Identifiability checking methods

Ensures that the inspection, measuring, and test equipment is capable of the accuracy and precision necessary Establishes, documents, and maintains calibration procedures, including details of equipment type, identification number, location, frequency of checks, check method, acceptance criteria, and the action to be taken when results are unsatisfactory Identifies, calibrates, and adjusts all inspection, measuring, and test equipment and devices that can affect product quality at prescribed intervals or, prior to use, against certified equipment having a known valid relationship to nationally recognized standards. Where no such standards exist, the basis used for calibration is documented. 

In identifying specimen-related errors, it is helpful to examine multiple test parameters, including hematological tests, because differences in a profile of test results often are more obvious and more statistically significant than are changes in individual tests. For example, in a 1979 study, the performance of several delta check methods was evaluated. 

For checking parameter identifiability, three methods have received most attention. 

Many safety professionals refer to this system as the recall and check method. Working from memory, the supervisor breaks the job down into basic steps, identifies the potential injuries associated with each... 

Because of the instability of many of the compounds involved, it is necessary to determine the chemical recoveries in all cases. This requires the use of macro quantities (10 mg up to several hundred mg) of carriers and target compounds. This, in turn, makes it impractical to use the various thin-layer methods, such as paper and thin-layer chromatography and paper electrophoresis, although such methods have proved useful in identifying products and in checking the purity of fractions. The separation methods now most commonly used are column chromatography and sublimation. 

High performance spectroscopic methods, like FT-IR and NIR spectrometry and Raman spectroscopy are widely applied to identify non-destructively the specific fingerprint of an extract or check the stability of pure molecules or mixtures by the recognition of different functional groups. Generally, the infrared techniques are more frequently applied in food colorant analysis, as recently reviewed. Mass spectrometry is used as well, either coupled to HPLC for the detection of separated molecules or for the identification of a fingerprint based on fragmentation patterns. ... 

This method is particularly useful for identifying large leaks, although small leaks may also be noticed, particularly in tanks with metered dispensing pumps. Interested readers can refer to U.S. EPA5 and API (American Petroleum Institute)20 for detailed procedures of inventory checking for tanks with metered or nonmetered pumps. 

As discussed in Chapter 1, analysis involves the determination of the composition of a material, i.e. the identification of its constituent parts and in many cases how much of each is present and, sometimes, in what form each is present. This chapter describes the process of selecting a suitable analytical method to carry out such determinations and how to check that the procedure selected is adequate for the job in hand. Before starting work on a sample, it is vital to enquire why the analysis is being done and what will happen to the result(s) and what decisions will be taken based on the constituent parts identified and the numerical values obtained. It is essential that the requirements of the customer, internal or external, are fully understood. Which property needs to be measured (the measurand) For example, is it the total amount of iron in a tablet that is required or the amount extracted into stomach acid simulant ... 

For complex sample types, if there is any doubt concerning the ability of the method to unambiguously identify and measure the analyte of interest, check the method using a closely matched matrix reference material, or check the sample using an alternative validated method. 

The previous chapters of this book have discussed the many activities which laboratories undertake to help ensure the quality of the analytical results that are produced. There are many aspects of quality assurance and quality control that analysts carry out on a day-to-day basis to help them produce reliable results. Control charts are used to monitor method performance and identify when problems have arisen, and Certified Reference Materials are used to evaluate any bias in the results produced. These activities are sometimes referred to as internal quality control (IQC). In addition to all of these activities, it is extremely useful for laboratories to obtain an independent check of their performance and to be able to compare their performance with that of other laboratories carrying out similar types of analyses. This is achieved by taking part in interlaboratory studies. There are two main types of interlaboratory studies, namely proficiency testing (PT) schemes and collaborative studies (also known as collaborative trials). 

There are various ways to identify a systematic large error (1) with a theoretical analysis of all the effects leading to a gross error, (2) with measurements of a given process variable by two methods with different precision, or (3) by checking the... 

In the data collection, a literature search was conducted to identify data source publications (1-40). The publications were screened and copies of appropriate data were made. These data were then keyed into the computer to provide a data base of critical properties for compounds for which experimental data are available. The data base also served as a basis to check the accuracy of the estimation methods. 

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