Firstly, I would ask the lab ...
Published by Adam Garland, Chief Science Officer at Water Lens
Firstly, I would ask the lab that ran the sample what their LOD and LOQ is for arsenic. They may quote you these values as they apply to the machine used for the measurment, most likely ICP if it is an environmental lab. I would also check, if it is an environmental lab, what the NELAP certification requirements are for the measurement of arsenic in water. These requirements tend to be significantly less precise than the precision of the instrument itself and are more representative of the precision of the result you received from them.
Secondly, I wouldn't trust a result from a single run of a field kit for arsenic. Any individual run of a field kit analysis can be influenced by mistakes/interferences and could be an outlier. Repeat the field kit diagnostic multiple times (at least 3) and average the results together. Compare these results with the information you get from the lab to determine if you truly have an arsenic problem.
1 Comment
Thank you Adam this is very useful - can you explain briefly the significance of the LoD, Loq and NELP would have on the results- i already repeated the arsenic test on the first sample within 20mins of the first result - it gave the same mg/L as the first one, 2 days later i went to the field and did the test in-situ as well as recorded the temp of the water to make sure it was within the range the manufactures of the portable test kit recommended and it was- and got the same results as the first test, then 10 days later a rd sample was taken and tested the next day, again recording the temp of the water - all 4 test came back with the same results
Published by Bibi Lamond