Visual Qualitative Evaluation

A visual evaluation is only adequate for identity tests. However, in accordance with GMP guidelines, in the absence of any further documentation a second person should also inspect the TLC plate immediately after derivatization and the result should be entered in a database. The same applies to results to be submitted as evidence in court. 

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A visual inspection of a two-sample chart provides an effective means for qualitatively evaluating the results obtained by each analyst and of the capabilities of a proposed standard method. If no random errors are present, then all points will be found on the 45° line. The length of a perpendicular line from any point to the 45° line, therefore, is proportional to the effect of random error on that analyst s results (Figure 14.18). The distance from the intersection of the lines for the mean values of samples X and Y, to the perpendicular projection of a point on the 45° line, is proportional to the analyst s systematic error (Figure 14.18). An ideal standard method is characterized by small random errors and small systematic errors due to the analysts and should show a compact clustering of points that is more circular than elliptical. 

Capture efficiency measurements may be used to evaluate the function of a canopy hood (see Section 10.5). Capture velocity is not a feasible evaluation tool, since a canopy hood does not generate an air velocity close to the source. It is also possible to use exposure measurements for workers outside the plume area. Since most hot processes generate visible contaminants, visual inspection of the flow, especially around hood edges, might provide a qualitative evaluation. Many contaminants could however be invisible when diluted and smoke generators (Section 10.5) may be necessary to find leakages (temporary or permanent) around the hood edges. 

The Importance of the subjective or qualitative aspects of protein gel systems should not be underestimated. For example, the visual appearance of measurably strong protein gels may range from that of an elastic translucent gel to that of a more opaque, curd-llke gel. Qualitative evaluation may be the most appropriate means of differentiating between these protein gels at the macroscopic level. Electron microscopic analyses have been extremely useful In evaluating protein gels (, ),... 

It is difficult to evaluate Bartell s ideas from a theoretical point of view other than to say that they are not unreasonable. So little is known about the precise magnitudes of the nonbonded interactions and their dependence on distance that even qualitative judgments are risky. The approach does have the disadvantage of being difficult to apply rigorously or even to visualize qualitatively for other than very simple molecules. 

Evaluation of Color - The color of a finished coating may be qualitatively evaluated by visual comparison to an established standard using appropriate test panels. Most color comparisons, however, are being made quantatively by measurement of the test panels on color measurement instruments which calculate color coordinates and determine the color difference. 

Evaluation can be performed by measuring capture efficiency using real contaminants and applying the real process or by substituting with tracer materials. A simpler, but qualitative, method of evaluation is the visualization of the airflow. If the relationship between capture efficiency and airflow rate is known, a measurement of the airflow rate can be used for frequent evaluation. See Section 10.5. 

The effect of particle size, and hence dispersion, on the coloring properties of aluminum lake dyes has been studied through quantitative measurement of color in compressed formulations [47], It was found that reduction in the particle size for the input lake material resulted in an increase in color strength, and that particles of submicron size contributed greatly to the observed effects. Analysis of the formulations using the parameters of the 1931 CIE system could only lead to a qualitative estimation of the effects, but use of the 1976 CIEL m v system provided a superior evaluation of the trends. With the latter system, the effects of dispersion on hue, chroma, lightness, and total color differences were quantitatively related to human visual perception. 

For qualitative determination of gelation ability, 3 ml aliquots of the WPC dispersions were dispensed In screw capped test tubes and heated In an oil bath at lOO C. Tubes were removed from the bath at 30-s Intervals and placed Into an Ice bath. Gel strength was evaluated on a visual rating scale of 0 to 5,0 (13, 1 ), The time required at lOO C for the formation of a gel with a rating of 4.0 or higher was reported as gel time. 

However, for many applications we do not need such a complete characterization of the state of the mixture in practice, simple methods often suffice. Commonly used methods, for example, are color comparison to a standard for qualitative visual homogeneity, or the measurement of some representative physical property. Between the two extremes of complete characterization and qualitative or semiqualitative practical evaluation, there is room for sound quantitative methods of characterization. We must keep in mind, however, that the goodness of mixing is not absolute, but dependent on the required needs. 

The plates, once developed, were checked visually under UY light at 254 nm, while qualitative and quantitative evaluation ensued with the aid of a Zeiss chromatogram spectrophotometer PMQ II in reflectance mode at a wavelength of 280 nm. 

Tphe bright colors of the coordination complexes of transition metal elements, including the platinum group metals, were of great assistance to pioneer workers with these materials. Thus, chemical changes could be followed visually it was frequently very easy from their colors to demonstrate the existence of isomers upon which Alfred Werner was able to base his monumental theory of coordination. Such early studies were limited to a simple qualitative visual evaluation of the color. 

Most descaling and passivation processes for steels were developed prior to the widespread use of electrochemical techniques. As a result, a variety of visual and chemical tests are widely used for determining the surface cleanliness. Chemical tests have also been established to verify the presence of a robust oxide film on austenitic and ferritic stainlesses (8). These methods are very simple to conduct in a manufacturing environment, but they are qualitative in nature and rely strongly on the judgment of the inspector. Outside of the laboratory, electrochemical methods have not been widely used to evaluate cleanliness of carbon and alloy steels after pickling. Nevertheless, they are well suited for this purpose and have been examined in considerable detail in laboratory studies. 

A similar type of assay was done with bacterial and yeast cultures treated similarly. Cultures were washed by centrifugation in 0.1 M phosphate buffer (pH = 7.0) and resuspended to an OD580 = 0.3. Attachment after 30 min at room temperature to plastic and Cell-Tak-coated plastic was evaluated qualitatively by microscopic visualization. 

Although the panel with the plasma deposited film followed by priming with E-coat is visually better, the use of the corrosion width provides a method for quantifying the improvement in the corrosion performance. Also the factor of about 2 difference in corrosion width between the two chromate conversion-coated panels is difficult to obtain from the qualitative difference observed from the scanned images. It can be seen from this comparison of three panels that the use of the measured corrosion width makes the differentiation of corrosion performance much easier. This method of evaluating corrosion test results is used to determine if the combination of the two bests could indeed yield the better corrosion protection of aluminum alloys. 

The graphical representations presented here are intended to enhance analysis and to provide guidance for the development of appropriate physical models. While visual inspection of data alone cannot provide all the nuance and detail that can, in principle, be extracted from impedance data, the graphical methods described in this chapter can provide both qualitative and quantitative evaluation of impedance data. 

The visual inspection of gas chromatograms (Figures 2-4) provides only a qualitative impression of the relative differences in composition of PCBs in the biota and their habitat. Therefore, we have calculated a parameter to provide a more quantitative means for evaluating the differences in composition. We have chosen a chlorobiphenyl, lUPAC No. 153, which is present in appreciable quantities in the industrial mixture of Aroclor 1254 and was identified as one of the major components in the samples of biota from the study area, and calculated the following ratio ... 

So, which is the greener route At the early stages of process development or at the discovery stage this evaluation is usually performed qualitatively by visual inspection of the reaction scheme. At first glance, the shorter route B probably has the lower E-factor. But how much lower And what about the environmental impact Will the... 

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