Dear Editor: I would like to comment on the article in your latest Industrial WaterWorld (see "Chlorine Testing Critical in Food Processing Applications," July/August 2004). The article was very good, but I am concerned about two points.
The authors mention the use of orthotolidine in chlorine testing. This chemical is considered a carcinogen per (California's) Proposition 65 and is very acidic. This should have been mentioned or this option should not have been presented. The second point is that high levels of chloramines, as encountered in processing waters, will "break through" to the free chlorine reading unless a minor modification of the test is done to freeze the free chlorine reading. The article's example of 3.0 ppm total, with 0.2 ppm free and 2.8 combined is a typical scenario for chloramine breakthrough.
As a side note, there was no mention of high range chlorine test strips. Although these only test total chlorine and aren't as precise as field kits, they seem to be the easiest and most popular way to monitor chlorine concentrations in the fresh-cut industry. Thank you.