A potentiometric Method for the Determination of 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

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