Ideally, pipettor performance should be checked using the actual dispense reagent as the calibrator solution. However, most dispense reagents are colorless and an absorbance measurement cannot be obtained in the visible range (400750 nm) without the addition of a dye. The SPECTRAmax PLUS microplate spectrophotometer overcomes this limitation by using the near infra-red absorbance of water to determine the pathlength in each well, which is proportional to volume. The dispensed volumes are calculated by reference to a pathlength/volume standard curve (prepared separately with a certified pipettor). The standard curve can be prepared once for a given dispense reagent and batch of microplates and stored for subsequent use.

This application note describes how to check the performance of multichannel pipettors with the SPECTRAmax PLUS. Pathlengths in the wells are measured directly and volumes are calculated automatically. The performance can be checked using the same buffers or reagents that are being dispensed by the pipettor, eliminating possible discrepancies in pipettor performance between normal dispense reagent and calibrator solution. Because initial separate calibration of one channel is not necessary (e.g., as in reference 10), the method is suitable for checking performance of automated pipetting stations, including 96channel pipettors. The spreadsheet capability of SOFTmax PRO software allows the data to be calculated automatically and final results to be displayed as overall Pass/Fail for each pipettor.

MATERIALS
1. SPECTRAmax PLUS microplate spectrophotometer

2. High-quality microplates; e.g.:
For dispense volumes >150 L

'"/>

Source: