QA 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. 

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

QA samples are collected only for a small number of projects in the USA. 

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. 

QA sample and primary sample results are compared on a qualitative basis only. Sample matrix variability and the use of different extraction and analysis techniques at different laboratories may affect the results to such extent that they cannot be compared quantitatively. If the same contaminants are detected in a primary sample and in a QA sample and their concentrations are within the order of magnitude of each other, the data are comparable. 

QA samples are valuable tools in detecting data quality problems, and as such, they are recommended by the EPA (EPA, 1997c). QA splits may be useful for making decisions on data quality, particularly if a data comparison is conducted while the project is still in the field. The reality, however, is quite different, and data... 

QA splits are particularly valuable for field screening with definitive analysis confirmation and for the verification of field laboratory analysis. The frequency of the QA sample collection is best determined based on the project duration and the total numbers of samples to be collected. Typically, they are collected at a 10 percent frequency (one QA sample for every 10 field samples). It is beneficial to establish data comparability in the early phase of field implementation. If data are comparable, the frequency of QA sampling may be reduced as the confidence in field screening or field laboratory results has been established. But if the data are not comparable, the project team needs to identify the cause of the differences and resolve them as soon as possible in order to avoid making decisions on inaccurate or unrepresentative data. 

When requesting analysis of QA samples for comparability studies, be sure to request the same preparation and analysis methods at both laboratories. 

Due to additional expenses for analysis and data evaluation, comparability is a rarely used DQI. However, if QA samples have been collected and analyzed, the chemist will assess comparability qualitatively by evaluating the following issues ... 

A methods file is created for each analysis to specify the standard conditions to be used such as autosampler sequence, use of blanks and QA samples, column temperature programme, mobile phase composition and flow-rate, split ratios, mass range to be scanned, scan rate and sample identification codes. A methods menu leads the analyst through the full set-up sequence. Methods are filed for future reference and for use in routine analysis. The software can be linked to other standard packages such as word processors so the methods data can be linked to the results file and then transferred to the analytical report. 

Appropriate [low-level] and double blind QA samples needed... 

A few NIST CRMs are used directly as QA samples in forensic science. For example, SRM 1511 (Figure 3.14) is freeze-dried urine containing drugs and metabolites. Other NIST materials are used for instrument verification and validation. 

In analytical chemistry QA often is used for and understood as good quality analytical work , which means to check all analytical parameters and keep them under control. A good example for this is the use of QA samples in ICP-MS analysis applying external calibration. These QA samples are regularly measured materials, similar in composition to the samples routinely analysed, except that the analyte content is known, and so serve as proof of the absence of drift effects. Should the bias between measured and known anal)fte content exceed a certain level, the calibration has to be repeated. The control of the calibration s validity however should be checked regularly even if no QA system is installed. 

The use of several QA/QC methods is described in this article, including control charts for monitoring the concentration of solutions of thiosulfate that have been prepared and stored with and without proper preservation the use of method blanks and standard samples to determine the presence of determinate error and to establish single-operator characteristics and the use of spiked samples and recoveries to identify the presence of determinate errors associated with collecting and analyzing samples. 

The EC type-examination is the process that the manufacturer may use to obtain independent verification that a design conforms to essential requirements, when a certified QA system has not been applied to the design process. The manufacturer must submit an application to the notified body, accompanied by documentation on the device design and physical samples of the device. The Notified Body examines the... 

EC verification provides an alternative to the model of establishing a certified production QA system. Independent testing of either all devices, or a statistically representative sample of each batch, is conducted by or on behalf of the Notified Body, which then issues a certificate of conformity for the tests conducted. This is not a popular option due to the costs involved. The procedure is not capable of providing adequate assurance as to the sterility of devices. Instead, an assurance of sterility must be based on the application of a production QA system to the sterilisation process. 

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. 

A protocol must be established and followed for sample preparation, labeling, packaging, shipping, and chain-of-custody procedures. Also, the volume of the samples will be specified by the analytical laboratory depending on the analytical methods to be used and the desired sensitivity. Accordingly, principal attention will be given here to the sampling methods, preparation of the samples for analysis, and QA/QC aspects of both. 

The grinding and mixing devices, as well as any sieves, must be carefully cleaned between each sample In order to avoid cross-contamination of the samples. The final rinse water should be sampled on 5% of the decontamination cycles In order to provide a blank for use In evaluating the decontamination efficiency. These samples should be submitted to the laboratory along with the other QA/QC samples. 

Analysis and Interpretation of the Information and data resulting from the exploratory study will provide the basis for designing the final definitive monitoring study Including all elements of the QA/QC plan. For example, decisions must be made on whether or not the selected control area Is adequate and appropriate whether the hypothesized model Is valid whether the study area should be stratified and If so, how what number of samples should be collected at what locations and whether or not the QA/QC plan for sampling is adequate and if not, how it should be changed. 

Assume that without the proper use of reference samples in an exploration program, a site is purchased that is in fact barren. Hill (1974), for example, cites a 20 % added analytical cost for quality control and quality assurance. He further cites a possible cost of 220 million for purchasing and developing a mine site. The analytical expense for QA QC based on use of reference samples is trivial in comparison to the potential loss, if the analyses of exploration survey samples are faulty and the mine worthless as a result. 

The OPMBS was sponsored by a task force, consisting of major registrants of organophosphate pesticides, and utilized three contract organizations to carry out study management, design and conduct of sample collection, and quality assurance (QA). Four analytical laboratories performed the necessary residue analyses. 

To be successful, an LSMBS requires a clear definition of the responsibilities of each participating individual or group. Preparation of an organization chart may be appropriate, as would its inclusion in the study protocol. Key study participants could include Study Directors, Principal Investigators in the sample collection and analytical phases, sponsor representatives, technical consultants, residue analytical laboratories, and QA specialists. 

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