Re: How to measure the volume of any fluid in nano levels?

From: James L. Powers (jlpowers_at_earthlink.net)
Date: 11/29/04 

Date: 29 Nov 2004 05:11:40 GMT

I assume that you want to calibrate and validate the performance of a
nanoliter liquid dispenser.

If you are working with water or another solvent that has a significant
vapor pressure, then weighing the droplet is not accurate. There will be a
significant loss of liquid by evaporation between the time the droplet is
generated by the liquid dispenser and the time it is weighed. To make
matters worse, the smaller the droplet, the greater the surface area/volume
and the faster the evaporation. Perhaps it is better to use an indirect
analytical chemical method by adding a known mass of a dye to the solution
to be dispensed. Set up your dispenser to nominally generate a droplet
containing a nonvolatile dye under the same conditions that you plan to
test. Dispense the droplet directly into a cuvette containing a known
larger volume of liquid (diluent) that has been previously pipetted into the
cuvette. Measure its absorbance or other optical property (e.g.
fluorescence) in an appropriate detector. Use Beer's Law or other principle
to calculate the concentration and mass of the dye in the cuvette, then
back-calculate the original droplet volume from this information. Design
and do enough experiments to satisfy yourself that the volume that you are
generating is accurate and reproducible. Use this data to calibrate your
dispenser.

Jim Powers
jlpowers@earthlink.net

"Oliver 'Ojo' Bedford" <acp29@campfire.rrz.Uni-Koeln.DE> wrote in message
news:cnqst402kgk@enews1.newsguy.com...
>
> raghuis@gmail.com (raghu) writes:
>
>> Is it only by measuring the weight and knowing the density or
>> are there any better ways to find it?
>
> Measuring weight (mass) is much more reliable and sensitive than
> measuring volume (due to interface effects like wetting). Also dealing
> with mass is better than dealing with volume, the latter being a
> function of temperature, pressure, composition etc.
>
> Oliver
>