You were assigned to determine the concentration of an unknown starch solution. [This unknown is different from Dr. Ford's unknown.] So you prepared a cuvette by mixing 5 drops of your unknown starch solution + 5 drops of water +3 ml buffer +1 drop of lodine. You used the same spectrophotometer Dr. Ford used to measure the absorbance of your unknown starch mixture and the absorbance was 0.127. What is the concentration (in micro-g starch/micro-L) of your unknown starch solution? Assume that 1 drop of the unknown starch solution = 40 micro-L. Give a numerical answer with 3 sig figs without any unit. Answer:

You were assigned to determine the concentration of an unknown starch solution. [This unknown is different from Dr. Ford's unknown.] So you prepared a cuvette by mixing 5 drops of your unknown starch solution + 5 drops of water +3 ml buffer +1 drop of lodine. You used the same spectrophotometer Dr. Ford used to measure the absorbance of your unknown starch mixture and the absorbance was 0.127. What is the concentration (in micro-g starch/micro-L) of your unknown starch solution? Assume that 1 drop of the unknown starch solution = 40 micro-L. Give a numerical answer with 3 sig figs without any unit. Answer:

Principles of Instrumental Analysis

7th Edition

ISBN:9781305577213

Author:Douglas A. Skoog, F. James Holler, Stanley R. Crouch

Publisher:Douglas A. Skoog, F. James Holler, Stanley R. Crouch

Chapter15: Molecular Luminescence Spectrometry

Section: Chapter Questions

Problem 15.7QAP

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In a Bradford assay, 11 µl of a protein isolate sample was diluted by adding 21 µl of water prior to the addition 2.0 mL Bradford reagent. Calculate the protein concentration (in mg/mL) of the original protein isolate sample whose absorbance reading at 595 nm is 0.304 after dilution. The protein standard solutions used for the calibration curve of the Bradford assay was constructed using bovine serum albumin (BSA) stock solution whose concentration is 200 µg/mL. The concentration and the corresponding absorbance reading at 595 nm of the protein standard solutions are summarized in the table below: Standard soln # 1 2 13 4 6 conc of BSA 12.00 24.00 36.00 48.00 60.00 (pg/mL) Absorbance at 595 nm 0.000 0.156 0.249 0.328 0.411 0.528 zNote: Final answer format must be x.xxx (three decimal places). Round off only in the final answer. Do not round off in the middle of the calculation.
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A student weighed out 0.150 g of protein powder and dissolved it in 100 mL of water (Solution 1). The student then diluted this solution by transferring 1 mL into a 25 mL flask and diluting with water (Solution 2). Finally, 1 mL of that solution was transferred to a test tube and combined with 4 mL Bradford reagent. The absorbance of the solution in the test tube was 0.144. Assuming that the best fit linear line of the standard curve was y=0.04144x+0.01521 (μgmL), calculate the percent protein by mass in the original protein powder.
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3. The lead in a swab sample, lead standards, together with a blank were made up in 5.00 mL volumetric flasks using 0.2 % HNO3. 20 μL aliquots of these solutions were injected into the spectrophotometer and the absorbance measured at 217 nm. The following results were obtained. lead / ppb Absorbance 0 0.0591 10.00 0.0858 50.00 0.1926 100.0 0.3260 150.0 0.4594 200.0 0.5929 Swab sample 0.3700 (a) Determine the amount of lead in the swab sample in μg.
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