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Standard Addition

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    1. A spectrophotometric method for the quantitative analysis of Pb2+ in blood yields an Ssamp of 0.193 when a 1.00 mL sample of blood is diluted to 5.00 mL. A second 1.00 mL sample of blood is spiked with 1.00 mL of a 1560-ppb Pb2+ external standard and diluted to 5.00 mL, yielding an Sspike of 0.419. What is the concentration of Pb2+ in the original sample of blood?









    1. An experiment looking for sodium content in blood serum uses a standard addition method. Each sample contained 25.00 mL of serum, a volume of 2.640 M NaCl standard and a total volume of 50.00 mL. The data below are obtained. What is the concentration of sodium in the sample?











    1. Sodium concentration may be determined by flame emission, but the flame emission is effected by a number of parameters including flow rates, temperatures and other variables that can be hard to control. To aid detection, lithium can be added as an internal standard. Using a constant 1000 ppm Li solution, the following response curve was constructed. If an unknown has a sodium to lithium intensity ratio of 0.0463, what is the concentration?


    Figure from Fundamentals of Analytical Chemistry by Skoog








    1. To test a glucometer, a spike recovery is carried out by measuring the amount of glucose in a sample of a patient’s blood before and after spiking it with a standard solution of glucose. Before spiking the sample the glucose level is 86.7 mg/100 mL and after spiking the sample it is 110.3 mg/100 mL. The spike is prepared by adding 10.0 μL of a 25 000 mg/100mL standard to a 10.0-mL portion of the blood. What is the spike recovery for this sample?






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