The criteria for choice of a method are usually based on convenience, availability of protein, presence or absence of interfering agents, and need for accuracy. For example, the Lowry method is very sensitive but is a two step procedure that requires a minimum of 40 minutes incubation time. The Bradford assay is more sensitive and can be read within 5 minutes, however proteins with low arginine content will be underestimated. Generally, estimates are more accurate for complex mixtures of proteins. Estimates of concentration of pure proteins can be very inaccurate depending on the principle of the method, unless the same pure protein is used as a standard. Criteria will be discussed in the individual documents.