ICP-OES LOQ value, for example Cd : 1 ug/L (ppb). Sample reading 0.5 pbb. (Sample prepared 0.5g/50mL). In this scenario, should I report result (0.5 ug/L(1000mL) x50mL/0.5g=0.05ug/g) or Less Than LOQ. How should I compare with LOQ concentration, with reading or calculative result?
The reporting format will usually be given by the SOPs of the organization/company. Typical ways of reporting results below LOQ are:
Dear Ma Salim,
Thanks for your nice and critical question. Actually, when you are injecting the real samples practically in few cases you may have detected few samples contaning analyte conc. below LOQ but above the LOD. In that case, you are able to report this samples mentioning that for example, out of 100 samples 5 samples contained residues below LOQ, but above the LOD, however, you can not count this samples along with the no. of positive samples. The positive samples should contained your desired analytes at or above LOQ as at the time of method development and validation you have declared your LOQ, so, you are not allowed to quantify your compound below that level, but you are able to report them.
If the sample is similar that the one when the LOQ was set, then you should report "Result < LOQ of 1 ppb" You might add, LOQ is based on 10 or 20% imprecision.
In addition you should add, results are probably not negative( so analyte is probably not absent), since the result is > LOD.
Depending on the importance of the analysis, you could ask the client if he wants a multi-analysis on the same sample. For example a triplicate of analysis or a five fold analyis improves your precision and may lead to a reportable result.
Dear M A Salam,
Did you read my answer in above. I hope it will be helpful for you.
Dear Jameson Dondo,
Thanks for your contribution. I would like to say you that when you develop a method you have to declare the LOQ and below LOQ you can not count the sample as a positive sample. I would like to request you please read my answer presented above.
If your value is below LOQ and above LOD, then it is better to report the actual value with a remark that it is below LOQ. If it is below LOD, then it can be reported as ND (Not Detected).
Dear R.Girijan Menon,
Thanks for your clarifications, I have also mentioned the same in avobe.
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