Physical properties testing, colorants

Color labs are outfitted with laboratory size equipment that simulates the larger machines used for production internally and by their customers. Typical processing equipment found in the lab are small extruders, two-roll mills, ban-burry mills, and media mills. Small rotational, injection and blow molding machines are used to duplicate the customers process. Instruments and computers are required for testing physical properties and color. Most labs have a computer-controlled color measuring system and a light booth to evaluate color. The spectrophotometer with computer is initially used to assist in colorant formulation and later as a quality control (QC) tool to provide certification of the quahty of match to standard. The light booth provides a standardized set of conditions to visually observe color and appearance. 

Composition is normally expressed by a distillation curve, and can be supplemented by compositional analyses such as those for aromatics content. Some physical properties such as density or vapor pressure are often added. The degree of purity is indicated by color or other appropriate test (copper strip corrosion, for example). 

Standard test methods for chemical analysis have been developed and pubUshed (74). Included is the determination of commonly found chemicals associated with acrylonitrile and physical properties of acrylonitrile that are critical to the quaUty of the product (75—77). These include determination of color and chemical analyses for HCN, quiaone inhibitor, and water. Specifications appear in Table 10. 

The important thing about such a spectrophotometric curve is that it describes a physical property of the material that is fundamentally related to its color. If, then, the color-determining component can be extracted from the product under test, a... 

Nitroguanidine and nitrosoguanidine both give a blue color with the diphenylamine reagent, and both give the tests described below, but the difference in the physical properties of the substances is such that there is no likelihood of confusing them. 

For each metal tested, list the color, malleability, ductility, and density. State any relationship observed between the metal s position on the periodic table and the physical properties listed. Do metals in the same family have similar physical properties ... 

The strength properties more often specified for plastics materials are (1) tensile strength and elongation, (2) flexural strength, (3) Izod and Gardner impact, and (4) heat deflection temperature under load. Our purpose here is not to describe each test in detail but to point out some of the known effects that colorants and other formulation ingredients can have on these properties. Table 22.1 lists the ISO and ASTM test methods for most of the physical properties, and ref. 1 (pp. 7-112) describes each of the methods in detail. Table 22.2 lists typical values of the above cite four properties for selected thermoplastics. 

The completed product at this stage is tested for viscosity, color, and physical properties pertinent to the formulation being prepared. The paint conforming to the required quality standards is then strained and filled into cans or drums, labeled, packed, and moved to storage. 

Adulteration of fats and oils is an old problem. Many older tests involved determination of physical properties such as refractive index, melting point, and viscosity. However, color tests were later used for this purpose. Thus, Baudonin reaction for sesame oil and the Halpben test for cottonseed oil have been noted. In both cases, a compound characteristic to an oil determines the presence of the oil. However, today such detections and quantitations are carried out with GC and HPLC procedures. Thus, cholesterol and phytosterols may be determined by gas chromatography for fingerprinting purposes however, fatty acid analysis might also be used for higher levels of contamination (31). Detailed discussion of issues related to oil authentication and adulteration has taken place (11). 

The optical microscope is a valuable tool in the laboratory and has numerous applications in most industries. Depending on the type of data that is required to solve a particular problem, optical microscopy can provide information on particle size, particle morphology, color, appearance, birefringence, etc. There are many accessories and techniques for optical microscopy that may be employed for the characterization of the physical properties of materials and the identification of unknowns, etc. Utilization of a hot-stage accessory on the microscope for the characterization of materials, including pharmaceutical solids (drug substances, excipients, formulations, etc.), can be extremely valuable. As with any instrument, there are many experimental conditions and techniques for the hot-stage microscope that may be used to collect different types of data. Often, various microscope objectives, optical filters, ramp rates, immersion media, sample preparation techniques, microchemical tests, fusion methods, etc., can be utilized. 

The laboratory procedures associated with identification comprise a process known as qualitative analysis. In Part A of this experiment, you will examine 11 household products to determine some specific physical and chemical properties and to establish a qualitative analysis scheme for their identification. The physical properties include characteristics associated with their physical appearance, including color, particle size, and texture, as well as their solubility in water, rubbing alcohol, and hot water. The chemical properties include the manner in which the white solids react chemically with various other chemicals. In Part B, you will have three to five unknown household products (taken from those tested in Part A) and your work will involve using your qualitative analysis scheme to identify them. The flow chart that follows the procedure (Figure 3.6) should be filled out while performing Part A and should help when you perform Part B. 

At the end of the exposure period, the samples should be examined for any changes in physical properties (e.g., appearance, clarity, or color of solution) and for degradation by a validated method. Because any photodegradation is limited to the sample surface, it is important to ensure that a representative portion of solid drug substance is used in individual tests. Similar sampling considerations, such as homogenization of the entire sample, apply to other materials that may not be homogeneous after exposure. Analysis of the exposed sample should be performed concomitantly with that of any protected samples used as dark controls. 

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