D. Step 2: Background corrections

Step 2: Background- and SBM zero-corrections, and 'total CPS' columns

The second step in the data-reduction is to correct ion-counts for measured background, and to perform the corresponding correction to SBM-counts using the measured SBM-zero value. These results are initially used to generate analysis-specific ‘total CPS’ columns for each of the measured species. These calculations are outlined in detail here.

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Calamari CSV (SQUID_02…)

In Calamari, these calculations culminate in the Calamari CSV file ‘SQUID_02…”, which is an array matching the contents of the ‘total [mass] cts/sec’ columns within the StandardData and SampleData worksheets of a SQUID-workbook. The output has one row per analysis, and one column per species. Its structure is described in detail here.

Value-by-value comparisons of the Step 2 outputs from SQUID 2.50 and Calamari for a specified demonstration XML file are documented at G. Synthesis of Steps 1–4: Cell-by-cell comparisons of SQUID 2.50 and Calamari output.

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Next: E. Step 3: Calculation of interpolated ratios of measured species