Sulfite Test Kits

Sulfite Test Kits as (SO3) comes in 1 drop = 2, 5, and 10 ppm.
Directions:

1. Fill the mixing bottle to 25 mL with the sample to be tested.
2. Add 6 drops of Phenolphthalein Indicator.
3. If the water does not change to red or pink, add one scoop of Starch Acid / Sulfite Indicator.
4. If the water turns pink or red, add one or to or more scoops until the pink or red disappears.
5. Add the potassium iodide-iodate titrating solution drop by drop, swirling the test bottle counting each drop until a permanent Blue/Black color appears.
6. Multiple the number of drops by the factor of the test for your results.

We have the M8447 Sulfite Test kit with a 2ppm drop count but when we do the test we don't get any changes (no pink, no blue, etc.). What could be the issue?
Our suspicion is that the range of the sample you are testing is out of range based on the test kit you are using. So couple of things I would suggest. First of all take some tap water and run it as if it was your sample. There is no sulfite in tap water so you should get a color change just by using the Phenolphthalein Indicator Solution. If you get a color change on the tap water then odds are the sample you are trying to test has too much Sulfite and the test kit at 1 drop = 2ppm is too low to be able to read it.

If the reagents are fine (based on getting the color change on tap water). We would recommend taking the sample you want to test and dilute it in half with tap water, then take a 25ml sample of that diluted sample and run the test. That hopefully should bring it into range to run the test. If it does and you get a result, at the end result let’s say you titrate with 10 drops (10 x 2 = 20ppm) then you take the 20ppm and multiply that by 2 since you diluted the sample in half so it would give you a total of 40ppm.