No matter how much I read here about getting consistent 10ml samples, holding the dropper bottle vertical, removing static, dropping slowly, constantly swirling, using the proper amount of powder, etc.......I am just not able to get consistent FC readings. From the same sample, if I do multiple tests, I get about a 1 ppm deviation in readings with an FC of about 12.0. That seems pretty bad.
I don't know, I guess 1ppm is not that critical unless I'm doing an OCLT. But my lack of consistency at relatively low FC levels, leaves me no confidence in my ability to perform an accurate OCLT at higher FC levels.
From everything I've read, I seem to be having trouble with 2 of the recommendations.....
1) Vertical dropper bottle: When I keep it vertical, the first several drops just flow out on their own by gravity, without even squeezing, so I have no control over the rate. At first they come out very fast and then after several drops, I need to squeeze a little so I am able to retain drop control. I seem to be able to get more consistent results by NOT holding the dropper in a vertical position as I seem to have more control. While this may be more consistent, I'm not sure it is accurate.
2) constant swirling while dropping: I drop with my right hand and I am not coordinated enough swirl with my left hand while dropping. Is constant swirling critical or can I drop 5 drops then swirl?