2011-04-04_REVISION - M1987143 - Laserfiche WebLink

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filtration because the elapsed time between sample collection and filtration greatly increases the risk of chemical alteration of the sample. Filtration can be a difficult task for those inexperienced, one of the many reasons why water sampling is best done by qualified individuals. Field parameters: Certain parameters are best measured in the field due to changes that start to occur to the water sample immediately after removal from its natural environment. Parameters that must be measured in the field are: • pH • Dissolved oxygen (not essential to most sampling programs, but may be part of some sampling and analysis plans, such as for in-situ uranium mines; during measurement of ground water DO, the sample must not be allowed to come in contact with the atmosphere) • Electrical Conductivity (aka Specific Conductance) • Oxidation-Reduction Potential (not always reliable and not necessary if dissolved oxygen is measured; measurements should be considered qualitative only; during measurement of ground water DO, the sample must not be allowed to come in contact with the atmosphere) • Suspended Solids (if required by the sampling and analysis plan) • Temperature • Turbidity (if required by the sampling and analysis plan) Parameters that are best measured in the field, but are not essential and are generally included only if the sampling and analysis plan requires them: • Alkalinity (can be analyzed by the lab from the anion container, but holding times must be observed) • Salinity (if required by the sampling and analysis plan) Holding Times: All analytes must be analyzed within a specific holding time, beyond which the data may be invalid. Assuming the samples have been properly preserved, holding times are as follows: Alkalinity 14 days Cyanide 14 days Ammonia 28 days Anions 28 days Mercury 28 days Nitrate, Nitrite, or Nitrate + Nitrite 28 days Dissolved metals 6 months Total metals 6 months Detection Limits: Detection limits must be below the regulatory limits or DRMS will reject the data. When presented with several alternative methods for analysis of their water samples, uninformed operators may make the mistake of selecting the least expensive analytical procedure without the knowledge that the method detection limits may be higher than the regulatory standard for some parameters. A recent example included an operator who used analytical method 6010B (ICP-AES) for water analyses. But the detection limits for all analytes reported were at or above the regulatory limits, rendering the data useless. Mistakes such as this may be avoided by referring to the regulatory