Re: mass vs. volume measurement

Old Man wrote:
0"Andy Resnick" <andy.resnick@xxxxxxxxxxx> wrote in message news:d6cp2c$307$1@xxxxxxxxxxxxxxxxxxxxxx


Here's a simple question- why is vit much easier to dispense small volumes than to measure small masses?

I routinely dispense single microliter volumes, and could do much better with a modest effort using common lab equipment, but it's very difficult to weigh a microgram of material.

Andrew Resnick, Ph.D. 


A lab balance isn't the only means: mass spectrometer.


No, that's not what I mean. I mean that if I want to prepare a 10 nM solution, I need to accurately weigh out some solid and accurately meter out some volume of fluid. Because I can't easily meter 10 ng of the solid (or however much I need), I have to prepare a concentrated (say) 1M solution and then dilute it down (in volume) to 10 nM.

Never mind the other reasons to prepare concentrated stock solutions. My question is simply regarding the ease of metering an accurate small volume vs. metering an accurate small mass.

--
Andrew Resnick, Ph.D.
Department of Physiology and Biophysics
Case Western Reserve University
.