Spike recovery and detection limit. Species of arsenic found in drinking water include AsO3 3 - (arsenite), AsO43- (arsenate), (CH3)2AsO23- (dimethylarsinate), and (CH3)AsO32- (methylarsonate) Pure water containing no arsenic was spiked with 0.40 μg arsenate/L. Seven replicate determinations gave 0.39, 0.40, 0.38, 0.41, 0.36, 0.35, and 0.39 μg/L.15 Find the mean percent recovery of the spike and the concentration detection limit (μg/L).