So, if I am not mistaken 0.5 ug/ml is 0.197 mols per liter EtBr

this is an abstract from 

Ethidium bromide: destruction and decontamination of solutions. (Armour Method ( Lunn, G.and E. Sansone)

Ethidium bromide in water, TBE buffer, Mops buffer, and cesium chloride solution may be completely degraded by reaction with sodium nitrite and hypophosphorous acid. Only non-mutagenic reaction mixtures were produced. Destruction was greater than 99.8% in all cases; the limit of detection was 0.5 micrograms ethidium bromide per milliliter of solution. Ethidium bromide also may be removed completely from the above solutions by using Amberlite XAD-16 resin. The limit of detection was 0.05 micrograms ethidium bromide per milliliter of solution (0.27 micrograms/ml when cesium chloride solution was used).

I haven't tested this next method but maybe follow this reaction at slight molar excess of the neutralizing reagents.

What is the best way to dispose of ethidium bromide ... www.researchgate.net What is the best way to dispose of ethidium bromide solutions and gels?

Ethidium bromide: destruction and decontamination of ... www.ncbi.nlm.nih.gov 1. Anal Biochem. 1987 May 1;162(2):453-8. Ethidium bromide: destruction and decontamination of solutions. Lunn G, Sansone EB. Ethidium bromide in water, TBE buffer, Mops buffer, and cesium chloride solution

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From: ACS Division of Chemical Health and Safety <DCHAS-L**At_Symbol_Here**PRINCETON.EDU> on behalf of Penny Manisco <pmanisco**At_Symbol_Here**G.HMC.EDU>
Sent: Thursday, August 9, 2018 5:37 PM
To: DCHAS-L**At_Symbol_Here**PRINCETON.EDU
Subject: [DCHAS-L] Dilute Ethidium Bromide Disposal in California

 

Hello All,

There seems to be varying opinion on how to dispose of very dilute solutions of ethidium bromide. The concentration in question is 0.5 micrograms/ml of buffer. By hazardous waste definition, this  would not be considered a hazardous waste, but I believe some of our California universities and colleges recommend filtration of the ethidium bromide before disposal at any concentration.

Any guidance would be very much appreciated.

Sincerely,

--

Penny Manisco,
Chemical Hygiene Officer
Harvey Mudd College

(909)6074217

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