Enthalpy Analytical, Inc. has initiated a new process to optimize accuracy and speed in its Hamilton Microlab Star™ automated liquid handling system. The company is making full use of Total Aspiration and Dispense Monitoring (TADM), an optional component of the unit’s Vector software system that provides real-time monitoring of each aspiration and dispensing operation.
The Hamilton Star robot contains separate dispensing mechanisms. One area encompasses 12 individual pipetting channels, while the other dispenses 96 samples simultaneously for mass transfers. TADM is used to supervise the 12-channel area of the robot by monitoring air pressure inside each pipetting chamber. A sensor in each pipetting channel enables Enthalpy to monitor air pressure vs. time. Pressure measurement, tracking, and analysis provide a significant data profile for each sample the robot dispenses.
Liquid samples have varying dispensing pressure, density and viscosity characteristics. Water, plasma, urine, solvents, and homogenates behave differently during the pipetting process. A sensor within each pipetting channel constantly records pressure during aspiration and dispensing, and the measured pressure is reported in 10ms increments.
"We can give the robot a different set of instructions for how to pipette plasma as compared to how to pipette methanol," explains Brad Kuebler, an automation specialist on Enthalpy's team. "TADM also allows us to visualize performance. It creates pressure vs. time curves, which gives us a very quick, visual tracking mechanism for every sample transfer."
Enthalpy recently completed an extensive validation study to develop TADM profiles for a variety of plasma types. "We ran 15 different types of plasma, encompassing various species and anticoagulants—monkey, human, rat, dog, K-2 EDTA, K-3, etc.—to compare a cross-section of density and viscosity profiles," Kuebler continued. "Our objective was to make certain we were giving the robot good enough instructions for pipetting plasma." Pipetted plasma samples of multiple volumes were weighed gravimetrically using a NIST traceable balance, treating the plasma samples as they would be in an actual development method.
"The next step was to look at the pressure curves the system generated," says Kuebler. "We did 48 repetitions for each of four different sample volumes, for each of the 15 plasma types we studied." Pressure curve analysis provided what can be considered 'normal' pipetting curves. The next part of the study sought to identify what 'bad' curves look like, and how those differ from normal, gravimetrically verified curves. Additional testing was done using clots from various types of plasma, using samples containing foam, and samples that were not actual plasma but had some of the same characteristics.
"Curves from bad samples look drastically different than those from the control group," Kuebler explains. "We can see on a pressure graph that if a curve enters a particular area of the graph, it contained clots; or if it enters another area of the graph, it was a foamy sample. The curves are drastically different between good and bad samples. Prior to using TADM, we did not have that level of control over robot pipetting. While the testing and validation effort was significant, TADM increases the overall safety and robustness of the entire pipetting process." Samples are traceable in real time throughout the analytical process, from the time a sample is put into solution until chromatograms are generated.
Scientist Kendall Powell, Ph.D., adds “Now we generate records with warnings when any transfer is out of specification. When a transfer fails due to clotting issues, the error handling instructs the robot to recover on its own, including getting new tips and repeating the transfer.”
TADM's benefits for Enthalpy accrue on different levels. For example, it is not necessary to wait until sample analysis to identify a defective sample transfer. The resulting time saving from avoiding reanalysis is substantial. For example, if the analysis is standard or a Quality Control, it can be necessary to redo an entire plate if analysts discover a sample hasn't been properly dispensed. "It's better for us, and better for our clients and research partners," says Brian Nofsinger, Ph.D., Associate Director Bioanalytical Division. "Everyone can be certain that the results we generate are faster, more accurate, and more easily traced."
Privately owned, Enthalpy Analytical was founded in 1993 to meet the marketplace need for fast, reliable analytical services. Enthalpy was the first lab in the Research Triangle to deploy the API 5000™. Enthalpy’s GLP-compliant LC/MS/MS Bioanalytical Division provides critical bioanalytical support at every stage of drug discovery and development.
