Analytical Equipment

Calibration_Review

3 min read

Calibration Review & Requantification — GCsolution

This page covers reviewing your calibration curve after a batch run, checking R², removing outliers, and requantifying unknowns with an updated method. For setting up calibration before running, see Quantification_Methods.

Evaluating the Calibration Curve

Step 1: Access the Calibration Curve Window

  1. Open the GC Postrun Analysis application (see Accessing the Postrun Application)
  2. Click the [Calibration Curve] icon on the Assistant Bar
  3. Open the method file (.gcm) that was used during your batch analysis — it now contains the updated calibration data

📋 From manual

Step 2: Check R²

The Calibration Curve window is divided into three areas:

  • Calibration curve graph — the plotted curve
  • Calibration curve data table — lists each level with its concentration and area
  • Calibration curve information — displays statistical results: the equation (e.g., Y = aX + b), the correlation coefficient (R), and the contribution rate (R²)

To view different compounds: click the [<] and [>] buttons above the graph, or select the compound ID directly in the Method view’s Compound Table.

📋 From manual

Step 3: Remove Outlier Points

If an outlier point is degrading your R² value, two methods are available. Both cause the software to automatically recalculate and re-plot the curve:

Method A — Uncheck the data point:

  1. In the Calibration Curve Table below the graph, find the outlier level
  2. Remove the check mark from its checkbox
  3. That level is immediately excluded — the graph re-plots with a new R² value

Method B — Delete the data file:

  1. In the [VERIFY: Data Explorer] view on the left, find the .gcd file assigned to the outlier calibration level
  2. Right-click → select Delete
  3. Confirm — the curve re-plots without that file’s data

📋 From manual

Step 4: Save the Updated Method

Once satisfied with the recalculated curve and R²:

File → Save Method (Data) File or Save Method (Data) File As…

The method file is updated with your modified calibration curve.

📋 From manual

Requantifying Unknown Samples

After modifying a calibration curve or compound settings, you can requantify unknowns without re-running them.

⚠️ Important: If you modified the calibration curve while viewing a specific data file in the Data Analysis window, those changes only apply to that file. To use the modified method on other samples, you must first save it as a standalone .gcm file by clicking the [Save Method] icon on the Assistant Bar.

📋 From manual

Requantifying a Single Sample

  1. Open the GC Postrun Analysis application
  2. Double-click the data file of your unknown sample from [VERIFY: Data Explorer]
  3. Select File → Load Method
  4. Select the .gcm method file containing your updated calibration curve
  5. The software automatically reanalyzes — new concentrations appear in the [VERIFY: Table] view
  6. File → Save Data File to save the updated results

📋 From manual

Requantifying Multiple Samples (Batch Post-run)

  1. Open the GC Postrun Analysis application
  2. Click the Batch Processing icon on the Assistant Bar
  3. Drag and drop the .gcd data files of your unknowns from [VERIFY: Data Explorer] into the batch table
  4. For each row, ensure Sample Type is set to 0:Unknown
  5. In the Method File column, enter the name of the updated .gcm file
  6. (If using Internal Standard): enter the IS concentration in the ISTD Amount column
  7. Click Start (green play icon)

The software sequentially processes each file, performs new quantitative calculations, and automatically saves the updated results.

📋 From manual

See Also

Graph View

Backlinks