WEF Discussion Forums
Laboratory Management and Technical Issues
QC standard for TSS
with the new Methods update Rule from May 2012, EPA established 12 QC guildlines for all methods, if they are not specific in the method.
One such method is 2540D, Total Suspended Solids. I was curious what labs used for thier QC standard for this test. I make a standard using cellulose to equal 100 mg/L - a lot cheaper than buying commercially prepared standards.
We make up a 100 ppm solution of diatomaceous earth, purchased as a reagent from one of the big lab suppliers (VWR, Fisher,...).
City of Portland, OR
We include in-house prepared standard suspension (diatomaceous earth) 30 - 50 mg/l range and run with each batch daily. We also utilize a commercially obtained quality standard weekly. In addition we include a duplicate and a blank.
Standard Methods SM2000-series methods call for a duplicate every 10 samples and residue(s) dried/weighed to constant weight (i.e. repeat cycles of drying, cooling, and weighing)....
Perhaps this applies to "certified" facilities only.
However, including some sort of quality control (qc) sample(s) is advisable even for the in-house and process control situations samples. Passing (data within expected range) of these qc samples will give confidence or meaning to the acquired results.