| Test Parameter |
|
Description |
| Alkalinity |
|
High halogen level may change indicator reaction from green/red to blue/yellow; to prevent, add thiosulfate prior to testing. |
| Alkalinity |
|
Some pH modification treatments (e.g., addition of sulphuric acid) may cause interference. |
| Chloride |
|
Sulfide, bromide, orthophosphate, and iodide titrate as chloride causing positive interference; to prevent, test for suspected interfering agent, dilute sample with DI water as necessary, and retest. |
| Hardness |
|
Metal ions may cause interference; to prevent, add titrant containing EDTA to sample before buffer and indicator, then test as normal making sure to count drops of titrant added initially in total required to reach endpoint. If interference still occurs, dilute sample with DI water as necessary and retest. |
| Molybdenum |
|
Test should be run on clean, clear sample; filter out colloidal color and turbidity before beginning test procedure. High concentrations of HEDP (over 30 ppm) may cause positive interference; to prevent, test for interfering phosphonate, dilute sample with DI water as necessary, and retest. Thiocarbamate-based biocides may cause interference; to prevent, do not test while feeding thiocarbamates into water system. Sodium nitrite over 800 ppm may cause negative interference; to eliminate, dilute sample with distilled, deionized, or molybdenum- and nitrite-free water then retest. |
| Nitrite |
|
Glycol may cause interference; to prevent, use "CAN" test method (cerium oxidation of nitrite) on glycol-treated systems. |
| Phosphonate |
|
Iron > 10 ppm may cause negative interference. Ortho- and polyphosphate may cause positive interference; to prevent, test for interfering agent, dilute sample with DI water as necessary, and retest. |
| Silica |
|
Iron may cause positive interference; to prevent, dilute sample with DI water as necessary and retest. Sulfide and tannin may cause negative interference; to prevent, dilute sample with DI water as necessary and retest. |
| Sulfite |
|
Sulfide and ferrous iron may cause positive interference; to prevent, test for suspected interfering agent, dilute sample with DI water as necessary, and retest. Copper and nitrite may cause negative interference; to prevent, test for suspected interfering agent, dilute sample with DI water as necessary, and retest. Delay between taking sample and testing may cause negative interference; to prevent, perform test immediately after sample is taken. |