pH of Depc H2O - Does anyone know? (Oct/04/2005 )

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Hi,

does anyone happen to know what is the pH of Depc H2O? I know it is a little bit acidic, but how much?

Thanks

-coco-

what is Depc H2O?

-Gincel-

QUOTE (Gincel @ Oct 4 2005, 02:34 PM)

what is Depc H2O?

Water treated with diethyl pyrocarbonate, a compound that destroys RNAse. Water used for RNA work is usually treated with this, then autoclaved.

As to pH, I'd suspect it'd depend strongly on the pH of your starting water. After autoclaving the DEPC-treated water, the DEPC hydrolyzes to CO2 and EtOH, which are lost. Thus, I'm not sure there's a significant impact on pH, all said and done.

Just guessing here, though -- maybe someone else can come up with a more definitive answer?

-HomeBrew-

hi
Depc water is di deionized water treated by diethyl pyrocarbonate. The DEPC molecule is inactivating RNases. after treatment, DEPC is eliminated by autoclaving twice the water.
I think the pH would be the pH of ddH20...

answer come from Alesia's post

QUOTE

MilliQ water absorbs CO2 from the air. The value of [CO2(aq)]in water at 25º C in equilibrium with air that is 350 parts per million CO2 (the current concentration of this gas in the atmosphere) is 1.146 x 10-5 moles/liter (M). The carbon dioxide dissociates partially in water to produce equal concentrations of H+ and HCO3-: pH = 5.65. (http://web.indstate.edu/thcme/mwking/ionic-equilibrium.html)

fred

-fred_33-

Thanks a lot for your reading and your writing!

coco

-coco-

Question about the DEPC/H2O preparation! How to do it? Is there a powder or else? Just to know if I have to order it ....

thanx

-SMH-

hi
ddH20 is prepared by filtration but that is basic
DEPC is liquid, generaly a 1000X concentred solution. Hence, you add 1ml of DEPC, let sit at RT for minimum 4h under a hood, and autoclave (destruction of DEPC). I autoclave 2 times since i've noticed a on-time-autoclaved water still smell DEPC. but 1 is ok.
fred

-fred_33-

I don't trust the stuff. I've autoclaved it overnight and still seen inhibition of RT reactions. The smell never goes away

In my experiance the pH of DEPC water can be as low as pH5, probably due to the dissolved CO2

-John Buckels-

I've been making my own RNAse free water for 10 years now with DEPC. Let it go into solution overnight on the stir plate and autoclave once. Never had any problems.

*knock on wood*

-pBluescript-

QUOTE (John Buckels @ Oct 11 2005, 12:07 PM)

I don't trust the stuff. I've autoclaved it overnight and still seen inhibition of RT reactions. The smell never goes away

Here's what Ambion says about the smell remaining after autoclaving:

QUOTE

3. Autoclaving DEPC-containing solutions should be of sufficient duration to rid the solution of any smell.

FALSE. A faint EtOH smell may linger after autoclaving, but more commonly a sweet, fruity smell is observed. This is caused by the EtOH by-product combining with trace carboxylic acid contaminates and forming volatile esters. It does not mean that trace DEPC remains in the solution.

This, by the way and completely off topic, is also a problem in brewing beer, unless you like fruity beers...

More here...

-HomeBrew-

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