What is the difference between total and dissolved metals?

Modified on: Tue, 7 May, 2019 at 1:59 PM

Depending on the sample preparation or sampling procedure, contaminants in water can be measured as “total”, “dissolved”, “mobile” or “suspended”. Samples can be analyzed unfiltered and preserved (“total”) or filtered with a wide range of filter sizes (where filter size will determine if “suspended”, “mobile” or “dissolved”). Historically, groundwater has been analyzed for “dissolved” constituents. Surface water, drinking water and wastewater are typically measured as “total” with no filtration. In short, “total” and “dissolved” can be differentiated by field collection or sample preparations practices as:

“TOTAL” – water samples are NOT filtered and are preserved (samples are typically preserved immediately at the time of sampling via the pre-charged preservative in the Bureau Veritas Laboratories sample bottle).  On the label of the sample bottles, check the box indicated as “Total - Preserved”.

“DISSOLVED” – water samples are filtered PRIOR to preservation.  It is best to filter in the field and immediately preserved (check the box indicated as “Dissolved – field filtered & preserved). If it is not possible to filter in the field, it may be done at the laboratory. In that case, you would rinse out the pre-charged preservative and on the sample bottle check the box indicated as “Dissolved – preservative rinsed out, lab to filter & preserve”.

For dissolved metals, do i use a preserved bottle if I don't field filter? When do I know to filter or preserve by sample? When do I filter/rinse/preserve bottles?

If you aren't going to field filter, you must rinse out the precharged bottle preservative.  Dissolved metals must be filtered BEFORE being preserved.

I don't have preserved containers for metals, mercury (Hg) or hexavalent chromium for waters, can you lab filter and preserve?

If you found yourself in the field with only unpreserved containers, you can collect your sample and indicate on the bottle label and the chain of custody that you require “TOTAL – sample not preserved, lab to preserve” or “DISSOLVED – sample filtered and not preserved, lab to preserve” or “DISSOLVED – sample not filtered, lab to filter and preserve”.  Additional fees will apply for lab filtration and/or preservation.

Note that field filtration and preservation for dissolved and preservation at the time of sampling for total is the best practice.  It is also important to note that in some jurisdictions, field filtration/preservation for dissolved parameters is required. Please view our Water Filtration Guide for more information.

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