Performance Assessment of a Liquid Handling Robot
Volume Determination of Dispensed Microlitre Droplets
Agreement between the Single-Dye Fluorescence-Based
and Gravimetric Method
The able below compares the average volumes across the plate for the requested volume 100 and 150 μL for three replicates. The average volumes were obtained from the Gravimetric Method and from the Single-Dye Fluorescence-Based Method, respectively. According to the table, the average volumes obtained from the two methods coincide very well, with the fluorescent results moderately lower than the gravimetric counterpart by about 1 μL, i.e. around 1% difference in inacc. This difference may result from the diversity of the error sources between two methods. The lower volume in fluorescence may be accounted for the photochemical decay.
Agreement between the Dual-Dye Absorbance-Based
and Gravimetric Method
Similar with the previous analysis, to verity the validity of the Dual-Dye Absorbance-Based Method, the average volume across the microplate determined by the Absorbance-Based Method are compared with that of the Gravimetric counterpart for theoretical-requested volume 20, 10 and 5 μL. By looking at the following table, one can find that the absorbance results are consistent with the gravimetric results corresponding to the same requested volume. As the data collected from two different approaches were consistent, it may be concluded that the Multichannel Pod, integrated with P20 tips, is accurate and precise after calibration. Besides, there is relatively small bias inherent in either approach, so it may verify the validity as well as the applicability of the Dual-Dye Absorbance-Based Method.
Agreement with the Previously Published Works
The above discussion demonstrates the validity and applicability of the Gravimetric and Fluorescence- and Absorbance-Based Volume Verification Methods. The post-calibration performance also verifies the high accuracy and precision stated by the manufacturer. Compared with the previous works, it is believed that the approaches were applied properly. The gravimetric method was carried out following the methodology guidelines of ISO 8655 for gravimetric calibration for pipettes. For the Dual-Dye Absorbance-Based Method, the baseline measurement was done by measuring and subtracting the blank absorbance, though the calibrator plate and barcode reader are simplified from the Artel MVS™ system designed by Bradshaw et al. (2005). The applicability of this developed method has been verified by the agreement of the post-calibration gravimetric data. Besides, the comparison between the gravimetric and photometric data is largely consistent with the previous findings in the work of Dong et al. (2006).