I'm using the ferric ion spectrophotometric method for thiocyanate determination and seem to be getting false positive readings.
The sample contains significant chloride which I am aware can bleach the color of the ferric-thiocyanate complex, but what might cause the opposite?
I have read that glycols can intensify the color and as the process involved usesa glycol based defoamer, this might be a possible cause, but I'm not sure the glycol concentration in the water samples would be high enough to have a measurable effect.
The process is a bacterial water treatment for thiocyanate degradation. Nutrients are potassium phosphate and molasses. The molasses contributes a faint color to the water sometimes but not enough to account for the higher than expected thiocyanate levels.
The discrepancy isn't huge but is enough to be a problem for our particular application. We expect
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