If I test FC more than once on the same sample, it seems like my first test is always 1ppm (2 drops) lower than the second and third tests which are identical.
Every time when I finish testing, I rinse the cylinder and stir bar 2 or more times with RO water, shake them off and put them away. Before I run the first test, I rinse the cylinder and stir bar 2 or more times with the sample water and shake them off before filling to the 10ml mark and testing. Between repeat tests I rinse with RO water 2 times then with sample water 2 times then fill to the 10ml mark.
Thoughts?
Every time when I finish testing, I rinse the cylinder and stir bar 2 or more times with RO water, shake them off and put them away. Before I run the first test, I rinse the cylinder and stir bar 2 or more times with the sample water and shake them off before filling to the 10ml mark and testing. Between repeat tests I rinse with RO water 2 times then with sample water 2 times then fill to the 10ml mark.
Thoughts?