About Calibrating Cassettes Gravimetrically | 105
BioTek Instruments, Inc.
About Calibrating Cassettes Gravimetrically
The gravimetric calibration method uses known values (the expected mass of a volume
of water/fluid) to set the accuracy of each dispense tube. BioTek ships a 12 X 8 strip
plate with the MicroFlo for this purpose. In this procedure, each strip is tared before
dispensing and weighted again after dispensing. When a tube dispenses too much or
too little fluid, it must be calibrated.
Tubes are calibrated by adjusting the tension screw in the cassette’s tube tensioner. A
clockwise rotation, , of the adjustment screw increases tension on the tubing and
reduces the volume of fluid dispensed. A counter clockwise rotation, , decreases the
tension and increases the volume dispensed.
Calibration is required for a cassette to meet the MicroFlo’s specifications.
Determining Expected Mass
The expected mass (
ected
m
exp
) of the fluid in the strip is the product of the density of the
fluid (
), the volume of fluid dispensed into each well (V), and the number of wells
being dispensed to and the number of runs performed:
RunsofNoWellsofNoVm
ected
..
exp
BioTek calibrates the cassettes using deionized water. The density of water at standard
temperature and pressure is 0.0010 g/L, and the number of wells on a single 1 x 12
strip is 12, so if we dispense to the plate once (1 run), the equation above becomes:
Vm
ected
0120.0
exp
This table shows the expected mass for various dispense volumes:
Volume Expected Mass
(µL) (g)
1 0.0120
2 0.0240
5 0.0600
10 0.1200
20 0.2400
50 0.6000
100 1.2000
You can determine similar values for the fluid type and dispense volumes regularly
used in your lab, if desired. The MicroFlo’s performance at small volumes may be
improved by calibrating the cassette with the specific fluid to be dispensed.
To Next Page
Loading...