Biophysical impact of lubricating base oil aerosols on natural pulmonary surfactant film.

Lubricating base oils have been extensively employed for producing various industrial and consumer products. Therefore, their environmental and health impacts should be carefully evaluated. Although there have been many reports on pulmonary cytotoxicity and inflammatory responses of inhaled lubricating base oils, their potential influences on pulmonary surfactant (PS) films that play an essential role in maintaining respiratory mechanics and pulmonary immunity remains largely unknown. Here a systematic study on the interactions between an animal-derived natural PS and aerosols of water and representative mineral and vegetable base oils is performed using a novel biophysical assessing technique called constrained drop surfactometry capable of providing in vitro simulations of normal tidal breathing and physiologically relevant temperature and humidity in the lung. It was found that the mineral oil aerosols can impose strong inhibitions to the biophysical property of PS film, while the airborne vegetable oils and water show negligible adverse effects within the studied concentration range. The inhibitory effect is originated from the strong hydrophobicity of mineral oil, which makes it able to disrupt the interfacial molecular ordering of both phospholipid and protein compositions and consequently suppress the formation of condensed phase and multilayer scaffolds in a PS film. ENVIRONMENTAL IMPLICATION: Understanding the biophysical influence of airborne lubricating base oils on pulmonary surfactant (PS) films can provide new insights into the environmental impacts and health concerns of various industrial lubricant products. Here a comparative study on interactions between an animal-derived natural PS film and the aerosols of water and representative mineral and vegetable base oils under the true physiological conditions was conducted in situ using constrained drop surfactometry. We show that the most frequently used mineral base oil can cause strong inhibitions to the PS film by disrupting the molecular ordering of saturated phospholipids and surfactant-associated proteins at the interface.

Optical tuning of copolymer-in-oil tissue-mimicking materials for multispectral photoacoustic imaging.

Objective. The availability of tissue-mimicking materials (TMMs) for manufacturing high-quality phantoms is crucial for standardization, evaluating novel quantitative approaches, and clinically translating new imaging modalities, such as photoacoustic imaging (PAI). Recently, a gel comprising the copolymer styrene-ethylene/butylene-styrene (SEBS) in mineral oil has shown significant potential as TMM due to its optical and acoustic properties akin to soft tissue. We propose using artists' oil-based inks dissolved and diluted in balsam turpentine to tune the optical properties.Approach. A TMM was fabricated by mixing a SEBS copolymer and mineral oil, supplemented with additives to tune its optical absorption and scattering properties independently. A systematic investigation of the tuning accuracies and relationships between concentrations of oil-based pigments and optical absorption properties of the TMM across visible and near-infrared wavelengths using collimated transmission spectroscopy was conducted. The photoacoustic spectrum of various oil-based inks was studied to analyze the effect of increasing concentration and depth.Main results. Artists' oil-based inks dissolved in turpentine proved effective as additives to tune the optical absorption properties of mineral oil SEBS-gel with high accuracy. The TMMs demonstrated long-term stability and suitability for producing phantoms with desired optical absorption properties for PAI studies.Significance. The findings, including tuning of optical absorption and spectral shape, suggest that this TMM facilitates the development of more sophisticated phantoms of arbitrary shapes. This approach holds promise for advancing the development of PAI, including investigation of the spectral coloring effect. In addition, it can potentially aid in the development and clinical translation of ultrasound optical tomography.

Comparison of carrier gases for the separation and quantification of mineral oil hydrocarbon (MOH) fractions using online coupled high performance liquid chromatography-gas chromatography-flame ionisation detection.

On-line coupled high performance liquid chromatography-gas chromatography-flame ionisation detection (HPLC-GC-FID) was used to compare the effect of hydrogen, helium and nitrogen as carrier gases on the chromatographic characteristics for the quantification of mineral oil hydrocarbon (MOH) traces in food related matrices. After optimisation of chromatographic parameters nitrogen carrier gas exhibited characteristics equivalent to hydrogen and helium regarding requirements set by current guidelines and standardisation such as linear range, quantification limit and carry over. Though nitrogen expectedly led to greater peak widths, all required separations of standard compounds were sufficient and humps of saturated mineral oil hydrocarbons (MOSH) and aromatic mineral oil hydrocarbons (MOAH) were appropriate to enable quantitation similar to situations where hydrogen or helium had been used. Slightly increased peak widths of individual hump components did not affect shapes and widths of the MOSH and MOAH humps were not significantly affected by the use of nitrogen as carrier gas. Notably, nitrogen carrier gas led to less solvent peak tailing and smaller baseline offset. Overall, nitrogen may be regarded as viable alternative to hydrogen or helium and may even extend the range of quantifiable compounds to highly volatile hydrocarbon eluting directly after the solvent peak.

A study on the impact of harvesting operations on the mineral oil contamination of olive oils.

During the 2020-21 olive oil campaign, the contribution of harvesting operations to mineral oil saturated (MOSH) and aromatic hydrocarbon (MOAH) contamination was studied. Oils extracted from hand-picked olives (15 different olive groves) generally had background MOSH (<2.7 mg/kg), and no quantifiable MOAH. In 40% of the cases, an important contamination increase was observed after harvesting operations. Except for one sample (325.8 and 111.0 mg/kg of MOSH and MOAH, respectively), other samples reached 4.3-33.7 mg/kg of MOSH and 1.1-11.3 mg/kg of MOAH. Accidental leaks of lubricants and/or contact with lubricated mechanical parts, were identified as important sources of contamination. Chromatographic traces obtained by on-line high-performance liquid chromatography (HPLC)-gas chromatography (GC)-flame ionization detection (FID) allowed for source identification. A comprehensive two-dimensional gas chromatographic platform (GC × GC) with parallel FID/MS detection was implemented for confirmation and to attempt the characterization of the contaminations. Good harvesting practices are suggested to minimize contamination risks.

Combination of Multidimensional Instrumental Analysis and the Ames Test for the Toxicological Evaluation of Mineral Oil Aromatic Hydrocarbons.

Mineral oil aromatic hydrocarbons (MOAHs) include mutagenic and carcinogenic substances and are considered a potential health risk. Current methods address the total MOAH content but cannot address the actual toxicological hazard of individual components. This work presents a combined methodology closing those gaps: high-performance liquid chromatography (HPLC) coupled to gas chromatography with flame ionization detection was used to determine the MOAH content. To characterize present substance classes, comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry was applied. Preparative HPLC separated MOAHs into subgroups, which were tested with a miniaturized Ames test evaluating DNA reactivity of isolated fractions. Combining these methods allowed a correlation between present subgroups and DNA reactivity. The developed approach was applied to a mineral oil and distinguished between not DNA-reactive mono- and diaromatics and DNA-reactive tri- and polyaromatics, providing a proof of concept. Hereinafter, it will be applied to diverse sample matrices including mineral oils, food, and food contact materials.

Development of an analytical method for the determination of mineral oil aromatic hydrocarbons (MOAH) from printing inks in food packaging.

An analysis method was developed to detect chemical markers of mineral oil aromatic hydrocarbons (MOAH) from offset printing inks in food packaging materials. 16 aromatic hydrocarbons were used as target analytes and different solid phase extraction procedures (SPE) and gas chromatography coupled to mass spectrometry (GC-MS) were tested. The concentration range studied was 0.1-7.5 µg g-1 with R2 higher than 0.9963, intraday RSD values below 5 %, RSD values between days lower than 12 %, recoveries higher than 80 %, LOD and LOQ lower than 0.09 µg g-1. Ten of the target analytes were identified in offset printing inks at concentrations between 2.28 and 8.59 µg g-1. Nine of them were also identified in the food packages examined in concentrations ranging from 0.10 to 0.33 µg g-1. These compounds were: methylnaphthalene, 2-methylnaphthalene, biphenyl, 2,6-dimethylnaphthalene, acenaphthene, 3,3',5,5'-tetramethylbiphenyl, 4,6-dimethyldibenzothiophene, 1-methylpyrene, benzo(b)naphtha(1,2-d)thiophene and 9,9'-dimethylfluorene. Mineral oil in food packaging was previously analysed by GC with flame ionization detection (FID).

Comparison of PAC and MOAH for understanding the carcinogenic and developmental toxicity potential of mineral oils.

The carcinogenicity and developmental toxicity of unrefined mineral oil is related to its 3-7 ring polycyclic aromatic compounds (PAC) content. Therefore, refining operations focus on the targeted removal PAC from mineral oil that may contain aromatics of low toxicological concern. There are thus, two types of aromatic substances in mineral oil: hazardous and non-hazardous. The first type consists of 3-7 ring PAC which may be naked (unsubstituted) or lowly alkylated. The second type or non-hazardous consists of 1-7 ring aromatics with high degree of alkylation or lack of bay or fjord regions. Although these are toxicologically different, they may both elute in the same fraction when using chromatography. To understand how these two aromatic types are related we have assessed the entire mineral oil refinement process by measuring total mineral oil aromatic hydrocarbons (MOAH) content by chromatography next to regulatory hazard tests which focus on 3-7 ring PAC. MOAH content is positively correlated to its molecular weight resulting in aromatic content bias for high viscosity substances. Hazard to 3-7 ring PAC is best controlled by the validated IP346 or modified Ames test. We explain the concept of high vs low alkylation by shortly reviewing new data on alkylated PAC.

Cell-Inspired Hydrogel Microcapsules with a Thin Oil Layer for Enhanced Retention of Highly Reactive Antioxidants.

In nature, individual cells are compartmentalized by a membrane that protects the cellular elements from the surrounding environment while simultaneously equipped with an antioxidant defense system to alleviate the oxidative stress resulting from light, oxygen, moisture, and temperature. However, this mechanism has not been realized in cellular mimics to effectively encapsulate and retain highly reactive antioxidants. Here, we report cell-inspired hydrogel microcapsules with an interstitial oil layer prepared by utilizing triple emulsion drops as templates to achieve enhanced retention of antioxidants. We employ ionic gelation for the hydrogel shell to prevent exposure of the encapsulated antioxidants to free radicals typically generated during photopolymerization. The interstitial oil layer in the microcapsule serves as an stimulus-responsive diffusion barrier, enabling efficient encapsulation and retention of antioxidants by providing an adequate pH microenvironment until osmotic pressure is applied to release the cargo on-demand. Moreover, addition of a lipophilic reducing agent in the oil layer induces a complementary reaction with the antioxidant, similar to the nonenzymatic antioxidant defense system in cells, leading to enhanced retention of the antioxidant activity. Furthermore, we show the complete recovery and even further enhancement in antioxidant activity by lowering the storage temperature, which decreases the oxidation rate while retaining the complementary reaction with the lipophilic reducing agent.

GTL synthetic paraffin oil shows low liver and tissue retention compared to mineral oil.

Oral exposure to mineral oil may result in a narrow fraction of mineral oil saturated hydrocarbon (MOSH) being retained in tissues. Excess of MOSH hepatic retention may lead to the formation of lipogranuloma caused by predominantly multiring cycloalkanes (naphthenics) in a critical range of C25-C35. Although hepatic lipogranuloma is of low pathological concern, MOSH tissue deposition could be minimized by using an oil of similar quality but devoid of naphthenic structures to decrease hepatic retention. Synthetic Gas to liquid (GTL) oils offer an alternative to petroleum derived mineral oils, because they do not contain naphthenic structures. To demonstrate this point, SD rats were fed either GTL oil (99% iso-alkanes) or naphthenic mineral oil (84% cycloalkanes) at 200 mg/kg bw/day for 90 or 134 days with a recovery group. Liver, fat and mesenteric lymph nodes were analyzed for alkane sub-type levels using Online-HPLC-GC-FID and GCxGC-TOF-MS. Results indicate that at equal external dose, GTL hydrocarbons result in lower tissue levels and more rapid excretion than MOSH. GTL retained hepatic fractions were also qualitatively different than MOSH constituents. Because chemical composition differences, GTL oil show low absorption and tissue retention potential and thus an advantageous alternative to conventional mineral oil.

Wax-oil lubricants to reduce the shear between skin and PPE.

Prolonged use of tight-fitting PPE, e.g., by COVID-19 healthcare workers leads to skin injuries. An important contributor is the shear exerted on the skin due to static friction at the skin-PPE interface. This study aims to develop an optimised wax-oil lubricant that reduces the friction, or shear, in the skin-PPE contact for up to four hours. Lubricants with different wax-oil combinations were prepared using beeswax, paraffin wax, olive oil, and mineral oil. In-vivo friction measurements involving seven participants were conducted by sliding a polydimethylsiloxane ball against the volar forearms to simulate the skin-PPE interface. The maximum static coefficient of friction was measured immediately and four hours after lubricant application. It was found that the coefficient of friction of wax-oil lubricants is mainly governed by the ratio of wax to oil and the thermal stability and morphology of the wax. To maintain long-term lubricity, it is crucial to consider the absorption of oil into the PPE material. The best performing lubricant is a mixture of 20 wt% beeswax, 40 wt% olive oil, and 40 wt% mineral oil, which compared to unlubricated skin, provides 87% (P = 0.0006) and 59% (P = 0.0015) reduction in instantaneous and 4-h coefficient of friction, respectively.

Survey of mineral oil hydrocarbons in Chinese commercial complementary foods for infants and young children.

Recently, mineral oil hydrocarbons (MOH) in various foods have raised significant concern, especially for infants and young children due to their potential adverse health effects. Two fractions can be distinguished by certain analytical techniques, mineral oil saturated hydrocarbons (MOSH) and mineral oil aromatic hydrocarbons (MOAH). The toxicological profile of MOSH and MOAH differs greatly. The toxicity of MOSH is linked with long-term accumulation of some hydrocarbons. MOAH with three to seven, non- or simple-alkylated, aromatic rings may be mutagenic and carcinogenic. However, data on the occurrence of mineral oils in commercial complementary foods for infants and young children are lacking in China. In the present study, 100 commercial food samples were collected, including 26 pureed or paste canned foods, 21 high-protein ground cereal foods (rice flour), 25 raw cereal foods (noodles), and 28 cereal-based molar sticks and biscuits. The content of MOSH and MOAH in those samples was determined by optimised sample preparation methods combined with on-line high-performance liquid chromatography coupled with gas chromatography and flame ionisation detector (HPLC-GC-FID), with a limit of quantification of 0.5 mg/kg. The results indicated that there were no MOAH detected in any of the foods, but MOSH and polyolefin oligomeric saturated hydrocarbons (POSH) existed in most of the food samples, at <0.5-23.68 mg/kg. Moreover, the data and chromatograms of the MOSH and POSH also indicated that these contaminants were closely correlated to their ingredients and manufacturers. The current study provides basic data to understand MOH exposure and consequent health impact.

Mild mixed-solvent extraction for determination of total mineral oil hydrocarbon contaminants in milk powder products.

A mild mixed-solvent of n-hexane/isopropanol is proposed for extracting total mineral oil hydrocarbons (MOH) from commercial milk powder products. Unlike acid-hydrolysis, the mixed-solvent extraction was performed at ambient temperature and the low-boiling-point hydrocarbons were retained to the greatest extent. After extraction, total MOH was determined by on-line liquid chromatography-gas chromatography with a flame ionization detector (LC-GC-FID). The validation of the proposed extraction method revealed a recovery efficacy of 83.0-107.5% and a limit of quantification of 0.5 mg/kg. Then, the total MOH in ten commercial milk powders was determined and mineral oil saturated hydrocarbons (MOSH)/polyolefin oligomeric saturated hydrocarbons (POSH) were found to be within the range of 0.61-5.46 mg/kg. The comparison of the total and surface MOSH/POSH indicated that a major part of the contamination was derived from sources before packaging. The present study provides a robust method for the extraction and determination of total MOH in milk powders.

Physicochemical characteristics of oil-based cuttings from pretreatment in shale gas well sites.

Understanding the physicochemical characteristics of oil-based cuttings (OBCs) is an important foundation for subsequent treatment and management. The macro- and microscopic properties of white oil-based cuttings (WOBCs) and diesel-based cuttings (DBCs) after the different pretreatment steps have been assessed using scanning electron microscopy. The organic and inorganic compositions of OBCs have been analyzed using X-ray diffraction, Fourier-transform infrared spectrometry, and gas chromatography-mass spectrometry. Inorganic matter (SiO2, BaSO4, and CaCO3), alkanes, aromatic compounds, and water were the main components of OBCs. The organic content (26.14%) and alkane content of the WOBCs were higher than that of the DBCs, whereas for the inorganic content (70.87%), the reverse was true. The macro- and micromorphologies of OBCs were quite different because their oil and water contents were different. The oil contents of OBCs decreased in the order A1 (14.64%) > A3 (12.67%) > A2 (11.06%) and B1 (9.19%) > B3 (8.94%) > B2 (4.66%); the water contents decreased in the order A1 (2.99%) > A3 (2.19%) > A2 (1.09%) and B1 (2.30%) > B3 (1.87%) > B2 (1.09%). Moreover, a skid-mounted treatment technology for OBCs was proposed. The results can be a scientific guidance for the treatment and management of OBCs.

Segregation of Dispersed Silica Nanoparticles in Microfluidic Water-in-Oil Droplets: A Kinetic Study.

Dispersed negatively charged silica nanoparticles segregate inside microfluidic water-in-oil (W/O) droplets that are coated with a positively charged lipid shell. We report a methodology for the quantitative analysis of this self-assembly process. By using real-time fluorescence microscopy and automated analysis of the recorded images, kinetic data are obtained that characterize the electrostatically-driven self-assembly. We demonstrate that the segregation rates can be controlled by the installment of functional moieties on the nanoparticle's surface, such as nucleic acid and protein molecules. We anticipate that our method enables the quantitative and systematic investigation of the segregation of (bio)functionalized nanoparticles in microfluidic droplets. This could lead to complex supramolecular architectures on the inner surface of micrometer-sized hollow spheres, which might be used, for example, as cell containers for applications in the life sciences.

Effects of mineral oil spray additives on the distribution and dissipation kinetics of pyraclostrobin and azoxystrobin in banana leaves, fruits, and soil.

Using LC-MS/MS, a rapid and sensitive method for the simultaneous determination of pyraclostrobin and azoxystrobin residues in banana matrices (leaf and whole banana) and soil was established. The samples were extracted using acetonitrile and purified through C18 dispersive solid-phase extraction. The average recovery of the analytes in various matrices was in the range of 77.3%-103.9% with an RSD range of 0.9%-9.5%. The initial deposition amounts of pyraclostrobin and azoxystrobin at 2 h in the banana leaves of the mineral oil group were 1.43 and 1.31 times in Guangxi, and 2.10 and 1.81 times in Hainan for the water group, whereas those in the soil of the water group were 3.45 and 3.03 times in Guangxi, and 2.14 and 3.48 times in Hainan for the mineral oil group. The half-lives in the leaves and soil of the mineral oil group were not remarkably different from those of the water group. The terminal residue of the analytes on the whole banana was <0.02 mg/kg at 14 days after application from the two sites. The results of this work may indicate and promote the safety of using pyraclostrobin and azoxystrobin in banana production, especially with mineral oil spray adjuvants.

Supercritical fluid chromatography as a rapid single-step method for the determination of mineral oil saturated and aromatic hydrocarbons in purified mineral oils for food and cosmetics applications.

Mineral oil hydrocarbons are used in the consumer goods sector for the elaboration of a wide range of foods and cosmetics. Traditional methods for determining their levels and composition are time consuming and laborious, besides requiring complex instrumentation. Here a simple and fast method was developed that uses columns packed with silver-modified silica in supercritical fluid chromatography with flame ionization and UV detection (SFC-FID/UV) for the determination of mineral oil saturated hydrocarbons (MOSH) and mineral oil aromatic hydrocarbons (MOAH) in purified mineral oil samples. The method requires no sample preparation apart from dilution. Direct quantification of MOSH and MOAH was possible for samples with MOSH/MOAH ratios around one. For other samples deconvolution of the MOSH and MOAH humps in the FID chromatogram using the UV signal was needed since baseline separation of the two fractions could not be obtained. Validation of the method performance showed an excellent linearity (R2 > 0.9995) in the range of concentrations tested (2.5-100 mgmL-1) and a better repeatability than the standard methods (<5%). MOAH detection limits were better than 0.36% MOAH, which makes the method sufficiently sensitive for analysis of all but the highest purity mineral oils. The proposed SFC-FID/UV method was suitable for the analysis of mineral oils with viscosities and molecular weights below approximately 56 mm2s-1 and 450 gmol-1. The quantitative results of the new method were not statistically significantly different from those obtained with the standard SPE-GC-FID method where the new method has the advantages of a better repeatability, simpler operation and a significantly shortened analysis time. This new method could potentially also be used for the analysis of mineral oil contaminations in consumer products such as foods. However, in this case additional sample clean-up and preconcentration steps are needed for reducing matrix interferences from e.g. triglycerides and olefins and for improving the detection limits.

Difference Analysis of Gas Molecules Diffusion Behavior in Natural Ester and Mineral Oil Based on Molecular Dynamic Simulation.

Natural ester, as a new environmentally green insulating oil, has been widely used in transformer. In an oil-immersed transformer, the normal aging, thermal failure, and discharge failure could easily lead to the decomposition of the oil-paper insulation system and produce different kinds of gases. Studying gas dissolution in natural ester and mineral oil could provide assistance in applying criteria to make a diagnosis of different kinds of faults in the transformer. In this paper, the molecular dynamics method was used to investigate the diffusion behavior of seven fault characteristic gases (including H2, CO, CH4, C2H2, CO2, C2H4, C2H6) in natural ester and mineral oil. The simulation parameters of free volume, interaction energy, mean square displacement, and diffusion coefficient were compared between the natural ester and mineral oil. Meanwhile, the influence of temperature on the diffusion of gas molecules in two kinds of oils was also analyzed. Results showed that the free volume, the interaction energy, and the relative molecular mass of gas molecules were the factors influenced by the diffusion of gas molecules in natural ester and mineral oil. The order of the diffusion coefficients of gas molecules in natural ester was as follows: H2 > CH4 > CO > C2H2 > C2H4 > CO2 > C2H6 and that in mineral oil was as follows: H2 > CH4 > CO> C2H2 > C2 H4 > C2H6 > CO2. By comparing the diffusion behavior of gas molecules in natural ester and mineral oil, it was found that the smaller free volume and higher interaction energy of gas molecules in natural ester were the major reasons for the gas molecules to be more difficult to diffuse in natural ester. The rising temperature could enhance the free volume and reduce the interaction energy between gas molecules and oil. The diffusion coefficient of gas molecules increased exponentially with the follow of temperature. However, the temperature didn't affect the ordering of diffusion coefficient, free volume, and interaction energy of gas molecules in natural ester and mineral oil.

Parameters of the Mouse Embryo Assay that affect detection of peroxides in mineral oil.

RESEARCH QUESTION: Can culture conditions influence the sensitivity of a Mouse Embryo Assay and its potential to detect peroxide-related toxicity in mineral oil samples? DESIGN: Protein type and concentration, embryo density and culture dish design were selected as the variables in the culture system with the potential to influence the assay's sensitivity. Fresh 1-cell mouse embryos were cultured under mineral oil samples with known peroxide concentrations. Protein type (human serum albumin [HSA] + α/ß-Globulins versus HSA versus bovine serum albumin [BSA]), concentration (5 mg/ml versus 0.5 mg/ml), embryo density (25 versus 3 µl/embryo) and culture dish (Petri versus micro-well dish) were adjusted to define the culture conditions with the highest sensitivity. RESULTS: High concentrations of peroxides can be easily detected by current quality control standards. However, for oil samples with a lower concentration of peroxides, supplementing the culture medium with 5 mg/ml of HSA + alpha/beta-globulins or with HSA resulted in an increased detection of embryo toxicity compared with when BSA was used as the protein supplement. The sensitivity of the assay was greatly reduced when embryos were cultured in groups and when certain micro-well dishes were used. CONCLUSIONS: Current quality control protocols may not be sensitive enough to identify low concentrations of peroxides, which, if undetected, can increase over time and become potentially harmful during gamete and embryo culture. The different parameters established in this study allow the sensitivity of the Mouse Embryo Assays to be optimized to specifically detect peroxides in mineral oil samples prior to their release into the market and their broad use in human IVF.

The selective determination of potentially carcinogenic polycyclic aromatic compounds in lubricant base oils by the DMSO extraction method IP346 and its correlation to mouse skin painting carcinogenicity assays.

Mineral oils are produced by vacuum distillation of crude oil at temperatures from ∼300 °C to ∼600 °C. Subsequent refining processes to eliminate the carcinogenic potential of mineral oils (by extraction and/or hydrotreatment) are based on the principle of removing substances associated with carcinogenic activity; i.e. PAC (polycyclic aromatic compounds), which include PAH and N or S heterocycles. Traditionally, the carcinogenic potential of the refined product was tested in the mouse skin painting assay. This bioassay is considered the gold standard for petroleum derived products since it uses the most sensitive species and route of exposure, and because mice and humans develop the same type of skin tumors it is a relevant model to assess the carcinogenic potential of mineral oils. Mouse skin painting studies have also been important in distinguishing two types of aromatic compounds found in mineral oil. The first type includes the 3-7 ring PAC associated with potential carcinogenic effects found in the 340-535 °C boiling range, which are removed by refinement. The second type includes highly alkylated aromatic compounds (predominantly 1-2 rings) which are not bioactivated and non-carcinogenic, which are typical of a refined oil. Because mouse skin painting studies are time consuming, a DMSO based method was developed that is capable to distinguish these two types of aromatics. Although this industry method, known as the IP346, has been applied for more than 30 years, the background experimental data underlying its development has not yet been published. This paper presents and discusses the chemical and biological features of mineral oil PAC structures assessed by IP346, especially the crucial role of the DMSO extraction step which allows to discriminate between the two types of aromatics. The DMSO selectivity towards the toxicological relevant PAC is discussed by comparing the composition of the DMSO extract of a distillate aromatic extract and mineral oils of varying viscosities and refining conditions. PAC which have >3 rings (naked or partially alkylated) are preferentially encompassed by the DMSO extract, whereas those PAC which have relatively long alkyl side chains are not. Thus, according to the IP346, refined oils will have lower levels of DMSO extractable material compared to less refined oils. DMSO selectivity towards the potentially carcinogenic >3 ring PAC makes the IP346 method therefore highly correlated to the outcome of mouse skin painting studies, using a pass/fail dichotomy. The accuracy, including the false negative results of the IP346 in the prediction of mineral oil carcinogenicity is discussed. The DMSO based IP346 is thus a simple but clear reflection of refinement efficacy. It links manufacturing conditions to carcinogenic potential of an oil, supported by solid physical-chemical and toxicological associations. In Europe it is the only legally binding method to assess, classify and label lubricating base oils and inherently more reliable for hazard assessment than the determination of an arbitrary selection of PAH.

Rapid screening of mineral oil aromatic hydrocarbons (MOAH) in grains by fluorescence spectroscopy.

On-line high-performance liquid chromatography coupled with gas chromatography with flame ionization detector (LC-GC) has become an important technique for the determination of mineral oil aromatic hydrocarbons (MOAH) in foods. However, the analysis is complicated and time-consuming. The present study aimed to develop a fluorescence spectrophotometry approach for the fast screening of MOAH in grains. A reference material, which is a mixture of diesel oils and lubricants, was selected for MOAH calibration. The excitation/emission wavelength of EX230 nm/EM330 nm was determined and the linear range was 0.125-2.5 mg/kg with an R2 of 0.999. The MOAH content determined by the fluorescence method showed good correlation with that determined by LC-GC (r = 0.946). This result suggested that the performance of these two methods was comparable, and thus fluorescence spectroscopy can be used for screening MOAH. A MOAH content of >0.1 mg/kg in grains could be rapidly determined by fluorescence spectroscopy.