European Commission project Life & the Environment click here ISO 9001 :2008 quality  company	Aquaculture & Aquaria Environmental & sustainable water treatment by Marine Biologists	| Homepage | Contact us  | Search  |   Shop ||
| DrydenAqua homepage |  AFM homepage  | Aquaria homepage | Fish Farms homepage |quarantine systems | Oxygen probes  |  Air diffusers  |  Ozone  | Mechanical filtration

Waters are susceptible to change as a result of physical, chemical or biological reactions which may take place between the time of sampling and the analysis. If precautions are not taken, at the time of sampling, changes may occur rendering analytical data unrepresentative. Changes may occur due to: consumption of certain constituents by bacteria, algae etc., certain compounds being oxidised by the dissolved oxygen in the sample, precipitation from the liquid, eg. calcium carbonate, aluminium hydroxide, loss into the vapour phase, absorption of carbon dioxide from the air, changing the pH value, adsorption of metals and certain organic compounds on to the container's surface, depolymerisation of polymerised products and vice versa.

water samplers

These changes will be affected by the storage temperature, exposure to light, the nature of the container used and the time between sampling and analysis. In adverse conditions, changes can occur in just a few hours.

Fortunately, preservatives are available to prevent these changes. However, it must be borne in mind that methods of preservation are less effective with heavily contaminated samples than with those with light contamination.

General Considerations

Always fill sample containers to the brim and stopper them so that no air is left above the sample.

Use an appropriate container. For example. polyethylene bottles should not be used for hydrocarbons, since adsorption on to the bottle's surface is likely to occur.

Glass containers are suitable for most determinations. Brown bottles should be used since this will reduce photosensitive reactions to a considerable extent.

Containers must be clean. Whilst this may seem obvious, scrupulous cleanliness is important due to the low detection levels now being adopted.

Samples should be kept at a temperature below that at the time of filling. Cooling between 2 degrees and 5 degrees (i.e.. in melting ice, refrigerator or cool bag with ice packs) is adequate. It is not suitable for long-term storage.

Suspended matter, sediment, algae and other micro-organisms should be removed at the time of sampling by filtration or centrifuging or immediately on receipt at the laboratory. Filtration should not be carried out if the filter is likely to retain one or more of the constituents to be analysed.

Generally filtration is achieved by use of 0.45 micron filter paper.

The following table gives an indication of the sample container and preservatives for a variety of parameters.