Storage of water samples

The effect of storage of water samples before determination of nitrogen and carbon associated with particulate matter was investigated. Freezing of the samples, and storage at 5°C, both affected the results obtained, but changes were minimized if the samples were filtered immediately after collection and the particulate matter stored on the filter paper. It is recommended that samples for determination of particulate carbon and nitrogen should be filtered immediately, and analysed as soon as possible. 

PRESERVATION AND STORAGE OF WATER SAMPLES FOR THE DETERMINATION OF ORGANIC COMPOUNDS... 

Sliwka-Kaszynska, M., A. Kot-Wasik, and J. Namiesnik. 2003. Preservation and storage of water samples. Crit. Rev. Environ. Sci. Technol. 33 31—14. 

Trichlorphon, Dichlorvos Discusses Trichlorophon degradation on storage of water samples [371]... 

Storage of water samples to detect trace metals is normally carried out in plastic containers fluorinated plastic materials i.e.. Teflon, fluorinated ethylene propylene (FEP), perfluoroalkoxy polymers (PFA) or polyethylene are used because if opportunely treated and conditioned they guarantee contamination-free samples. However, FEP or Teflon bottles are preferable to those made of polyethylene when speciation studies are carried out. In fact, polyethylene over long periods of storage can release plasticizers (above all phthalates or amines), which behave as ligands and modify the complexation equilibria of the solution. When Hg is to be determined plastic materials must be avoided because they are permeable to gases and vapours glass or quartz are therefore used. 

Once the water samples are collected, they should be stored at 4°C until extraction, which is usually performed within 48 h. Storage of water samples for longer periods may lead to degradation of target compoimds in water samples [50]. For longer preservation of water samples, chemical agents such as formaldehyde (1% v/v) and sulfuric acid (pH < 3) can be added to the water samples to prevent bacterial activity. 

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