Selecting the Best Selenium Analysis
Using IF, THEN, AND, OR, but not AI
In the current world where artificial intelligence (AI) is gaining acceptance and utilized across many fields from drug discovery to creative writing, one might expect this article to employ that technology. But instead, I have chosen to employ a set of logic – an IF, THEN, AND, OR set of statements to explore how you might reduce your frustration should you suffer from issues with selenium analyses. I find this line of logic the best way to get to the point since we are overwhelmed with writing, not necessarily information, in our work. With that in mind, consider the following:
IF – Selenium is one of the analytes that you must measure to be in environmental compliance.
AND – Since low analytical sensitivity for selenium is largely due to its toxicity to aquatic life, it is likely your issue revolves around a discharge permit (viz., NPDES). The table below shows some common selenium discharge limits illustrating that the need for single-digit µg/L sensitivity is common.
AND – You are not meeting the discharge limits.
AND/OR – Your analytical sensitivity does not provide sufficient separation between the laboratory reporting limit and your discharge limit. Note, if neither of these statements is true, consider yourself among the fortunate.
THEN – Consider evaluating, or contacting an independent Chemist to help assess:
- What methods of analysis are you using for selenium?
- Is the analytical method specified by the permit?
US EPA methods for selenium include:
o Graphite Furnace AA
§ US EPA 270.2
o Inductively Coupled Plasma (ICP)
§ via US EPA Method 200.7, possibly by SW-846 Method 6010.
o Hydride Atomic Adsorption
§ via US EPA 7741, US EPA 7742, Standard Method 3114.
o Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) via US EPA Method 200.8, possibly by SW-846 Method 6020.
- What are the concentrations of major cations and anions and other potential interfering parameters in your discharge water?
With this background, you can infer if your method may suffer from interferences that could result in artificially high results (high bias). Typical Interferences are method dependent, but all methods can suffer from interferences to selenium. These might include high anions such as chloride, nitrate, and nitrite; other metals and metalloids including copper, lead, nickel, molybdenum, and some rare earth elements; and argon (with ICP-MS). Yes, wow that is a lot to consider. To further dig into the evidence indicating a high bias:
THEN – Review the methodology of analysis, the laboratory-supplied quality assurance (QA) and historic data for clues to failure. With these data, can one infer there are one or more lines of evidence supporting analytical issues as the basis for permit failure? Within the analysis, consider if the failure is not static, with occasional failure possibly related to seasonal or process changes.
IF – The analysis appears to be the source of concern:
THEN – Have the Chemist recommend a better analytical method. Strongly consider employing ICP-MS as interferences and reporting limit requirements can largely be overcome by modern ICP-MS instrumentation. To verify this, one should develop an analytical plan with replication and QA used to statistically compare methods. Plan the study using one or more laboratories experienced with your type of matrix interferences.
IF – The analytical does not appear to be at issue:
THEN – Consider if you require new/better treatment technology to meet your selenium discharge limits. ECT2, a Montrose Env. Group Company has technology specifically designed for meeting single-digit ppb selenium discharge levels. This technology provides:
- Reduction of soluble Se to elemental form, followed by sorption to media, with removal to to <1 µg/L demonstrated.
- Iron-based media
- Short reaction time, simplicity of operation
- Sulfate, nitrate, other metals have minimal effect of efficacy
- Removal of other elements of concern: molybdenum
I do hope you found this way of writing easy to follow and helpful. Perhaps I should use more AI applications to create more interesting stories. But sometimes AI text just seems to lead you on when simplicity is sufficient.
Selenium Limits – Several States
