Analytical procedures data handling

The EPA publishes Series Methods that describe the exact procedures to be followed with respect to sample receipt and handling, analytical methods, data reporting, and document control. These guidelines must be followed closely to ensure accuracy, reproducibility, and reliability within and among the contract laboratories. 

Hyphenated analytical methods usually give rise to iacreased confidence ia results, eaable the handling of more complex samples, improve detectioa limits, and minimi2e method development time. This approach normally results ia iacreased iastmmeatal complexity and cost, iacreased user sophisticatioa, and the need to handle enormous amounts of data. The analytical chemist must, however, remain cogni2ant of the need to use proper analytical procedures ia sample preparatioas to aid ia improved seasitivity and not rely solely on additional iastmmentation to iacrease detection levels. 

The analytical uncertainty should be reduced to one-third or less of sampling uncertainty (16). Poor results obtained because of reagent contamination, operator errors ia procedure or data handling, biased methods, and so on, can be controlled by proper use of blanks, standards, and reference samples. 

INAA is well suited to study homogeneity of small samples because of its dynamic range of elemental sensitivity. The technique allows for the use of small solid samples, with the smallest usable sample size in the range of 0.5 mg to i mg as determined by handling and blank considerations. The INAA analytical procedure is well understood and characterized with mathematical relationships. Its analytical uncertainties can be sufficiently controlled and can be well determined for a particular procedure. This allows the calculation of the contribution of material heterogeneity to the uncertainty budget based on experimental data. 

Work by Catanzaro et al. in 1968 (6) led to a new analytical procedure permitting the measurement of isotopic ratios to about 0.05% (95% L.E.) this resulted in the availability of three standard reference materials, so that results could be placed on an absolute basis. This procedure, still the most precise and accurate one available, requires about 1 mg of lead for an analysis. A second procedure (7) has been developed which utilizes silica gel as an ionization enhancer. This method permits the measurement of isotopic ratios to about 0.1% (95% L.E.), but it requires only 0.1 /xg of lead per analysis. In addition, the instrumentation and data handling have been vastly improved so that many samples can be studied quickly and conveniently. 

Comparability of environmental chemical data encompasses the concepts of precision, accuracy, and representativeness. Because accuracy and precision depend on the analytical procedure and representativeness depends on the sampling procedure, comparability is greatly affected by the sampling and analysis procedures used in data collection. For the data sets to be comparable, the samples must be collected and handled in a similar manner and the measurements must be obtained under the exact same analytical conditions. The observance of standard field and laboratory protocols and procedures, the use of EPA-approved or standard analytical methods and accepted QA/QC practices assure data comparability. 

In addition to the functions outlined above, the computer is also used to generate requests for new samples, validate results, perform statistical analyses of experimental data, and finally produce a report sheet setting out all the relevant information in tabular form. The fact that the computer is required to handle such a diversity of different tasks, many of which, must be performed simultaneously, necessitates the use of sophisticated software. The relationship between the analytical procedures, the computer files, and the control programme BRANDER is shown in Fig. 23. 

Assay application. At this point major differences appear between the historical use of clinical immunoassays and the potential applications of environmental and pesticide immunoassays. Most clinical assays have been applied to simple or well defined and consistent matrices such as urine or serum. In contrast, most matrices likely to be analyzed for pesticides are more complex, less well defined, and more variable. The potential for serious problems with matrix effects in the environmental field is far greater than most clinical immunoassays have encountered. The application of immunoassays to environmental analysis requires sampling strategies, cleanup procedures, and data handling fundamentally similar to those presently in use in any good analytical lab. The critical factor in the success of immunochemical technology will likely be competence... 

The GLP principles are a managerial concept defining the organizational processes and conditions under which laboratory and field research is planned, performed, monitored, recorded, and reported. They were designed to ensure that sampling and analytical procedures and results are complete and of known, documented quality. When a study is GLP compliant, an auditor, regulator, or analyst should be able to review the smdy some years after its completion and easily determine what work was done, when, where, by whom, and with what equipment and methods who supervised the study what results were obtained and whether there were any problems encountered and, if so, how they were handled. Considerable effort and dedication in planning, support, and implementation is required to achieve this standard of documentation and attention to detail. Successful implementation of GLP provides reliable data for which the precision, accuracy, comparability, and completeness is known. 

Over the past few years, GCxGC has been utilised in air and aerosol analysis. Particularly, GCxGC in combination with a fast acquisition mass spectrometer, for example, time-of-flight mass spectrometer (ToF MS) with a unit-mass resolution, provides extremely high analytical resolution with mass spectral information. Thus, the GCxGC-ToF MS is an exceptionally powerful tool in the air and aerosol analysis. It should be noted, however, that, as already mentioned in previous chapters, the system produces large amounts of data, and it is difficult to identify compounds from these datasets even with the structural nature and the mass spectral information. Therefore, automated procedures for data handling have been developed for identification purposes. 

No single method can be recommended for handling special samples. These might include special research preparations, archeological samples, forensic materials, and other nonroutine substances. The size of the sample available, the desired data, and the value of the sample all affect the selection of analytical procedures. A qualitative analysis, obtained by totally vaporizing the sample, can often provide much useful information concerning major and minor constituents of the sample and the photographic plate provides a permanent record of the sample composition. 

The book does not cover first aid or medical practice, nor does it supply complete details on safe handling of materials. Readers must refer to the literature, material safety data sheets, suppliers, and users of the various chemicals and equipment that are discussed. While there are summaries of material specifications and suggested analytical schedules, there is likewise not a section on analytical procedures. 

Automated methods not only increase the amount of chemical data obtainable during a cruise, they also avoid some of the main pit falls of manual analytical procedures. Most of the standard manual analytical methods include multiple handling of samples in open vessels while adding reagents or during titration, etc. The resulting risk of sample contamination, though tolerable in a clean laboratory, becomes incalculable under the somewhat provisional conditions in a ship s laboratory even if the floor is not in constant motion. 

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