Table 1 Checks for feature consistency and quality

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