High performance criteria

Glancing at the list, the second association of inferior performance becomes apparent. The two single largest biopolymers on the market are PE/PET types and PLA/PHA types PE and PET are pure commodity products and even their durable petrochemical equivalents are not necessarily associated with any particularly high performance criteria. They are primarily price driven. Starch and cellulose, as well as PLA/PHA, are a new breed of polymers, which mostly have even worse properties than existing olefins. 

Control of pollutants by oxidation is another exothermic process in which high conversion is the most important performance criterion. Interest in efficiency is limited to minimize byproduct formation the byproducts can be more damaging and more refractory than the original pollutants were. Commercially, most adiabatic reactors used for pollution control are of the least expensive construction. 

For each dmg substance, the maximum acceptable levels of the various impurities are described in the drug substance monograph or the specification included in the submissions to the regulatory authorities. In this chapter, the ICH Q6A [4] and Q6B [5] definition of specification is used. A specification consists of three parts the test (e.g. moisture content, impurities), references to the analytical procedure (e.g. high-performance liquid chromatography [HPLC], gas chromatography [GC]), and the acceptance criterion (e.g. not more than 0.50%). 

Technical ceramics ate classed highly because of their high performance index. However, these materials are often used by sintering, and are liable to exhibit porosity, which is incompatible with the function of hermetic sealing. This criterion corresponds to a suitability for processing yet it carmot be expressed as a material property available in the databases, but it eliminates these materials. 

High performance liquid chromatography has been used as a criterion of specificity when coupled with a bioassay or radioimmunoassay. With regard to the opioid peptides, brain extracts were chromatographed on an HPLC column that had previously been calibrated with known opioid peptides (Lewis et ai, 1979), and the collected fractions were assayed for activity (Stern et ai, 1980) (Fig. 12). The bioassay provides the quantitation and the HPLC provides the identity of each component. It would be interesting to use HPLC coupled with radioimmunoassay to confirm the identity of the many peptides that have been found in brain by immunohistochemical techniques. 

In an attempt to deal with this irony, the Department of Defense introduced cost-as-an-independent-variable, or CAIV for short. This mouthful, developed in the math-proficient defense engineering community, means that cost is a design criterion on a par with technical capability. Under CAIV, a high-performing, but costly system no longer meets the specification. 

Precision of peak areas or heights is important because they are used for calculating amounts during quantification. It is also the most important performance criterion for an LC injection system. Precision should be determined using a minimum of five rephcate chromatograms. For bioanalytical samples, precision is studied at least at low, medium, and high concentrations. This is repeated on separate days to calculate intraday and interday precision. 

The modem technologies impose stringent demands of macro-molecular systems up to high performance. The fundamental criterion in the achievement of this desideratum is the elucidation and efficient exploitation of the relation between their structure and performance properties. The nature enlightened such systems, offering practically perfect models. 

Thermosets may be omitted In some lists of high performance polymers but they meet specifications and would not be used today If they were not high performance material. This criterion applies to carbon fibers, barrier resins, thermotropic polyesters, interpenetrating network polymers and many specialty elastomers. Likewise, the introduction of UV/EB curing techniques has brought about a new era in the polymer industry. 

Flow rate, F, is expressed as the volume of mobile phase per unit time. This is a very important criterion for suitable column development. For a satisfactory resolution it is absolutely necessary that the eluant flow should be maintained at a stable rate. The easiest way to maintain a stable flow rate Is to use a peristaltic pump to force the eluant on to or out of the column. An increase in the flow rate of the mobile phase through the column leads to shortening of the time necessary for separation. It may therefore be preferable to work with the maximum possible flow rate (indeed this is one of the reasons for the quicker resolution obtained in high performance liquid chromatography as we will see later). However, an undue Increase In the flow rate decreases the efficiency of resolution and time economy. The flow rates used differ with respect to the nature of the sample and the nature of the stationary phase. However, commonly used flow rates fall between 30-120 ml/hour cm. ... 

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