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crystallisation of PBS (10X)


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#1 Thom

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Posted 05 February 2014 - 04:31 AM

Hello everyone,

 

I prepared a fresh PBS stock solution (10X) and after few days in the fridge (4°C) I observe some crystallisation on the bottom... which disappears when i heat up the whole solution again...

 

Is that normal? For information, i mixed the following (in 1L of milliQ water):

 

- 80 g NaCl

- 2g KCl

- 18.05 g (Na2,HPO4)(2H2O)

-2.4 g KH2PO4

 

and then i adjusted the pH at 7.4 with HCl.

 

 

 



#2 mdfenko

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Posted 05 February 2014 - 04:56 AM

can you describe the crystals (shape, color, etc)? that may give a clue as to their origin.


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#3 Thom

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Posted 05 February 2014 - 06:39 AM

It is very nice actually :)

 

It is sharp, more or less leaf-shaped, several arborescent monolayers ... Not sure that will help you^^



#4 jerryshelly1

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Posted 05 February 2014 - 09:12 AM

Do you always use that much disodium phosphate? We only use ~14g, it is possible that you oversaturated the solution and it is precipitating out. 



#5 mdfenko

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Posted 05 February 2014 - 09:23 AM

sodium phosphate (and that includes the potassium phosphate in your solution due to ion exchange) will crystallize at refrigerator temperatures (~4C).


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#6 acidfast

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Posted 05 February 2014 - 01:32 PM

Stock solutions at 10X or 20X PBS usually precipitate in the fridge. I leave mine out at room temp though. 



#7 El Crazy Xabi

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Posted 05 February 2014 - 07:24 PM

Autoclave and leave at room temp, that's what I do. Such saturated solutions alway precipitate in the fridge.



#8 Missle

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Posted 06 February 2014 - 05:05 AM

I've seen 10x PBS precipitate in the fridge as well.  I've also noticed that some buffers will precipitate when stored in a glass bottle but not in a plastic and that in both cases they re-disolve when warmed.



#9 Thom

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Posted 07 February 2014 - 05:39 AM

Ok thank you all of you for your responses, this comfort me, as suggested i think that the best remains to autoclave and leave at RT...



#10 Biologist91

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Posted 08 April 2014 - 09:35 AM

I had prepared a 10X PBS autoclaved and kept it in room temperature for many days (a little over a month). It was okay for a long time but recently some thread like (i mean white cloudy strands) floating in the solution. I had also filtered the solution prior to autoclaving and storage. What  could be the cause? 



#11 El Crazy Xabi

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Posted 08 April 2014 - 04:07 PM

It doesn't sound good... either is some precipitate forming or something is living there. If you have a microscope take a look.

 

It never happened to me with this recipe and using borosilicate glass. There are plenty of recipes for PBS and I don''t know if you make it in Schott bottles or not. I leave it here just in case

PBS 10X    Concentration   Quantity

NaH2PO4               30 mM             3.5994 g

Na2HPO4               70 mM             9.9372 g

NaCl               1300 mM            75.972 g

dH2O                       -                Up to 1 L

 

 

Edit: fixing table


Edited by El Crazy Xabi, 08 April 2014 - 04:10 PM.


#12 mdfenko

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Posted 09 April 2014 - 03:54 AM

if it's "stringy" then it's almost certainly something growing.

 

even though you autoclaved it, after opening the bottle you exposed it to whatever is in the air.


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#13 Biologist91

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Posted 09 April 2014 - 09:33 AM

oh alright I get it. And about which bottle I use. I used a Schotts Bottle



#14 jerryshelly1

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Posted 09 April 2014 - 11:55 AM

We use those and they work fine. Just practice better aseptic techniques. If it is common lab reagent, make sure everyone is informed on the proper handling of the chemicals. Sounds like someone was careless pouring the solution and introduced a contaminant.



#15 Biologist91

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Posted 12 April 2014 - 04:34 PM

Also in the above mentioned chemicals list he hasn't mentioned KCl. I use KCl also along with NaCl, Na2HPO4 and KH2PO4. Is that a problem?






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