Detection and quantification are different

A laboratory may observe a signal consistent with an analyte without assigning it a sufficiently reliable quantity. Results can therefore be detected but below the quantification limit. Reports must distinguish these from absence of a signal and state the criterion used. An estimated numerical value does not acquire the same quality as one within the validated range.

Units change interpretation

Limits may be expressed as mass per sample or concentration. In active sampling, converting mass to concentration requires the effective air volume. Two samples analysed with the same procedure may have different air quantification limits if collected volumes differ. Units must always accompany the value.

Plan useful sensitivity

Before an occupational hygiene measurement and sampling survey, the laboratory is asked whether it can quantify within the range of interest. Increasing volume indiscriminately is not a solution: it can overload a filter or exceed sorbent capacity. A method compatible with sensitivity, duration and collection capacity is needed.

Handling results below the limit

Results are not automatically replaced by zero or half the limit in every assessment. Treatment depends on the objective and applicable statistical or regulatory procedure. Retaining the censored result and its limit prevents a database from turning an analytical limitation into false certainty of zero exposure.

False reassurance example

In a hypothetical example, a company receives a non-quantifiable result, but the quantification limit exceeds the concentration it needed to check. The sample does not demonstrate that the objective is met. The technician requests a more suitable method or redesigns sampling; repeating a conclusion of absence provides no new information.

What to review with the laboratory

It is useful to confirm how both limits were determined, whether they cover the complete method and whether the matrix has interferences. Reports must state working range and relevant restrictions. This review supports choosing measurement capable of guiding decisions, instead of discovering afterwards that the method lacked sufficient sensitivity.