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weighing reagents is difficult due to static, any adivse?

weighing reagents is difficult due to static, any adivse? - Protocols and Methods Forum

weighing reagents is difficult due to static, any adivse? - Post Any Protocol, Method, Technique, Procedure or Tips / Troubleshooting for any Molecular Biology Technique.


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  #1  
Old 03-23-2007, 07:45 PM
Anwar Khan
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Default weighing reagents is difficult due to static, any adivse?



Hello everyone, while measuring in sub mg quantities of a precious reagent
(dry powder) I could not keep it at one place due to static and the reagent
would go everywhere but down on the weighing boat. is there any way to
avoid this. thank you.

sincerely,
Anwar Khan



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  #2  
Old 03-23-2007, 09:09 PM
Brian Ballard
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Default weighing reagents is difficult due to static, any adivse?

In article <I7WMh.1839$[Only registered users see links. ].prodigy.net>,
"Anwar Khan" <[Only registered users see links. ]> wrote:


Weigh out onto a piece of foil.

Brian
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  #3  
Old 03-23-2007, 09:31 PM
WS
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Default weighing reagents is difficult due to static, any adivse?

Dear Anwar,

let me suggest to do it by difference: weigh the vial with the
substance and with lid and stoppers etc, then dissolve it, remove the
solution, let the vial dry and weigh again with all parts. Then
calculate the difference.

Another possibility would be measuring the concentration by
spectrophotometry, if extinction coefficients are available.

A third possibility is to believe the manufacturer and just assume
what's printed on the label...


All the best,

Wo

On Mar 23, 8:45 pm, "Anwar Khan" <[Only registered users see links. ]> wrote:


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  #4  
Old 03-24-2007, 03:44 AM
Tom Knight
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Default weighing reagents is difficult due to static, any adivse?

"Anwar Khan" <[Only registered users see links. ]> writes:


You can find information on radioactive anti-static sources made for
balances here:
[Only registered users see links. ]

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  #5  
Old 03-24-2007, 08:01 PM
Dr Engelbert Buxbaum
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Default weighing reagents is difficult due to static, any adivse?

Anwar Khan wrote:


In such cases I just trust the manufacturers statement of weight and add
water to the vial directly to make a stock solution. That I then
aliquote and snap-freeze. With some substances you can measure the
concentration of the stock solution (i.e. absorbance or fluorescence
measurements), just as a sanity-check.

Note that with most balances you get 0.1 mg precision, so weighing
sub-mg amounts gives you an error of > 10%. On top of that you get the
error from trying to get the weighted substance into solution
completely. Together that's much larger than the error a reputable
manufacturer may have made.
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  #6  
Old 03-24-2007, 08:14 PM
DK
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Default weighing reagents is difficult due to static, any adivse?

In article <[Only registered users see links. ]>, Dr Engelbert Buxbaum <[Only registered users see links. ]> wrote:

100% seconded! When they say it's a mg, just assume it is. Add solvent,
close the original vial, vorted very, very thouroughly, spin down, collect.
And keep in mind that if the conclusion of the work include hard numbers,
those numbers are +/- 10% at least.

But with many things you can simply determine concentration of the
resulting stock using a spec.

DK


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