Each digestion batch contained a reagent blank to allow background
correction. CRM were measured regularly throughout the
duration of the experiment. Calibration blank (2% v/v nitric acid)
and quality check (QC) standard (i.e., a mid-concentration calibration
standard) solutions were measured every 20 and 15 samples
during ICP–OES and ICP-MS analyses. Matrix effects on sample uptake
and nebulisation were monitored by internal standardisation
with yttrium (ICP–OES) and rhodium (ICP-MS), and measurements
automatically corrected by the respective ICP software. Peanut
samples were grown as triplicate sub-samples in the field. Each
of these sub-samples was digested and analysed in duplicate