Uncovering Mineral Oil Hydrocarbon Contamination: The Power of Pressurized Solvent Extraction

As the detectives arrive in the office, Cornlumbo is hunched over his laptop, tapping away furiously. “What are you up to, Cornlumbo?" Asks Nancy Beef. “I’m checking the price of cocoa; it has to come down at some point, right?” questions Cornlumbo. “You only wrote your guidance for the industry last week,” says Nancy. 

“What if I told you that chocolate might not be safe,” says Shallot Holmes. “You’re not going to bang on about being ‘treatwise,’ are you? Miss Mapple has already told me about the importance of not overindulging in treats,” says Cornlumbo. “No, I’m talking about mineral oil hydrocarbons, the topic for our latest case,” says Holmes. 

What are mineral oil hydrocarbons?

“Mineral oil hydrocarbons; aren’t they mainly derived from petroleum distillation and refining? What are they doing in chocolate?” asks Eggcule Poirot. “That’s exactly what our client is researching; you see, these hydrocarbons, like microplastics, can enter food in several ways: from the lubricants in machinery, release agents, environmental contamination, food or feed additives, or migration from food contact materials,” says Holmes. “So, why is chocolate at risk?” asks Cornlumbo. “Well, it’s not just chocolate; many foods contain mineral oil hydrocarbons, including:

• Vegetable oils
• Dairy products
• Crisps
• Ready-made meals
• Cereals
• Baby food
• Legumes, nuts, oil seeds, and spices
• Canned fish
• Chocolate

Our client is researching dried foods as these are particularly at risk due to their direct contact with packaging. Recycled paper and cardboard may contain mineral oils from inks, adhesives, printing processes, etc. Dried foods are often in direct contact with such packaging and lack any natural moisture barrier that may delay or reduce the migration of mineral oil hydrocarbons,” explains Holmes. “So, what can we do to help? What does the client need from us?” says Miss Mapple. 

“There are two main categories of mineral oil hydrocarbons, called MOSH and MOAH.

• MOSH: Mineral Oil Saturated Hydrocarbons (open chain paraffins, isoparaffins, and cyclic naphthenes)
• MOAH: Mineral Oil Aromatic Hydrocarbons (alkylated 1-3 ring compounds)

In humans exposed to MOSH, microgranulomas have been observed in the liver, spleen, lymph nodes, and other organs. Still, these changes have not been associated with inflammatory reactions or other adverse consequences. Since 2022, there have been limits to the amount of MOAH in dry food samples, and more research is being conducted to provide clarity and regulatory guidance. 

Our client needs to test a wide variety of food products to detect MOSH and MOAH; therefore, they need to know the most efficient and effective method to analyze these to save time and resources. The aim of their research is the detection of surface and deep contamination to distinguish between contamination from packaging and pre-existing contamination in food products. I’d like us to develop a fast and efficient method for our client to assist them in their research. Ready?” says Holmes.

The detectives get to work analyzing different methods to find the best solution for their clients. After a busy few days, the detectives put together their findings.

What is the most efficient method for the analysis of MOSH and MOAH?

The detectives tried various extraction methods, including reference methods, but by far, the most effective was Pressurized Solvent Extraction (PSE). Holmes presents the detective’s findings to the client and suggests two PSE methods optimized for different types of contamination.

⦁    Method A: Targets superficial contamination from packaging materials, suitable for unground dry food samples with low fat content. This method extracts contaminants on the surface of the food.
⦁    Method B: Focuses on total contamination (including deep and pre-existing contamination) and can be used after Method A for a comprehensive extraction by grinding the food samples.

The procedures involve sample preparation, pre-cleaning of the extraction components, and loading of samples into extraction cells. Key steps include pre-cleaning filters and components to avoid external contamination. Method A uses intact food pieces, while Method B requires ground and homogenized samples mixed with quartz sand for total contamination extraction.

By comparing pasta that has been in contact with packaging and pasta that has not, the impact of packaging on MOSH and MOAH content can be determined. Also, by applying the methods sequentially, the methods can distinguish between surface and deep contamination.

In the detective’s tests, both methods achieved good recovery rates and repeatability and demonstrated faster extraction times compared to traditional methods, significantly shortening the process from hours to under 30 minutes. With its high efficiency, this optimized PSE method offers an improved approach for detecting and quantifying mineral oil contamination in dry foods.

What makes PSE so efficient?

Pressurized solvent extraction (PSE) is highly effective at reducing the extraction time while maintaining accurate results due to several key factors:

• High Pressure and Temperature: PSE utilizes elevated pressure and temperature, which enhances the solubility and diffusion rate of analytes in the solvent.
• Efficient Solvent Use: The increased pressure allows solvents to penetrate samples more effectively, reaching all contamination points, including deep or embedded residues. This ensures thorough extraction in a shorter timeframe with minimal solvent usage.
• Automated and Parallel Processing: Certain PSE instruments can handle multiple samples simultaneously (in parallel). This significantly decreases the extraction time by processing multiple samples in one run.
• Direct Injection Compatibility: PSE extracts can often be injected directly into analytical systems like LC-GC without requiring additional clean-up steps. This minimizes user error and streamlines the workflow, maintaining accuracy while reducing time spent on post-extraction steps.
• Consistent and Precise Conditions: The controlled environment of PSE (consistent temperature, pressure, and solvent flow) minimizes variability and maximizes reproducibility. 

Having gathered their evidence, Holmes presents their findings to the client, who is pleased by how much time they will save using parallel processing and pressurized solvent extraction. 

Meanwhile, Cornlumbo is looking with hesitation at the bar of chocolate he had bought to enjoy as a snack. “So, what you’re telling me is that currently, the data is inconclusive, and as it stands, this chocolate bar is technically safe?” asks Cornlumbo. “I can’t imagine any chocolate possessed by you would ever remain in the packaging long enough for there to be a concern, Cornlumbo,” says Miss Mapple as the detectives fall about laughing.