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avatar: Khalid Khan
Khalid Khan
50 posts
Replied to Khalid Khan's post on August 6th, 2018

Hi,

I want to ask why we need to acidify and purge the sample in the NPOC method of the TOC analyzer to determine Total organic carbon.

Thanks you

Khalid

avatar: Panter
Panter
14 posts
Replied to Khalid Khan's post on August 6th, 2018

While analyzing samples in differential method, the sample is introduced into acid environment. (phosphoric acid) It is, then purged.

What happens here is that IC has enough energy to oxidize to CO2, and therefore, purged by the carrier gas (which also has O2).

Most of TOC does not oxidize, since it needs more energy. (note, the word MOST OF)

Since it all happens inside TIC rector, which is sealed, that CO2 is gathered and sent to detector. (NDIR)

This measures the IC level directly.

In NPOC mode, to measure TOC, you have to remove IC, and you do it the same way.

Except it is all done by purging in the open vessel (or with septa, that leaks under pressure), so the CO2 coming from IC is lost.

When purged enough, you are left with, again, most of the TOC still in the sample.

The dufference is that, now when these vapors do not go into detector, you can use more aggressive HCl. And you do.

Without foolowing that, sorry, no good results will come your way. :)

Best of luck.

avatar: Khalid Khan
Khalid Khan
50 posts
Replied to Panter's post on August 7th, 2018

Dear Panter, 

Thanking you for your responce. its clear now

 

regards