Expanding the Understanding of Mineral Oil Analysis - - Chromatography Online
Expanding the Understanding of Mineral Oil Analysis

The Column
Volume 10, Issue 15, pp. 1013

Photo Credit: pearleye/Getty Images



The Column spoke to Laura Barp of the University of Udine (Udine, Italy) about her research into mineral oil migration in food packaging, the potential impact on human health, and the importance of pressurized-liquid extraction (PLE) in this project.

Q: What area of food analysis are you currently focusing on?
A. My research at the Department of Food Science at the University of Udine (Udine, Italy) focuses on all the steps involved in the extraction, purification, and analytical determination of mineral oil saturated hydrocarbons/mineral oil aromatic hydrocarbons (MOSHs/MOAHs). These projects are supervised by Professor Sabrina Moret.

Regarding the extraction steps, we investigated traditional ones and some newer ones, such as microwave‑assisted extraction (MAE), microwave‑assisted saponification (MAS), and pressurized‑liquid extraction (PLE). We investigated PLE in more detail and went on to develop and optimize a method for the analysis of paper and board intended for contact with food products,1 and for the superficial and total (pre‑existing) contamination in dry food, which mainly derived from migration from food packaging2 — all based on the use of PLE.

Another research area is the off-line purification and MOSH/MOAH separation, which uses SPE (solid-phase extraction) based on different packed materials, including silvered silica, activated silica, and aluminum oxide. An off‑line method based on the use of a silvered silica SPE cartridge was developed for the purification and MOSH/MOAH separation in vegetable oils and paperboard.3,4

The instrumental part of the analysis is an interesting issue. MOSH and MOAH analysis can be performed using an on-line LC–GC–FID (liquid–gas chromatography–flame ionization detection) system (much more expensive than the off‑line approach which involves a GC–FID system), which has the advantage of minimizing sample manipulation, preventing sample contamination, and allowing the complete transfer of the fraction of interest into the GC column. In particular, the analytical determination was investigated in terms of a comparison of different LC–GC interfaces, namely PTV and on‑column,5 and it was concluded that the use of different instruments did not significantly interfere with the final analytical results, even though specific instrumental features required attention for correct quantification. Furthermore, a high sample‑throughput LC–GC method was developed to reduce time and solvent consumption6 — both very important aspects in routine analysis. In addition to this, I think that LC–GC×GC–FID/MS could be a useful approach to simultaneously characterize, identify, and quantify MOSHs and MOAHs.

Another important topic that drew our attention is the migration of mineral oil from packaging into food. We performed several studies on migration from different kinds of packaging material into dry semolina and egg pasta, both under conventional and accelerated conditions. Furthermore, the effect of food simulants, such as MPPO (modified polyphenylene oxide), was tested (data not yet published)

Q: How did you come to study mineral oils in dried food and how serious is the threat posed by mineral oils in dried foods to human health?
A. I started studying mineral oil in vegetable oils during my Master’s degree thesis and I have never stopped! In recent years the attention has been focused on mineral oil migration from packaging into food. Pasta is the staple food of the Mediterranean diet and according to the present legislation (DM. 21/03/73), dry foods, such as cereals, flour, sugar, rice, and pasta can be packaged in direct contact with recycled paperboard.

Furthermore, the latest European Food Safety Authority (EFSA) opinion on mineral oil hydrocarbons (MOHs) in foods (7) stated that exposure to MOHs via packaging could contribute significantly to the total exposure and may pose a human health hazard. Up to now only two surveys — from the German and Austrian markets — have been conducted, but only a low number of pasta samples (n = 4 for each of the surveys) packaged in direct contact with recycled cardboard were examined.7,8 It was for these reasons that we started to investigate the mineral oil content in this kind of matrix, paying particular attention to the migration from recycled paperboard.

Q: What analytical challenges did you face in this work, and how did you overcome them?
A. As mentioned previously, all the steps of the mineral oil analysis can represent a challenge, but thanks to a strong literature base and the use of innovative techniques, it is possible to overcome the difficulties. For example, one of the most debated topics is the real presence of saturated or aromatic hydrocarbons under the unresolved hump obtained from GC–FID analysis. By using two‑dimensional chromatography equipped with a dual detector (FID and MS), we succeeded in elucidating mineral oil contamination in both food9 (in collaboration with Dr. Giorgia Purcaro of the University of Udine) and human tissues10 (in collaboration with Maurus Biedarmann and Koni Grob of the Official Food Control Authority of the Canton of Zurich).

Q: Can you comment on the use of pressurized-liquid extraction (PLE) in this type of analysis?
A. PLE is a well‑established sample preparation technique that uses high temperature and high pressures for efficient analyte extraction from solid samples. The high pressure allows the solvent liquid to be maintained at temperatures well above its atmospheric boiling point, while the high temperatures reduced the viscosity of the solvent, increasing its ability to wet the matrix and solubilize the analytes. By taking advantage of these characteristics, mineral oil extraction can be quickly and efficiently performed on solid samples, such as soil, food, or packaging materials, and can consume a moderate amount of solvent. Furthermore, the technique reduces sample manipulation and the possibility of an external contamination, if all the parts of the system are adequately rinsed (the parts in contact with the sample are of stainless steel). Optimizing the extraction conditions, such as the temperature, the number of cycles, the solvent, and the time, allowed us to distinguish between the superficial contamination (mostly coming from mineral oil migrated from packaging) and the total contamination (coming from different sources) into dry semolina pasta.

Q: What other areas do you think PLE could be used more commonly in?
A. PLE is one of the most often applied and promising extraction procedures of organic or inorganic species for environmental, food, and biological samples. Soil and sediments represent the main environmental target samples for pollutants extraction. The determination of contaminants in food and animal tissues and the extraction of target species from animal and plant tissues represents another application of PLE. In recent years, PLE has been used increasingly in the pharmaceutical (extraction of active substances from plants) and industrial fields as well, particularly for the extraction of additives from polymers.

Q: You have also studied the impact of mineral oils in human tissues. Could you talk a little about this research?
A. The EFSA opinion published in 20127 concluded that MOSH can accumulate in human tissues, but no values for tolerable daily intakes (TIDs) were specified because of insufficient data, especially with regard to accumulation. Several animal tests were performed to understand absorption, metabolization, and accumulation of mineral oils, while studies on humans are still limited.

In addition, the transfer of animal data to humans introduces uncertainties and accumulation is not adequately reflected, mainly because animal tests last for far less time than human lives. To collect some data on MOSH accumulation in humans, between February and August 2013, liver, spleen, mesenteric lymph nodes (MLN), lungs, and subcutaneous abdominal fat tissues were collected from 37 patients (11 females and 26 males) during autopsies at the Medical University of Vienna. Mineral oil analysis was performed at the Official Food Control Authority of Zurich.

The concentrations determined in human tissues are high compared to values that could be extrapolated from rat experiments (the highest values were found in the spleen and in the MLN, which presented about 1400 mg/kg): In particular, on the basis of the exposure estimated by EFSA,7 concentrations in the human liver are more than 100 times higher than those predicted in animal tests. The measured concentration confirmed that the MOSH are the predominant contaminants of the human body. This is not necessarily indicative of a health problem, but calls for a particularly careful toxicological evaluation.11

Comparing the profiles of mineral oil that humans can be exposed to and that are found in human tissues, we can conclude that the composition found in tissues seems determined not so much by the mineral oils the individuals are exposed to, but more by the selectivity of the uptake, elimination by evaporation, and metabolic degradation. A more detailed characterization of hydrocarbons in mineral oil and human tissues by comprehensive two-dimensional chromatography provided additional evidence that saturated hydrocarbons detected in humans are of mineral origin.

Q: Where will your research into mineral oil migration take you in the future?
A. Currently I am working with the Official Food Control Authority of Zurich with K. Grob and M. Biedermann on the EFSA project titled “Combined bioaccumulation/toxicity study on a broad mixture of mineral oil saturated hydrocarbons”. This study will improve information on the toxicological profile of mineral oil saturated hydrocarbons and will serve as supporting background documentation for the possible refinement of scientific opinion on MOHs.7

Furthermore, the collaboration with Prof. S. Moret from the Department of Food Science of Udine still continues: We are currently working on the development of an off-line method focusing on the MOAH fraction, with an emphasis on the removal of olefins.

References

1. S. Moret, M. Sander, G. Purcaro, M. Scolaro, L. Barp, and L.S. Conte, Talanta 115, 246–252 (2013).
2. S. Moret, M. Scolaro, L. Barp, G. Purcaro, M. Sander, and L.S. Conte, Food Chemistry 157, 470–475 (2014).
3. S. Moret, L. Barp, and L.S. Conte, Food Chemistry 129, 1898–1903 (2011).
4. S. Moret, L. Barp, G. Purcaro, and L.S. Conte, Journal of Chromatography A 1243, 1–5 (2012).
5. G. Purcaro, M. Zoccali, P.Q. Tranchida, L. Barp, S. Moret, L.S. Conte, P. Dugo, and L. Mondello, Analytical and Bioanalytical Chemistry 405, 1077–1084 (2013).
6. L. Barp, G. Purcaro, S. Moret, and L.S. Conte, Journal of Separation Science 36, 3135–3139 (2013).
European Food Safety Authority (EFSA). Scientific Opinion on Mineral Oil Hydrocarbons in Food, EFSA Journal 10(6), 2704–185 (2012) http://www.efsa.europa.eu/en/efsajournal/pub/2704.htm
7. A. Vollmer, M. Biedermann, F. Grundböck, J.-E. Igenhoff, S. Biedermann-Brem, W. Altkofer, and K. Grob, European Food Research and Technology 232, 175–182 (2011).
8. G. Purcaro, P.Q. Tranchida, L. Barp, S. Moret, L.S. Conte, and L. Mondello, Analytica Chimica Acta 773, 97–104 (2013).
9. M. Biedermann, L. Barp, C. Kornauth, T. Würger, M. Rudas, A. Reiner, N. Concin, and K. Grob, Science of the Total Environment (2014) http://dx.doi.org/10.1016/j.scitotenv.2014.07.038
10. L. Barp, C. Kornauth, T. Wüger, M. Rudas, M. Biedermann, A. Reiner, N. Concin, and K. Grob, Food and Chemical Toxicology (2014) doi: http://dx.doi.org/10.1016/j.fct.2014.04.029.

Laura Barp obtained a Bachelor’s and a Master’s degree in food science and technology at the University of Udine in 2010, with 110/110 and with laudem for the thesis titled “Mineral oil in vegetable oils: Optimization of several analytical approaches and investigation”. In March 2014 she achieved her PhD in food science (scientific supervisor Prof. Sabrina Moret), with the thesis “Mineral oil hydrocarbons: Development/optimization of analytical methods, investigation of migration from food packaging into semolina and egg pasta, and occurrence in human tissues”. She currently works at the Official Food Control Authority of Zurich to participate in the EFSA project titled “Combined bioaccumulation/toxicity study on a broad mixture of mineral oil saturated hydrocarbons”.

Email: laura.bap.unid.it

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