Factorial analysts

Some customers will require the results of the analysis to be interpreted or an opinion given, e.g. does the discharged water from the factory comply with the current legislation ) or how many cigarettes can be made from 2 kg of cannabis leaf There is now provision for this aspect of the work of an analyst to be included in the scope of accreditation of the laboratory to the Standard ISO/IEC 17025 2005 [1]. It is important to be clear about what is meant by Opinions and Interpretations. In the context of this book, it is the subjective expression given that is based on results, academic or scientific knowledge and experience gained over a period of time. 

Given the care with which laboratory equipment (balances, burets, instruments, etc.) is calibrated at the factory, why should the chemical analyst worry about errors ... 

Precision studies can be planned in a full factorial matrix-type format involving multiple analysts, days, capillaries, buffer preparations, instruments, etc. Table 9 displays an example matrix for intermediate precision testing involving two analysts, two instruments, and two capillaries over a multiple day period. Typically, qualification targets for acceptable precision will be pre-defined based on method type, capability, and intent. Acceptable targets can also be mathematically determined by the method of Horwitz. ... 

It is possible to check the calibration of a pipet, flask, or buret. The process involves weighing with a calibrated analytical balance. The volume of water (temperature noted) delivered or contained by the glassware is weighed. Then the analyst converts this weight to volume (using the density of water at the temperature noted), corrects the result to 20°C (the usual temperature of the factory calibration), and compares it to the factory calibration. If the difference is not tolerable, the piece of glassware is either not used for accurate work or a correction factor is applied. It should be pointed out that the thermometers used must be properly calibrated and that the timer used to measure the delivery time for the burets and pipets must also be calibrated. 

The examination of more than one of the non-procedure related factors (e.g. different laboratories, analysts, instruments, columns or batches of reagents, days) by Plackett-Burman and fractional factorial designs causes problems. These designs require combinations that are impossible to... 

Two algorithms are available to perform all the calculations in a very simple way, namely the Box, Hunter and Hunter (BH ) algorithm and Yates s algorithm. Both are considered below for a typical and simple example of a 2 factorial design. Assume we are studying the influence of pH (A), temperature (B) and time (C) over the yield (response in %) of the extraction of a metal from a complex analytical matrix, just before conducting the extracts to an ICP device. The levels of each factor, fixed by the analyst, are pH (A), 3 (—), 5(4-) temperature (B), 40 (-), 60 C ( + ) and time (C), 1 (-), 2h. (- -). The matrix design and the experimental data are as follows ... 

Once a report is written, the analyst might not be involved in what is done with the information, such as modifying the raw material supply for a factory or creating new laws to regulate food additives. The more clearly a report is written, the less likely it is to be misinterpreted by those who use it. 

Problems encountered in HPLC analysis most often stem from a lack of knowledge of the influence of the slight variation of the experimental parameters (pH, temperature, solvent composition, flow rate, etc.). The analyst has to set up the list of parameters and their possible interactions. There are hardware parameters (e.g., flow control, temperature control, lamp current) and software parameters used to interpret and report the results from stored data. The use of factorial designs is of great help. Software such as Validation Manager, from Merck, produces, in a table for each parameter and interaction, its percentage and confidence interval as well as information to help the analyst in concluding the study. 

Official analysts are appointed to the Home-office for toxicological work, as well as in connection with the Explosives Department and the Factory Department. The Local Government Board possesses a Department for the inspection of food and a staff of specially qualified inspectors to assist in the administration of the Alkali, Ac., Works Regulation Ac . The Metropolitan Water Board and the Rivers Boards in various parts of the country have their chemical and bacteriological laboratories, and so have the Sewage Boards and Works. The Scottish Office also appoints inspectors under the Alkali Act and Rivers Pollution Prevention Act. 

S. Edwards and M. Allen. Rapid and precise method for the determination of the chemical oxygen demand of factory effluent samples. Analyst, 109 671-672, 1984. 

In many experimental design problems, it is necessary to design the trials or runs in such a way that the variability arising from some nuisance factors can be controlled. These nuisance factors (or "blocking variables ) may affect the response but are neither factors nor fixed variables. They can be analysts, instruments, reagents, sample materials, working day, etc. Let us consider the simple case of a 2 factorial design to improve an automated extraction step in a... 

Accident-concentration analysis is dependent on the analyst s analytic skills and knowledge about the studied industrial system. There are today statistical tools such as FAC (Factorial Analysis of Correspondence) and HAC (Flierarchical Ascendant Classification) that may help identify accident concentrations and thus make the analysis more objective. Such analyses do not replace but are complementary to the more intuitive analysis made by SFIE experts. In a study of accidents among female automobile assembly workers, Laflamme (1996) identified four such concentrations by applying FAC and HAC ... 

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