Comparison of donor–acceptor and alumina columns for the clean-up of polycyclic aromatic hydrocarbons from edible oils

Two methods for clean-up and sample enrichment for the analysis of polycyclic aromatic hydrocarbons (PAHs) in edible oils are compared; a clean-up based on a donor–acceptor complex chromatography (DACC) column and a standardized method widely used in the food industry consisting in a low pressure column chromatography with alumina as stationary phase. Both methods are followed by a reversed-phase high-performance liquid chromatography with fluorescence detection for the separation and quantitation of each PAH. Certified materials were used in order to validate the methods. The limits of detection were lower than 1 ng/g and good selectivity was achieved in both cases. The DACC column clean-up is faster and better accuracies were obtained. The advantages and disadvantages of both methods are discussed.     

Determination of mineral oil paraffins in foods by on-line HPLC–GC–FID: lowered detection limit; contamination of sunflower seeds and oils

A method is described to lower the detection limit for mineral oil saturated hydrocarbons (MOSH) in foods as compared to the on-line HPLC–LC–GC–FID method described previously: samples are preseparated (enriched) by conventional liquid chromatography on activated silica gel and activated aluminum oxide. The silica gel retains up to 1 g of fat or oil, the aluminum oxide up to 2 mg n-alkanes of at least 24 carbon atoms, i.e. plant paraffins which may severely hinder the analysis of the mineral paraffins. The efficacy of the method is shown for an apple and sunflower oil. Oils extracted from manually harvested seeds grown in fields or gardens contained between 0.14 and 0.77 mg/kg MOSH. In the oils from seeds sampled in an oil mill, this value was increased to 3.3–9.3 mg/kg, indicating a contamination during harvest, transport and/or storage. Concentrations in commercial refined sunflower oils ranged between 2.7 and 32 mg/kg, averaging 11.2 mg/kg. Since deodorization removes a substantial part of the MOSH, this suggests a further contamination in the oil mill. The contamination affected all samples at a similar level, indicating that it occurs systematically by the presently used technology.     

The analysis of saturated and aromatic mineral oil hydrocarbons in dry foods and from recycled paperboard packages by online HPLC–GC–FID

ABSTRACT

The purpose of this study was to determine the concentrations of mineral oil hydrocarbons in dry foodstuffs packed in recycled paperboard, which were imported from different foreign countries to Germany. After collection, mineral oil saturated hydrocarbons (MOSH) and mineral oil aromatic hydrocarbons (MOAH) in dry foodstuffs and recycled paperboard were analysed using online coupled high-performance liquid chromatography–gas chromatography–flame ionisation detection (online HPLC–GC–FID) far before the end of the shelf life of the samples. Our results showed that recycled paperboard has MOAH content higher than that of dry foodstuffs. The proportion of MOAH within total mineral oil hydrocarbons was determined to be 7–45% in dry foodstuffs and 4–48% in paperboard. In addition, 29% of the products were found to contain over 1.00 mg/kg MOAH, with a maximum of 2.72 mg/kg in oatmeal. White colour recycled paperboard contained lower amounts of MOSH and MOAH than that of brown and grey colour recycled paperboard. The MOSH concentration in dry foodstuffs ranged from 0.11 to 21.92 mg/kg (?C25 hydrocarbons), which may be an indication of rapid migration. The lowest determined MOSH concentrations (?C25 hydrocarbons) were found in sea salt and soda samples, even when their paperboard contained high mineral oil hydrocarbons. Our three samples in packages containing internal bags (for complete barriers) were found to have low mineral oil concentration due to reduced migration through plastic (acrylate-coated polypropylene). However, one sample, a ‘crispy’ product with an internal bag, contained the extreme amount of 21.92 mg/kg. Differences in contaminants observed in both dry foodstuffs and recycled paperboard may have been due to the different packaging and production techniques of the different countries. In addition, 8 of 24 dry foodstuff samples contained MOSH concentrations frequently exceeding the 2.0 mg/kg limit for MOSH C₂₀–C₃₅.     

Lowering of concentration of polycyclic aromatic hydrocarbons in liquid media by sorption into polyethylene terephtalate—a model study

Rapeseed oil and water were spiked with polycyclic aromatic hydrocarbon (PAH) solutions at the total levels of 955.1 and 711.4 g kg^–1, respectively, filled into polyethylene terephtalate (PET) cylindrical receptacles and the PAH concentrations in both liquid media followed for more than 90 h by HPLC. During this time, the PAH concentrations decreased by 315.1 in oil and 212.7 g kg^–1 in water due to an interaction of PAHs with PET. Using a modified kinetic equation, the diffusion coefficients for PAHs in both liquid media were determined. Values of the diffusion coefficients obtained indicate that the polarity of medium did not affect the rate of PAH removal. Calculation of the area occupied by a PAH molecule on the PET surface suggests that either the multilayer adsorption or the diffusion of PAHs into PET bulk came into account as the decisive factor bringing about the decrease of PAH concentrations in both media.     

Determination of Sulfite in Water and Dried Fruit Samples by Dispersive Liquid–Liquid Microextraction Combined with UV–Vis Fiber Optic Linear Array Spectrophotometry

A simple and rapid dispersive liquid?Cliquid microextraction (DLLME) method was applied to preconcentrate sulfite ions from aqueous samples as a prior step to its determination by fiber optic-linear array detection spectrophotometry. The procedure is based on the color reaction of sulfite with o-phthaldialdehyde (OPA) in the presence of ammonia to form isoindole and extraction of the formed isoindole derivative using the DLLME technique. The conditions for the microextraction performance were investigated and optimized. The calibration graph was linear in the range of 2?C100???g?L^?1with a detection limit of 0.2???g?L^?1. The relative standard deviation for five replicate measurements of 10 and 50???g?L^?1of sulfite were 2.8 and 2.0?%, respectively. Under the optimized conditions, the enrichment factor of ~133 was obtained from a sample volume of 10?mL. The proposed method was successfully applied to the sulfite determination in drinking water and in food samples.     

Determination of brominated flame retardants in food by LC–MS/MS: diastereoisomer-specific hexabromocyclododecane and tetrabromobisphenol A

The levels of the brominated flame retardants (BFRs) hexabromocyclododecane (α, β and γHBCD diastereoisomers) and tetrabromobisphenol A (TBBPA) have been determined in two studies using LC–MS/MS. The methodology developed was validated in-house and used to analyse UK 2004 Total Diet Study (TDS) samples and shellfish (oysters, mussels and scallops) collected from Scotland. HBCD was detected in most samples; in both studies the αHBCD diastereoisomer was generally the most abundant as opposed to the γ diastereoisomer that tends to dominate in environmental samples and manufactured products. It is reported that selective metabolism or biotransformation of the β and γ diastereoisomers may be taking place. TBBPA was not detected in any samples above the limit of detection, which was as low as 0.05 µg kg^–1. This may be because TBBPA, unlike HBCD, is chemically bound to the polymer matrix during manufacture and not readily leached. The UK Committee on Toxicity of Chemicals in Food, Consumer Products and the Environment (COT) concluded that the concentrations of HBCD and TBBPA detected in the TDS study did not raise toxicological concerns and, as levels in the shellfish samples were in a similar concentration range, it was concluded that exposure to the BFRs measured is not significant when compared to exposure from the rest of the diet.     

Indoor and outdoor polycyclic aromatic hydrocarbons in residences surrounding a Söderberg aluminum smelter in Canada

Ambient air in 18 residences surrounding an aluminum smelter were sampled to study the relationship between indoor and outdoor polycyclic aromatic hydrocarbons (PAHs). Objectives of the study were to quantify the indoor distribution of PAHs, indoor/outdoor (I/O) concentration ratios, and the relationship among PAH compounds. Correlation coefficients inside residences suggested an indoor source of 2-3 ring PAHs and an external source of 4-6 ring PAHs. The I/O ratios of 4-6 ring PAHs for homes without any substantial indoor sources were below unity, indicating that the presence of these PAHs was attributable to the aluminum smelter. Least squares linear regression of the coupled measurements without indoor sources of 5-6 ring PAHs resulted in average infiltration efficiencies (P(PAH)) of 0.49, 0.20, and 0.47 for benzo[a]pyrene, benzo[k]fluoranthene, and benzo[g,h,i]perylene, respectively. These P(PAH) values suggest that simultaneous measurements of indoor and outdoor concentrations of PAHs > 4 rings predominantly associated with the fine fraction of particulate matter could provide useful estimates of particle infiltration efficiency. Overall, study results indicate that when an industrial facility is the main source of outdoor 4-6 ring PAHs, the contribution of facility emissions may greatly exceed indoor sources in nonsmoking residences.     

Determination of Total Phenolic Content in Olive Oil Samples by UV–visible Spectrometry and Multivariate Calibration

The viability of determining the total phenolic content in olive oil samples by chemometric analysis of UV?Cvis spectral data was studied. As a result, a novel spectrophotometric method that does not require prior analyte separation is proposed. The method uses partial least squares (PLS) regression modeling in conjunction with UV?Cvis absorption spectral data obtained on oil samples dissolved in hexane. The resulting PLS model was developed by correlating the total phenolic content determined by Folin?CCiocalteu assay with the spectral data of oil solution between 210 and 340?nm. The predictive ability of the model was good as indicated by the root mean square error of prediction (RMSEP) and relative error (6.7?mg?kg^?1 and 6.1%, respectively) obtained for analysis of the validation set of samples. The principal figures of merit, namely limit of detection (7.3?mg?kg^?1), analytical sensitivity (1.0?mg?kg^?1) and precision (<10% RSD) were considered adequate for routine analysis. The proposed method was applied in the determination of total phenolic content in Chilean extra virgin olive oil (VOO) samples from the 2009 and 2010 harvest period. The results were compared to those determined with liquid chromatography.     

Determination of aflatoxins in edible oil from markets in Hebei Province of China by liquid chromatography–tandem mass spectrometry

Analysis of aflatoxin B₁ (AFB₁), B₂ (AFB₂), G₁ (AFG₁) and G₂ (AFG₂) in 76 edible oil samples (peanut oil, soybean oil, corn embryo oil and blended oil) was performed by liquid chromatography–tandem mass spectrometry (LC–MS/MS). The oils were sampled from three areas (Shijiazhuang, Baoding and Tangshan) of Hebei Province of China. AFB₁ was detected in 22 samples representing 28.9%, followed by AFB₂ (7.89%) and AFG₁ (3.95%), while no AFG₂ contamination was detected in any samples. AFB₁ levels in oil samples ranged 0.14–2.72?µg?kg^?1 and AFB₂ ranged 0.15–0.36?µg?kg^?1, while lower levels of 0.01–0.02?µg?kg^?1 for AFG₁ were recorded. The paper is part of an on-going investigation of aflatoxin contamination in Chinese edible oils.     

Determination of ochratoxin A in traditional Chinese medicinal plants by HPLC–FLD

Traditional Chinese medicinal plants (TCMPs), commonly used as spices, additives or foods, are also widely used in China to prevent and cure human disease. Due to their provenance, TCMPs may be contaminated by various fungal species, including ochratoxigenic fungi, during growth, collection, transportation and, especially, storage. A reliable method for the determination of ochratoxin A (OTA) in TCMPs of different origins was developed to monitor OTA levels in China. Analyses involved the extraction of OTA by methanol/water, immunoaffinity column (IAC) clean-up and HPLC quantification with fluorescence detection (FLD). Positive results were further confirmed by LC–ESI–MS/MS. The limit of detection (LOD) was 0.3 µg kg^?1, based on a signal-to-noise ratio of 3 : 1. Among the total of 57 TCMPs samples collected from six different areas, 31 were visibly moldy due to inappropriate storage; 26 sample, purchased from local TCMPs markets, were not visibly moldy. The results showed that 23 of the visibly moldy samples and two of the not visibly moldy were contaminated with OTA at levels ranging 1.2–158.7 and 2.5–5.6 µg kg^?1, respectively. This is the first report of the natural occurrence of OTA in TCMPs.     

Monitoring the Oxidative Stability of Monovarietal Extra Virgin Olive Oils by UV–Vis Spectroscopy and MCR–ALS

The extra virgin olive oil (EVOO) has a certain oxidation resistance when compared to other vegetable oils without refining process, due to their large composition of monounsaturated fatty acids, antioxidants, and bio-compounds. The main of this research was to evaluate and monitor the behavior of autoxidative processes through the storage time in two packaging systems of different EVOO monovarietals produced in Minas Gerais, Brazil by using ultraviolet and visible spectroscopy (UV–Vis) with multivariate curve resolution with alternating least squares (MCR–ALS). We analyzed six EVOOs produced from different monovarietals (Arbequina, Empeltre, Coratina, Grappolo, Koroneiki, and Maria da Fé), over the course of 1 year, performed the analysis in times 0, 30, 90, 180, and 365 days, and storage in glass bottles and tinplate cans. The UV–Vis spectroscopy coupled with MCR–ALS was a feasible tool to monitor autoxidation processes in EVOO through storage time and in the monitoring of the EVOO quality in different package systems. The glass bottles were a package system that provides more protection for the autoxidation processes with the time for the EVOO from monovarietals Empeltre, Arbequina, and Coratina. In addition, it was possible to make a differentiation between the monovarietal olive oils produced in Brazil by observing the amount of phenolic compounds present in the chemical composition of each oil. Allowing gather information about the formation of oxidative products may correlate with the shelf life of the EVOO.     

Comparison of microbiological and HPLC – fluorescence detection methods for determination of niacin in fortified food products

A comparison has been made between results obtained by a recently published HPLC method, involving post-column reaction and fluorescence detection, with a microbiological assay using Lactobacillus plantarum. The HPLC method includes a modified acid hydrolysis extraction step (0.1 M HCl) and yields niacin values from fortified foods somewhat lower than by the microbiological assay. The most significant differences were observed for the cereal-based products. These differences arise principally from the lack of specificity of L. plantarum and from the stronger acid hydrolysis extraction conditions (1 M HCl) of the microbiological assay, which probably releases a part of the non-bioavailable niacin. Moreover by HPLC, excellent recoveries of added nicotinic acid and nicotinamide (95–100%) were obtained and better precision (RSDr=0.3–0.8%) was observed than from the micobiological assay.     

Carbon isotope signature of polycyclic aromatic hydrocarbons (PAHs): evidence for different sources in tropical and temperate environments?

In tropical soils, naphthalene and, partly also, perylene occur at elevated concentrations while pyrolytic higher molecular weight PAHs are almost absent. We hypothesize that there are recent biological PAH sources in the tropical environment related with woody plants and termites. We used the C isotope signature of individual PAHs in temperate and tropical soils and in tropical wood and termite nests to distinguish different PAH sources. The mean delta13C values of the benzo[b+j+k]fluoranthenes and of benzo[a+e]pyrenes in temperate soils ranged between -24.6/1000 and -25.3/1000, being similar to values reported in the literature for PAHs with pyrolitic origin. The mean delta13C values of perylene decreased in the order temperate soils (-27.0/1000) > termite nests (-31.4/1000) > tropical soil (-32.4/1000), while those of naphthalene (-24.6/1000 to -26.2/1000) were similar among the tropical and temperate soils, tropical wood, and termite nests. Our results support the assumption that perylene in the tropical environment is recently biologically produced, as indicated by the depletion in 13C. The C isotope composition of naphthalene, however, cannot be used to distinguish different sources.     

Evaluation of Dispersive Liquid–Liquid Microextraction–HPLC–UV for Determination of Deoxynivalenol (DON) in Wheat Flour

A fast and simple method for the extraction of deoxynivalenol (DON) from wheat flour using dispersive liquid–liquid microextraction (DLLME) followed by high-performance liquid chromatography–UV detection has been developed and compared with immunoaffinity column cleanup (IAC) process. The influence of several important parameters on the extraction efficacy was studied. Under optimized conditions, a linear calibration curve was obtained in the range of 50–1,000 μg/L. Average recoveries of DON from spiked wheat samples at levels of 500 μg/kg for DLLME and IAC ranged from 72.9?±?1.6 and 85.5?±?3.1, respectively. A good correlation was found for spiked samples between DLLME and IAC methods. The limit of detection was 125 and 50 μg/kg for DLLME and IAC method, respectively. Advantages of DLLME method with respect to the IAC have been pointed out.     

Qualitative and quantitative electroanalysis of synthetic phenolic antioxidant mixtures in edible oils based on their acid–base properties

A simple electroanalytical method using square wave voltammetry at a Pt band ultramicroelectrode to perform a qualitative and quantitative analysis of different synthetic antioxidant mixtures permitted by official regulations in edible oils is proposed. The methodology was based on the comparison of voltammetric signals obtained in acetonitrile + 0.1 M (C₄H₉)₄NF₆P with those recorded in the same reaction medium when different aliquots of (C₄H₉)₄NOH were added to allow a qualitative differentiation between antioxidants. Firstly, studies on solutions prepared from commercial reagents were carried out. Then, the results obtained were transferred to the analysis of a real matrix, i.e., an edible olive oil. From real samples spiked with a known amount of different synthetic antioxidant mixtures, we could deduce the presence of these antioxidants by comparing results obtained in the neutral medium with those obtained after the successive addition of base. The standard addition method was used to quantify the individually spiked synthetic antioxidants in the real sample. Recovery percentages were between 88% and 118%. The reproducibility was 1.5%, 3.1%, 4.1% and 4.1% in ACN + 0.1 M TBAHFP and 1.5%, 4.6%, 6.6% and 2.5% in Bz/EtOH (1:2) + 0.1 M H₂SO₄ for TBHQ, BHA, BHT and PG, respectively. The repeatability was 1% for PG in both media. These parameters show a good system performance.     

Determination of acetaldehyde,methanol and fusel oils in distilled liquors and sakès by headspace gas chromatography

Food Science and Biotechnology - In this study, a headspace gas chromatography (HS-GC) method was carried out to determine the contents of acetaldehyde, methanol and fusel oils in distilled liquors...     

Simultaneous determination of aspartame,acesulfame-K,saccharin, citric acid and sodium benzoate in various food products using HPLC–CAD–UV/DAD

A newly developed method for simultaneous determination of aspartame, acesulfame-K, saccharin, citric acid and sodium benzoate in various diet supplements and non-alcoholic beverages in a single run is presented. The analytes were analysed by high-performance liquid chromatography coupled to a charged aerosol (Corona CAD) and ultraviolet–diode array detectors simultaneously connected in series. Mass spectrometer MicrOTOF-QII from Bruker Daltonik (Bremen, Germany) was used to obtain the mass spectra for peak identifications. The method was validated using a Thermo Hypersil Gold-C18 column packed with 5 μm shell particles (150 × 4.6 mm) and methanol–water with 0.05 % TFA gradient mobile phase at a flow rate of 0.80 mL/min. The elaborated method was validated for linearity, precision and accuracy. The analytical results obtained in the validation study were highly satisfying; the recoveries for the analytes studied ranged between 98.1 and 101 % and the precision values from 0.11 to 1.73 %. By these procedures, the three sweeteners (aspartame, acesulfame-K and saccharin), citric acid and sodium benzoate could be well separated and quantitatively determined in varied food products. Hundred millilitres of soft drinks contained on average 5.50 mg of aspartame, 6.38 mg of saccharin, 8.94 mg of acesulfame-K, 9.05 mg of sodium benzoate and 111 mg of citric acid. Citric acid was the most abundant additive in all the samples analysed except for table sweeteners, and its highest concentration was determined in diet supplements, i.e. 347 mg/g. The percentage of adequate daily intake realisation in case of all additives is lower than 10 %, except for sodium benzoate in isotonic drinks (10.1 %).