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I'd rather not use mercury compounds in the classroom anymore, especially ones that I have to make!  Does anyone know of an alternative to test for ammonia that I previously used Nessler's Reagent for?  The lab is testing the influence of acidification on ammonification using B. cereus and P. aeruginosa grown in 4% peptone broth at pH 7.0, 5.5, and 3.5.


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Hi Audrey - you might want to try The Salicylate method as an alternative to Nessler's Reagent. I don't have an actual procedure for you, but here is some info I found on the following site: http://www.chemetrics.com/ammonia. As described below, the test typically involves the use of sodium nitro-ferricyanide, which is toxic. But, if you click on the link to the MSDS for the kit on the website, then it does not list nitro-ferricyanide, so perhaps they have found a better way. Here is a link to the MSDS with a list of ingredients: http://www.chemetrics.com/products/pdf/k1410_msds.pdf - it looks pretty good. It seems like a better option than Nessler's Reagent - but, again, we don't have a procedure for you, it would probably take some testing.

The Salicylate Method

References: Krom, Michael D., Spectrophotometric Determination of Ammonia: A Study of a Modified Berthelot Reduction Using Salicylate and Dichloroisocyanurate, The Analyst, V105, pp. 305-316, 1980.

In the ammonia test method that employs the Salicylate chemistry, free ammonia reacts with hypochlorite to form monochloramine. Monochloramine reacts with salicylate, in the presence of sodium nitro-ferricyanide, to form 5-aminosalicylate, a green-colored complex. This test method measures free ammonia and monochloramine. Results are expressed in ppm (mg/L) ammonia- nitrogen, NH3-N.

The Salicylate Method offers sensitivity similar to the Nesslerization Method and there is no generation of mercury-containing waste.


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