View source for Limit of Quantification LOQ - TX

===Limit of Quantification===
'''LOQ''' means '''Limit of Quantification'''.

It is the '''lowest concentration of a substance that can be measured with acceptable accuracy and precision by the analytical method'''.

== Simple explanation ==

* '''Below LOD''' → the lab cannot reliably detect the substance
* '''Between LOD and LOQ''' → the substance may be detected but cannot be measured accurately
* '''Above LOQ''' → the substance can be '''quantified and reported with confidence'''

== Example from a PFAS lab report ==

{| class="wikitable"
! PFAS compound
! Result
! LOQ
! Interpretation
|-
| PFOA
| &lt; LOQ
| 5 µg/kg
| If present, it is below 5 µg/kg and cannot be quantified reliably
|-
| PFHxA
| 8 µg/kg
| 5 µg/kg
| Measured concentration is reliable
|}

When a lab writes '''&lt; LOQ''', it means:

<blockquote>
The substance was '''not quantifiable above the method’s limit''', but small traces might still exist below that level.
</blockquote>

== Relation with LOD ==

{| class="wikitable"
! Term
! Meaning
|-
| '''LOD'''
| Limit of Detection – smallest amount that can be detected
|-
| '''LOQ'''
| Limit of Quantification – smallest amount that can be reliably measured
|}

Typical relation:

<pre>
LOD &lt; LOQ
</pre>

Example:

* LOD = 2 µg/kg
* LOQ = 5 µg/kg

== Why this matters for packaging compliance ==

In packaging lab reports such as PFAS, heavy metals, and migrants:

* '''Regulations compare limits against quantified values'''
* Results reported as '''&lt; LOQ''' are usually treated as '''not measurable at regulatory level'''

This is why '''LOQ must always be shown in the lab report'''.

It can also be useful to represent LOQ in a structured compliance dataset for PPWR technical files, instead of storing only PDFs.