Polycyclic aromatic hydrocarbons (PAHs) represent one of the most significant environmental contaminants in our world today. These complex organic compounds, composed of multiple fused aromatic rings, are ubiquitous pollutants that demand our attention due to their profound impact on both environmental and human health.<h3>What are PAHs?</h3>PAHs are a class of over 100 different chemicals that generally occur as complex mixtures. They form during the incomplete combustion of organic matter, including coal, oil, gasoline, diesel, wood, and garbage [6]. The simplest PAH is naphthalene with two aromatic rings, while more complex PAHs like anthracene or phenanthrene have three or more rings.These compounds are characterized by their uncharged, non-polar, and planar structure. Many PAHs are colorless and can be found in fossil fuel deposits such as coal and petroleum. The United States Environmental Protection Agency (U.S. EPA) has designated sixteen PAHs as high priority pollutants due to their widespread occurrence and potential health risks [6].<h3>Health and Environmental Impacts</h3>The health risks associated with PAH exposure are substantial and well-documented:<ul><li>Carcinogenicity: Many PAHs are recognized as carcinogens, mutagens, and teratogens. Prolonged exposure is linked to increased risk of lung cancer, as well as cancers of the skin, pancreas, esophagus, bladder, colon, and breast [8].</li><li>Cardiovascular Effects: PAH exposure has been associated with increased risk of cardiovascular diseases, including atherosclerosis, thrombosis, hypertension, and myocardial infarction [12]</li><li>Reproductive and Developmental Toxicity: Studies show that PAHs can cause reproductive issues and developmental complications.</li><li>Immunotoxicity: PAHs have been linked to weakened immune systems, potentially compromising the body's defense mechanisms.</li></ul><h3>Sources of PAH Exposure</h3>Understanding the sources of PAH exposure is essential for mitigation efforts:<ul><li>Food: Charred or barbecued food represents one of the highest rates of exposure to people [8].</li><li>Tobacco smoke: Both cigarette smoking and secondhand smoke are significant sources. Ambient air is another source.</li><li>Industrial activities: Coking plants, incomplete combustion from industrial processes, and waste incineration contribute significantly to atmospheric PAHs.</li><li>Vehicle Emissions: Exhaust fumes, tire wear, and improper motor oil disposal all release PAHs.</li><li>Wood Burning: Using wood stoves and fireplaces releases PAHs into the environment.</li><li>Treated Wood: Creosote-treated wood products release PAHs into the environment.</li></ul><h3>EPA Method 3546: Microwave Extraction</h3><a target="_blank" rel="noopener noreferrer" href="https://www.organomation.com/epa-methods-3510-and-3546-optimizing-sample-preparation">EPA Method 3546</a> is a crucial procedure for extracting PAHs from environmental samples. This method uses microwave-assisted solvent extraction (MASE) for extracting water-insoluble or slightly water-soluble organic compounds from soils, clays, sediments, sludges, and solid waste [7].<h4>Key Features of EPA 3546</h4><ul><li>Procedure: The method involves grinding samples to a powder, loading them into extraction vessels, adding appropriate solvents, sealing the vessels, and heating them to extraction temperature, extracting for around 10 minutes [7].</li><li>Target Compounds: EPA 3546 is designed for extracting organochlorine pesticides, semi-volatile organics, PAHs, PCBs, phenoxyacid herbicides, phenols, dioxins, and furans [1].</li><li>Advantages: Compared to traditional extraction methods, EPA 3546 offers:<ul><li>Reduced extraction time (10-20 minutes vs. hours for traditional methods) [1] [11]</li><li>Lower solvent consumption</li><li>Higher extraction temperatures and pressures</li><li>Improved efficiency and throughput [11]</li></ul></li><li>Operating Conditions: The extraction typically occurs at 100-115°C and 50-175 psi pressure [2] [11].</li><li>Solvent Systems: The most commonly applied solvent mixtures are acetone-hexane (1:1) and acetone-methylene chloride (1:1) [1].</li></ul><h4>Recent Developments in EPA 3546 Implementation</h4>Recent technological advances have addressed some limitations of traditional EPA 3546 implementations:<ul><li>Increased Sample Capacity: Modern systems like the Milestone Ethos X can process up to 24 samples simultaneously with up to 30g of sample per vessel, improving limits of quantitation and allowing for the extraction of over 200 samples in an 8-hour workday [11].</li><li>Disposable Vessels: The use of disposable glass vials eliminates potential contamination, memory effects, and cleaning requirements [11].</li><li>Temperature Control: Advanced systems feature contactless temperature control in all positions, ensuring consistent extraction conditions [11].</li></ul><h3>Analytical Methods for PAH Detection</h3>Several analytical techniques have been developed for PAH detection in environmental and biological samples:<h4>Chromatographic Methods</h4><ul><li>High-Performance Liquid Chromatography (HPLC): <a target="_blank" rel="noopener noreferrer" href="https://www.organomation.com/hplc-sample-preparation">HPLC</a> coupled with fluorescence detectors (FLD) or ultraviolet detectors is frequently used for PAH detection [4] [9]. This method offers high sensitivity and good selectivity but can be affected by matrix interferences and lacks positive confirmation as identification is based solely on retention time [3].</li><li>Gas Chromatography (GC): GC coupled with mass spectrometry (<a target="_blank" rel="noopener noreferrer" href="https://www.organomation.com/preparing-samples-for-gc-ms/ms-analysis">GC-MS</a>) provides high selectivity, sensitivity, and a simple operating system [4]. It's one of the most common methods for PAH determination and provides compound confirmation through spectral libraries. The DB-5 MS capillary column is most often used for determination of 16 EPA priority PAHs [4].</li><li>Supercritical Fluid Chromatography: This is an emerging technique for PAH determination in different food and water matrices [4].</li></ul><h4>Advanced Detection Techniques</h4><ul><li>Selected Ion Monitoring (SIM): When GC-MS is operated in SIM mode, it collects data only at masses of interest, increasing sensitivity for detecting PAHs at lower concentrations [3].</li><li>Surface Enhanced Raman Spectroscopy (SERS): Significantly improves the intensity of molecules, while holding a low detection limit and high sensitivity [8].</li><li>Microwave Plasma Torch Mass Spectrometry (MPT-MS): Shows promise as a versatile platform for PAH research with advantages including simple construction, easy operation, and relatively high sensitivity [8].</li></ul><h4>Emerging Technologies</h4><ul><li>Electrochemical Sensors: Recently developed for onsite detection of PAHs [4].</li><li>SERS-based Optical Sensors: Allow for rapid, field-deployable detection capabilities [4].</li><li>Biosensor Methods: Portable, field-deployable antibody-based PAH biosensor methods can provide rapid measurements of PAH availability [10].</li></ul><h3>Challenges in PAH Detection</h3>Despite advances in analytical techniques, several challenges remain:<ul><li>Complex Mixtures: PAHs typically exist as complex mixtures, making individual compound identification difficult. For example, the gas chromatographic procedure does not adequately resolve certain pairs of compounds, including anthracene and phenanthrene; chrysene and benzo(a)anthracene; benzo(b)fluoranthene and benzo(k)fluoranthene; and dibenzo(a,h)anthracene and indeno(1,2,3-cd)pyrene [9].</li><li>Trace Concentrations: PAHs often exist in trace amounts, requiring highly sensitive detection methods and applications that can identify low limits.</li><li>Matrix Effects: The complex matrices in which PAHs are found (soil, water, food) can interfere with detection methods.</li><li><a target="_blank" rel="noopener noreferrer" href="https://www.organomation.com/environmental-sample-preparation">Sample Preparation</a>: Many methods require complicated pre-processing that is time-consuming and labor-intensive.</li></ul><h3>Recent Advances in PAH Analysis</h3>Recent technological developments have improved PAH analysis capabilities:<ul><li>Advanced GC-MS Technology: Modern GC-MS systems demonstrate excellent sensitivity with low instrument detection limits (IDLs) and method detection limits (MDLs) in the low picogram range, exceeding regulatory requirements and ensuring accurate quantification of even trace levels of PAHs [12].</li><li>Automated Extraction Systems: Systems like the <a target="_blank" rel="noopener noreferrer" href="https://labrulez.com/en-us/all/products/746">Thermo Scientific EXTREVA ASE Accelerated Solvent Extractor</a> combine extraction and evaporation in one seamless operation, saving time, reducing errors and solvent usage, enabling unattended operations, and significantly increasing analytical throughput [6].</li><li>Improved Calibration Methods: Average Response Factor calibration curves for PAHs now span over 5 orders of magnitude (from 2.5 to 20,000 ng/mL), enhancing the accuracy of quantitative analysis [12].</li></ul><h3>Conclusion</h3>The detection of polycyclic aromatic hydrocarbons remains a critical aspect of environmental and public health protection. As analytical capabilities continue to improve, particularly through advancements in EPA Method 3546 implementation and detection technologies, we gain better insights into the distribution, fate, and impact of these widespread contaminants.Continued research and development of more sensitive, rapid, and field-deployable detection methods will be essential in our ongoing efforts to monitor and mitigate PAH exposure. By understanding where and how PAHs exist in our environment, we can develop more effective strategies to reduce their impact on human health and the ecosystems we depend upon.Through collaborative efforts between environmental scientists, analytical chemists, public health officials, and regulatory agencies, we can work toward a future with reduced PAH contamination and its associated health risks.Be sure to check out our other installments of our&nbsp;<a target="_blank" rel="noopener noreferrer" href="https://blog.organomation.com/blog/introducing-our-environmental-contaminants-series-making-sense-of-the-alphabet-soup">Environmental Contaminant Series</a>&nbsp;covering&nbsp;<a target="_blank" rel="noopener noreferrer" href="https://labrulez.com/en-us/all/article/8059">Persistent Organic Pollutants (POPs)</a>, <a target="_blank" rel="noopener noreferrer" href="https://blog.organomation.com/blog/the-importance-of-detecting-semi-volatile-organic-compounds-svocs">Semi-Volatile Organic Compounds (SVOCs)</a>, <a target="_blank" rel="noopener noreferrer" href="https://blog.organomation.com/blog/the-importance-of-detecting-polychlorinated-biphenyls-pcbs">Polychlorinated Biphenyls (PCBs)</a>, and <a target="_blank" rel="noopener noreferrer" href="https://labrulez.com/en-us/all/article/7810">Per- and Polyfluoroalkyl Substances (PFAS)</a>.

The Importance of Detecting Polycyclic Aromatic Hydrocarbons (PAHs)

Austin "Augie" Dobrecevich is a PhD researcher at the University of Washington who built an ultra-fast gas chromatograph small enough to fit in a carry-on suitcase — paired with a portable time-of-flight mass spectrometer — to measure biogenic VOCs like alpha-pinene, beta-pinene, and limonene straight from a forest canopy in real time.In this episode, Augie takes us inside his summer deployment on a 43-meter tower in northern Alabama, where he captured a chromatogram every second to track how forest terpenes react in the atmosphere and seed the massive thunderstorms the region is known for. We dig into:<ul><li>Why ultra-fast GC sub-second separations matters for atmospheric chemistry and chemical ionization mass spec (CIMS)</li><li>How isomer-specific data solves a blind spot in direct-inlet CIMS instruments</li><li>The engineering trade-offs behind building a 300-watt, TOF-based system for field deployment</li><li>Potential applications in oceanography, coral reef VOC sampling, and contaminant screening</li><li>His path through the patent process at UW's CoMotion tech transfer office — provisional patents, IP strategy, and the Innovation Gap Fund</li><li>Lessons from pitching a science-heavy invention to a business audience, and advice for grad students on cross-disciplinary PhD paths</li></ul>Whether you're an analytical chemist, an atmospheric scientist, or a grad student weighing the leap from bench science to commercialization, this conversation covers the technical depth and the entrepreneurial reality of turning a lab prototype into a real instrument.<h3>Video Transcription</h3>What if a gas chromatograph could deliver a complete separation every second, even while operating more than 40 metres above a forest canopy? Austin “Augie” Dobrecevich, a doctoral researcher at the University of Washington, is helping develop a compact ultra-fast gas chromatography system coupled to chemical ionization time-of-flight mass spectrometry (GC–CI-TOFMS). The goal is to measure rapidly changing atmospheric compounds while retaining the ability to distinguish chemical isomers.<h4>Why conventional GC is not always fast enough</h4>Traditional gas chromatography offers powerful chemical separation, but analyses that take many minutes cannot fully capture processes changing from second to second. Dobrecevich's interest in faster measurements grew from his work with Robert Synovec's research group, particularly the rapid second-dimension separations used in comprehensive two-dimensional gas chromatography (GC×GC).Developing chromatography on a sub-second timescale required careful attention to injection performance, dead volumes and extra-column band broadening. The team focused on producing short, reproducible injection pulses and efficient separations of targeted mixtures. Unlike conventional methods designed to resolve hundreds of compounds, the ultra-fast approach prioritizes a smaller set of analytes and repeated measurements at very high temporal resolution.This becomes especially valuable when combined with chemical ionization mass spectrometry (CIMS). Direct-inlet CIMS can monitor volatile compounds rapidly and sensitively, but mass spectra alone often cannot distinguish structural isomers sharing the same molecular formula. Adding ultra-fast GC provides an additional separation dimension without losing the one-second measurement timescale.<h4>Measuring forest emissions from a 43-metre tower</h4>The prototype was deployed at a US Department of Energy research site in northern Alabama, where Dobrecevich installed it on a 43-metre tower above a forest canopy. The hot, humid environment offered a demanding test of the instrument's reliability outside the laboratory.The study focuses on biogenic volatile organic compounds (BVOCs) released by trees, particularly monoterpenes such as α-pinene, β-pinene and limonene. Although these compounds have the same molecular formula, their structures and atmospheric reaction pathways differ. Rapid chromatographic separation allows researchers to follow how the concentrations of individual monoterpene isomers change with wind direction, atmospheric mixing and environmental conditions.The instrument's sampling inlet was positioned near a sonic anemometer, which measures wind velocity in three dimensions. Combining these measurements with one-second chemical data is intended to support flux analysis, helping researchers investigate how compounds move between the forest canopy and the atmosphere.Monoterpenes can react with atmospheric oxidants to form lower-volatility products that contribute to secondary organic aerosols and potentially to cloud condensation nuclei. Understanding the emissions and chemistry of individual isomers could therefore improve models of atmospheric processes.<h4>A portable GC–MS system with low power requirements</h4>To make these measurements possible in remote locations, the researchers combined their custom-built ultra-fast GC with a compact chemical ionization time-of-flight mass spectrometer developed with Swiss instrument manufacturer TOFWERK.According to Dobrecevich, the integrated system is approximately the size of a carry-on suitcase and operates at less than 300 W.The portable mass analyzer has a reported resolving power of approximately 1,300 (m/Δm). Although this is lower than that of many larger high-resolution TOF instruments, chromatographic separation helps compensate for the reduced mass selectivity by resolving isomers before they enter the ion source. The result is a promising balance between speed, selectivity, instrument size and power consumption.The Alabama deployment was designed primarily to stress-test this early-stage prototype and demonstrate the feasibility of isomer-resolved flux measurements. It does not yet establish a routine commercial method, but it shows why compact GC–MS technology could open up experiments that previously required difficult compromises between chemical specificity and measurement speed.<h4>Applications beyond atmospheric research</h4>While forest emissions are the current focus, the underlying concept could be useful wherever chemical compositions change rapidly. Potential applications include mobile monitoring of urban air pollutants, targeted screening of industrial emissions, process control and rapid detection of selected contaminants.Dobrecevich also sees opportunities in marine research. Volatile compounds released from seawater or biological samples could potentially be transferred into the gas phase and analyzed close to the sampling site, reducing delays associated with sample transport and storage. These remain prospective applications for the GC-coupled prototype rather than established workflows.<h4>Moving from research to commercialization</h4>Developing the instrument has also introduced Dobrecevich to intellectual property and technology transfer. With support from the University of Washington's CoMotion program, the team pursued a provisional patent before publicly disclosing key elements of its design.The project subsequently received approximately $75,000 through an Innovation Gap Fund award, helping support further development and field testing.An important lesson has been that technical performance alone does not establish commercial demand. Through planned customer-discovery activities, including the NSF I-Corps program, the team aims to understand where rapid, isomer-specific measurements solve genuine laboratory or field-analysis problems.For Dobrecevich, interviewing prospective users without leading them toward a desired answer is as important as testing a scientific hypothesis.<h4>A lesson in interdisciplinary science</h4>Dobrecevich's path from chemistry into atmospheric instrumentation also highlights the value of working across disciplines. Advances in field-deployable analytical systems depend on chromatography, mass spectrometry, engineering, physics and environmental science, often developed through close collaboration between specialists.The broader significance of ultra-fast GC is not simply shorter analysis time. By matching chromatographic measurements to the speed of real-world processes, researchers may gain access to chemical information that conventional laboratory workflows cannot capture.<blockquote>This text has been automatically transcribed from a video presentation using AI technology. It may contain inaccuracies and is not guaranteed to be 100% correct.</blockquote><blockquote><h4>Concentrating on Chromatography Podcast</h4>Dive into the frontiers of chromatography, mass spectrometry, and sample preparation with host David Oliva. Each episode features candid conversations with leading researchers, industry innovators, and passionate scientists who are shaping the future of analytical chemistry. From decoding PFAS detection challenges to exploring the latest in AI-assisted liquid chromatography, this show uncovers practical workflows, sustainability breakthroughs, and the real-world impact of separation science. Whether you’re a chromatographer, lab professional, or researcher you'll discover inspiring content!You can find Concentrating on Chromatography Podcast in podcast apps:<ul><li><a target="_blank" rel="noopener noreferrer" href="https://open.spotify.com/show/1wZg67rCjoGju4yhqxI3tL">Spotify</a></li><li><a target="_blank" rel="noopener noreferrer" href="https://podcasts.apple.com/tz/podcast/concentrating-on-chromatography/id1788429185">Apple podcast</a></li><li><a target="_blank" rel="noopener noreferrer" href="https://podscan.fm/podcasts/concentrating-on-chromatography">podscan</a></li></ul>and on <a target="_blank" rel="noopener noreferrer" href="https://www.youtube.com/@ChromatographyTalk/videos">YouTube channel</a></blockquote>

Ultra-Fast GC Meets Mass Spec: Measuring Forest Chemicals That Create Storm Clouds

<div><div><div>Molecules are never still. Driven by thermal energy, they are constantly moving through space, while their individual parts also rotate relative to one another. Scientists at IOCB Prague have now shown that random motion within a molecule can be dramatically suppressed. Using light, they can slow down the relative rotation of two different parts of a single molecule by up to five orders of magnitude, paving the way for more complex molecular machines.</div></div><div>Driven by thermal energy, individual parts of molecules are constantly vibrating, rotating, and changing their positions – a phenomenon known as Brownian motion. Unlike conventional engineers, scientists building molecular machines therefore work with components that are constantly in motion. To assemble them into a functioning mechanism, they need to be able to control this motion. This is precisely what the <a target="_blank" rel="noopener noreferrer" href="https://kaleta.group.uochb.cz/en">team of Jiří Kaleta</a> at IOCB Prague has achieved.The scientists created a molecular system incorporating two key components: a light-controlled molecular motor and a rotor that randomly rotates around its axis because of thermal motion. “When we shine light on the molecule, the motor changes its spatial arrangement, which in turn affects the motion of the rotor. In the ‘unbraked’ state, the rotor can rotate easily, while in the ‘braked’ state, the motor physically obstructs its motion and significantly increases the energy barrier the rotor must overcome to turn,” explains Lukáš Severa, first author of the study.The principle can be pictured as a hand freely mounted on an axis and constantly jostled by tiny vibrations. If nothing stands in its way, it can rotate easily. But when an obstacle is placed in its path, its rotation slows dramatically. In the molecule, this obstacle is created by the moving part of the molecular motor.</div><blockquote><h5><a target="_blank" rel="noopener noreferrer" href="https://www.youtube.com/watch?v=2gTTUUdyekQ">Video</a></h5></blockquote><div><h3>Up to a 300,000-Fold Slowdown</h3><div>The difference between the two states is striking. “In previous similar systems, it was possible to change the rotation rate by no more than a factor of one hundred. With our approach, we have achieved a slowdown of approximately 300,000-fold, which represents a major breakthrough,” says Jiří Kaleta.The difference between the two states becomes even more dramatic as the temperature decreases. If, at a very low temperature, the unbraked rotor completed one rotation per second, under the same conditions the braked rotor would take approximately 350 billion years to complete a single rotation – about twenty-five times the current age of the universe.The ability to control the motion of individual components is essential for constructing more complex molecular machines. “If you want to build a more complex mechanism, having a motor alone is not enough. You also need elements that can regulate and coordinate the motion of individual components. We are demonstrating one principle for achieving this at the molecular level,” concludes Jiří Kaleta.</div><img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/UOCHB_Jak_zkrotit_nahodny_pohyb_uvnitr_molekuly_Vedci_to_umi_svetlem_1624400c8f.webp" alt="IOCB Prague/Tomáš Belloň: How to tame random motion inside a molecule? Scientists can do it with light: Lukáš Severa and Jiří Kaleta" srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_UOCHB_Jak_zkrotit_nahodny_pohyb_uvnitr_molekuly_Vedci_to_umi_svetlem_1624400c8f.webp 234w," sizes="100vw" width="810" height="540"></div><blockquote><h4>The original article</h4><h4><a target="_blank" rel="noopener noreferrer" href="https://onlinelibrary.wiley.com/doi/10.1002/anie.7061287">Light-Gated Control of Brownian Rotation by a Molecular Motor</a></h4>Severa, L., Bezděková, K., Majerová Varga, K., Bastien, G., Stroka, M., Císařová, I., Dračínský, M., &amp; Kaleta, J.&nbsp;Angew. Chem. Int. Ed., 2026, 65, e7061287<a target="_blank" rel="noopener noreferrer" href="https://doi.org/10.1002/anie.7061287">https://doi.org/10.1002/anie.7061287</a><h6>Licensed under <a target="_blank" rel="noopener noreferrer" href="https://creativecommons.org/licenses/by-nc/4.0/">CC-BY 4.0</a></h6></blockquote></div>

How to tame random motion inside a molecule? Scientists can do it with light

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The Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences (IOCB Prague) is a leading scientific institution in the Czech Republic, recognized internationally. Its primary mission is basic research in the fields of chemical biology and medicinal chemistry, organic and material oriented chemistry, chemistry of natural compounds, biochemistry and molecular biology, physical chemistry, theoretical chemistry, and analytical chemistry. 

Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences

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