3.4.Calculation of resultsU.K.
Every non-ionic surfactant has its own factor, depending on its composition, particularly on the length of the alkene oxide chain. The concentration of non-ionic surfactant is expressed in relation to a standard substance — a nonyl phenol with ten ethylene oxide units (NP 10) — for which the conversion factor is 0,054.
Using this factor the amount of surfactant present in the sample is found expressed as mg of NP 10 equivalent, as follows:
(b — c) xfx 0,054 = mg non-ionic surfactant as NP 10
where:
b
=
volume of ‘carbate solution’ used by the sample (ml),
c
=
volume of ‘carbate solution’ used by the blank (ml),
f
=
factor of the ‘carbate solution’.