SANDA CORPORTION 1D

							                                                         SANDA CORPORTION
                                                                                             TM
                                               APPLICATION NOTES FACTS

                               ANIONIC SURFACTANTS                                          1D
Thermometric titration of surfactants was investigated earlier by Jordan* with hyamine
(ABS) and Weiner & Feldmeister* with cetylpyridinium chloride (CPC). The precision of
these titrations was tabulated in Vaughan. See facing insert.

SANDA from experiments has found that CPC gives a sharper endpoint. Thus, the
precision is better with CPC.

Sodium lauryl sulfate (SLS), titrated with 0.4M CPC in a solvent mixture of 2:3
methanol/water, resulted in:

              Standard Deviation: 0.007 (8 titrations)
              Slope:              0.99994
              Percent (%) SAA: 91.07, repeated: 91:21

Commercial sulfonates, in the titration with CPC, usually agreed well with the
conventional, time-consuming hyamine test. A solvent mixture of 1:1 methanol/water
enabled us to increase the titrant strength to 1 molar. This was useful since the reaction of
sulfonates is not as exothermic as is that of SLS. The addition of a few drops H2O2 seems
to catalyze this reaction favorably. Moreover, the addition of 5 mL acetonitrile prior to
titration sharpened the relative weaker endpoint. These commercial surfactants, different
in composition, in all cases, have given at least two distinct reactions, typically shown in the
titration graph below.

Sodium lauryl sulfate added to sulfonate has been found in between the two reactions
of sulfonate. This is noticeably more exothermic than the reaction of sulfonate. See the
following graphs:

Sulfates, determined by precipitation with barium chloride in sulfonic acid, as well as in
sulfonates, have given accurate and precise results. However, prior to titration an excess
of CPC should be added to prevent a partial precipitation of organic sulfates in surfactants.
 The SANDA 2-buret titration system makes this type of titration easier. It can be set up for
a two titrant delivery, first the CPC titration and then the barium chloride titration--one after
another. A program for such titrations is provided.

                                    Water Determination

Sulfonic acid, less than 0.6%, could be rapidly determined by thermometric titration with
a ketal, which is a stable titrant and not moisture sensitive, since the reaction has to be acid
catalyzed. Surfactants, in the very same way, can be accurately determined for water
content with the same titrant.
Comments:
Rapid information, including a very unique water determination, can be obtained on
surfactants by thermometric titration. We realize, however, that the information gathered
here is just a beginning in the study of surfactants, whether it be reactivity, composition or
simplification of methodology.