An analytical procedure used in the laboratory for assessing a sample of something either qualitatively or quantitatively in terms of an amount of a substance, its composition, or some other entity under investigation. Biochemical assays of samples taken from bioreactors that often feature complex mixtures involve procedures for determining cell content, substrate utilization, and product formation. The complexity of the samples that require various prescribed steps to be followed does not permit conventional forms of chemical analysis such as titration.