Human K3EDTA whole blood spiked with working solutions (at LQC and HQC level) were prepared and after spiking spiked sample was split into two aliquots (A and B).
Sample batches consisted of 15 field samples plus three quality control (QC) samples: a lab duplicate, a solvent method blank, and a duplicate spiked sample (spiked with either 50 ng or 250 ng) or solvent spiked sample (100 ng/analyte).
Each consisted of 10 standards (0, 1, 2, 5, 10, 25, 50, 100, 200, 400 ng ml−1), seven reagent blanks, one or two reagent blank spikes, two unspiked sample replicates, two spiked sample replicates and about 20 samples, each analysed in duplicate, per batch.
Each analytical batch consisted of 10 standards (0, 0.05, 0.1, 0.25, 0.5, 1.0, 2.0, 5.0, 10 and 20 ng ml−1, seven reagent blanks, one or two reagent blank spikes, two unspiked sample replicates, two spiked sample replicates, duplicates of a milk powder SRM (NIST 1545) and duplicates of about 20 samples.
While detection of all other miRNAs remained unaffected, in the 33 pM spiked sample there was a slight cross reaction between let-7e spike-in and other let-7 family members resulting in 1.3 to 1.9 fold difference compared to the 3.3 pM control.
Endogenous values determined for the untreated sample were subtracted from that of the spiked sample and recovery was calculated as a percentage of the nominal spike level (2,200 pg/mL).
The applicability of the new electrode was demonstrated on the analysis of tap water (spiked sample).
