Performance Assessment of a Liquid Handling Robot

Gravimetric Results

 

Performance Assessment of the Span-8 Pod

 

The calibration factors configuration applied to all channels, so it was not essential to repeat the calibration process for each channel. The Gravimetric Method was performed to test the performance of each channel after calibration.

 

For 20 μL liquid transfer, all channels fulfilled relative inaccuracy < 3% and coefficient of variation < 1% (see the red columns). This meant when pipetting 20 μL of distilled water, all the channels of the Span-8 Pod were capable of delivering the requested amount of volume accurately and precisely.

 

Likewise, regarding 10 μL (see the blue columns), though most channels (apart from Channel 1) had a tendency to dispense liquid less than requested, the absolute values of the relative inaccuracy were still below 5%, which no doubt met the acceptability criteria. Also, all channels of the Span-8 Pod could transfer 10 μL of distilled water with CV lower than 5%, except for Channel 6 in which an outlier was found .

 

In contrast, the performance of transferring 5 μL liquid was not as accurate or precise as the former two (see the green columns). Nevertheless six out of eight channels fulfilled the acceptability criteria of volume lower than 10 μL (< ±20% inacc and < 10% CV). Note that 5 μL is the one of the critical target volumes of P20 tips, so it may be unacceptable for Channel 4 and 7 slightly outweighing the CV criteria. However, this might also indicate that the replicate numbers were not large enough to show the actual performance of the liquid handling robot. Still, according to the results, it is recommended to select Channel 1, 2 and 5, when high accuracy and precision are required for a specific step in assays.