Use an EZChrom calibration curve to quantify OpenLab CDS data
OpenLab CDS allows you to continue using a calibration curve that has been created in EZChrom. Follow the steps below if you cannot acquire calibration standards with OpenLab CDS, or if you want to benefit from the calibration standards acquired with EZChrom.
Use the EZchrom Migration Tool to migrate your EZChrom methods.
Import the migrated EZChrom methods.
Acquire your samples with OpenLab CDS, and process them with the imported method.
This tool aligns the different scales in EZChrom and OpenLab CDS.
The calibration curve is built with the information coming from EZChrom.
Please note the differences in quantitation between EZChrom and OpenLab CDS described below.
Last calibration date
Just after the import, the Last calibration date displayed in the method is the date and time of the import. After processing the samples, it is the date and time of the processing.
Disabled calibration points
The import does not differentiate between enabled and disabled calibration points. If you had disabled calibration points in EZChrom, you must disable them again in the imported method.
Forced origin
If the calibration curve is forced through the origin (Origin=Force), OpenLab CDS calculates the uncentered determination coefficient.
Residuals
If RF definition is set to Response per amount, residuals are calculated differently in EZChrom and OpenLab CDS.
In EZChrom, a residual is the difference between the concentration entered by the user and the concentration read from the calculated calibration curve.
In OpenLab CDS, the residual is the difference between the measured and the predicted response or amount (depending on the curve orientation).
If the RF definition is Amount per Response, residuals will be the same in OpenLab CDS and in EZChrom.
Response scaling
If the method contains compounds with Response scaling set to log(response) or sqrt(response), EZChrom and OpenLab CDS may use different algorithms.
Calculations differ in the scenarios described below.
Curve calculation is set to From average per levelCurve calculation is set to From average per level
In EZChrom, the log or the square root is applied to the averaged response:
In OpenLab CDS, the log or the square root is applied first the individual responses, and then the resulting values are averaged:
In EZChrom, first the response of the group is calculated by summing area or height of the peaks belonging to the group. Then the log or the square root is applied to this response.
In OpenLab CDS, the log or the square root is applied first to responses. Then the resulting values are summed.
Internal standards (ISTDs)Internal standards (ISTDs)
In EZChrom, first the ratio between the compound response and the ISTD response is computed. Then, the log is applied to the ratio.
In OpenLab CDS, first the log is applied to the responses. Then, the ratio is calculated.
Identified compounds in timed groups
The calculation for timed groups with identified compounds differ if the option Quantify each peak individually is selected.
In EZChrom, identified compounds for which no calibration settings are defined are not quantified.
In OpenLab CDS, identified compounds for which no calibration settings are defined are quantified with the group response factor or calibration curve of the group.