Field QC samples

The following field QC samples may be collected during a sampling event and analyzed together with the field samples ... 

Field QA samples are replicates or splits of field samples that are analyzed at a different laboratory to establish data comparability. QA field samples may have their own set of associated field QC samples. 

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. 

Not directly related to field QC samples, but nevertheless part of laboratory QC samples that originate in the field, are MS/MSD samples. The laboratory must use field samples to determine the effects of matrix interferences on analytical accuracy. If required by the project DQOs, additional aliquots of field samples, designated as MS/ MSD, are collected for this purpose. The RPD between MS and MSD results provides information on the variability of contaminant distribution in the sampled matrix, which is particularly important for soil samples. 

An accepted standard for the frequency of MS/MSD analysis is 5 percent or one MS/MSD pair for every 20 field samples. This frequency may be insufficient for some projects and excessive for others. Similar to other field QC samples, MS/MSDs should be collected and analyzed only if their data will be used for project decisions. 

Number of samples for each matrix, including field QC samples... 

Be accompanied by field QC samples justified by the project DQOs... 

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 ... 

Field Experience. On the first day of field use, 40 soil and 10 QC samples were analyzed in six hours. This included lunch and 40 minutes down time when the field generator ran out of gasoline. Most runs were completed in less than nine minutes, and many very low level samples had the run aborted after about four minutes when it was evident that the second major 1254 peak was almost totally absent. Concentrations were calculated from periodic standard runs, and PCB levels ranged from less than. 2 ppm to 24,000 ppm of 1254. 

The analytical data for soil, water, and vegetation samples from the 2007 field season plus an evaluation of QC samples are found in Fey et al. (2008). A similar publication for 2008 data will be completed in 2009. 

Qualitative and quantitative acceptance criteria for the PARCC parameters are derived in the planning phase. Whether they are specific statistical values or represent accepted standards and practices, they must be always selected based on the project objectives and be appropriate for the intended use of the data. The DQI acceptance criteria are documented in the SAP and serve as standards for evaluating data quality and quantity in the assessment phase of data collection process. The primary DQIs are established through the analysis of field and laboratory QC samples and by adhering to accepted standards for sampling and analysis. 

The collection of field QA/QC samples prescribed by the EPA and DOD guidance documents is part of every sampling event. Typically, QA/QC samples are collected to satisfy the protocol requirements and the obtained data are rarely used for project decisions. And yet, field QA/QC samples, like all other samples collected for the project, must have a well-defined need, use, and purpose and be relevant to the project objectives. 

Table 2.4 summarizes existing practices for the collection and analysis of the field QC and QA samples and their practical value. 

Trip blanks are QC samples associated with the field samples collected for VOC analysis, such as chlorinated and aromatic hydrocarbons and volatile petroleum products. Trip blanks are sometimes called travel blanks. 

Table 2.4 Field QA/QC samples and their meaning Purpose and frequency of collection Practical value...

Quality assurance samples are replicates of field samples that are analyzed at two different laboratories, a primary laboratory that provides analytical services to the project and a referee or QA laboratory. The purpose of QA samples is to establish data comparability. QA samples are collected in the same manner as field duplicates and usually from the same sampling points. Three replicate samples from a single sampling point will represent a field sample, a field duplicate (QC sample), and a QA sample. 

Prior to the preparation of field and laboratory QC samples for organic compound analysis, sample preparation personnel amend them with surrogate standards to monitor the efficacy of extraction for each sample matrix. Surrogate standards are organic compounds that are similar in chemical behavior to the target analytes and that are not expected to be present in samples. 

Organize Analytical Batches—These include analytical QC checks (instrument blanks and other QC checks as required by the method), CCV standards, prepared field samples, and laboratory QC samples. 

Internal standard calibration is used when the changes in the analytical system are known to be frequent and substantial. To compensate for these changes, internal standards at known concentrations are added to all calibration standards, field samples, and laboratory QC samples prior to analysis. Internal standards are synthetic analogs of specific target compounds or compounds that are similar in nature to the target analytes and that are not found in environmental samples. Internal standard calibration is a requirement of GC/MS methods. Laboratories sometimes use it for GC methods as it significantly improves the accuracy of compound quantitation. 

A preparation batch is a group of up to 20 field samples, prepared together for the same analysis using the same lots of reagents and associated with common QC samples. In addition to field samples, a preparation batch must, at a minimum, include a method (extraction or digestion) blank, an LCS, and an LCSD. Other laboratory QC checks may be part of the preparation batch, such as an MS/MSD pair or a laboratory duplicate. If laboratory QC checks in a preparation batch meet the laboratory acceptance criteria, the batch is considered be in a state of control and every sample in it is acceptable, provided that individual QC checks are also acceptable. If the method blank and the samples in a preparation batch show contamination that makes sample results inconclusive or if the LCS and LCSD recoveries are not acceptable, the whole batch may be prepared again. 

Internal standards are brominated, fluorinated or stable isotopically labelled analogs of specific target compounds or other closely related compounds not found in environmental samples that are added to all standards, field, and laboratory QC samples as part of internal standard calibration procedure. The addition of internal standards takes place after the samples have been prepared and before they are analyzed. 

The interpretation of field QC data and their effects on the quality of sample data is conducted in DQA Step 4. This task may be also conducted in Step 4 of the data evaluation process, particularly if one and the same chemist performs data evaluation and DQA. Regardless of when it is performed, it is a distinctive and important task. 

Quality control (QC) is as important when collecting samples in the field as it is in the laboratory. A valid and defensible laboratory result is meaningless if the sample has been collected improperly or the extent of its reliability is not known (see Section 11.3.3). Many of the pitfalls associated with collection and preservation of environmental samples are enumerated in MARSSIM (EPA 2000c) and HASL-300 (Chieco 1997). The steps taken for field QC vary with the matrix being sampled. The following QC samples that pertain to the sample collection process should be integrated with the QC samples appropriate to laboratory practices that are listed in Section 11.2.9 ... 

The frequency with which this set of field QA/QC samples, namely blanks, spiked blanks, and spiked samples (in replicate), should be prepared would be dictated by the water quality study or project and available resources. 

The field data QA/QC samples consisted of duplicate samples, field spikes with NIST (National Institute of Standards and Technology) traceable spike standards, field blanks, and breakthrough sections. Frontier Global Sciences (FGS), the project laboratory, provided all analytical services as well as all sampling media including spiked sorbent trap. FGS is a NELAP (National Environmental Laboratory Accreditation Program) accredited and ISO 17025 accredited laboratory specializing in the analysis of trace and heavy metals. 

The design of this fish study centered on sample collection, preservation, preparation, analysis, and QA/QC. There was no discussion of the effect of compositing on the sample population. No description was given of statistical techniques to be applied to the data for reporting results and for comparison with action levels and future data. Unfortunately, the omission of a statistical framework during planning of the field study is the rule rather than the exception in hazardous waste investigations. 

The hydrogeological and QA/QC aspects of hazardous waste field investigations are fairly well advanced. Yet needed, however, is a systematic approach to the design of field sampling, to the selection of compounds for analysis, and to the methods for interpretation of analytical data. 

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