Storage and disposal of chemicals

Essential information all laboratory managers and personnel should be familiar with about the storage and disposal of chemicals. This includes safe methods of use and the dilution guide.

Storage of chemicals


Read the University’s safe methods of use for the:

Disposal of chemicals


Compounds that must be disposed by a licensed contractor


The following list is of compounds that must be disposed by a licensed contractor. Please note that these compounds may not be discharged to sewer.

  • Compounds that are reactive - UN Class 4, UN Class 5.1 and 5.2 compounds.
  • Organic solvents - UN Class 3 Flammable liquids such as ethers, xylene, toluene, benzene, chloroform, acetone.
  • Compounds containing heavy metals - salts of silver, lead, nickel, osmium.
  • Compounds that are toxic - UN Class 6 compounds.
  • Compounds that are very acidic or very basic - acids and bases.
  • Buffer solutions containing Ethidium Bromide that have not been pre-treated to remove the ethidium bromide.
  • Untreated media that has had contact with infectious organisms or GMOs.
  • Mercury – for more information about the clean up and disposal of Mercury, please refer to the Mercury Safe Methods of Use.

To arrange the disposal of any of the compounds mentioned above, please contact:

David Jenkins
Hazards and Containment Manager
Ext: 86714
Email: d.jenkins@auckland.ac.nz

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Compounds that may be discharged to sewer without pretreatment


These compounds include:

  • buffer solutions pH 6- 10 provided they do not contain toxic organic compounds, salts of heavy metals, ethidium bromide or azides (TAE, SSC, TBE, Tris/HCl)
  • media solutions that have had no contact with infectious organisms or GMOs.
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Compounds that require pretreatment before discharge to sewer


Compounds that may be discharged after dilution at sink include:

  • buffer solutions pH 6 - 10 containing azide and have been diluted at sink by a factor of 20 (tap opened at standard bore flow)
  • small volumes of acid/base (<200 ml) provided that they have been diluted at sink with at least 8 litres of water (tap opened at standard bore flow for at least 2 minutes)
  • small volumes of concentrated ethanol, acetone, acetonitrile, methanol and formaldehyde (<200 ml) provided they are diluted at sink with the appropriate volumes of water at the sink
  • larger volumes of dilute solutions of ethanol, acetone, acetonitrile, methanol and formaldehyde provided they are diluted at sink with the appropriate volumes of water at the sink and are less than 2 litres
  • HPLC buffers provided that they contain no more than 70% Acetonitrile and provided they are diluted at sink with the appropriate volumes of water at the sink and are less than 2 litres.

Please note: standard bore flow is a tap opened to provide the greatest flow without significant splashing. The flow rate is approximately 4 litres per minute.

For further information about the appropriate volumes to dilute compounds with, please refer to the dilution guide.

Compounds that may be discharged provided that they have been pretreated:

  • buffer solutions, pH 6 - 10 containing Ethidium Bromide that have been pre-treated to remove Ethidium Bromide

  • Diaminobenzidine containing solutions that have been pre-treated to remove Ethidium Bromide
    • for further information, please read disposal of DAB.

  • all media used for E coli, yeast and human cells that has been pre-treated by chemical sterilisation (Sodium hypochlorite/Virkon) or autoclaved as prescribed in the Containment Manuals.
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Dilution guide


Formaldehyde (allowable limit is 5 g/l)


The required dilution can be achieved by using tap water for the following times (in minutes) provided that the volumes are less than 2 litres.

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  Volume to be discharged (litres)
  0.5l 1l 2l
4% Formaldehyde 1 min 2 min 4 min
3% Formaldehyde 1 min 2 min 3 min
2% Formaldehyde 1 min 2 min 2 min
1% Formaldehyde 1 min 1 min 1 min
Assuming a tap flow rate of 4 l/min.

Ethanol (allowable limit is 50 g/l)

The required dilution can be achieved by using tap water for the following times (in minutes) provided that the volumes are less than 2 litres:

  Volume to be discharged (litres)
  0.5l 1l 2l
70% EtOH 7 min 14 min 28 min
60% EtOH 6 min 12 min 24 min
50% EtOH 5 min 10 min 20 min
40% EtOH 4 min 8 min 16 min
30% EtOH 3 min 6 min 12 min
20% EtOH 2 min 4 min 8 min
10% EtOH 1 min 2 min 4 min

Assuming a tap flow rate of 4 l/min.

Methanol (allowable limit is 10 g/l)

The required dilution can be achieved by using tap water for the following times (in minutes) provided that the volumes are less than 2 litres:

  Volume to be discharged (litres)
  0.5l 1l 2l
70% Methanol 7 min 14 min 28 min
60% Methanol 6 min 12 min 24 min
50% Methanol 5 min 10 min 20 min
40% Methanol 4 min 8 min 16 min
30% Methanol 3 min 6 min 12 min
20% Methanol 2 min 4 min 8 min
10% Methanol 1 min 2 min 4 min

Assuming a tap flow rate of 4 l/min.

Acetonitrile (allowable limit is 2 g/l) 

The required dilution can be achieved by using tap water for the following times (in minutes) provided that the volumes are less than 2 litres:

  Volume to be discharged (litres)
  0.5l 1l
30% Acetonitrile 15 min  
20% Acetonitrile 10 min  
10% Acetonitrile 5 min 10 min

Assuming a tap flow rate of 4 l/min.

Discharging large volumes and/or high concentrations of acetonitrile should not be attempted.