Equipment blank

The only contaminants usually found in equipment blanks are common laboratory contaminants phthalates, methylene chloride, acetone. 

Occasionally, oily materials, PCBs, and VOCs retained by groundwater pumps are found in equipment blanks after samples with high contaminant concentrations. 

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. 

Equipment blanks enable us to assess the collected sample representativeness. The purpose of collecting equipment blanks is to detect the presence of contamination from the sampling equipment itself or any cross-contamination with previously collected samples. For example, metal liners for core barrel or split spoon samplers are not always precleaned by the manufacturer or distributor. They must be cleaned in the field prior to sampling to eliminate the potential for sample contamination. 

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. 

Generally, equipment blanks provide useful information only if all of the following conditions are met ... 

Equipment blanks are relics of the non-disposable sampling equipment era. Today we use a variety of disposable equipment to collect a vast majority of environmental samples. Precleaned disposable sampling equipment is available for most types of sampling, and the wide selection of modern non-adsorbing materials available today enables us to reduce or even eliminate the risk of cross-contamination. 

What is the criterion that determines whether a decontamination procedure was effective It is not the absolute absence of any chemical contaminants in the equipment blank. Important for the project are only the contaminants of concern and their concentrations. For site investigations, when no information is available on existing pollutants, it may be important that no contaminants of concern are present in equipment blank samples above the laboratory PQLs. On the other hand, for site remediation projects, the presence of contaminants of concern in equipment blank samples may be acceptable, if these concentrations are only a fraction of the action levels. The decision to decontaminate equipment and the selection of the acceptability criteria for equipment blanks are made in the DQO process based on the intended use of the data. 

The collection of equipment blank samples increases the total cost of sample handling and shipment. 

Equipment blanks create additional analytical and data management costs. 

What data are we going to obtain from the analysis of equipment blanks ... 

Will equipment blank data affect our decisions ... 

How many equipment blank samples are sufficient for documenting the cleanliness of sampling equipment ... 

The collection of equipment blank data is unavoidable for the types of equipment that require decontamination prior to each use (for example, non-disposable bailers, non-dedicated submersible pumps, augers, split spoons). However, the number... 

One equipment blank collected after the sampling equipment has been cleaned the first time may often provide a satisfactory resolution of this issue. Once a decontamination procedure has been established and verified by an equipment blank analysis, the application of the same procedure should render the same level of cleanliness of the sampling equipment. If site conditions suddenly change with respect to the type of the sampled medium or the contaminant nature and suspected concentrations, another equipment blank sample may be collected to verify that the change in conditions did not reduce the effectiveness of the established decontamination procedure. 

Reduce excessive collection of equipment blanks by using disposable sampling equipment whenever possible. 

Sample type (field sample, field duplicate, equipment blank)... 

To avoid the decontamination of mixing equipment and equipment blank analysis, use disposable mixing tools whenever possible. Disposable equipment will be less expensive than the cost of analysis and the disposal of decontamination wastewater. 

The use of non-disposable sampling equipment creates a potential for crosscontamination between samples. To eliminate the risk of cross-contamination, we must always decontaminate non-disposable sampling equipment and collect and analyze equipment blank samples to document the effectiveness of decontamination. Sampling containers that are not precleaned by the manufacturer must be also decontaminated prior to sampling. 

Decontamination procedure consists of washing the equipment with a detergent solution and rinsing it with tap water and with analyte-free water. The water from the final rinse is collected into sample containers and as the equipment blank is analyzed for the contaminants of concern. 

If VOCs are not among the contaminants of concern, bottled drinking water or commercially available deionized water often serves as an equitable substitute for analyte-free reagent water. (Certain VOCs are present in drinking water as the artifacts of water disinfection process.) If VOCs are among the project contaminants of concern, commercially available distilled water may be used for a final rinse. When bottled water is not available, and water of unknown quality is used for equipment blank collection, a source blank of such water is analyzed. The only situation when a source blank may be needed is when the sampled medium is water and low contaminant concentrations of organic compounds and metals are a matter of concern. 

To collect equipment blank, place a clean funnel into the sample container. Spray the cleaned surface with analyte-free water from the squeeze bottle and direct the water from the cleaned surface into the funnel. Alternatively, pour the water from the cleaned surface directly into the sample container. (This step requires substantial manual dexterity and may need two persons.)... 

Results of the field QC samples (trip blanks, field duplicates, equipment blanks, etc.) are part of the data packages and, together with field samples, they are evaluated to establish whether they are valid. But what is the significance of these data Like the field samples, these data were collected for a well-defined need, use, and purpose. They provide part of the answer to the question Are the data representative of the sampled matrix ... 

The chemist interprets the results of trip and equipment blank analyses to identify sample management errors during sampling, sample handling, and decontamination procedures and to determine whether these errors may have affected the collected sample representativeness. The chemist qualifies the data according to the severity of the identified variances from the SAP specifications and may even reject some data points as unusable. Example 5.8 shows a logical approach to the interpretation of the trip and equipment blank data. 

No. A clean trip or equipment blank signifies proper sample handling and shipping or adequate equipment decontamination. The sample data are representative of the sampled matrix. 

If any contaminants are present in the trip or equipment blank, are they among the... 

Conversely, on occasion, invalid data may still be used for project decisions. In DQA Step 4, the chemist made decisions related to the effects of trip and equipment blank contamination on sample data by applying the logic demonstrated in Example 5.8. In DQA Step 6, this decision logic will be extended further to compare the contaminants of concern concentrations in the samples to the action levels as demonstrated in Example 5.12 on the next page. 

In DQA Step 4, the chemist interpreted the trip and equipment blank data as shown in Example 5.8. The chemist discovered that the concentrations of contaminants of concern in the trip or equipment blanks and in the samples are comparable and concluded that samples were contaminated in the field or at the laboratory. Based on these considerations, the chemist rejected the sample results. In DQA Step 6, the chemist revisits this issue and compares the contaminant of concern concentrations, found in samples, to the action levels, using the following logic ... 

Are the contaminants of concern concentrations in the trip or equipment blank and in the samples close to the action level ... 

If the concentrations of contaminants of concern in the trip and equipment blanks and the samples are significantly lower than the action levels (at least by a factor of 10), then the sample data, although technically invalid, may still be used for project decisions. 

Summary statement on the observance of sample handling requirements (holding time container preservation trip and equipment blanks) with exceptions interpreted in context of the contaminant of concern... 

As a rule OPCW equipment is used for sample collection and handed to the ISP/facility representative who will perform the sampling activity. If ISP equipment is used for sample collection, the IT will prepare a respective equipment blank sample. Sampling can be observed either directly by an inspector or from an on-site close circuit television system. The sampling operation and subsequent chain of custody procedures must be well established between the ISP and the IT before activities commence. 

Equipment blanks—a sample of contaminant-free water poured through decontaminated field sampling equipment before the collection of field samples. For pump blanks, two blanks may be taken one before the pump is cleaned and one after. 

Apart from these samples, some other quality control samples such as duplicate samples and equipment field blanks are used by different laboratories. Duplicate samples are taken from the same collection site to determine the variability of results for the same sample after the AMS analysis. Generally, one duplicate sample should be collected for every 20 samples. Equipment blanks are collected using laboratory-provided water, which has been run over the decontaminated soil sampling equipment. These samples are used to determine the efficiency of cleaning procedures for soil sampling equipment. 

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