Comparison of two different multidimensional liquid–gas chromatography interfaces for determination of mineral oil saturated hydrocarbons in foodstuffs

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.

Determination of mineral oil hydrocarbon contamination in Citrus essential oils by using on-line liquid-gas chromatography: critical aspects

The present manuscript reports and discusses critical issues related to the determination of mineral oil hydrocarbon contamination in Citrus essential oils (EOs); an on-line liquid-gas chromatography system equipped with a Y-interface was used (with no additional off-line step for pre-concentration). In total, eighteen samples were analyzed, specifically eleven cold-pressed (CP) and seven distilled EOs. With regard to the CP EOs, various degrees of mineral oil saturated hydrocarbon (MOSH) contamination were detected, ranging between 10.7 and 338.4 mg kg-1 (only one sample was MOSH-free); different MOSH sub-fractions were determined, with the  > C25- ≤ C35 sub-fraction always present, with an average concentration of 74.5 mg kg-1. Based on the EO composition, different sample amounts were injected to avoid the overloading of the LC column and consequently the GC one, thus leading to different limits of quantification (LoQ), which were either 2 mg kg-1 (for bergamot EO) or 5 mg kg-1 (for all the other investigated samples). For all samples, the mineral oil aromatic hydrocarbon level was always lower than the LoQ.

Occurrence of Mineral Oil Hydrocarbons in Omega-3 Fatty Acid Dietary Supplements

Omega-3 fatty acid dietary supplements have become increasingly popular with consumers due to their multiple health benefits. In this study, the presence of mineral oil hydrocarbons (MOH) was investigated in seventeen commercial samples of such supplements, characterized by different formulations. The analyses were performed using on-line liquid chromatography–gas chromatography (with flame ionization detection), which is considered the most efficient method for the determination of MOH in foodstuffs. Analyte transfer was performed by using the retention gap technique, with partially concurrent solvent evaporation. Various degrees of mineral oil saturated hydrocarbon contamination (from 2.4 ppm to 375.7 ppm) were found, with an average value of 49.9 ppm. Different C-number range contaminations were determined, with the >C₂₅–≤C₃₅ range always found with an average value of 26.9 ppm. All samples resulted free of mineral oil aromatic hydrocarbons, except for two samples in which a contamination was found at the 9.9 and 6.6 ppm levels, respectively.

Latest Trends on the Future of Three-Dimensional Separations in Chromatography

Separation and characterization of complex mixtures are of crucial importance in many fields, where extremely high separation power is required. Three-dimensional separation techniques can offer a path toward achieving high peak capacities. In this Review, online three-dimensional separation systems are discussed, including three-dimensional gas chromatography, and hyphenated combinations of two-dimensional gas chromatography with liquid chromatography or supercritical-fluid chromatography. Online comprehensive two-dimensional liquid chromatography provides detailed information on complex samples and the need for higher peak capacities is pushing researchers toward online three-dimensional liquid chromatography. In this review, an overview of the various combinations are provided and we discuss and compare their potential performance, advantages, perspectives, and results obtained during the most recent 10-15 years. Finally, the Review will discuss a novel approach of spatial three-dimensional liquid separation to increase peak capacity.

Use of a low-cost, lab-made Y-interface for liquid-gas chromatography coupling for the analysis of mineral oils in food samples

Consumers are daily exposed to a range of mineral oil hydrocarbons via food consumption. Major sources of MOH in food are packaging and additives, processing aids, and lubricants. In 2019, an EU guidance was released covering specific directions for sampling and analysis of mineral oil saturated hydrocarbons (MOSH) and mineral oil aromatic hydrocarbons (MOAH) in food and food contact materials within the frame of Recommendation (EU) 2017/84 for the monitoring of mineral oils. The parameters required by the guide are increasingly stringent, and coping with this type of analysis is now very challenging. It is within such a context that the present research is confined, inasmuch that it is focused on the construction of a low-cost, lab-made Y-interface for liquid-gas chromatography coupling used for the determination of MOSH and MOAH in foodstuffs. The response ratios of alkanes comprised between C₁₀ and C₅₀ were measured and were comprised between 0.9 and 1.1, with a maximum coefficient of variation of 4% (n = 5). Intermediate precision was evaluated for the fat/oil category during a period of 48 days obtaining a value of 10%. Qualitative and quantitative analysis of both MOSH and MOAH were performed in a single run and in a fully-automated manner. Seventeen different foods were analyzed in order to cover the categories reported in the EU guide. Saturated hydrocarbon contamination was detected only in a few samples (in the range 1-153 ppm); MOAH contamination was found only in one sample (sunflower oil: 15 ppm).

Epoxidation for the analysis of the mineral oil aromatic hydrocarbons in food. An update

On-line coupled high performance liquid chromatography-gas chromatography-flame ionization detection (HPLC-GC-FID) used for determining mineral oil aromatic hydrocarbons (MOAH) in foods, particularly in certain oils and fats, may be disturbed by interfering olefins present as natural food components or resulting from raffination of the oils and fats. While some interference can be coped with by disregarding their peaks, others overload GC to the extent of obscuring the MOAH or form humps which need to be distinguished from the hump formed by the MOAH. In the latter cases, it is necessary to remove these interferences prior to HPLC-GC analysis. So far, epoxidation of the olefins to increase their retention time beyond that of the MOAH in HPLC is the best method available, though imperfect by causing some loss of MOAH and sometimes incomplete removal of the interference. Two methods are re-evaluated; preference is given to a slightly modified version of that proposed by Nestola and Schmidt. The performances are comparable: the losses of MOAH are similar and with both methods not all interfering olefins may be removed from refined edible oils. However, the Nestola/Schmidt method has practical advantages, the main ones being that no cooling is necessary and no solvent needs to be evaporated, which facilitates automation. Potential residual interferences must be recognized and subtracted, which can be by the characteristics of the hump they form in HPLC-GC-FID, by GCxGC-FID or by GCxGC-MS using characteristic mass fragments.

Analytical Methods for the Determination of Mineral Oil Saturated Hydrocarbons (MOSH) and Mineral Oil Aromatic Hydrocarbons (MOAH)-A Short Review

Mineral oils (such as paraffinum liquidum or white oil), which consist of mineral oil saturated hydrocarbons (MOSH) and mineral oil aromatic hydrocarbons (MOAH), are widely applied in various consumer products such as medicines and cosmetics. Contamination of food with mineral oil may occur by migration of mineral oil containing products from packaging materials, or during the food production process, as well as by environmental contamination during agricultural production. Considerable analytical interest was initiated by the potential adverse health effects, especially carcinogenic effects of some aromatic hydrocarbons. This article reviews the history of mineral oil analysis, starting with gravimetric and photometric methods, followed by on-line-coupled liquid chromatography with gas chromatography and flame ionization detection (LC-GC-FID), which still is considered as gold standard for MOSH-MOAH analysis. Comprehensive tables of applications in the fields of cosmetics, foods, food contact materials, and living organisms are provided. Further methods including GCxGC-MS methods are reviewed, which may be suitable for confirmation of LC-GC-FID results and identification of compound classes. As alternative to chromatography, nuclear magnetic resonance (NMR) spectroscopy has recently been suggested for MOSH-MOAH analysis, especially with the possibility of detecting only the toxicologically relevant aromatic rings. Furthermore, NMR may offer potential as rapid screening especially with low-field instruments usable for raw material control.

Separation and Analysis of Sucrose Esters in Tobacco by Online Liquid Chromatography-Gas Chromatography/Mass Spectrometry

In this work, a strategy of in-series combination of ultrasound-assisted extraction and online LC-GC/MS was constructed for effective separation and analysis of sucrose esters in tobacco. Sucrose esters were first extracted by ultrasound-assisted extraction with high efficiency and easyhandling. Online LC-GC/MS was then applied for sucrose ester clean-up and analysis. To better evaluate the effectiveness of this strategy, we limited our focus to five groups of sucrose ester isomers. Each group differed in mass from the next by 14 Da. The obtained coefficient of the calibration curve was 0.9986. Limit of detection (LOD) and limit of quantitation (LOQ) were 0.05 and 0.16 μg/ mL, respectively. The recovery was above 90% and the reproducibility was below 4%. This strategy was subsequently applied to the comparison of relative amounts of five groups of sucrose esters extracted from three different parts of aromatic tobacco. The satisfactory performance indicated that this strategy has great prospect for the rapid and high-throughput analysis of sucrose esters in tobacco.

Performance evaluation of a versatile multidimensional chromatographic preparative system based on three-dimensional gas chromatography and liquid chromatography-two-dimensional gas chromatography for the collection of volatile constituents

The present research deals with the multi-collection of the most important sesquiterpene alcohols belonging to sandalwood essential oil, as reported by the international regulations: (Z)-α-santalol, (Z)-α-trans bergamotol, (Z)-β-santalol, epi-(Z)-β-santalol, α-bisabolol, (Z)-lanceol, and (Z)-nuciferol. A versatile multidimensional preparative system, based on the hyphenation of liquid and gas chromatography techniques, was operated in the LC-GC-GC-prep or GC-GC-GC-prep configuration, depending on the concentration to be collected from the sample, without any hardware or software modification. The system was equipped with a silica LC column in combination with polyethylene glycol-poly(5% diphenyl/95% dimethylsiloxane)-medium polarity ionic liquid or β-cyclodextrin based GC stationary phases. The GC-GC-GC-prep configuration was exploited for the collection of four components, by using a conventional split/splitless injector, while the LC-GC-GC-prep approach was applied for three low abundant components (<5%), in order to increase the quantity collected within a single run, by the LC injection of a high sample amount. All target compounds, whose determination is hampered by the unavailability of commercial standards, were collected at milligram levels and with a high degree of purity (>87%).