Used properly, statistical DOE (design of experiments) techniques can be more efficient and produce better results than OFAT (change one process factor at a time) in many applications. Tecan discussed a study in which DOE, automation of sample preparation, and multiparameter LC-MS/MS analysis enabled efficient and reproducible optimization of sample prep and yield for immunosuppressant drugs simultaneously.
In the study, a half factorial design was employed with five parameters at two levels, where a total of 15 parameters were screened in three sessions (five parameters each). The critical factors identified proved to work well (e.g., increase of signal in this study).
Although powerful, manual execution of DOE series is error-prone and tedious. To mitigate this problem, Tecan used an automated liquid handler (Freedom EVO®) driven by flexible software (Freedom EVOware®) that can pipette according to dedicated scripts using input for variables from Excel tables.
“In such a table, the concentrations defined in the DOE software can be converted to liquid volumes to be pipetted, if appropriate stock solutions representing all factors are defined,” explained Roland Geyer, Ph.D., innovation manager, Tecan.
Another key piece of technology used is Tecan’s AC extraction plate, still in development, which facilitates sample cleanup by a modified type of Liquid-Liquid extraction.
“It consists of a deep-well plate with wells coated with an immobilized liquid used as the extraction substrate. The coated-well surface as such enables simplification of the entire sample-preparation process. The procedure works without any protein precipitation, filtration, centrifugation or solvent evaporation, hence accelerating and streamlining the complete sample-preparation workflow,” said Dr. Geyer.