[Histonet] pH of 10% NBF

[Tony Henwood]

Greg,

A pH "around" 7 is the aim:

Abler et al (J Histotechnol 6(4):181-184,1983) surveyed several neutral
buffered formalin solutions received from different laboratories and
found a great variation in osmolarity, pH, buffering capacity and
formaldehyde concentration. They recommend the following quality control
parameters be routinely checked on neutral buffered formalin solutions
prepared and used in histopathology laboratories:

Osmolarity	1,000 - 1,600 milliosmols
pH	6.5 - 7.5
Buffering Capacity *	Greater than 0.75ml
Formaldehyde Concentration	3 - 5%w/v

* Buffering Capacity is obtained by titrating the amount of 0.1N
hydrochloric acid required to lower the pH of the solution to 2

Comparing the osmolarity in the above table with that recommended for
Millonig's buffered formalin obviously indicates some disagreement. The
importance of osmolarity in fixation is debatable. Carson et al (Am
J.Clin Pathol 59:365, 1973) recommend that Millonig's Phosphate Buffered
Formalin should have a pH of 7.4 and the effective osmolarity is about
290mOsM. 

Regards

Tony Henwood JP, MSc, BAppSc, GradDipSysAnalys, CT(ASC)
Laboratory Manager & Senior Scientist
Tel: 612 9845 3306
Fax: 612 9845 3318
the children's hospital at westmead 
Cnr Hawkesbury Road and Hainsworth Street, Westmead 
Locked Bag 4001, Westmead NSW 2145, AUSTRALIA 




-----Original Message-----
From: histonet-bounces <@t> lists.utsouthwestern.edu
[mailto:histonet-bounces <@t> lists.utsouthwestern.edu] On Behalf Of Greg
Dobbin
Sent: Friday, 8 January 2010 5:49 AM
To: Histonet <@t> lists.utsouthwestern.edu
Subject: [Histonet] pH of 10% NBF


Hi Folks,
If the pH of our 10% Neutral Buffered Formalin is reading 7.01
(recycled) and 7.12 (made from new formaldehyde), should I try to get to
7.2? If yes-how- add sodium bicarbonate? 
I look forward to your responses. 
Warm regards,
Greg

Greg Dobbin, R.T.
Chief Technologist, Anatomic Pathology
Dept. of Laboratory Medicine,
Queen Elizabeth Hospital,
P.O. Box 6600
Charlottetown, PE    C1A 8T5
Phone: (902) 894-2337
Fax: (902) 894-2385

"I find that the harder I work, the 
more luck I seem to have."
- Thomas Jefferson


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