Analytical Characterization of Soap

TABLE 36.1 Fatty Acid Distribution and Analytical Characterization of Soap Base Fatty Acids... 

There are a variety of analytical methods commonly used for the characterization of neat soap and bar soaps. Many of these methods have been pubUshed as official methods by the American Oil Chemists Society (29). Additionally, many analysts choose United States Pharmacopoeia (USP), British Pharmacopoeia (BP), or Pood Chemical Codex (FCC) methods. These methods tend to be colorimetric, potentiometric, or titrametric procedures. However, a variety of instmmental techniques are also frequendy utilized, eg, gas chromatography, high performance Hquid chromatography, nuclear magnetic resonance spectroscopy, infrared spectroscopy, and mass spectrometry. 

Despite the evidence of fiscal and competitive benefits enjoyed by the various industries which have embraced process analytics, pharmaceutical companies have been notoriously restrained in their efforts to deploy PAT. Indeed, the pharmaceutical industry has slipped so far behind peer industries that a well-known Wall Street Journal article from 2003 [34] characterized the manufacturing prowess of drug makers as lagging far behind potato-chip and laundry-soap makers. While the declaration was shocking to many, it was, nonetheless, an accurate assessment. Before indicting the industry for gross negligence, however, it is important to consider the various factors which have acted over time to create the current state of affairs. 

Industry uses a number of analytical methods to characterize oils and fats, in terms of a number of parameters which include moisture, titer (solidification point), free fatty acid, unsaponifiable material, iodine value, peroxide value, and color. Moisture content of the oils and fats is an important measure for storage stability at elevated temperature because it facilitates hydrolysis which in turn impacts odor and color quality. Titer is a measure of the temperature at which the material begins to solidify, signifying the minimum temperature at which the material can be stored or pumped as a fluid. Free fatty acid is a measure of the level of hydrolysis the oils and fats have undergone. Increased fatty acid content usually negatively impacts product color stability because fatty acids are more susceptible to oxidation. Unsaponifiable material is a measure of the nontriglyceride fatty material present, which affects the soap yield of the material. The iodine value is a measure of the amount of unsaturation present in the oils and fats. Peroxide value is a measure of the... 

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