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Help I clearly shouldnt be doing a degree in forensics if I cant do this!! A suspect in a shooting incident had his hands swabbed with 5% nitric acid. The swabs were then extracted into 20 cm3 of nitric acid. A portion of the sample solution was analysed by atomic emission spectroscopy and a response of 125 mV obtained. Next a 0.100 cm3 of a standard solution containing 40 µg of lead per cm3 was added to 10 cm 3 of the sample solution and the analysis repeated. A response of 157 mV was obtained from the "spiked" sample. Calculate the amount of lead recovered by the swabs in µg.

I have this question to do.. and I've been stuck on it for AGES! Please help! Calcium in a sample solution was determined by atomic absorption spectrophotometry. A stock solution of calcium was prepared by dissolving 3.668 g CaCl2.2H2O in water and diluting to 1000 cm3. This was diluted 1:10. Standards were prepared by diluting the second solution, respectively, 1:20, 1:10 and 1:5. The sample solution was diluted 1:25. Strontium chloride was added to all solutions before dilution. Absorbance signals, when the solutions were aspirated into an air-acetylene flame, were as follows: standards, 9.1, 18.6, 37.0; sample 20.9. What was the concentration of calcium in the sample in parts per million?