Evaluation and Selection of Preferred Solution

The optimization scheme can become very difficult when the design requires a human operator and a man-machine interface. This difficulty exists because no two human beings are the same. The basic anatomical and physiological differences between humans makes the human factors of the design difficult to quantify. One human user may find a design very acceptable and efficient, while another may consider it to be intolerable therefore, the optimization of human factors becomes a matter of statistical comparisons. Hence, the user population must be identified and characterized before attempting to optimize any designs that involve human operators. 

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A set of processes is introduced to achieve the improvement in question. Data from such processes are analyzed and evaluated and the causes requiring improvement are identified. The objectives for improvement are also identified. Possible solutions are devised and the preferred one is selected. The implementation of the solution is then planned. 

Number of parts, reliability, and ease of maintenance (1 each). The other designers preferred to use formal evaluation methods (e.g., Pahl Beitz, 1996) for selecting not only concept variants early in the design process, but also solution principles for subfunctions and detailed variants later in the design process. These methods provide a list of widely qiplicable evaluation criteria that the designer can use as support. 

For parenteral IV formulations, a sterile solution of the compound is required. A terminal sterilization method is preferred, rather than aseptic filtration, because there is a greater assurance of achieving sterility. As noted by Moldenhauer (1998), the FDA requires a written justification to explain why a product is not terminally sterilized. Therefore, it is mandatory to assess whether the candidate drug is stable to autoclaving as part of any preformulation selection process. Autoclaving (usually 15 min at 121°C) at various pHs is undertaken, after which the solutions should be evaluated for impurities, colour, pH and degradation products. Clearly, if one compound shows superior stability after autoclaving, then this will be the one to choose. 

An interesting property of cyanide-bridged molecular cubes is their ability to bind alkali metals (especially and Cs" ) selectively within the cube interior. Crystallographic analysis of a Rh-Mo molecular cube indicates bond formation between the cationic guest and the cube s CN edges. When K is encapsulated, the ion is distributed over two equivalent positions, both slightly displaced from the cube center. Encapsulated cesium ions, on the other hand, occupy a central position. The locational differences reflect differences in ionic radii 2.02 and 1.78 A for Cs" and K, respectively, with coordination numbers of 12 for each. The structural differences translate into a nearly 4000-fold preference for uptake of Cs versus from salt solutions, where the difference was evaluated competitively via Cs-NMR measurements. 

The selectivity coefficient, defines the ability of an ISE to distinguish a particular ion from others (5). According to lUPAC, can be evaluated in mixed in solutions of primary and interfering ion (Fixed Interference Method), or separate solutions (Separate Solution Method and Matched Potential Method). The smaller the value of the greater the electrode s preference for the principal ion. 

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