Lamps performance characteristics

The lamp performance, which affects cure, is expressed by the following characteristics ... 

In practice, PQ can mean system suitability testing, where critical key system performance characteristics are measured and compared with documented, preset limits. For example, a well-characterized standard can be injected five or six times and the standard deviation of amounts are then compared with a predefined limit. If the limit of detection and/or quantitation are critical, the lamp s intensity profile or the baseline noise should be tested. Following are the steps recommended for (system suitability) PQ tests. 

As a result of these differences in dependence on source intensity, fluorescence methods are generally one to three orders of magnitude more sensitive than methods based on absorption. Mercury arc lamps, xenon arc lamps, xenon-mercury arc lamps, and lasers are typical fluorescence sources. Monochromators and transducers are typically similar to those used in absorption spectrophotometers, except that photomultipliers are invariably used in high-sensitivity spectrofluorometers. Fluorometers and spectrofluorometers vary widely in sophistication, performance characteristics, and cost, as do absorption spectrophotometers. Generally, fluorescence instruments are more expensive than absorption instruments of corresponding quality. 

It is already a fact that lasers are replacing conventional lamps in a great variety of spectroscopic applications. The origin of this substitution lies in their superior performance over incoherent light in many experimental situations. Many spectroscopic experiments have been improved, and moreover new techniques have been developed due to the particular advantages provided by lasers. The characteristics of laser radiation on their own constitute real advantages and justify their widespread use in many applications. 

This chapter sheds light on the different validation requirements and methods to investigate them. Evaluation of the typical validation characteristics, namely accuracy, precision, specificity, DL, QL, linearity, and range in CE, has been discussed in details. Validation in CE is similar to validation in other separation techniques such as HPEC, but in CE, the capillary surface properties and namely the EOF have to be especially addressed. Eurther, the instrument performance has to be carefully considered during validation and method transfer. Here, the condition of the lamp and the thermostating system is of particular importance. 

The observations are performed with a Leitz Ortholux polarizing microscope equipped with the ftOpak illuminator, lamps for reflected and transmitted light, immersion objectives, and verniers. Characteristics of the polished thin sections and of the nuclear emulsion plates are observed in transmitted light with the same immersion optics after removing the Berek prism. 

The characteristics of an equipment may change over time, e.g., LfV detector lamps lose intensity, or pump piston seals abrade, or short-term noise affecting the LOD is increased because of flow cell contamination. These changes will have a direct impact on the performance of... 

When the solvent has reached the top of the plate, the plate is removed from the developing chamber, dried, and the separated components of the mixture are examined. Because the components are usually colourless or white, a UV lamp or blacklight (UV264) is used to make the spots fluoresce. Iodine vapour, copper sulphate and other coloured reagents can also be applied to induce characteristic colours to spots of antioxidants. Once visible, the Rf values of the spots can be determined by dividing the distance travelled by the coloured product by the total distance travelled by the solvent (the solvent front). Each antioxidant has a distinctive Rf value. These values should be the same regardless of the distance travelled by the solvent, but are dependant on the solvent used, and the type of TLC plate. For this reason, TLC should be performed on reference samples of antioxidants at the same time as the tmknown materials are analysed. 

The characteristics of an equipment may change over time, e.g., UV detector lamps lose intensity, or pump piston seals abrade, or short-term noise affecting the LOD is increased because of flow cell contamination. These changes will have a direct impact on the performance of the HPLC instrument. The frequency of performance tests will be determined by experience and is based on need, type, and history of equipment performance. Intervals between the checks should be shorter than the time the instrument drifts outside acceptable limits. New instruments need to be checked more frequently, and, if the instrument meets the performance specifications, the time interval can be increased. 

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