Analytical Chem istry - DePauw University

Chapter 10 Spectroscopic Methods659sampleabsorbance2.5-mL sample + 2.5 mL of 0 ppb Mn 2+ 0.2232.5-mL sample + 2.5 mL of 2.5 ppb Mn 2+ 0.2942.5-mL sample + 2.5 mL of 5.0 ppb Mn 2+ 0.361Report the parts per billion Mn 2+ in the sample of seawater.37. The concentration of Na in plant materials may be determined by flameatomic emission. The material to be analyzed is prepared by grinding,homogenizing, and drying at 103 o C. A sample of approximately 4 gis transferred to a quartz crucible and heated on a hot plate to char theorganic material. The sample is heated in a muffle furnace at 550 o Cfor several hours. After cooling to room temperature the residue is dissolvedby adding 2 mL of 1:1 HNO 3 and evaporated to dryness. Theresidue is redissolved in 10 mL of 1:9 HNO 3 , filtered and diluted to50 mL in a volumetric flask. The following data were obtained duringa typical analysis for the concentration of Na in a 4.0264-g sample ofoat bran.sample mg Na/L emission (arbitrary units)blank 0.00 0.0standard 1 2.00 90.3standard 2 4.00 181standard 3 6.00 272standard 4 8.00 363standard 5 10.00 448sample 238Determine the mg Na/L in the sample of oat bran.38. Gluodenis describes the use of ICP atomic emission to analyze samplesof brass for Pb and Ni. 32 The analysis for Pb uses external standards preparedfrom brass samples containing known amounts of lead. Resultsare shown in the following table.%w/w Pb emission intensity0.000 4.29 10 40.0100 1.87 10 50.0200 3.20 10 50.0650 1.28 10 60.350 6.22 10 60.700 1.26 10 732 Gluodenis, T. J. Jr. Am. Lab. November 1998, 245–275.