Your method can be taken into routine use when we you have an instruction (SOP) in you lab, the internal QC set up and a validation report covering the scope of your method, i.e. the matrices, and the concentration ranges.
- Reporting below LOQ. When further calculations shall be performed on the results, e.g. annual amount discharged calculated from daily results and flow, reporting below LOQ may be needed. We know that the result is somewhere between 0 and LOQ (could even be higher tan LOQ). The EU directive 2009/90/EU says the following in Article 5
Calculation of mean values
1. Where the amounts of physico-chemical or chemical measurands in a given sample are below the limit of quantification, the measurement results shall be set to half of the value of the limit of quantification concerned for the calculation of mean values.
2. Where a calculated mean value of the measurement results referred to paragraph 1 is below the limits of quantification, the value shall be referred to as ‘less than limit of quantification’.
3. Paragraph 1 shall not apply to measurands that are total sums of a given group of physico-chemical parameters or chemical measurands, including their relevant metabolites, degradation and reaction products. In those cases, results below the limit of quantification of the individual substances shall be set to zero.
So here is recommended to report half LOQ and an expanded uncertainty of LOQ/2.