Potentiometric Determination of the Perborates in Detergents

Potentiometric Determination of the Perborates in Detergents

Equipment
Potentiometer = 751 GPD Titrino / Titroprocessor
Electrodes = 6.0420.100 LL combined Pt electrode; input 1

Reagents
c(KMnO4) = 0.02 mol/L; D0

Sample
5 mL sample solution
20 mL w(H2SO4) = 0.30 (30%)

Remarks
Determination reaction:

5 NaBO₂*H₂O₂ + 2 MnO₄^- + 6 H⁺ → 2 Mn²⁺ + 5 O₂ + 8 H₂O + 5NaBO₂

Calculations:

Perborat=EP1*C01*C02*C03*C04*C05/C00;2;%

Perborat = fraction of perborates in %
C01 = concentration of titrating agent (0.02 mol/L)
C02 = factor for “normality“ (5/2=2.5)
C03 = molecular mass of NaBO2*H2O2*3H2O (153.86 g/mol)
C04 = conversion mL L * factor for % (0.001*100 = 0.1)
C05 = factor for dilution (20)

Answer

Perborat = 1.289 x 0.02 x 2.5 x 153.86 x 0.1 x 20 / 2.5023 = 7.93 %

EP1 = 1.289 mL
C00 = 2.5023 g

Sample preparation:
Weigh 2.5 g in a measuring flask of 100 mL. Dissolve sample with c(H2SO4) = 1 mol/L and wait for the reaction of the carbonate. When gas evolution has stopped, fill measuring flask to the mark. Pipette 5 mL of solution, add 20 mL of w(H2SO4) = 0.30 (30%) and titrate. The 6.0431.100 Pt Titrode may be used instead of the 6.0420.100 LL Pt electrode.

Literature
G. Jander, K.F.Jahr, “Massanalyse“, Sammlung Gröschen de Gruyter, Berlin, New York (1973), p. 67

Method documentation

'pa
751 GPD Titrino 15215 751.0010
MET U …Perborat
parameters
>titration parameters
V step …0.10 ml

dos.rate max…. ml/min

signal drift …OFF mV/min

equilibr.time …10 s

start V: ….abs.

start V ….0.5 ml

dos.rate max…. ml/min

pause …30 s

dos.element:…. internal D0

meas.input: ….1

temperature ….25.0 °C

>stop conditions

stop V: ….abs.

stop V ….5 ml

stop U ….OFF mV

stop EP ….9

filling rate max…. ml/min

>statistics

status: ….OFF

>evaluation

EPC ….30 mV

EP recognition:…. all

fix EP1 at U ….OFF mV

pK/HNP: ….OFF

>preselections

req.ident: …OFF

req.smpl size:… OFF

activate pulse: …OFF

------------

'fm

751 GPD Titrino 15215 751.0010

MET U Perborat

>calculations

Perborat=EP1*C01*C02*C03*C04*C05/C00;2;%

C00= 2.5023

C01= 0.02

C02= 2.5

C03= 153.86

C04= 0.1

C05= 20

------------

'fr

751 GPD Titrino 15215 751.0010

U(init) 697 mV MET…. U Perborat

smpl size ….2.5023 g

EP1 ….1.289 ml 933 mV

Perborat…. 7.93 %

stop V reached

============

'cu

751 GPD Titrino 15215 751.0010

start V ...0.500 ml MET... U Perborat