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Table 1 Checks for feature consistency and quality

From: Volatile organic breath components and exercise induced bronchoconstriction in asthmatic children

Check Resolution
Qualifier and quantifier ions were specific for a feature across all samples to prevent misidentification, particularly for those ions selected for calculating peak area Alternate related ions identified and examined for specificity or feature removed
Ions correlated in RT to within 1.5 s within a single sample and 15 s between samples Selected ions were removed or added to ensure criteria was met
Correlating peak shape and time alignment between all qualifier and quantifier ions Ions not possessing matching peak shape were removed
RT extraction window was checked for consistency across all samples RT window adjusted to ensure peak area was correctly captured in all samples
Ion ratios between selected fragments were flagged if outside ± 15% of the target ion ratio If ion ratio consistency could not be achieved across multiple samples, the feature was removed.a
Feature present in at least 5 samples If not present in at least 5 samples, feature was removed
  1. aThis criterion was relaxed for the lowest intensity samples (~ 103 counts on the EIC) as the ratio error increased and in cases where there was an interfering peak on the secondary ion but not with the ion which was selected to have its area extracted