A new method is devised to extract marijuana from hair for subsequent injection into a gas chromatograph.
An external calibration curve determined an unknown hair sample to contain 0.53 ng/g marijuana in hair.
A replicate portion of hair was spiked to 0.61 ng/g.
Analysis of the spike sample gave a concentration of 1.08 ng/g.
What is the percent recovery of the method (to the nearest 1%)?