How are LOD and LOQ calculated in TargetLynx? - WKB12661

ENVIRONMENT

• MassLynx 4.1 and 4.2 and TargetLynx (also QuanLynx on older systems)
• Limit of Detection (LOD)
• Limit of Quantitation (LOQ)

ANSWER

1. The measured "chromatogram noise" (which can be displayed in TargetLynx) is converted into a noise area by dividing the noise by the ratio Peak Height [IS]/Peak Area [IS]. [IS = Internal Standard]

2. The noise area is converted into a peak response by multiplying the area by the ratio IS Concentration/IS Area.

3. The peak response is converted into a Limit of Detection (LOD) by multiplying the response by the LOD factor and dividing by the gradient of the calibration curve (linear calibration) or by the response factor (RF calibration).

It gets more complicated if target ions are being used in the calculations ("Use trace in response calculation" parameter is enabled):

• If they are including the Target peak in the primary compound response, the noise used in (1) is the target noise height + the primary noise height.
• If they are including the Target peak in the Internal Standard compound response, the "IS Area" used in (2) is the target [IS] area + IS area.

You should be able to do the calculation in Excel and produce the same result as in TargetLynx.

ADDITIONAL INFORMATION

Note: If no peak is found for a compound in sample, no LOD or LOQ is reported for that compound in said sample.