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Q. When did you first encounter chromatography and what attracted you to the subject?
A: I first encountered chromatography very early in my chemistry study, during a summer internship in a food safety laboratory. I was asked to integrate some new analytes into an existing high performance liquid chromatography (HPLC) method and was fascinated by the task. I really enjoyed “playing” with the different parameters and seeing the influence on the chromatography, and then finally applying my developed method onto real samples. That was when I decided to focus on analytical chemistry and food chemistry for my future career.
Q. What chromatographic techniques have you worked with?
A: I did my master’s degree and my PhD at the Institute of Analytical Chemistry and Food Chemistry under the supervision of Professor Leitner at the University of Technology Graz. The group mainly focuses on gas chromatography (GC)-based techniques with different detection systems, and I tried to get my hands on as many instruments as possible. For example, I worked with conventional one-dimensional GC systems with flame ionization detection (FID), flame photometric detection (FPD), or nitrogen–phosphorus detector (NPD), and quadrupole mass spectrometer (qMS and MS/MS). I also worked with two‑dimensional comprehensive GC systems: a GC×GC-qMS and a GC×GC–time-of-flight (TOF). During my PhD, I also started working on the topic of mineral oil hydrocarbons (MOHs), where the state-of-the art analysis is done using an online-coupled HPLC–GC–FID system.
Q. Can you tell us more about your PhD thesis and the work you published related to this (1)?
A: During my PhD, I worked with cellulose‑based packaging materials—mainly recycled paper and board. The problem with the recycling of materials for food contact is that during the recycling process contaminations are not removed but instead are enriched in the final product, from where they then can be transferred into the packed food. The only fast and practical way to prevent this migration seems to be the application of functional barriers in the packaging. Recently applied barriers include polyethylene (PE), polypropylene (PP), aluminium, or multilayer materials. The problem is that recycling of most of the resulting packaging is—if possible—really difficult. The aim of my thesis was therefore to evaluate different bio-based or biodegradable polymers for their
I started by using the different conventional GC methods and GC×GC—as mentioned earlier—to comprehensively characterize recycled paper and board samples, including the analysis of mineral oil hydrocarbons content, migration of mineral oil hydrocarbons, overall and specific migration, and permeation of odour-active substances. Afterwards, the barrier materials were applied and I did the analysis again. I developed a method that allowed me to determine the migration and permeation parameters fast and easily in one single experimental setup, not only for paper and board but also for a wide range of other packaging materials. The work I published related to that describes the developed method and the application on to functional barriers made of the biopolymer chitosan acetate and conventionally applied polymer films such as PE or PP, and compares the barrier properties, showing that the chitosan acetate can work perfectly as a barrier material.
Q. You are currently focused on the analysis of MOHs, and your latest paper on mineral oil hydrocarbon risk assessment talks about knowledge gaps in analytical methods (2). Why is MOH analysis important and what knowledge gaps do you think exist?
A: Discussion about mineral oil residues in food began in the early 1990s,
but it was only in 2008 that the public became aware of this, mainly because high concentrations were found in sunflower oil. Mineral oil hydrocarbons are divided into two groups: saturated (MOSH) and aromatic (MOAH) mineral oil hydrocarbons. The MOSH fraction is known to accumulate in the human organism, resulting in negative impacts on the respective tissue. The MOAH fraction contains potentially mutagenic and carcinogenic substances. So, the presence in food of both is a concern for human health and should be avoided.
Since then, a lot has been done in terms of reducing contamination levels and analytical detection. Back then we talked of several grams of mineral oil per kilogram of food, today we deal with a few milligrams. This—of course—increases the analytical challenge. Highly specific methods, adapted to the complex matrix “food”, are necessary to meet the requirements. We are lacking a common sense of the best practice and therefore standardized and validated methods for different food types.
Q. Can you comment further on the potential of mutagenic and carcinogenic substances being present in MOAHs.
A: Probably the main statement to say about MOAHs is that they may contain potential mutagenic and carcinogenic substances. According to the scientific opinion of the European Food Safety Authority (EFSA, 2012), the three- to seven-ring MOAH may form carcinogenic DNA adducts. Therefore, those may be the actual substances of interest. Analytical methods should be applied to identify the presence of those substances routinely.
Q. What cutting-edge analytical techniques are being used in MOAH analysis?
A: The problem with state-of-the art analysis using online-coupled HPLC–GC–FID is that MOSH and MOAH are only determined as a sum parameter, without any further information about what is actually present (2,3). Two-dimensional comprehensive GC×GC is therefore a key method to provide the information needed. It allows for a detailed characterization of the substances and substance classes present. Attempts have been taken to develop an LC–GC×GC system with MS and FID detector, allowing on the one hand identification of the present substance classes, and on the other hand quantification (4). The missing information is then which substances are the ones responsible for the carcinogenic character and in what amount are they present in the food? In my current work, I try to answer this question.
Q. How do you see MOH analysis developing in the future?
A: Very important in terms of sample preparation is the possibility of automation, for example, automated aluminium oxide clean-up for the MOSH fraction, or automated epoxidation for MOAH, which would save a lot of time and resources in routine analysis. On the other hand, the GC×GC method should be routinely applied when MOAH is detected to provide the needed information on present substance classes for risk assessment and hazard characterization.
Q. Can the problems associated with MOH analysis be solved?
A: I believe if all involved stakeholders, from the food producer, the analyzing laboratories, the toxicologist, right up to the different authorities, work together, giving their individual input and finding a common purpose, we will finally be able to solve the “challenge” of mineral oil residues in food.
The use of GC×GC-based techniques is and will continue to be a driving analytical technique to solve the challenge. Furthermore, we have seen a huge attempt to bring GC×GC to routine analysis in recent years, including lots of developments for easier data evaluation (5). Therefore, I strongly believe that it is possible to use it in routine analysis, and once it is implemented there, we will be able to use it to its full potential. There are already a lot of different methods and applications published (6), including petrochemical, environmental, or food and fragrance samples, and there will be many more.
Andrea Hochegger graduated in chemistry from Graz University of Technology (TU Graz), Austria, in 2017. She did her PhD in the field of analytical chemistry, focusing on packaging-related food safety aspects and analytical contributions to the characterization of food and food contact materials. Her main research interests include the analysis of MOH and the characterization of biopolymers to be used as a functional barrier on cellulose-based packaging materials to reduce the migration of MOH into food. For this work she was awarded with the Leslie S. Ettre Award at the ISCC and GC×GC symposium in Riva del Garda in 2018, with an Advancement Award for Young Scientists of the Austrian Chemical Society in 2021, and with the Young Analytical Scientists Award of the Austrian Society of Analytical Chemistry, also in 2021. She finished her PhD in 2020 and now works as a postdoctoral researcher at the Institute of Analytical Chemistry and Food Chemistry at the TU Graz.