Bromide
Br⁻The ELIT bromide electrode offers wide pH tolerance and low detection limits for bromide determination in water and industrial samples.
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 Ion | Selectivity Coefficient | Notes |
|---|---|---|
| Silver (Ag⁺) / Sulphide (S²⁻) | very high | All poly-crystalline membranes — unreliable in presence of Ag or S ions. |
| Cyanide (CN⁻) | very high | Must be absent or at insignificant levels. Removable by adding 1 ml 0.1M NiSO₄ per 100 ml (also add to standards). |
| Iodide (I⁻) | very high | Must be absent or at insignificant levels. |
| Chloride (Cl⁻) | ~0.002 | — |
| Hydroxyl (OH⁻) | 0.00003 | — |
Apparatus Required
- Ion-Selective Electrode: ELIT 8271
- 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, 0.1 ppm Br solutions. For high ionic strength samples (> 0.01 M), add 2 ml ISAB to each 100 ml standard.
Sample Preparation & Measurement
Low ionic strength: immerse in 50–100 ml sample. High ionic strength: add 2 ml ISAB to 100 ml sample and stir well. If CN or S present, add 1 ml 0.1M NiSO₄ to all standards and samples.
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.
- Cyanide and sulphide can be removed by adding 1 ml of 0.1M nickel sulphate per 100 ml (add equally to all standards).
- Wide pH operating range (1–12) makes this electrode suitable for a broad range of sample types.