VA Application Note No.
V-93
Title:
Cadmium, lead and copper in red wine
Summary:
For the determination of heavy metals in wine UV digestion is required to mineralize the sample. The determination of cadmium, lead and copper is carried out by anodic
stripping voltammetry (ASV) at the HMDE.
Sample:
Red wine (from Switzerland)
Sample preparation:
Pipet 1 mL wine into a digestion tube, then add 10 µL
w(HCl) = 30%, 2 mL ultrapure water as well as 2 mL
w(H2O2) = 30%. Place the sample solution in the 705 UV
Digester and irradiate for 2 h at 90 °C. After 1 h add another 0.5 mL w(H2O2) = 30%.
Determination of cadmium and lead
Electrolyte
Measuring solution
not required
The digestion solution (approx. 5.5 mL) is rinsed into the
measuring vessel with 1 mL ultrapure water.
Measuring vessel
Volume 5 ... 70 mL (6.1415.150)
Working electrode (WE)
MME (Multi-Mode Electrode) 6.1246.020
Auxiliary electrode (AE)
Pt 6.0343.000
Reference electrode (RE) Ag/AgCl/KCl (3 mol/L): 6.0728.020 + 6.1245.010
Parameters
V-93 Version 1.0
Working electrode
HMDE
Stirrer speed
2000 rpm
Mode
DP
Purge time
300 s
Deposition potential
–800 mV
Deposition time
60 s
Equilibration time
10 s
Pulse amplitude
50 mV
Start potential
–800 mV
End potential
–100 mV
Voltage step
6 mV
Voltage step time
0.1 s
Sweep rate
60 mV/s
Peak potential Cd
–560 mV
Peak potential Pb
–360 mV
1/3
Determination of copper
Electrolyte
KCl solution:
c(KCl) = 3 mol/L, suprapur
Measuring solution
Digestion solution (approx. 5.5 mL)
+ 1 mL ultrapure water
[analysis solution from the determination of Cd and Pb]
+ 0.5 mL KCl solution
Auxiliary electrode (AE)
Pt
Reference electrode (RE) Ag/AgCl/KCl (3mol/L)
Parameters
Results:
V-93 Version 1.0
Working electrode
HMDE
Stirrer speed
2000 rpm
Mode
DP
Purge time
300 s
Deposition potential
–700 mV
Deposition time
30 s
Equilibration time
10 s
Pulse amplitude
50 mV
Start potential
–450 mV
End potential
+75 mV
Voltage step
6 mV
Voltage step time
0.1 s
Sweep rate
60 mV/s
Peak potential Cu
–140 mV
Cd
Pb
Cu
0.31 µg/L
32 µg/L
51 µg/L
2/3
Determination of Cd, Pb and Cu
Substance: Copper VR(**)
I (nA)
I (nA)
Segment: CdPb_ASV VR(**)
50
30
40
25
20
30
15
20
10
10
5
0
-800
-700
-600
-500
-400
-300
-300
-200
-250
-200
-150
-100
-50
U (mV)
Standard addition curve: Lead
9
Standard addition curve: Copper
I (nA)
I (nA)
I (nA)
Standard addition curve: Cadmium
30
0
U (mV)
60
8
25
7
6
50
20
40
5
4
3
15
30
10
20
5
10
2
1
0
1
V-93 Version 1.0
2
3
rho(eff) (µg/L)
5
10
3/3
15
20
rho(eff) (µg/L)
10
20
30
40
50
rho(eff) (µg/L)