A potentiometric Method for the Determination 0f Metals

A Potentiometric Method for the
Determination of Metals

Equipment
Potentiometer = 751 GPD Titrino / Titroprocessor
Electrodes = 6.0502.140 Cu²⁺ sensitive indicator electrode; input 1
6.0726.100 Ag/AgCl double junction reference electrode (KNO₃ sat.)

Reagents
c(Na₂EDTA) = 0.1 mol/L; D0

Sample
2 mL c(ZnSO₄) = 0.1 mol/L
5 mL buffer pH = 10
1 mL c(CuEDTA) = 0.1 mol/L
40 mL dist. Water

Remarks
· Calculations:

Content=EP1*C01*C02/C00;2;g/l

Content = content of metal in g/L
C01 = concentration of titrating agent (0.1 mol/L)
C02 = molecular mass of metal (65.38 g/mol)

. Answer

Content=2.006x0.1x65.38/2=6.56 g/L

EP1=2.006 mL
C00=2.000 mL

· Buffer pH = 10:
Dissolve 54 g NH₄Cl and 350 mL w(NH₃) = 0.25 (25%) in dist. water and fill up to 1 litre.

· Buffer pH = 4.7:
Dissolve 123 g Na-acetate and 86 mL acetic acid in dist. water and fill up to 1 liter.
· The following metals can be determined according to this method:
buffer solution molar mass
Water, total hardness (Ca + Mg) pH = 10… 64.40
Barium Ba pH = 10… 137.36
Cadmium Cd pH = 10… 112.41
Cobalt Co pH = 10… 58.94
Nickel Ni pH = 10… 58.71
Zinc Zn pH = 10…65.38
Lead Pb pH = 4.7…207.21

Literature
· Metrohm Application Bulletin No. 101: Complexometric titrations with the Cu ISE

Method documentation
'pa
751 GPD Titrino 15215 751.0010
DET U...Metals
parameters
>titration parameters
meas.pt.density… 2
min.incr. …10.0 ml
dos.rate max…. ml/min
signal drift …20 mV/min
equilibr.time …38 s
start V: …OFF
pause …0 s
dos.element:… internal D0
meas.input: …1
temperature …25.0 °C
>stop conditions
stop V: …abs.
stop V …10 ml
stop U …OFF mV
stop EP …9
filling rate max…. ml/min
>statistics
status: …OFF
>evaluation
EPC …5
EP recognition:… all
fix EP1 at U …OFF mV
pK/HNP: …OFF
>preselections
req.ident: …OFF
req.smpl size: …all
activate pulse: …OFF
------------
'fm
751 GPD Titrino 15215 751.0010
DET U …Metals
>calculations

Content=EP1*C01*C02/C00;2;g/l

C00= 2.0
C01= 0.1
C02= 65.38
------------
'fr
751 GPD Titrino 15215 751.0010
U(init)... -50 mV
DET U …Metals
smpl size… 2.0 ml
EP1 …2.006 ml… -145 mV
Content …6.56 g/l
stop V reached
============
'cu
751 GPD Titrino 15215 751.0010
start V 0.000 ml DET U Metals
1.0 ml/div dU=50.0 mV/div
============