How BAL Uses Speciation to Complement Total Elemental Analyses

Mar 15, 2018

Most regulations – whether for the environmental, pharmaceutical, or consumer product sectors – are based on the total concentration of an element present in a given sample.  Many regulatory bodies and standards organizations have promulgated methods to support total elemental analyses in a variety of matrices, which can lead to the impression that providing quality data for such analyses is routine and uncomplicated.  However, many methods fail to consider what impact the molecular forms (also known as chemical species) of an element may have on the accuracy of the procedure, which can lead to inaccurate analytical results.  With our unique focus not just on total elemental quantitation but also on advanced speciation methodology, Brooks Applied Labs (BAL) can be trusted to provide accurate data for your project.

To begin to understand how the speciation of an element can impact the accuracy of total elemental analyses, consider that nearly all methods are validated using only a small subset of the wide variety of real-world sample types that a data end user may be interested in analyzing.  While it is generally the responsibility of the laboratory to ensure that the applied methods are fit-for purpose, not all samples of a given matrix type will be identical or contain the same forms of an element.  Therefore, even if a method has been purportedly validated for a specific type of sample, unexpected biases can remain hidden if the specific chemistry of the sample and the element of interest are not understood and addressed when developing an analytical plan.  All steps, ranging from sample collection, preservation, preparation, and analysis must be taken into consideration.

For example, in the case of selenium, numerous literature sources state that water samples will typically contain selenite and/or selenate.  These selenium species may be accurately quantified by the techniques found in most promulgated methods, including sample collection into polyethylene bottles followed by preservation and digestion using mineral acids.  However, more than a dozen other selenium species have been identified in both natural and anthropogenically-impacted waters, including volatile forms like dimethylselenide and reduced forms like selenocyanate.  Standard analytical methods have been shown to generate biased data if samples contain volatile species, in part because standard sample containers are permeable to these forms of selenium.  Similarly, low-biased results can be obtained if standard sample methods are applied to water samples containing reduced selenium species, as these forms can precipitate from solution during acidification with dilute mineral acids. Since many other elements can form volatile or reduced species – including arsenic, mercury, lead, antimony, tin, and iodine – biases due to blind application of standard methods are not limited to just selenium.

When you work with Brooks Applied Labs, you not only benefit from our state-of-the-art instrumentation and robust methods, but also from our experienced staff who can identify and anticipate these potential issues to ensure the quality of your data.  Including speciation analyses alongside more traditional total elemental analyses can also provide you with greater confidence in your data, particularly when the results of these two separate analyses agree.  And in cases where the two analyses may differ, our staff will work with you to interpret the results and recommend additional analyses to identify the source of the discrepancy.  To learn more about how partnering with Brooks Applied Labs can help ensure the success of your project, please contact us today!