Potentiometric Determination of Non-Ionic Surfactans with the NIO Electrode

Potentiometric Determination of Non-ionic Surfactants with the NIO Electrode

Equipment
Potentiometer = 751 GPD Titrino / Titroprocessor
Electrodes = 6.0507.010 NIO surfactant electrode; input 1
6.0726.100 Ag/AgCl double junction reference electrode
(inner electrolyte c(KCl) = 3 mol/L, outer electrolyte
c(NaCl) = 1 mol/L)

Reagents
c(STPB) = 0.01 mol/L; D0
STPB = sodium tetraphenylborate

Sample
5 mL sample solution
3 mL c(BaCl2) = 0.1 mol/L
60 mL dist. water

Remarks
Titrating agent:

Dissolve 3.4223 g sodium tetraphenylborate in 300 mL dist. water. Dissolve separately 10 g polyvinyl alcohol in 300 mL dist. water and heat it slightly. Allow to cool and rinse both solutions in a 1000 mL flask. Add 10 mL buffer pH = 10 and fill up to 1 liter.

BaCl2 solution:
Dissolve 21 g BaCl2 or 25 g BaCl2*2H2O in dist. water, add 1 mL
conc. HCl and fill up to 1 liter.

Buffer pH = 10:
Dissolve 1.24 g H3BO4 in dist. water, add 10 mL c(NaOH) = 1 mol/L and fill up to 100 mL.

Sample preparation:

Dissolve app. 0.5 ... 1 g detergent (Renex 650 ICI; polyoxyethylene-(30)-nonylphenol, molecular mass 1541 g/mol) in 100 mL dist. water.

Calculations:

Nonionic=EP1*C01*C02/C00;4;meq/g

Nonionic = concentration of nonionic Tensides in meq/g
C01 = concentration of titrating agent (0.01 mol/L)
C02 = dilution factor for the sample solution, aliquot (20)

Nonionic = 8.795 x 0.01 x 20 / 0.5145 = 3.4189 meq/g

EP1 = 8.795 mL
C00 = 0.5145 g

Literature
Metrohm Application Bulletin No. 230: Titrimetric/potentiometric determination of non-ionic tensides (oxyethylates) with the NIO electrode

Method documentation

'pa
751 GPD Titrino 15215 751.0010
DET U Tenside
parameters
>titration parameters
meas.pt.density… 4
min.incr. ….100 ml
dos.rate ….5 ml/min
signal drift… 5 mV/min
equilibr.time …60 s
start V: ….OFF
pause ….60 s
dos.element:…. internal D0
meas.input: ….1
temperature… 25.0 °C
>stop conditions
stop V: ….abs.
stop V ….12 ml
stop U…. OFF mV
stop EP …9
filling rate max….. ml/min
>statistics
status:… OFF
>evaluation
EPC …10
EP recognition:…. all
fix EP1 at U …OFF mV
pK/HNP: ….OFF
>preselections
req.ident: ….OFF
req.smpl size:…. OFF
activate pulse:… OFF
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'fm
751 GPD Titrino 15215 751.0010
DET U Tenside
>calculations

Nonionic=EP1*C01*C02/C00;4;meq/g

C00= 0.5145
C01= 0.01
C02= 20
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