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Resources/Ion Guides/Copper

Copper

Cu²⁺

The ELIT cupric electrode provides excellent sensitivity for copper determination down to ppb levels. It is widely used in environmental monitoring, electroplating effluents, and water quality analysis.

Cation (+)ELIT 8227Valence: Divalent
Electrode Specifications
Model
ELIT 8227
Membrane Type
Solid-state crystal membrane
Ion Type
Monovalent cationDivalent cation
Molar Mass
63.546 g/mol — 1000 ppm = 0.016 M
Physical Size
130 mm body (excl. contact) × 8 mm diameter. DC resistance < 2.5 MΩ at 25°C. Min. sample volume: 5 ml.
Operational Specifications
Concentration Range
0.006 to 6,400 ppm (9×10⁻⁸ to 0.1 Molar)
Electrode Slope at 25°C
26 ± 3 mV/decade
pH Range
pH 2 to 7
Temperature Range
0 to 80°C
Response Time
< 10 seconds (90% response)
Potential Drift
< 3 mV/day in 1000 ppm (8 hours)
Reagents
Reference Electrode
Double junction (ELIT 003). Outer filling solution: 0.1M CH₃COOLi.
ISAB / Buffer
5M NaNO₃ — Add 2% v/v. ISAB should always be added to give a background matrix of ~0.1M NaNO₃.
Standard Preparation
Dissolve 3.929g copper sulphate pentahydrate (CuSO₄·5H₂O) in 1 litre deionised water.
Typical Applications
Environmental MonitoringIndustrial EffluentWater Quality MonitoringElectroplating IndustryResearch
Interference

The Selectivity Coefficient (SC) represents the approximate apparent increase in the measured concentration caused by 1 unit of the interferent. Effect (% error) = (interferent concentration × SC / analyte concentration) × 100.

Interfering IonSelectivity CoefficientNotes
Silver (Ag⁺) / Sulphide (S²⁻)very highAll poly-crystalline membranes contain Silver Sulphide — unreliable readings if Ag or S ions present.
Mercury (Hg²⁺)very highCan only be tolerated at very low concentrations relative to Cu.
Bromide (Br⁻)>1Causes significant negative error if present at > one tenth the copper concentration.
Chloride (Cl⁻)>1Causes significant negative error if present at > one tenth the copper concentration.
Standard Analytical Method

Apparatus Required

  • Ion-Selective Electrode: ELIT 8227
  • Reference electrode: Double junction (ELIT 003)
  • Dual electrode head (ELIT 201)
  • ELIT Computer Interface/Ion Analyser, or Ion/pH/mV meter
  • 150 ml polypropylene beakers, 100 ml volumetric flask, 1, 2, 5, 10 ml pipettes

Calibration

Calibrate with 1000, 100, 10, 1 ppm Cu solutions. Add 2 ml ISAB to each 100 ml standard and sample — the Cu electrode works most reliably with a ~0.1M NaNO₃ background matrix.

Sample Preparation & Measurement

Add 2 ml of 5M NaNO₃ to 100 ml of each sample before measurement. Wash electrodes between samples and allow 2–3 minutes stabilisation after immersion.

Results

Results are displayed as ppm and mol/l. If buffer solution has been added equally to standards and samples, figures will not need adjusting as all are affected by the same dilution factor. Allow 2–3 minutes stabilisation after electrode immersion. Wash and dry electrodes between samples to avoid cross-contamination.

Analytical Notes
  • ISAB addition is mandatory (not just recommended) for the copper electrode to ensure reliable performance.
  • Keep pH within 2–7 — outside this range electrode response becomes unreliable.