Polyaromatic hydrocarbons (PAH) are harmful organic compounds formed during incomplete combustion of carbon-containing materials. They can be present in, for example, air, fuels, and food.
The maximum levels of PAHs are defined in EU legislation and thus analyzing the presence and concentrations of PAHs in different products is necessary. PAH analyses can be performed with various methods, such as GC-MS, HPLC, and SFC.
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Polycyclic aromatic hydrocarbon (PAH) analysis from solid and fabric materials
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What are polyaromatic hydrocarbons?
Polycyclic aromatic hydrocarbons or polyaromatic hydrocarbons (PAH) are a group of organic compounds whose molecular structure contains two or more aromatic rings fused together. PAHs are formed as a result of incomplete combustion of fossil fuels, for example in the oil industry and transport, or when organic material such as wood or animal fat burns incompletely. PAHs are considered to be mutagenic, as many of them cause mutations or other damage to the genome. Some PAHs cause cancer through these mutations and these 15 compounds (listed in the Commission Recommendation (EC) No 108/2005 in EU legislation) are classified as carcinogenic.
PAHs in materials
PAHs can be found in multiple materials. Polyaromatic hydrocarbons are naturally present in petroleum-based bitumens, but high PAH concentrations can also be found in products made from coal tar. These coal tar-based products, petroleum-based bitumens, and their mixtures have previously been used as water and moisture insulators in buildings, which is why they are the main source of PAHs in indoor air. The handling of these PAH-containing materials in demolition and renovation requires protective actions and thus it is necessary to perform a PAH analysis on the materials before starting the demolition. If the total amount of PAHs in waste exceeds a certain limit, the material must be treated as hazardous waste.
PAHs in food
PAHs can be formed during forest fires from which they can travel as small particles with air currents and spread efficiently to air, water, and soil. This is why food industry raw materials like grains, fish, and filter-feeding shellfish such as mussels and oysters can be contaminated by PAHs. The contamination of food by PAHs can also happen during the manufacturing processes. Products that have been smoked, roasted, grilled, or dried can contain PAHs, but also frying and baking can cause their formation.
If the maximum level of PAHs in food is exceeded, the product is not allowed to be sold in the EU. Therefore, the contents of PAHs in foods should be determined at regular periods of time. The Commission Regulation (EC) No 1881/2006 (with changes) outlines the maximum levels of PAHs in different types of food and the Commission Regulation (EC) No 2065/2003 describes the corresponding values for smoke flavors. Finland has a special permit to allow meat and fishery products traditionally smoked in Finland with higher maximum PAH levels on their own markets.
Determining the PAH composition of a sample
The concentrations of different polyaromatic hydrocarbons in mixtures can be determined with various analytical methods. Gas chromatography-mass spectrometry (GC-MS) and high-performance liquid chromatography (HPLC) are the most common techniques used for analyzing PAHs from food. GC-MS is also used for determining the PAH content of environmental samples, such as air samples. After collecting air, its compounds are extracted from the collector with a solvent and the kind and concentration of the individual PAHs are determined from the solution.
In the petroleum industry, PAHs are determined indirectly by testing the aromatic component content of different products and feed-stocks using various methods such as GC-MS or inductively coupled plasma mass spectrometry (ICP-MS). Additionally, supercritical fluid chromatography (SFC), liquid chromatography (LC), and heavy distillates analyzer (HDA) can be used. The chosen method for analyzing aromatic hydrocarbons depends on the boiling range of the sample along with product specifications and regulations.
Solid, liquid, and gaseous samples are suitable for PAH analyses. Some solid materials (e.g. concrete and cement) must be ground finer prior to the analysis. In the air, PAHs are composed of gaseous and particle-bound phases called vapor and particle fractions. In vapor fraction, the major PAH component is naphthalene, which is the most volatile PAH. Instead, PAHs which are present only in particle fractions or in both fractions, are low-volatile at room temperature. Therefore two different collectors are required when collecting air for a PAH analysis. Gaseous PAHs are collected from the air to an adsorbent (a XAD tube) using a calibrated pump. PAHs which are bound to particles are collected by means of the pump on a Teflon filter.
Suitable sample matrices
- Coal tar -based products and oil-based bitumens (old water insulators)
- Petroleum and refined products (hydrocarbon feed-stocks, fuels and distillates such as diesel and aviation turbine fuel)
- Fuel residues (for example vacuum gasoils)
- Processed food (for instance grilled or dried)
- Food raw materials (for example grain or mussels)
- Environmental air, water and soil samples
- Waste material
Ideal uses of PAH analysis
- Measuring the concentrations of PAHs in old water insulators in order to define protective actions for construction workers
- Determining the PAH content in petroleum and refined products
- Measuring the PAH levels in processed food or their raw materials
- Analysing air, water and soil samples for environmental PAH content
- Determining the amount of PAHs in waste to determine if it should be classified as hazardous waste
Frequently asked questions
PAH analysis is commonly used for determining the PAH content of different products in industry. Old water insulators can be analysed for PAHs in order to guarantee sufficient protective actions for construction workers. Petroleum products, such as hydrocarbon feed-stocks and different fuels are commonly analysed to find out their PAH contents. Food can also be contaminated by PAHs through its raw materials or manufacturing processes. Thus, foods must be tested for PAHs in order to find out if they meet the EU regulations for maximum PAH levels. In waste treatment, information about PAHs is needed for defining a certain waste as a regular or hazardous waste. Additionally, the environmental PAH content of air, water and soil can be determined.
If the analysis is performed with GC-MS, the limit of determination varies depending on the sample. GC-MS is an effective method for tracing PAHs from the sample, because its compound-specific limit of determination is usually very small. When analyzing PAHs from an air sample, the limits of determination vary depending on whether the sample includes gaseous or particle bound PAHs. However, low concentrations can be determined from both kinds of samples.
Solid, liquid and gaseous samples can be analysed for PAH content. Petroleum and refined products, hydrocarbon feed-stocks and fuels, as well as light, middle and heavy distillates (including crude oil, gasoline, diesel, heavy fuel oil, gas-oil and jet fuel) are possible to analyse. Also food, waste material and environmental samples can be analysed.
Some solid materials must be ground before examination in order to achieve a finer form which is more suitable for the analysis. With air samples, two different techniques are needed to collect the sample because in air, PAHs are composed of two phases: gaseous and particle bound. Gaseous PAHs are collected from the air to an adsorbent (a XAD tube) using a calibrated pump. The PAHs bound to particles are collected by means of the pump on a teflon filter.
Measurlabs offers a variety of laboratory analyses for product developers and quality managers. We perform some of the analyses in our own lab, but mostly we outsource them to carefully selected partner laboratories. This way we can send each sample to the lab that is best suited for the purpose, and offer high-quality analyses with more than a thousand different methods to our clients.
When you contact us through our contact form or by email, one of our specialists will take ownership of your case and answer your query. You get an offer with all the necessary details about the analysis, and can send your samples to the indicated address. We will then take care of sending your samples to the correct laboratories and write a clear report on the results for you.
Samples are usually delivered to our laboratory via courier. Contact us for further details before sending samples.