Keith J. Albert

Importance of Integrating a Volume Verification Method for Liquid Handlers: Applications in Learning Performance Behavior

Nearly all assays performed within a microtiter plate are volume dependent. In turn, all concentrations of biological and chemical components in these assays, as well as the associated dilution protocols, are volume dependent. Therefore, it is imperative to quantify the volumes transferred to and from an assay. A volume verification method, which can be used to quantify the amount of transferred volume, is an essential component that enables proper interpretation of experimental results. A volume verification method can be used to help an operator optimize volume transfers as well as troubleshoot automated methods. Moreover, these methods can be used to compare performance between liquid handlers, show dispense drift over time, compare channel-to-channel (tip-to-tip) reproducibility, or statistically compare individual dispenses from a multisequential dispense. The focus of this paper, in part, is to discuss some of the many situations where a volume verification method should be implemented. This paper addresses important factors and their associated applications in understanding liquid handler behavior and is not meant to be specific to the volume verification process or the specific liquid handlers used. A robust and reliable volume verification method allows for measurement of transferred volumes at all levels in assay development, from a pure research level to a highly regulated laboratory environment. The goal is to achieve liquid delivery quality assurance through accurate and precise measurement of critical volume transfers. (JALA 2007;12:172–80)

Verifying Liquid-Handler Performance for Complex or Nonaqueous Reagents: A New Approach:

Multichannel volume dispensing devices, such as automated liquid handlers, are widely used in drug discovery assays and other high-throughput screening processes. The performance of these systems is heavily based on the ability to deliver proper volumes of specific reagents. For instance, because concentrations of species within an assay are volume dependent, assay integrity and the subsequent interpretation of assay results are directly tied to liquid-handler performance. When liquid handlers are used to aspirate/dispense aqueous-based reagents, there are many accepted methodologies used to calibrate/verify the systems ability to properly perform within a users tolerance window. In other situations, however, liquid handlers are used to dispense complex or nonaqueous reagents, such as dimethyl sulfoxide (DMSO), serum, and aqueous-based mixtures with detergents, for which there may not be standard, or simple, methodologies to verify liquid-handler performance. Discussed herein is the recent research on broadening existing methods for accurately assessing liquid-handler performance when dispensing complex or nonaqueous reagents. Accurate and reliable adjustment of liquidhandler protocols for varied reagent types could have farreaching adoption in all scientific communities. Using this methodology, target aliquots of multiple solutions were dispensed with a calibrated syringe and subsequently validated via dual-dye ratiometric photometry. Various custom sample solutions were prepared to incorporate (a) 75–90% DMSO (v/v), (b) 20% glycerol (v/v), and (c) 50% ethanol (v/v). (JALA 2006;11:172-80)