Thin layer chromatography limit tests

Ordinary impurities are considered innocuous in that they have no significant undesirable biological activity at or below the specified limits. These impurities arise from the synthesis, formulation, or degradation of the drug. The USP monograph for glycopyrrolate contains a thin-layer chromatography (TLC) test for ordinary impurities for which the limits are 0.5% for individual impurities and 2.0% for the total of all impurities. 

Screening tests for the trichothecene mycotoxins are generally simple and rapid but, with the exception of the immunochemical methods, are nonspecific. A number of bioassay systems have been used for the identification of trichothecene mycotoxins.73 Although most of these systems are very simple, they are not specific, their sensitivity is generally relatively low compared to other methods, and they require that the laboratory maintain vertebrates, invertebrates, plants, or cell cultures. Thin-layer chromatography (TLC) is one of the simplest and earliest analytical methods developed for myco-toxin analysis. Detection limits for trichothecene mycotoxins by TLC is 0.2 to 5 ppm (0.2 to 5 pg/ mL). Therefore, extracts from biomedical samples would have to be concentrated 10- to 1,000-fold to screen for trichothecene mycotoxins. 

Oscik s relationship (Eq. 33) referring to solute retention in adsorption chromatography has been widely tested by means of thin-layer chromatographic data (36-39). Due to the excessive complexity of its general form it was usually limited to binary mobile phases only. In this particular case, Eq. 33 was transformed in the following way (39) ... 

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