Limit of quantitation

The limit of determination or limit of quantification ( English limit of quantification , LOQ) is the lowest concentration of an analyte that quantitatively with a fixed precision can be determined. Quantitative analysis results are only given above the limit of quantification. The limit of quantification always has a higher accuracy than the limit of detection .

As with the detection limit , the criterion of the desired accuracy is usually related to the precision of the blank value , i.e. H. on the statistical error (expressed by the standard deviation ) of the measuring method with a zero measurement or blank measurement.

A measured value is often considered quantitative (determined) if the accuracy of the measurement is a factor of 3.33 higher (better) than the accuracy of the detection limit.

${\displaystyle {\text{Bestimmungsgrenze}}=y_{B}+10\cdot s_{B}}$

• ${\displaystyle y_{B}}$: Mean value of the background signal or blank value
• ${\displaystyle s_{B}}$: Standard deviation of the background signal or blank value

In an earlier version of DIN 32645 (from 1994) 9 times the standard deviation was still considered sufficient. As the factor 10 is much more widespread, it was increased in favor of standardization in the newer version of DIN (from 2008).

literature

• DIN 32645: 2008: 11 chemical analysis; Detection, detection and quantification limits; Determination under repetitive conditions; Terms, procedures, evaluation

Web links

• Quality assurance through DIN-compliant calibration

Individual evidence

1. ↑ DA Armbruster, MD Tillman, LM Hubbs: Limit of detection (LQD) / limit of quantitation (LOQ): comparison of the empirical and the statistical methods exemplified with GC-MS assays of abused drugs. In: Clinical chemistry. Volume 40, Number 7 Pt 1, July 1994, pp 1233-1238, PMID 8013092 .