Multiple upstream devices and various forms of detection allow the analysis of many kinds of samples
Humans and nature can pollute the environment, and our health often depends on tracking and analyzing the toxic compounds. “Certain toxins and pollutants are naturally made in the oceans,” says Vinayak Agarwal, Helen Hay Whitney Foundation Postdoctoral Scholar at the University of California at San Diego’s Scripps Institution of Oceanography, “and they resemble some of the most toxic molecules that humans have ever synthesized.” Humans can stop making toxic compounds, but what can we do when nature makes them?
The source of a dangerous compound determines how it can be avoided, if at all. “If [it’s] naturally made, you can’t do anything unless you know where the exposure is coming from,” Agarwal says. “So if a fish causes mercury poisoning, you need to not eat that.”
To find such toxic compounds, Agarwal says, “MS is a fundamental tool.” He adds, “This work depends critically on liquid or gas chromatography plus MS.” With LC/MS, a quadrupole time of flight (QTOF) MS works well and is relatively inexpensive, according to Agarwal. “For brominated samples, electron capture negative ion MS gives good ionization.” Single, tandem and triple quadrupole MS can be used with GC. So the right MS depends on the problem.
Tailoring the tool
“Depending on the configuration, MS provides a broad-reaching technique for answering environmental questions,” says Craig Marvin, global environmental industry manager for Agilent Technologies (Santa Clara, Calif.).
Some compounds work best with LC, some with GC, and others with both techniques. “Things amenable to analysis by GC/MS, like volatiles, are not good candidates for analysis by LC/MS,” Marvin says. Composition of the sample also determines the best MS to use. “Triple quadrupole MS systems, like the Agilent 6470 Triple Quadrupole LC/MS System, eliminate chemical interference, which provides additional selectivity and can better identify the targeted compounds in complex matrices,” says Marvin.
The Agilent 7010 Triple Quadrupole GC/MS System gets more of the sample to the detector to increase its sensitivity. (Image courtesy of Agilent Technologies.)
“QTOF is used for nontargeted screening—identifying things you don’t know are in the sample—critically important for monitoring emerging contaminants. The Agilent 7010 Triple Quadrupole GC/MS System produces more ions for a given injected concentration and draws a higher percentage of those ions to the detector, providing environmental scientists with a very valuable tool for [detecting] trace chemicals in complex environmental matrices.” Marvin explains. “This system provides an order-of-magnitude improvement in sensitivity compared to conventional MS/MS systems—allowing analysts to meet detection-limit requirements using reduced volume of sample and organic solvent in the sample processing.”
Enhancements in mass spectrometry systems, like SCIEX’s X500R QTOF, expand use of the technology to a wide range of environmental samples. (Image courtesy of SCIEX.)
In some cases, scientists want to test environmental samples with little preparation, and this can be done with an MS system that uses an ambient ionization source, such as JEOL’s AccuTOF-DART 4G. The system can analyze fungicide on an orange peel or test other foods for pesticide contaminants. “This system has also been used to identify endangered species of wood, like Brazilian rosewood, illegally imported into the United States,” says Robert Cody, mass spectrometer product manager for JEOL USA (Peabody, Mass.). “It was recently used to identify biodiesels from an accidental spill.”
Testing for traces
The accuracy of MS even lets researchers map out the isotopic distribution of a sample.
This comprehensive two-dimensional gas chromatography (GC×GC) combined with high-resolution mass spectrometry (EOL AccuTOF-GCx) shows nontargeted analysis of environmental contaminants in dust from an electronics recycling facility. (Figure adapted from Ubukata, M.; Jobst, K.J. et al. J. Chromatogr. A May 2015, 1395, 152–9. Image courtesy of JEOL.)
“Something made naturally, for example, doesn’t include lots of 14C, but a sample derived from petroleum contains lots of 14C,” Agarwal says. “So with really accurate mass measurements, you can see if a pollutant is from a natural or human-made source.”
To look for traces of metals in samples, scientists often use inductively coupled plasma MS (ICP/ MS). This technology detects metals down to one part per quadrillion. For nonmetals at trace levels, scientists might use the JEOL AccuTOFGCx, which provides highly sensitive GC/MS analysis. “This system can identify trace contaminants in a sample,” says Cody. One study used this platform to identify polybrominated and polychlorinated contaminants in dust.
In many cases, environmental samples contain target compounds at trace levels. “Environmental analysis can also be extremely complex, because real-life samples include an awful lot of components, like dirt or foods or dust,” says Cody. “So you need all the tools that you can get for a complete analysis.”
“Every time we turn on the tap or faucet to have a drink of water, fill a saucepan or a sink to wash in, we take it for granted that the water is safe and fit for purpose,” says Vincent Paez, senior director for food, environmental and forensics testing at SCIEX (Framingham, Mass.). “LC/MS/ MS can play a key role in analysis throughout the whole water cycle.” Public-health scientists use this technology to analyze raw water that reaches a treatment facility. “By employing MS to screen the raw water before it gets treated, water companies can improve the efficiencies of the treatment works operation,” Paez says. “The treatment process can be dictated by the acquired MS data so that it can be tailored to the required level of purification as opposed to expensively running the plants at full capacity.”
MS can also be used at various steps in water treatment “to monitor how the process is performing in the removal of pesticides, for example,” Paez explains. “Then, before the water goes out into supply, a sample can be quickly analyzed without any extraction using our direct injection workflow.”
For routine water testing, Paez says, SCIEX’s new MS platform, the X500R QTOF, “delivers the sensitivity to help ensure compliance to legislation, and the resolution of the acquired data offers the high levels of accuracy you need.” Paez says that this platform is easy to use, even for a nonexpert, and small enough for a benchtop.
As MS systems improve, scientists expect more and more. Marvin says, “The current technology drivers are producing better-quality data at lower and lower detection limits.” He adds, “Agilent is continually asked by customers to help them achieve new reporting limits, or improve detection limits by an order of magnitude to provide greater confidence in measurements.” Improving sensitivity will increase the range of applications for MS applied to environmental samples.
Mike May is a freelance writer and editor living in Ohio. He can be reached at [email protected]