Decontamination and Destruction of Aflatoxins in Laboratory Wastes
Two methods for the treatment of laboratory wastes contaminated with aflatoxins :
1. Treatment with sodium hypochlorite, NaOCl, Technical grade, 12% w/w or 48% w/v
2. Treatment with conc, H2SO4 and a saturated solution of Potassium permanganate, KMnO4.(about 0.4M soln. at room temp.)
Notes :
1. Wastes present in organic solvents are first evaporated to dryness under vacuum with rotary evaporator.
2. Wastes present in oils are first extracted with 1:2 methanol water and the methanol evaporated to dryness under vacuum using rotary evaporator.
3. Wastes present in water solutions are treated directly.
Treatment with Hypochlorite
A hypochlorite solution of about 1.3% w/w or about 5% w/v will degrade 20ug of pure aflatoxins. However, other components in the waste may react with sodium hypochlorite and efficiency of degradation should be checked.
Smaller volumes of stronger solution can be used but the final volume must have an excess of hypochlorite to dissolve and degrade the aflatoxins.
Aflatoxins in organic solvent
1. Evaporate to dryness. If solvent is DMSO, add an equal volume of dichloromethane and then evaporate to dryness.
2. Add small quantity of methanol dissolve residue and wet glassware.
3. Add xs (twice estimated amount required) of hypochlorite.
4. Shake and allow to stand for at least 2 hours or overnight.
5. Dilute this solution to reduce strength of hypochlorite to below 1.3%.
6. Add an amount of acetone equal to 5% of the total volume. (to destroy any 2,3-dichloro aflatoxin B1 which may be formed)
7. Allow to react for 30 minutes and discard. You can test for degradation due to abscence of fluorescence under UV light.
Aflatoxins in oil
1. Transfer waste to conical flask.
2. Add xs (twice estimated amount required) of hypochlorite.
3. Stopper flask and shake on shaker for at least 2 hours or overnight.
4. Follow steps 5 to 7 as outlined above.
Aflatoxins in water solutions.
1. Add twice the amount of hypochlorite required.
2. Follow steps 4 to 7 as outlined above.
Treatment with saturated solution of KMnO4
Decontamination is effected by means of reaction with potassium permanganate and concentrated sulphuric acid. (Caution! Exothermic reaction, add acid slowly with stirring to the water solution, preferably in water/ice bath. Put chromate waste solutions in labelled containers for proper disposal.)
10 ml of 0.1 mol/l potassium permanganate in 1 mol/l sulphuric acid will degrade 20 ug of aflatoxins in 3 hours. Other components in the waste may react with permanganate and turn purple color to brown.
Aflatoxins in organic solvent
1. Evaporate to dryness.
2. Add enough water to dissolve residue.
3. Add 10 ml conc. H2SO4 for every 100 ml water added (care!).
4. Add sufficient KMnO4 to retain purple color.
5. Leave to react for about 3 hours or overnight, and discard. You can test for degradation due to abscence of fluorescence under UV light.
Aflatoxins in oil
1. Extract each 100 ml oil waste twice with 150 mls. 2 to 1 methanol water mixture.
2. Combine the extracts and evaporate the methanol on rotary evaporator.
3. Follow steps 3 to 5 above.
Aflatoxins in water solutions
1. Proceed as in the instructions 3 to 5 above.
References :
1. M. Castegnaro et al: IARC Publications No.37 (1980)
2. Stoloff,L. & Trager W. (1965): J. Assos. of Anal. Chem.,48, 681-682
3. Trager, W. & Stoloff, L. (1967): J Agric.Food Chem.,15, 679-681
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