External methods

The goals of quality assessment are to determine when a system has reached a state of statistical control to detect when the system has moved out of statistical control and, if possible, to suggest why a loss of statistical control has occurred so that corrective actions can be taken. For convenience, the methods of quality assessment are divided into two categories internal methods that are coordinated within the laboratory and external methods for which an outside agency or individual is responsible. The incorporation of these methods into a quaKty assurance program is covered in Section 15C. 

Internal methods of quality assessment should always be viewed with some level of skepticism because of the potential for bias in their execution and interpretation. For this reason, external methods of quality assessment also play an important role in quality assurance programs. One external method of quality assessment is the certification of a laboratory by a sponsoring agency. Certification is based on the successful analysis of a set of proficiency standards prepared by the sponsoring agency. For example, laboratories involved in environmental analyses may be required to analyze standard samples prepared by the Environmental Protection... 

Agency. A second example of an external method of quality assessment is the voluntary participation of the laboratory in a collaborative test (Chapter 14) sponsored by a professional organization such as the Association of Official Analytical Chemists. Finally, individuals contracting with a laboratory can perform their own external quality assessment by submitting blind duplicate samples and blind standard samples to the laboratory for analysis. If the results for the quality assessment samples are unacceptable, then there is good reason to consider the results suspect for other samples provided by the laboratory. 

The third approach is to install an external monitoring system that can detect the presence of the stored chemical in or on the groundwater or in the backfill and soil surrounding the tank system. In many instances both internal and external methods are used in conjunction as a way to increase the liability of detection. 

Regardless of the methods used to create the descriptors and construct the equation for the models, there is a need to validate the model by comparing the predicted bioactivities with the Experimental Bioactivities. Using the data that created the model (an internal method) or using a separate data set (an external method) can help validate the QSAR model. To determine if the model can be... 

Rehkamper, M., and Halliday, A. N. (1998) Accuracy and long- term reproducibility of lead isotopic measurements by MC-ICPMS using an external method for correction of mass discrimination. Int. J. Mass Spec. Ion Proc., 181, 123-133. 

The mass of the packing material in the column is a largely underestimated parameter. As it was discussed in the theory chapter, the retention is proportional to the total surface area of the adsorbent in the column. External methods of the surface area measurement determine the specihc surface area (in square meters per gram of the material), and the total surface in the column is a product of the specific surface area of base material and the mass of the adsorbent in the column. 

Reactions can be analyzed almost instantaneously through in-line analyses, i.e., by analyzing the reaction using a probe inserted into the reactor or a reactor stream. In-line assays may be used for analyzing reactions run in dedicated equipment, which is often the case in manufacturing, or to assay reactions that are difficult to assay by conventional external methods (see below). Relatively few analytical techniques have been adapted for in-line assay. 

The different humidification approaches could be classified as internal or external methods. Internal humidification means that humidification procedure concerns exclusively the inner spaces of fuel cell stack, while external humidification involves modifications in feeding stream humidity ratio outside of the stack [1. 29]. 

In quantitative analysis, in which absolute intensity of signal of interest is required, an external15 or internal16 17 standard method can be used. In the external method, there is a possibility of instrumental variation during the interval between recording the spectra of the sample and that of the standard. In the internal method, contamination of the sample by the standard compound cannot be avoided, and it is difficult to mix a reasonable amount of the standard with the sample solution. 

Various methods of constructing a unitary matrix V with localizing properties have been proposed [for a review, see Ref.45>]. For the present analysis we have adopted Boys method4 ), as being the simplest intrinsic method (for a definition of intrinsic versus external methods, see Ruedenberg47)]. 

Step 4 may be redundant if the covariates were tested directly in the nonlinear mixed effects model. If the covariates were screened using some external method, e.g., regression models, then these covariates are included in the model in a forward stepwise manner. Improvement in the goodness of fit in the model is tested using either the LRT or T-test. In addition, reduction in parameter variability is expected as well. Further discussion of this topic will be made later in the chapter. 

In the external method, a light ray strikes the electrode surface from the solution phase. On hitting a well-polished electrode surface, the light is reflected from the interface back to the solution. A quantitative comparison is then made of the properties of the incidental and reflected light. It should be noted that the reflection causes change in the properties of the light, that is, in amplitude and phase, so that the reflected light provides information about the interface. 

If carbohydrate-based transformations are indeed as stereoselective as we had initially claimed (ref. 5), it should be possible to avoid such stereochemical uncertainties. Thus, our objective is to synthesize 4 in a manner that is not only highly stereocontrolled, but also does not require verification by external methods. 

Similar to external method but adding the same amount of a structurally similar IS to each sample prior to extraction... 

For external method evaluation results from interlaboratory studies may be presented in tables and figures including mean, standard deviation, ratio/recoveiy, relative mean square error, a histogram of all results, and plots of the method evaluation function, Youden, and Z score. Furthermore, limits for acceptance of the performance characteristics parameters after which the methods have to be evaluated, e.g., tolerance limits as well as confidence and/or prediction intervals are essential. 

Use analysis of their own and others practical experience as a eore problemsolving and learning methodology, rather than imposed external methods and algorithms associated with standard textbooks and corrrses. 

An external method for the treatment of reaction water is leading or transporting it to a biological waste water treatment plant (WWTP). 

Waste water in the produetion of polyester is mainly reaction water. This water is treated either on site or externally. An external method for the treatment of reaction water is leading or transporting it to a biological waste water treatment plant (WWTP) or in an anaerobic digester. 

Dust control includes both external and internal methods. Source ventilation, hood ventilation, and room ventilation are typical external methods. Interned methods include reactor ventilation and the use of a closed charging system, which provides a suction transfer of powder into an evacuated reactor. Dust control equipment should be interlocked with production machinery to assure simultaneous operation and protection. 

Nowadays, all analytical laboratories are aware of the cmdal importance of proper quality assurance activities. Although quality control directives explain how an analysis should be conducted, they do not indicate whether the system is under statistical control. Therefore, the written guidelines of a quality control program are a necessary, but not a sufficient, condition for obtaining and maintaining proper statistical control. This is the role of quality assessment, which includes internal methods coordinated within the laboratory and external methods organized and maintained by an outside agency. 

The inductive mold temperature control can be externally or internally applied. The external method is particularly suitable for mass production of micro components. The internal method enables temperature control in large-scale, three-dimensional geometries. 

Internal cooling with air or water is also effective but more complicated than the external method. Water requires a special system that vents out the steam produced during the cooling. Water drops can leave marks on the molten resin which are called pock marks and are considered quality defects. The most common technique is air cooling, in which air is forced into and out of the mold. In addition to cooling, air pressure coun-... 

With this method the electrochemical generation of the radical ions is carried out directly in the cavity where the EPR spectrum is recorded. The radical ions are usually generated continuously, which compensates for their loss and creates a steady concentration. This gives two main advantages compared with the external method ... 

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