Compounds with multiple halides in the solution may show interference from these other halides. It may be hard, to impossible, to read both accurately. Other elements may also cause interference with the electrode.
| Chloride | OH-, Br-, I-, S-2, CN-, NH3 and S2O3-2, Bi+3, Cd+2, Mn+2, Pb+2, Sn+2 and Tl+3 |
|---|---|
| Bromide | Hg, OH-, Cl-, I-, S-2, CN-, NH3 and S2O3-2, Bi+3, Cd+2, Mn+2, Pb+2, Sn+2 and Tl+3 |
| Fluoride | Al, Si, lots of H, Fe+3 |
| Iodide | Hg, Cl-, Br-, S-2, CN-, NH3 and S2O3-2, Bi+3, Cd+2, Pb+ |
Source: Orion™ Ion Selective Electrode manuals
The limit of detection of our pH/Ion meter is 0.2ppm for its calibration tables. Samples which need to be combusted or diluted up to volume for using with the electrodes need to be above the limit of detection.
Talk to the technician if you have theoreticals of less than 100ppm / 0.01%.
Halogenated solids are weighed out into a paper flag, which is then folded so as to fit into a platinum holder attached to the stopper of a Schöniger oxygen combustion flask. If the sample is in an air-sensitive capsule (aluminum capsules for bromine, chlorine or iodine analysis, tin capsules for fluorine), the capsule is weighed and then placed intact into the flag.
The flask contains an absorption solution based on the halogen to be analyzed and is purged with oxygen. The paper flag end is lit and the stopper/lit paper flag is placed into the oxygen-filled flask, sealing the flask tight. The flag and compound are then allowed to burn until consumed, trying to keep any unburned bits from falling into the absorption liquid. The fumes from the burned sample are allowed to absorb into the solution while the standard calibration curve for the upcoming analysis is performed, setting the limits for the ion meter. The analysis is then treated the same as liquid samples.
Calibration curves are created from standard solutions, which are used to calibrate the specific halogen’s ion-selective combination electrode and the Accumet pH/Ion meter. Strength Adjustment solutions are added to the calibration solutions and the sample solutions to aid in analysis. The sample solution is then analyzed and the resulting ppm is used to calculate the weight-percentage of the specific halide.