A sample of pure water was spiked with 0.590 ng/mL silver ion. Ten replicate determinations of the spiked water sample gave 0.600 , 0.580 , 0.557 , 0.543 , 0.584 , 0.564 , 0.568 , 0.572 , 0.550 , and 0.535 ng/mL silver ion. Determine the mean percent recovery of the spike and the detection limit of the analytical method used for the silver ion determination.