Potentiometric Determination of the Anionic Surfactants in Shampoo

Potentiometric Determination of the Anionic Surfactants in Shampoo


Equipment
Potentiometer = 751 GPD Titrino / Titroprocessor
Electrodes = 6.0507.120 Ionic surfactant electrode; input 1
6.0733.100 Ag/AgCl reference electrode (c(KCl) = 3 mol/L)

Reagents
c(TEGOtrant A100) = 0.004 mol/L; D0
1,3-didecyl-2-methyl-imidazolium chloride (DDMICl)
Metrohm 6.2317.000

Sample
app. 0.2 g sample (shampoo)
5 mL Methanol puriss p.a.
10 mL Buffer solution pH = 3.0, citrate/HCl, e.g. Merck Tirisol No. 9883
60 mL dist. water

Remarks
Calculations:

Anionic=EP1*C01/C00;4;meq/g

Anionic = concentration of anionic Tensides in meq/g
C01 = concentration of titrating agent (0.004 mol/L)

Answer

Anionic = 12.638 x 0.004 / 0.2128 = 0.2376 meq / g

EP1 = 12.638 mL
C00 = 0.2128 g

Electrode preparation, maintenance and storage:
Store the Ionic Surfactant electrode dry. They are conditioned by two to three titrations. Rinse the electrode after several titrations with methanol or wipe it with a cloth moistend woth methanol and rinse with dist. water. If you use the electrode frequently, it may also be stored in a solution of 1% polyethyleneglycol 1000. In this case, the electrode is always ready to use.

Sample preparation:
Adjust the sample size in order to have a titrating agent consumption of at least 10 mL. The pH of buffer solution, the amount of added methanol may change according to the type of surfactant. See also Application Bulletin No. 233.

Literature
Metrohm Application Bulletin No. 233: Titrimetric / potentiometric determination of anionic and cationic detergents with the high-sense surfactant electrode.

Method documentation
'pa
751 GPD Titrino 15215 751.0010
DET U Tens.An
parameters
>titration parameters
meas.pt.density 3
min.incr…. 10.0 ml
dos.rate max….. ml/min
signal drift ….OFF mV/min
equilibr.time …10 s
start V: ….OFF
pause ….30 s
dos.element:…. internal D0
meas.input: ….1
temperature ….25.0 °C
>stop conditions
stop V: ….abs.
stop V ….20 ml
stop U… OFF mV
stop EP ….9
filling rate max….. ml/min
>statistics
status: ….OFF
>evaluation
EPC ….5
EP recognition:… greatest
fix EP1 at U ….OFF mV
pK/HNP: …OFF
>preselections
req.ident: …OFF
req.smpl size: …value
activate pulse: …OFF
------------
'fm
751 GPD Titrino 15215 751.0010
DET U Tens.An
>calculations
Anionic=EP1*C01/C00;4;meq/g
C00= 0.2128
C01= 0.004
------------
'fr
751 GPD Titrino 15215 751.0010
U(init) 103 mV DET U Tens.An
smpl size 0.2128 g
EP1 12.638 ml 271 mV
Anionic 0.2376 meq/g
stop V reached
============
'cu
751 GPD Titrino 15215 751.0010
start V 0.000 ml DET U Tens.An