- 9 15 Points A 5 00 G Soil Sample Was Analyzed For Biologically Available Pb By Suspending 50 00 Grams Of Sample In 50 1 (34.78 KiB) Viewed 56 times
9. (15 points) A 5.00 g soil sample was analyzed for biologically available Pb by suspending 50.00 grams of sample in 500.00 mL of 2.4% (w/w) acetic acid. The sample is shaken in a mechanical wrist action shaker for 24 hours. The sample is then centrifuged, and the liquid phase is removed and filtered through a 0 Sum filter. The sample is analyzed by anodic stripping voltammetry. A 10.00 mL aliquot of the sample is placed into a 25.00 mL volumetric flask then 0 to 200 L of a 10 ppm Pb standard was added, followed by 100 ul. of 16 M HNO. The sample is then diluted to volume. The sample is quantitatively transferred to the electrolysis cell. The sample is analyzed on a static mercury drop electrode. Lead deposition occurs by applying a -700mV potential to the mercury drop for 4 minutes. The deposited lead is then stripped from the Hg drop using a square wave voltammetry (-700 V to -100 V). The current peak is recorded. The results from a series of analysis are presented below. What is the concentration of Pb in the sample in ppb and moll? What is the concentration of Pb in the soil (use ppm units or mg/Kg)? Note that the units of standard addition are ul. Pb by ASV y=1.43E-095.98E-OB 9.98E- 4.000E-07 3.500E-07 3.000E-07 2.500E-07 Signal (A) 2.000E-07 1.500E-07 1000E-07 5.000E-ON 0.000.00 0 50 200 250 100 150 uL of 10 ppm std