Rinsate blanks

Equipment blank is a sample of water collected from the surface of a decontaminated sampling tool to verify the effectiveness of a cleaning procedure. Equipment blanks are sometimes called rinsate blanks. They are collected as samples of the final rinse water from non-disposable sampling tools after they have been cleaned between samples. The field crew pours analyte-free water over the tool s surface that has come in contact with the sampled medium. The water is diverted directly into sample containers and analyzed for the project contaminants of concern. 

The intent of equipment rinsate blank collection as a field QC sample seems reasonable. In reality, however, equipment blank analyses rarely provide information that can be meaningfully related to the field samples because the only contaminants that are usually present in equipment blanks are common laboratory contaminants or byproducts of water disinfection process. 

As a rule, we should use only precleaned sample containers certified by the manufacturer. Manufacturers clean glass and HDPE containers for water samples according to the EPA specifications and provide a certificate of analysis with each case of containers. Metal liners for core barrels and split spoons are usually not precleaned by the manufacturer, but they may be precleaned by the distributor. If precleaned liners are not available or the level of their cleanliness is questionable, we should decontaminate them prior to sampling. In this case, we may verify the effectiveness of the cleaning procedure by collecting a rinsate sample from a cleaned liner and analyzing it for the contaminants of concern. A decision on analyzing the liner rinsate blank should be solely based on the nature of the contaminants of concern and the project DQOs. 

First, routine tests should be conducted to check the effectiveness of the cleaning of sampling devices and sample containers. This can be done in the laboratory by applying equipment or rinsate blanks. The blanks should be collected after each decontamination and before resampling, and where necessary, corrective action should be taken. The tests should be made to check whether the material, from which the device/container is made and which is in contact with the sample, does not adsorb or react with or release relatively significant amounts of target analytes. 

Rinsate blanks, if dedicated sampling tools are not used. One rinsate blank per parameter per 20 samples. 

Method blanks, rinsate blanks, trip blanks, as in QA2. 

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