Maximum Residue Limit Proposals 'at or about the Limit of Analytical Quantitation'

Residue Guideline No. 4
February 2000

Maximum residue limit proposals

Definition

At or about the limit of analytical quantitation (LOQ), previously called  'at or about the limit of analytical determination', is the lowest concentration of a pesticide residue in a defined matrix where positive identification and quantitative measurement can be achieved using a specified method.

It is expected that such a limit of analytical quantitation will be at the level of 0.05 mg/kg or less.

The method must be sufficiently sensitive to accommodate pesticides that have low ADIs, e.g. an active where the LOQ is set at 0.002 mg/kg because the ADI is 0.0002 mg/kg/d.  Furthermore, it is appreciated that matrices may make it difficult to have the LOQ as low as 0.05 (e.g. hops).

Evaluation of Data to Decide on LOQ

In practical terms the LOQ is the lowest concentration where quantitative recoveries are achieved.

The word 'quantitative' in this context is defined as recoveries being in the range 70-120%. If substantial recovery data is available, a practical specification is defined as: 80% of recovery values at the LOQ to be between 70 and 120%; and all recoveries at the LOQ to be between 60 and 130%.

(Recoveries should also be determined at levels where residues are likely to occur).

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