Subject:
Re: I have problem to ask you.
Date:
Thu, 11 Mar 1999 12:03:07 +0000
From:
"Prof. J. F. Scamehorn" <scamehor@ou.edu>
Organization:
University of Oklahoma
To:
suvena somabutr <s_somabutr@hotmail.com>
CC:
Kitipat.S@chula.ac.th, k_thitipong@hotmail.com, bkunchan@pioneer.netserv.chula.ac.th
References:
1


Here is the result of some disscussion I have had with Dr. Riviello
about your project. He basically recommends that for the octanoate, you
use a regular reverse phase packing in the column, but use a long column
with a flush before the normal HPLC solvent to get rid of any carbon not
from the surfactant.

Lle:

I would like your advice on a project. I have two MS students from
Chula who I am assigning the following projects: measured detailed
adsorption isotherms for surfactants and calcium at different pH
on ink (for student no. 1) and on paper fiber (for student no. 2). This
is to understand below the CMC the interesting effects you found. I
mailed the students your dissertation last week and they are studying
it.

My question related to the surfactants. Clearly, I want to study sodium
octanoate since that is the one you found the most synergism with and
SDS as a model anionic. Of course, the conductivity detector will work
for SDS. For the soap, I was thinking of using TOC. I am a little
concerned with the ink particularly of getting some crap interferrring
with the TOC from that source. My students at Chula was inquiring about
"why don't we just use HPLC". I will send him your paper on the new
packing. But my basic question is what would you do if you were me
about analyzing octanoate concentrations in this project? Would you try
the new packing or some thing else?

To: Dr. Scamehorn

As for the analysis of the sodium octanoate, you are correct that there
can
be significant interference from the carbon in TOC analysis. In fact, I
actually saw inseparable, even by centrifugation (7000 rpm in Harrison's
centrifuge), suspensions of carbon at high surfactant concentrations.
If
your students are not playing with extremely low concentrations of C8 or
relatively high salt concentrations, they might be able to use a longer
(say 20-30 cm) C18 column to do the analysis. Alternately, they could
attempt to manufacture a PLM column as I did. For simplicity, I think
I'd
start them with the C18 column using an isocratic water-only or
water/methanol (95/5-- for a bit of lubrication) system. Make certain
they
wash the carbon thoroughly before using it as it contains a lot of
soluble
ionics.



--

********************************************************
John F. Scamehorn
Asahi Glass Chair in Chemical Engineering
Institute for Applied Surfactant Research
School of Chemical Engineering and Materials Science
100 E. Boyd
University of Oklahoma
Norman, Oklahoma 73019

Ph. 405-325-4382
FAX 405-325-5813

e-mail: scamehor@ou.edu

********************************************************