I am collecting surface water samples and storing them in a cooler and then a fridge before testing. I am testing the zinc, iron, nitrate, ammonia, nitrite, and sodium chloride concentrations in my samples. I unable to test all of these samples immediately. How long can I allow these samples to sit in the fridge for before receiving inaccurate measurements?
the metals should not be a problem.
Ammonia and Nitrate on the other hand might get if You have biomass involved. - So better freeze that down (-20). in a clean PP or PE bottle that should not be a problem.
Typically, water samples have a maximum holding time that ranges anywhere from six hours to six months.
Some attributes, however, require immediate analysis, such as the following:
- Dissolved oxygen
- pH
- Sulfite
- Temperature
- Total residual chlorine
It's depends on the parameters to be tested. pH, temperature, conductivity, turbidity etc should be done immediately (on site) for heavy metals 6 months if nitric acid is added, for oil and grease few weeks if sulphuric acid is added. Water to be analyzed for Heavy metals should not be stored in metal containers, samples for organics should not not be stored in plastics
Thank you everyone. So what I am getting is that my metal concentrations should stay stable, but the ammonia and nitrate concentrations might change if there is biomass involved. If I strain any biomass out of the sample will that increase the testing time? I am testing pH, temperature, conductivity and turbidity on site, but testing metal, nutrient and salt concentrations within the next couple of days, is this acceptable? Garuav H Tandon, you indicated that total residual chlorine should be analyzed immediately, is this the same for sodium chloride (salts)?
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