On a recent flight, I came to appreciate the ability to reduce the background din of fellow passengers and, more importantly, the unavoidable roar of the jet engine. If that noise wasn’t there, I’d definitely start to worry, but I also don’t want to have that loud buzzing in my ears for the entire journey. Fortunately, I have discovered a solution that has become an absolutely essential addition to my carry-on bag: noise-canceling headphones. Once these have been properly positioned over your ears and activated, as soon as the engine’s turbines start to rev up and you take to the air, you are powerless to prevent a smile from appearing on your face. Aside from that welcome feeling of isolation from the hubbub that surrounds you, the real benefit of background noise reduction is the ability to clearly hear the audio from the video you are watching or the music you are playing that helps pass the hours. I no longer need to crank up the volume to distinctly hear the quiet passages. My ears thank me, especially when the video I’m streaming is interrupted by the flight attendant requesting passengers to not congregate around the restrooms, despite having just loaded them up with liquids. Because I would have to crank up the volume when using regular headphones, this message would have come through at an ear-piercingly high volume that would have had me yanking them from my head.
This transformation of a previously uncomfortable travel experience got me thinking about where else background noise reduction might have a dramatic impact. Putting my scientist hat on led me to ponder how this might be applied to analytical data collection. I recently visited a group of researchers in the SWAMP lab at the University of Alberta who take background reduction to a whole new level. One of their primary goals is to determine ultra-low concentrations of elements in field samples to monitor the impact of industrial activities on the environment.
Every step in the data collection process has been critically evaluated to identify potential sources of contamination and minimize them. In their metal-free, ultraclean facility, a clean suit is donned before entering a class 10,000 (<10,000 ≥0.5 µm particles/ft3) room in which sample collection bottles are washed using in-house distilled nitric acid and ultrapure water, prior to being transferred into clean bags destined for field sample collection. Upon return from the field, collection vessels are wiped down and samples prepared prior to entering a class 1,000 room where elemental analysis of samples takes place using a Thermo Scientific™ iCAP™ RQ Inductively Coupled Plasma Mass Spectrometer (ICP-MS) system. What this heightened attention to cleanliness achieves is the ability to lower the background levels to the point where, for some elements, sub-ppt (part per trillion) analyte concentrations can be determined with confidence.
The relentless focus of the SWAMP lab on identifying and eliminating sources of contamination is readily demonstrated by Dr. William Shotyk himself, the lab director. Even in something as mundane as an espresso cup, the potential for the introduction of contaminants into a solution cannot be discounted.
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Another area where minimizing background contamination can be critical is elemental species determination. Because elements can be present in multiple forms that vary in toxicity, determination of total element present gives no indication of its true harmfulness. One example is innocuous, organic arsenic vs. highly toxic, inorganic arsenic (see Application Note 43255). Another is Chromium (Cr), which can be present in two species, nutritionally essential Cr (III) and toxic Cr (VI; See Application Note 44407). Metal speciation can be done by preceding an ICP-MS system with some form of chromatographic separation, either ion, liquid or gas chromatography. For liquids, Ion Chromatography (IC) has a distinct advantage because it uses a completely metal-free flow path, eliminating the potential for introduction of metal contamination from the instrument itself, which can contribute to an elevated background signal, limiting the detection levels that can be achieved (visit the IC-ICP-MS Speciation Analyzer page for more info.). This potential for metal leaching is of particular concern for ion-exchange chromatography due to the caustic eluents that are typically used. Leachates can also accumulate on the column itself, diminishing performance.
If we turn our focus to the IC part of the system, another type of background reduction can be achieved with the use of a suppressor. This inline device reduces the amount of salt in the mobile phase, making it compatible with direct injection into an ICP-MS system. It also increases the conductivity of the ionic analytes of interest, which enhances the signal to noise that can be achieved with conductivity detection. See the blog post “Suppression Unravelled: Understanding the Role of Suppression in Modern Ion Chromatography” for a more in-depth discussion of this topic.
Just as donning noise-canceling headphones when in the air lets you hear things that you might otherwise have missed, paying close attention to potential sources of contamination can have you arriving at conclusions that had previously seemed unachievable. The difference will come through loud and clear.