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A wide variety of contaminants with the potential to cause harm to humans and animals can make their way into the environment. They can be found in the air, water and soil and may come from sources such as industrial waste, landfill sites, pesticides and pharmaceutical drugs.
Identifying these contaminants is challenging because of the huge variety of potential compounds with varying chemical compositions. In addition, there are likely to be unknown contaminants produced by degradation, or by transformation processes like hydrolysis. Regulation often requires monitoring for the presence of very low concentrations of a variety of contaminants. These challenges call for sophisticated analytical techniques which are sensitive robust, fast and cost-effective. Chromatography and Mass Spectrometry are two techniques which can help. In the past few decades, developments in both techniques has improved their applicability to environmental analysis.
Chromatography in Environmental Analysis
Liquid chromatography (LC) is becoming a popular separation technique in environmental analysis. Most LC nowadays is High Performance Liquid Chromatography (HPLC) which uses small particles packed together at high pressure.
While gas chromatography still remains popular in environmental analysis, particularly for volatile and non-polar compounds, it does not lend itself to analyzing compounds which are polar, non-volatile, thermolabile or have a high molecular weight. For such compounds, LC is better.
Continual improvements to LC are increasing its potential to separate a wide variety of complex mixtures in environmental analysis. New sample preparation methods are being developed, such as Quick Easy Cheap Effective Rugged Safe (QuEChERS) which is a popular sample treatment method for multi-residue and polar pesticide residue analysis in food.
Different stationary phases are also being experimented with to improve separation. Reverse phase with alkylsiloxane-bonded silica is used for separating highly polar compounds in environmental analysis because it is widely applicable and easy to use.
A common problem in environmental analysis is interference because samples are likely to contain a variety of compounds. To combat this, clean up is often necessary during sample preparation, which adds to the analysis time. Turbulent flow chromatography (TFC) is a cost-effective high throughput technique where clean up is not necessary. It has been particularly successful at reducing the sample preparation time when analyzing perfluorooctane sulfonate in river water.
Mass Spectrometry in Environmental Analysis
Mass Spectrometry (MS) is a popular technique for environmental analysis because of its ability to carry out sensitive qualitative and quantitative analysis.
A number of developments, particularly in the analyzers used to separate ions based on their mass-to-charge ratio, make it increasingly useful for environmental analysis. Analyzers vary depending on their mass measurement accuracy, resolving power, acquisition speed and linearity. Analyzers like time-of-flight and orbitrap have been investigated for environmental applications.
Tandem MS using hybrid analyzers is further improving MS by using two rounds of mass analysis. It lends itself to environmental analysis because it is useful for analyzing analytes in complex mixtures, or with high sample matrix background. It has been used in pesticide analysis to identify compounds like nitrophenols, which are readily water soluble and can run-off into river water and make their way into drinking water supplies.
Combining LC with MS
Combining the selectivity of LC with the sensitivity of MS makes it possible to overcome some of the challenges presented by environmental analysis. MS provides more reliable detection of microcontaminants than other detectors commonly used with LC. With the right set-up, LC/MS can analyze unknown compounds or those at low concentrations. It has even been used to detect concentrations as low as parts per trillion.
LC-MS is the most popular technique for detecting and analyzing pesticides which encompass a diverse range of compounds. It has also been used to detect steroid oestrogens which can be a problem in waste water and can disrupt the endocrine system.
Coupling LC with MS only became possible when electrospray ionization was developed as a suitable interface to transfer ions from LC to MS. Electrospray ionization moves ions in solution into the gas phase. Since then new ionization techniques like atmospheric-pressure ionization (API) have become available. API is good for analysing highly polar ionic, high molecular weight and heat sensitive compounds.
LC combined with a variety of MS techniques has been investigated for environmental analysis. MS with an orbitrap analyzer is one example. Orbitrap gives high mass resolution and high mass accuracy. However, it’s slow scanning speed at a resolutions above 100,000 makes it difficult to couple with Ultra HPLC which has peak widths lasting a few seconds. It has been investigated for environmental applications such as analyzing nitrosamines in wastewater, as well as quantifying target analytes and identifying unknowns.
LC-MS with the analyzer Quadrople Time-of-Flight (QTOF) has been used for screening compounds ranging from antibiotics to pesticides. LC with tandem MS, known as LC-MS/MS, has been used to detect perfluorinated organic compounds (PFOS) at a low concentration. PFOS are found in cleaning products, textiles and photographic materials.
Combining LC with High Resolution Mass Spectrometry (HRMS) is great for wide-scope screening of diverse organic pollutants in the environment, including degradation products. HRMS offers sensitivity, high mass accuracy and is suitable for target and non-target compounds.
Plenty more developments are on-going and as the emphasis on keeping environmental pollution in check is unlikely to dissipate, these are likely to continue.
This year’s Pittcon, Pittcon, a leading conference and exposition for laboratory science, will take place between the 6th and 10th of March in Atlanta, Georgia. With an impressive technical program, the event will feature more than 2000 presentations. Among these, topics will include chromatography and mass spectrometry for environmental Analysis
We will also hear about the analysis of hydraulic fracturing additives by LC/Q-TOF-MS, using high resolution mass spectrometry to uncover new iodinated and nitrogen-containing disinfection byproducts and the analysis and effects of pharmaceuticals in surface waters.
Among the 683 exhibitors at Pittcon will be Shimadzu, world-leaders in the field of liquid chromatography. With a wide range of systems and components, including data systems, and outstanding reputation for long life, precision, and practically maintenance-free operation, Shimadzu has the resources to meet user requirements in nearly every market and application.
Visit pittcon.org for more information.