Mg, Na, and Zn. Since the samples contained very low amounts of Al, Cu, Co, Cr, K, Ni, Mn, and Pb, these elements were measured by GFAAS. Differences of metal concentrations for edible oils obtained in this preliminary study represent a starting basis for the development of an additional analytical procedure applicable for oil characterization.     

Simplified pesticide multiresidue analysis in virgin olive oil by gas chromatography with thermoionic specific, electron-capture and mass spectrometric detection

In the present work, an analytical multiresidue method has been developed for the analysis of 32 organochlorine, organophosphorus and organonitrogen pesticides at microg kg(-1) levels in virgin olive oil. The method consists of the extraction of the pesticides with acetonitrile saturated in n-hexane followed by a clean-up process based on gel permeation chromatography (GPC) with ethyl acetate-ciclohexane (1:1) as mobile phase to separate the low-molecular mass pesticides from the high-molecular mass fat constituents of the oil. The target compounds were determined in the final extract by gas chromatography (GC) using thermoionic specific (TSD) and electron-capture (ECD) detection. In the case of positive samples, the amounts found were confirmed by GC-MS/MS, being the results in good agreement. Recoveries and RSDs (n = 10) values were 91-124% and 1-8% (GC-ECD), 82-100% and 9-20% (GC-TSD), and 89-105% and 4-14% (GC-MS/MS), respectively. The three proposed methods were applied to samples collected directly in two olive mills located in the Jaén province (Spain). Specifically, 24 samples of virgin olive oil were collected. The most frequently pesticide residues found were the herbicides terbuthylazine and diuron and endosulfan sulfate, a degradation product of the insecticide endosulfan. The herbicide concentration was higher in those oil samples obtained from olives which were collected from the ground after they had fallen down than in those oil samples from olives harvested directly from the tree. The GC-MS/MS developed method was also applied to the analysis of an olive oil sample from a proficiency test spiked with organochlorine pesticides and all the values obtained were within the specified "satisfactory" range.     

Determination of Metals in Olive Oil by Electrothermal Atomic Absorption Spectrometry: Validation and Uncertainty Measurements

The determination of trace metals in organic matrices is still highly demanding despite improvements in analytical instrumentation. The present study was undertaken in order to evaluate electrothermal atomic absorption spectrometry for the determination of cadmium, copper, iron, lead, and nickel in olive oil. A variety of approaches were used. The most suitable digestion procedure was heating the samples at 300°C for 24 hours and ashing in a muffle furnace at 450°C for 16 hours. The validation data were detection limits of 0.2–153 ng g^?1; mean trueness on certified reference materials of 81–94%; mean recovery on spikes of 90–120%; and repeatability of 12–53%. The combined relative uncertainty was 0.298–0.766. Oils processed by pressing had higher copper, iron, and lead concentrations than oils processed by centrifugation. The reported method provides an efficient way for monitoring trace metal content during olive oil production.     

Enrichment of benzo[a]pyrene in vegetable oils and determination by HPLC-FL

We have developed a simple method for the determination of the carcinogen Benzo[a]pyrene (BP) in vegetable oils. The method consists of extraction of the vegetable oil in acetonitrile, concentration to dryness in rotary evaporator and redissolution of the residue in hexane. The purification of the hexane extract was on Sep-Pack Silica Plus cartridges, and the determination of the BP in the isolated extract was by HPLC-FL. Detection and quantification limits were 0.23 and 0.32 μg kg⁻¹ of olive oil, respectively. Recovery (>93%) and RSD (<4%) were satisfactory. When applied to 18 oil samples, BP levels varied from not detected to 1.99 μg kg⁻¹.     

双重净化-气相色谱法测定植物油中指示性多氯联苯

为了考察食用油中7种指示性多氯联苯(PCBs)的残留情况,建立了食用油中痕量多氯联苯测定的双重净化-气相色谱法。以乙腈提取样品,提取液浓缩至干后用正己烷溶解,经浓硫酸、硅胶分散固相萃取双重净化后进行气相色谱分析,外标法定量。优化的色谱条件为:HP-5石英毛细管柱(30 m×0.32 mm×0.25 μm)程序升温分离,流速0.8 mL/min,进样量1.00 μL,电子捕获检测器检测。结果表明:在优化的条件下,7种多氯联苯在10~500 μg/L范围内线性良好,相关系数大于0.999,不同基质中的检出限(S/N=3)范围为1.8~8.9 μg/kg,定量限(S/N=10)范围为5.9~29.8 μg/kg。在橄榄油、花生油和棕榈油空白样品中添加10、20、100 μg/kg 3个水平的7种多氯联苯,其加标回收率范围为71.0%~105.5%,相对标准偏差(RSD)范围为4.0%~11.3%。该方法具有操作简便、快速、准确的特点,可用于植物油中指示性多氯联苯残留量的日常检测。     

Fluorescence spectra measurement of olive oil and other vegetable oils

Fluorescence spectra of some common vegetable oils, including olive oil, olive residue oil, refined olive oil, corn oil, soybean oil, sunflower oil, and cotton oil, were examined in their natural state, with a wavelength of 360 nm used as excitation radiation. All oils studied, except extra virgin olive oil, exhibited a strong fluorescence band at 430-450 nm. Extra virgin olive oil gave a different by interesting fluorescence spectrum, composed of 3 bands: one low intensity doublet at 440 and 455 nm, one strong at 525 nm, and one of medium intensity at 681 nm. The band at 681 nm was identified as the chlorophyll band. The band at 525 nm was at least partly derived from vitamin E. The low intensity doublet at 440 and 455 nm correlated with the absorption intensity at 232 and 270 nm of olive oil. The measurements of these fluorescence spectra were quick (about 5 min) and easy and could possibly be used for authentification of virgin olive oil.