If this is your first time visiting www.teledyneleemanlabs.com and/or stumbling upon our blog, Teledyne Leeman Labs has been in the business of making benchtop mercury analyzers for over 30 years. Myself, I’ve been with the company, wearing a variety of different hats, for 24 years. Prior to landing this 24-year gig, I was an analytical research chemist at the University of North Dakota’s Energy and Environmental Research Center (EERC) in Grand Forks, ND. So, with a career like this, I’ve seen a lot of data - some good, and some not so good!
When a laboratory analyst receives samples for analysis, it initiates a process that includes numerous considerations. The assay needed for the sample could include one, two, and/or multiple parameters to report each sample’s respective concentration. Depending on the parameters, the starting process could be ultra-trace and/or run-of-the-mill preparations. At the completion of the entire process, what value will your data have, and will it be scrutinized by someone else? What quality assurance processes should you employ? Can you anticipate any potential reason to take a deeper dive into the sample data? How will your environmental laboratory report be reviewed?
A typical sample analysis scenario is outlined below:
Inside the lab:
Outside of the lab:
As an environmental laboratory analyst, there is a high probability that your data will be examined by an outside reviewer. In order to support your data, what tools can you use to identify and assess biased data? Considerations include:
Let’s discuss your laboratory control sample (LCS), matrix spike, method control blanks, and duplicates in greater detail:
So, when we review all our checks and balances, we report what we believe is the value in the sample – IF AND ONLY IF - they all check out.
REALITY CHECK! Let me tell you about a real-world example I was studying recently:
Lately I was working of a new project: Mercury Concentration in Beverages. One of my first beverage solutions tested was coffee - I drink a lot of coffee, so this study was relevant to my health! I used a microwave ICP-MS digestion method referenced in USFDA Elemental Analysis Manual (EAM 4.7) as a starting reference point, but with the intent to use CVAA as the analysis technique.
I digested seven coffee samples along with a control blank and pre-digest spike. I also performed a post-digest spike for inclusion in the analytical batch. Even though CVAA is a very different technique from the scope of the original method, I was hopeful the analysis would be successful. I reviewed the printed results for the coffee data and on the surface everything looked great, but that was only a superficial view. Here were the results:
So, with the quality control information above I should be able to submit my results and deem the analytical process a success, correct? Or, should I take a deeper look at the results, before I tell someone not to drink coffee?
Below are the spectra for the control blank and an extracted coffee sample. The QC data indicated that the sample didn’t have any issues, BUT if that was true then the spectra of the control blank and the sample should match – they should mirror each other - BUT they don’t!
Figure 1: Spectra of Control Blank
Figure 2: Spectra of Digested Coffee Sample
After further review of the spectra, it appears that either a kinetics issue or a valence state problem was affecting the digest’s ability to oxidize the mercury to Hg2+ in the sample. I’ll be working out the kinks in my process and I let you know how it all turns out in Part 2 of this blog (to be posted shortly).
In conclusion, environmental laboratory reports contain a lot of valuable information for better or worse, and the case study presented here should give one pause to not take the results at face value. As an analyst we should always strive to look beyond the horizon for the truest answer we can possibly report!
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