Dr Jacob Jaine, ALS Global
The Background
A concept in the lab testing which is becoming increasingly common is ‘non-targeted analysis’, or NTA for short. This refers to analytical techniques which can be used, typically for research purposes, to measure a very large number of things in a sample simultaneously. The general principle has been around for several decades, but is becoming more mainstream with the commercial availability and adoption of tools to do it with.
Normally a sample is submitted to a laboratory for the analysis of a particular chemical compound, for example glyphosate or tributyl tin, and the laboratory will process the sample in accordance with a validated reference method for those compounds. The lab will measure the designated compound and only the designated compound, ignoring all other components in the sample. This is like having a television which is stuck on a single channel – if you only like watching the news then you are in luck, but if you want to channel-surf from MTV to Home and Away, then you have a problem.
If you submit a sample to a laboratory for NTA the process is very different. Instead of measuring particular compounds, information can be obtained on all of the detectable species in a sample. Collecting that data can be complicated, and interpreting it even more so – like having a television which displays all of the channels simultaneously, including foreign language and strange cable shows, but there is a metaphorical sea of information to be obtained.
The Tools
Testing labs will have a range of different machines for measuring things, and many of them are called mass spectrometers. These are machines which are the size of an oven but the price of a house, which can exclusively measure compounds in a sample having a particular atomic mass. Some are better at this job than others, and a particular type called high resolution mass spectrometers, or HRMS for short, excels at this job. These are typically what is used for NTA, especially in the case of analysing trace levels of compounds, like PFAS.
HRMS systems are available commercial in several different styles, including time of flight (TOF) machines, Orbitrap machines, and the extremely powerful but hard-to-say Fourier transform infrared cylcylotron resonance (FT-ICR) machine. All three of these can be used for NTA, and all three are powerful analysis platforms for investigating the composition of a sample.
Figure 1. This is what an Orbitrap HRMS looks like – a nondescript square box. The exciting parts are inside.
In ALS laboratories we use Orbitrap™ HRMS systems to do NTA, which offer good sensitivity, great accuracy, and excellent versatility. In these systems, the sample is atomized and the resulting molecules are transferred electrostatically into a small metal apparatus resembling a tiny barrel, held at one billionth of an atmospheric pressure, where they orbit millions of times, travelling literally hundreds of kilometers. Using the power of mathematics, the electrical currents they induce are converted into data on what is present in the sample.
Figure 2. This is the exciting parts. The silver barrel is the detector mechanism which identifies the components in a sample, represented by the red cloud of mist. Credit: Wikipedia
The Past, Present, and Future
There are lots of reasons to do NTA, not least of which is to gain some insight about what exciting new contaminants might be in a sample. For those with a keen eye to the future and interested in proactively engaging with risk management, NTA can be indispensable. For example, where conventional lab tests for a compound may be unavailable, NTA can be used to inspect a sample and gain evidence for the presence or absence of emerging problem compounds. Perhaps your favourite lab only does a paltry 40 PFAS, but new regulations mention some other, exotic PFAS? No problem, perform some NTA and look for the compound there. You can even come back to the data years after it was recorded and look for new problem compounds in data from old samples. For those diligent enough to have an extensive archive of NTA data for risky sites (e.g water wells or leachy landfills) this can help paint a comprehensive picture of when and where contaminants might be present, and even give an idea of the magnitude of the problem.
The usage of NTA is becoming an increasingly important tool in the environmental scientist’s toolbox, sitting on the top shelf next to the other important tools like spanners, screwdrivers, and targeted residue testing methods. Talk to your favorite laboratory today, and we can help you find problems before they find you!
About Dr Jacob Jaine
Dr Jaine is a research scientist at ALS New Zealand. His specialty is using expensive machines to measure very small amounts of chemicals that people don’t like inside things which they do.