NaOH use for cleaning validation and TOC: What's your experiment?

Hi all!
Happy new year 2011!

I am actually developping an analytical method (TOC) for cleaning validation.
Our acceptance criterion is very low ~0.2ug/cm^2 (is it really low?).
Our solvent for cleaning and doing the analysis is NaOH 2%. The analytical method used is TOC. We have to acidify the sample in NaOH 2% until pH 2 to permit analysis in TOC (persulfate+UV+Heat system).
We have a lot of problem to get stable analytical blank (NaOH 2%+acid). Absolute signal varies on each test that we do and is not small (sometimes bigger than signal of Sucrose standards solutions made of the same solvent +acid).
Low carbon Swabs are not stable in NaOH (acid add create sometimes snow in our vials :frowning: ) and gives more contamination.

In this way, analytical contamination is impossible to manage.

Did anyone already had these problems? What others problems did you have?

How do you manage to work with NaOH in TOC analysis for cleaning validation?

ideas are welcome!

Thanks all

PS: My english is bad, but my problems are real^^

Nobody use NaOH?

The best way to find out prevention of contamination and stability of Swabs in 2% NaoH is to contact the swab manufacturer.
They have application notes.
Iam attaching an application note from GE which probably may not be useful for you but atleast gives you an idea what are the application notes are.

Application Note.pdf (27.6 KB)

Hello Ricopalazo,

Which TOC instrument r u using? I have developed several TOC methods using pH-10 water (prepared by adding 1N NaOH in water) as a solvent. If you are using Sievers TOC 900 analyzer, then you don’t have to acidify the sample, since instrument itself will add acid (H3PO4) to your sample during the analysis. I would also suggest you to use Texwipe swabs

Nikunj Vasoya

[quote=ricopalazo]Nobody use NaOH?

I know that we shouldn’t add any solvent but water to TOC