Table 5.

Extraction Recovery evaluation.

DBS
ZNS	<RZNS>, %	IS	<RIS>, %
low QC 0.375 µg/mL	103.24	20 ng/mL	101.11
medium QC 3.75 µg/mL	101.19		107.16
high QC 19 µg/mL	100.83		102.30
overall <R>, %	101.75	overall <R>, %	103.52
SD	1.30	SD	3.21
RSD, %	1.28	RSD, %	3.10
DPS
ZNS	<RZNS>, %	IS	<RIS>, %
low QC 0.750 µg/mL	101.62	20 ng/mL	103.19
medium QC 7.5 µg/mL	95.83		99.82
high QC 38 µg/mL	94.32		99.08
overall <R>, %	97.26	overall <R>, %	100.70
SD	3.58	SD	2.19
RSD, %	3.96	RSD, %	2.18

n = 3, where n represent number of replication per each QC level; <R_ZNS>—average value of ZNS extraction recovery, calculated by dividing average ZNS peak area from DMS (P_ZNS) with average ZNS peak area from post-extraction added working solution of ZNS (P_ZNSpe); P_ZNS/P_ZNSpe × 100; <R_IS>—average value of IS extraction recovery, calculated by dividing average IS peak area from DMS with average IS peak area from post-extraction spiked samples; overall <R>—average value of recovery calculated basing to the average Recovery value obtained for each QC level; SD—standard deviation of average Recovery values calculated for all QC levels; RSD—a coefficient of variation that represent the variation in average Recovery value of ZNS and IS calculated for all QC levels; The results indicated consistent and reproducible Recovery values, demonstrating the uniform contribution of the extraction procedure to ZNS quantification regardless the change in concentration, i.e., the extraction procedure was efficient and reproducible.