White Work practice

The Dust Study, which is described elsewhere in the preamble, assessed the proposed work practices. As one component of the proposed work practices, the cleaning verification was evaluated in the Dust Study. It should be noted that the Dust Study was not designed specifically to evaluate the cleaning verification in isolation of the rest of the work practices. Unlike the earlier Disposable Cleaning Cloth Study that was intended to test the effectiveness of the use of the white glove test in isolation, the Dust Study was meant to evaluate the effectiveness of the proposed work practices, including cleaning verification. 

While using the 0.1 % threshold as a determinant for when an impurity should be isolated to meet regulatory requirements is a good practice, there are other times when it becomes necessary to work with extraneous compounds at still lower levels. During the development of process chemistry for the synthesis of the protease inhibitor Tipranavir several synthetic lots of the drug were discolored, appearing pinkish rather than white as they should. It was determined that a low-level ( 0.1%) highly colored material was responsible for the problem with those lots and a request for the isolation and characterization of that contaminant was received [66]. 

The early work of Sommer and associates established a good mouse assay for the poison in shellfish products which made quantitative work with the poison practical. A mouse unit (NU) was defined as the minimum amount of poison that would kill a 20-gram white mouse in 15 minutes when one ml of an extract of shellfish was injected intraperitoneally. Higher amounts than the minimum kill in shorter time, i.e., death times of 3, 4, 6, and 8 minutes are equivalent to 3.7, 2.5, 1.6, and 1.3 MU, respectively, as illustrated in Figure 1. 

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