Exploring Chemical Analysis
Exploring Chemical Analysis
5th Edition
ISBN: 9781429275033
Author: Daniel C. Harris
Publisher: Macmillan Higher Education
Question
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Chapter 19, Problem 19.12P

(a)

Interpretation Introduction

Interpretation:

Concentration of transferrin in mg/mL and iron in μg/mL have to be calculated.

Concept Introduction:

Expression to compute absorbance as per Beer’s law is as follows:

  A=εbc

Here,

ε denotes molar absorptivity of species capable top absorb.

b denotes path length in centimeters.

c denotes concentration of species capable top absorb

A denotes absorbance.

T denotes transmittance.

(a)

Expert Solution
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Explanation of Solution

Expression to compute concentration as per Beer’s law is as follows:

  c=Aεb        (1)

Substitute 0.463 for A, 4170 M1cm1 for ε, and 1 cm for b in equation (1).

  c=0.463(4170 M1cm1)(1 cm)=1.11×104 M

Since transferrin can bind twice as much as Fe3+ ion, so concentration of Fe3+ is calculated as follows:

  [Fe3+]=(2)(1.11×104 molL)(55.85 g1 mol)(106 μg1 g)(1 L1000 mL)=12.39 mg/mL12.4 mg/mL

Since, molar mass of transferrin is 81000 g/mol so concentration of transferrin is calculated as follows:

  [transferrin]=(1.11×104 molL)(81000 g1 mol)(103 mg1 g)(1 L1000 mL)=8.99 mg/mL

Thus, concentration of transferrin and iron are 8.99 mg/mL and 12.4 mg/mL respectively.

(b)

Interpretation Introduction

Interpretation:

Fraction bound by transferrin has to be calculated.

Concept Introduction:

Refer to part (a).

(b)

Expert Solution
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Explanation of Solution

Relation between concentration of transferrin and desferrioxamine at 470 nm is as follows:

  0.424=4170cT+2290cD        (2)

Relation between concentration of transferrin and desferrioxamine at 428 nm is as follows:

  0.401=3540cT+2730cD        (3)

Multiply equation (3) by 2290/2730.

  0.336=2969cT+2290cD        (4)

Subtract equation (4) from (2).

  0.4240.336=(4170cT+2290cD)(2969cT+2290cD)0.088=1201cTcT=7.327×105 M

Substitute 7.33×105 M for cT in equation (2).

  0.424=4170(7.327×105 M)+2290cDcD=5.173×105 M

Total concentration of Fe3+ in both transferrin and desferrioxamine is calculated as follows:

  [Fe3+]Total=(2)(7.327×105 M)+5.173×105 M=1.98×105 M

Formula to compute fraction bound by transferrin is as follows:

  Fraction of Fe3+ in transferrin=[Fe3+]Transferrin [Fe3+]Total(100 %)        (5)

Substitute 1.98×105 M for [Fe3+]Total and 1.46×104 M for [Fe3+]Transferrin in equation (5).

  Fraction of Fe3+ in transferrin=1.46×104 M1.98×105 M(100 %)=73.7 %

Thus, fraction bound by transferrin is 73.7 %.

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