Laboratory evaluation interpretation

Photo 40 Linus Pauling with Dr. Ewan Cameron, a physician firom Scotland who had conducted clinical tests of effects of vitamin C on cancer, and who collaborated with Pauling in evaluating, interpreting, and publishing the results (SP 139, SP 140, SP 141, SP 144). Photo in early 1980 s, in the laboratories of the Linus Pauling Institute for Science and Medicine, Palo Alto, CA. 

The above considerations show that although considerable advances have been made in developing laboratory controlled potential tests for evaluating crevice corrosion and pitting, the results must be interpreted with caution. 

Everyday laboratory reactions are emphasized, and the working practice of kinetics takes precedence over the theoretical. The audience remains the first-year graduate student (or advanced undergraduate) as well as research workers from other areas who seek guidance in the concepts and practice of kinetics and in the evaluation and interpretation of kinetic data. 

This is important not only in field investigations. Even in laboratory experiments on the metabolism of xenobiotics, problems of association between the substrate and the microbial cells may occur. If this were not quantitatively evaluated or eliminated, the results and interpretation of such experiments would be seriously compromised. 

NMR has proven to be a valuable tool for formation evaluation by well logging, downhole fluid analysis and laboratory rock characterization. It gives a direct measure of porosity as the response is only from the fluids in the pore space of the rock. The relaxation time distribution correlates with the pore size distribution. This correlation makes it possible to estimate permeability and irreducible water saturation. When more than one fluid is present in the rock, the fluids can be identified based on the difference in the fluid diffusivity in addition to relaxation times. Interpretation of NMR responses has been greatly advanced with the ability to display two distributions simultaneously. 

Also, the test procedure (protocol) is fundamental because it allows comparing results from different laboratories and from different experimental sets. Moreover, selected test protocol could affect the interpretation of the results, the information content and its application in the safety evaluation process, as stated by Frazer if the biological system is exposed to a test chemical for 24 h and the endpoint assay is immediately conducted, the data produced would be most relevant to the acute toxicity of the test material. If, on the other hand, the system is exposed to material for 24 h and the system is cultured in the absence of the test material for additional 48 h before the endpoint assay is conducted, the data would be more relevant to recovery from toxicity rather than acute toxicity [7]. 

Analytical investigations are always carried out to serve a definite purpose. In this respect analytical results have to be evaluated and interpreted. In modern fields of applications like environmental monitoring, foodstuff control, medical laboratory diagnostics etc., conclusions have to be drawn about the presence of given species and their amount as well as the exceeding of limit values or falling significantly below them. 

The chief significance of reaction rate functions is that they provide a satisfactory framework for the interpretation and evaluation of experimental kinetic data. This section indicates how a chemical engineer can interpret laboratory scale kinetic data in terms of such functions. Emphasis is placed on the problems involved in the evaluation and interpretation of kinetic data. 

This chapter has considered two of the types of interlaboratory comparison exercise in which your laboratory may participate. It is important to remember that proficiency testing schemes and collaborative studies have different aims. The former is a test of the performance of the laboratory, whereas the latter is used to evaluate the performance of a particular analytical method. Laboratories should participate in proficiency testing schemes (where an appropriate scheme is available) as this provides an independent check of the laboratory s performance. This chapter has described the key features of proficiency testing schemes and explained how the results from participation in a scheme should be interpreted. 

Needs for the Future. One significant need in the area of ocular alternatives is for the validation of current in vitro assays. The key point is that users of the assay(s) need to have confidence in their ability to interpret and reliably use the data generated. This confidence level can only be achieved by parallel testing in one s own laboratory with compounds similar to those likely to be evaluated as unknowns. The validation process will be a long, somewhat tedious project, but will be necessary before in vitro alternatives can be used responsibly... 

A comprehensive two-volume Handbook of Chemometrics and Qualimetrics has been published by D. L. Massart et al. (1997) and B. G. M. Vandeginste et al. (1998) predecessors of this work and historically interesting are Chemometrics A Textbook (Massart et al. 1988), Evaluation and Optimization of Laboratory Methods and Analytical Procedures (Massart et al. 1978), and The Interpretation of Analytical Chemical Data by the Use of Cluster Analysis (Massart and Kaufmann 1983). A classical reference is still Multivariate Calibration (Martens and Naes 1989). A dictionary with extensive explanations containing about 1700 entries is The Data Analysis Handbook (Frank and Todeschini 1994). 

A principal components multivariate statistical approach (SIMCA) was evaluated and applied to interpretation of isomer specific analysis of polychlorinated biphenyls (PCBs) using both a microcomputer and a main frame computer. Capillary column gas chromatography was employed for separation and detection of 69 individual PCB isomers. Computer programs were written in AMSII MUMPS to provide a laboratory data base for data manipulation. This data base greatly assisted the analysts in calculating isomer concentrations and data management. Applications of SIMCA for quality control, classification, and estimation of the composition of multi-Aroclor mixtures are described for characterization and study of complex environmental residues. 

This is the waste coming from the production of more units than demanded. The optimum number of products to be produced must balance the demand, including that in high season periods, the cost of holding the stocks in the warehouse and the cost of setting up the production to produce one lot of the product. In terms of an analytical laboratory, overproduction could be interpreted as any activity that is not necessary for customer service or for adding value to the experience and knowledge of the laboratory. There is no need to analyse too many samples unless we have reasons to do so. Furthermore, there is no need to perform more analyses than necessary. Too many analytical results are a waste. For example, the optimum number of replicates must balance the need for statistical evaluation. 

There are several different kinds of laboratory safety data that require interpretation. These include routine screening for study subject selection, diagnostic evaluation of the subject, identification of risk factors, monitoring the progress of the disease or treatment, detection of adverse reactions, determination of appropriate dosages for certain at-risk subject groups (e.g. those with renal impairment). 

Assuming that the quality of the input is maximal then improving the output will be dependent upon the analysis and evaluation of the data. Because the spontaneous report alone will seldom, if ever, contain sufficient information to determine causality satisfactorily, it is usually necessary to seek additional data which may be available from hospital records, laboratory investigations or post-mortem reports. It is highly desirable that comparable methods and formats of reporting should be used as widely as possible, particularly if international comparisons are to be made. A major benefit of formalised systems of causality assessment, which will be considered in greater detail later in this chapter, is the element of standardisation that is brought to the process of interpretation. 

Interpretation of ecotoxicity is still more of an art than a science. Perhaps the greatest advances in this area will come from increasing understanding of the structure-activity correlations for chemicals. However, further effort is necessary to integrate the wide range of different types of assessment currently employed, which range over almost every scientific discipline. In the strictest sense, the laboratory methods described can permit only comparative evaluation of chemicals under the test conditions. Extrapolation from laboratory results to predict what will happen when chemicals enter the natural environment must be improved (Duffus, 1986). 

There is still some doubt as to the validity of the assignments of the ESR spectra for high energy-irradiated polypropylene. It is difficult for us to evaluate the probability of the different interpretations, even though these problems have been treated previously in this laboratory (50). 

Problems relating to measurement and interpretation of the hardness of brittle materials are still awaiting suitable analysis and assessment, to give valid evaluation of the results of measurements often carried out by methods very different from the technique applied to the tested material. This idea has served as the basis of this book. It is addressed primarily to industrial laboratory workers and theoretical research workers who are trained at academic level. The material it contains also qualifies it as a practical training textbook for students of mineralogy, solid body physics and materials engineering. 

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