Quality control recovery tests

For Test Method D, when the recovery of oxygen from the QC SRM is less than 0.8S (that is, 8S %), take corrective action and repeat the quality control. Recoveries that are greater than 0.85 but less than unity can be used to correct the calculated result (refer to the r parameter in Section 10). 

Untreated (control) soil is collected to determine the presence of substances that may interfere with the measurement of target analytes. Control soil is also necessary for analytical recovery determinations made using laboratory-fortified samples. Thus, basic field study design divides the test area into one or more treated plots and an untreated control plot. Unlike the treated plots, the untreated control is typically not replicated but must be sufficiently large to provide soil for characterization, analytical method validation, and quality control. To prevent spray drift on to the control area and other potential forms of contamination, the control area is positioned > 15 m away and upwind of the treated plot, relative to prevailing wind patterns. 

Method performance study All laboratories follow the same written protocol and use the same test method to measure a quantity (usually concentration of an analyte) in sets of identical test samples. The results are used to estimate the performance characteristics of the method, which are usually within-laboratory- and between-laboratory precision and - if relevant - additional parameters such as sensitivity, limit of detection, recovery, and internal quality control parameters (IUPAC Orange Book [1997, 2000]). 

The accuracy of an analysis can be determined by several procedures. One common method is to analyze a known sample, such as a standard solution or a quality control check standard solution that may be available commercially, or a laboratory-prepared standard solution made from a neat compound, and to compare the test results with the true values (values expected theoretically). Such samples must be subjected to all analytical steps, including sample extraction, digestion, or concentration, similar to regular samples. Alternatively, accuracy may be estimated from the recovery of a known standard solution spiked or added into the sample in which a known amount of the same substance that is to be tested is added to an aliquot of the sample, usually as a solution, prior to the analysis. The concentration of the analyte in the spiked solution of the sample is then measured. The percent spike recovery is then calculated. A correction for the bias in the analytical procedure can then be made, based on the percent spike recovery. However, in most routine analysis such bias correction is not required. Percent spike recovery may then be calculated as follows ... 

If any individual P falls outside the designated range for recovery, that parameter has failed the acceptance criteria. When this situation occurs, a quality control check standard containing each parameter that failed the criteria must be analyzed independent of the matrix, that is, spiked reagent water, to demonstrate that the laboratory is operating in control. If this second test is failed, the sample results for those parameters are judged to be out of control, and the problem must be immediately identified and corrected. The analytical results for those parameters in the unspiked sample are suspect and may not be reported for regulatory purposes. 

Among the elements of quality control in mycotoxin analysis, proficiency tests, control materials (reference materials and certified reference materials), traceability in spiking, and recovery checks have been demonstrated to be particularly relevant. 

GMP risk assessment Qualified/trained resource System life-cycle validation System environment Current specifications Software quality assurance Formal testing/acceptance Data entry authorization Data plausibility checks Communication diagnostics Access security Batch release authority Formal procedures/contracts Change control Electronic data hardcopy Secure data storage Contingency/recovery plans Maintenance plans/records... 

Results. Good recoveries are obtained for all samples providing they are thoroughly mixed prior to sampling. This is a rapid test that could be useful in quality control laboratories where rapid analysis and accurate results are required. 

Formaldehdye generation and recovery studies 3.) Air exchange measurement techniques 4.) Preconditioning of test boards 5.) Temperature effect on chamber formaldehyde concentrations 6.) Relationship of popular quality control test methods to the large chamber 7.) Loading, air exchange rate, and wood product combination effects on chamber formaldehyde concentrations 8.) Chamber Round Robin studies between Georgia-Pacific s chamber and other outside lab chambers 9.) Chamber concentrations and its relationship to actual field measurements. 

HS-SPME is a very useful tool in polymer analysis and can be applied for absolute and semi-quantitative determination of the volatile content in polymers, for degradation studies, in the assessment of polymer durabihty, for screening tests and for quality control of recycled materials. For quantitative determination of volatiles in polymers, SPME can be combined with multiple headspace extraction to remove the matrix effects. If the hnearity of the MHS-SPME plot has been verified, the number of extractions can be reduced to two, which considerably reduces the total analysis time. Advantages of MHS-SPME compared to MAE are its higher sensitivity, the small sample amount required, solvent free nature and if an autosampler is used a low demand of labor time. In addition, if the matrix effects are absent, the recovery will always be 100%. This is valuable compared to other techniques for extracting volatiles in polymers in which the recovery should be calculated from the extraction of spiked samples, which are very difficult to produce in the case of polymeric materials. 

Rheological test more often used for product quality control is a measurement of the elastic recovery in polymer melts and their compounds. This is usually accomplished by measuring the swell (or shrinkage) of materials undergoing extrusion. The tendency of polymers, whether thermoplastic or rubber, to enlarge when emerging from an extruder die is called die swell. 

Quality control (QC) is as important in speciation analyses as it is in other areas of analysis. While there are a growing number of certified reference materials available that contain specific forms of an element, for example, tributyltin, methylmercury, this is the exception rather than the rule. Instead, other standard QC approaches need to be used. These include the use of spike-recovery tests and internal standards, comparisons with the results from other methods. 

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