Analyst, certification

Foreign uranium resources, 17 522 Foreman and Veatch cell, 9 664 Forensic analysts, certification of, 12 95 Forensic biology, 12 102-104 Forensic chemistry, 12 89-104 physical evidence in, 12 90-95 Forensic laboratories, local and state, 12 98 Forensics, liquid chromatography applications, 6 465 Forensic science laboratories, 12 95 Forensic science, supercritical fluid extraction in, 24 14 Forensic testing, 12 95-104 Forensic toxicology, interpretation of results in, 12 98... 

A second advantage of standard methods is that they are optimized and validated. As tire name implies, a validated method has been thoroughly tested and characterized. The performance limitations of the method are understood and quantifiable criteria for its satisfactory performance exist. As with mass spectrometers, tests can determine whether the method is working to specifications. If it is, then the data are comparable and reliable. Finally, because data generated by standard methods are comparable, it is possible to measure performance at the analyst and laboratory levels. The topics of analyst certification and laboratory accreditation will be addressed shortly. 

Forensic laboratories are accredited by the American Asscxiation of Crime LaboratcMy EMrectors LabcaatCMy Accreditation Board (ASCLD/LAB). Accreditation is an arduous multistep process that examines everything from the physical plant of a laboratory through its analysts and management structure. As of November 2003,255 crime labs had earned this accreditation, which, like analyst certification, must be renewed periodically. 

D. Analytical Testing Methods PROTOCOL EXECUTION ANALYSIS OF RESULTS/STATISTICAL PACKAGES DOCUMENTATION OF RESULTS ANALYST CERTIFICATION AND TRAINING TRANSFEROR TECHNICAL OWNERSHIP... 

A final component of a quality control program is the certification of an analyst s competence to perform the analysis for which he or she is responsible. Before an analyst is allowed to perform a new analytical method, he or she may be required to successfully analyze an independent check sample with acceptable accuracy and precision. The check sample should be similar in composition to samples that the analyst will routinely encounter, with a concentration that is 5 to 50 times that of the method s detection limit. 

Lee H-B and Chau ASY (1987) Analytical reference materials Part VII. development and certification of a sediment reference material for total polychlorinated biphenyls. Analyst 112 37-40. Meinke WW (1971) Standard reference materials for clinical measurements. Anal Chem 43(6) 28A-47A. 

A review is presented here of certification approaches, followed by several of the major agencies and individual developers of RMs for chemical composition, addressing some of the many associated scientific aspects that significantly impinge on the conduct and outcome of the analytical characterization exercises. These include definition of analytical methods selection of analytical methodologies, analysts and laboratories in-house characterization and cooperative inter-laboratory characterization. 

Independence of analysts and analyses in one organization is a fundamental question. It is important to have, even for the most reliable methods, more than one analyst/laboratory involved to avoid possible analyst/laboratory-specific biases. Certification by a single laboratory, without confirmation by another laboratory or method is risky. Measurement by a single definitive method is usually performed by two or more analysts working independently to minimize possible biases. Frequently, an accurately characterized back-up method is employed to corroborate the data. Some agencies feel that a certification campaign should not be based on a single measirrement procedure and therefore do not normally certify values on the basis of a definitive method applied in one laboratory. 

Veecoutere K, Cornelis R, Mees L, and Qubvauviller Ph (1998) Certification of the contents of the chromium(IIl) and chromium(VI) species and total chromium in a lyophOised solution (CRM 544). Analyst 123 965-969. 

Evolution of analytical techniques can cause data, once considered to be state of the arf to be shown to be unreliable. A good example is provided by the work of Houba et al. (1995), who demonstrated that a number of older methods for the determination of trace levels of boron in plant materials were subject to the interference by high levels of copper. This and other evidence suggest that older data, even when presented on a certificate, have to be viewed critically see also Section 3.2. The analyst must stay aware of developments and be ready to disregard certified values if the date of certification of the CRM predates the release of new developments and the certification authority concerned cannot confirm that the certified value is good in the light of the new knowledge. 

A form of this approach has long been followed by RT Corporation in the USA. In their certification of soils, sediments and waste materials they give a certified value, a normal confidence interval and a prediction interval . A rigorous statistical process is employed, based on that first described by Kadafar (1982,), to produce the two intervals the prediction interval (PI) and the confidence interval (Cl). The prediction interval is a wider range than the confidence interval. The analyst should expect results to fall 19 times out of 20 into the prediction interval. In real-world QC procedures, the PI value is of value where Shewhart (1931) charts are used and batch, daily, or weekly QC values are recorded see Section 4.1. Provided the recorded value falls inside the PI 95 % of the time, the method can be considered to be in control. So occasional abnormal results, where the accumulated uncertainty of the analytical procedure cause an outher value, need no longer cause concern. 

The reasons for such vagueness may lie in a combination of factors, the lamentable level of proper understanding of statistics amongst many analysts and, as mentioned above, the inconsistent and complex manner in which many certification bodies use statistics to produce their certified values and the willingness of journals to accept papers that lack proper validation of restdts and do not describe the proper use of CRMs. 

The posting of product and certificate data on a producers web site is but a first step. Through the work of REMCO and others, it has been realized that there is a need to organize this mass of data into a usable form, so that analysts can quickly find the information they need about both a RM and its apphcations. It is anticipated that by about 2002 there will be available searchable databases, either on line or as a CD-ROM, that will open the door to the needed information, and act as a gateway to the mass of data provided by the producers and in the literature. 

The revised database holds over 23 000 analyte values for 660 measurands and 1670 reference materials produced by 56 different producers, from 22 countries. The database is restricted to natural matrix materials (i.e. made from naturally occurring materials, excluding calibration standards manufactured from pure chemicals). Information has been extracted from the relevant certificates of analysis, information sheets, and other reports provided by the reference material producers. As a general rule, the authors have only included in the compilation reference materials for which a certificate of analysis or similar documentation is on file. Information included in the survey is on values for measurands determined in reference materials, producers, suppliers, the cost of the materials, the unit size supplied, and the recommended minimum weight of material for analysis, if available. The new searchable database has been designed to help analysts to select reference materials for quality assurance purposes that match as closely as possible, with respect to matrix type and concentrations of the measurands of interest and their samples to be analyzed see Table 8.3. 

Quality assurance includes all the quality controls, the generation of expectations (acceptance limits) from the quality controls, plus a great number of other activities, such as (1) analyst training and certification (2) data review and evaluation (3) preparation of final reports of analysis (4) information given to clients about tests that are needed to fulfill regulatory requirements (5) use of the... 

For other sources this experimental approach is not possible. E.g. for the purity of a material, the traeness of a balance or a volumetric equipment or similar uncertainties om knowledge is purely based on other information like certificates published by the manufacturer or a calibration laboratory. In some cases the only available information is the analyst s experi-... 

Note that no allowance has been made for the uncertainty of the certified reference material. Analysts often assume that the value of the reference material has been determined with much greater precision than their experiments. Suppose the certificate does give an expanded uncertainty of 0.0004 ppm (95% probability). The standard uncertainty is u = 0.0004/2 = 0.0002 ppm with, in the absence of any other information, infinite degrees of freedom. The t value can now be recalculated as... 

Some examples include evaluation of uncertainty components associated with published values (i.e., the analyst did not measure them), uncertainties in a certificate of a certified reference material, manufacturer s statements about the accuracy of an instrument, or perhaps even personal experience. The latter could be viewed as an opportunity for anyone to just make up an uncertainty, but experience does count for something, and it is indeed usually better than nothing. Leaving out a component because of lack of exact knowledge immediately underestimates the uncertainty. 

If the analyst in a field laboratory can identify a CRM for calibration of working calibration solutions, and its certificate gives sufficient evidence that the CRM embodies a metrologically traceable quantity value, then his or her work is just about done (figure 7.10). The intricacies of what national measurement institutes and calibration laboratories did to ensure that the CRM has metrologically traceable quantity values are all paid for in the certificate. 

All training should be documented. Some professional associations have introduced an accredited portfolio for members in which the career of an analyst can be documented and their skills clearly listed. Ideally, performance in any course taken should be assessed. Certificates on a wall for merely showing up for class are not sufficient. 

Major component, best determined by other means,—i.e., the analyst has little confidence in this value. b Sample 3 is standard reference material 124c from the United States National Bureau of Standards. The last line (NBS values) shows the values on the analysis certificate, based on a number of wet determinations for each element using 1-gram samples. The alloy also contains P =. 024%, Si =. 002%,... 

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