Analytical Chemistry... Serum ion and standard iron solutions were analyzed acco

Question

Analytical Chemistry...

Serum ion and standard iron solutions were analyzed according to the following procedure: To 1.00 mL of unknown & std samples are added 2.00 mL of reducing agent and 2.00 mL of acid to recude and release Fe from transferrin. The serum proteins are then precipitated with 1.00 mL of 30% by weight trichloroactic acid. The mixture is then centrifuged to remove the protein. A 4.00 mL aliquot of each solution is then transferred to a fresh test-tube and treated with 1.00 mL of a solution containing ferrozine and buffer. The absorbance of this solution was then measured after a 10-minute period to develop the color. The following data were obtained:

Blank = 0.018 Abs at 562 nm in a 1.0 cm cell

Std, 1.00 mL of 3ug/mL Fe standard solution, treated as the above procedure = 0.209 abs

Unknown serum sample, 1.00 mL treated as above = 0.169

Find the concentration of Fe in the sample, in ppm and M.

Also, if the complex that formed is the complex FeI3, calculate the epsilon value for the complex.

Explanation / Answer

We will be finding Fe concentration in the sample.

First we had standard and unknown solution 1 mL.

Then we added 2 mL reducing agent, 2 mL of acid and then 1 mL trichloroacetic acid for precipitation.

So we have added total 5 mL solutions to 1mL, making it 6 mL

Initial concentration was 3µg/mL. Now it is 6µg/mL = 0.5 µg/mL

Then 4 mL was taken and 1.0 mL trichloroacetic acid was added.

Now concentration of standard solution is 0.4 µg/mL.

Let us use proportionality approach to calculate concentration of Fe in unknown solution.

We know concentration of standard solution = C1 = 0.4 µg/mL. = 0.00716 M

                       Absorption of standard solution = A1 = 0.209

                       Absorption of unknown solution = A2 = 0.169

C1/C2 = A1/A2

C2 = A2*C1/A1 = 0.169*0.4/0.209 = 0.323 µg/mL

Concentration of unknown solution is 0.323 µg/mL

To calculate the molarity, we must know the molecular weight of iron(Fe). Which is 55.846.

Concentration = Mass/Volume*Molecular weight

                           = 0.323 µg / 1 ml * 55.846 = 0.00578 M

Ppm

= 0.00578 * 55.846 = 0.3227 g/L * 100 = 32.27 ppm Fe

Now we will calculate epsilon value.

A = ebc

Where A is absorbance, e is molar absorptivity, b is path length and c is concentration.

We will calculate it for standard,

0.209 = e * 1 * 0.00716

e= 0.209/1*0.00716 = 29.189

Related Questions

Navigate

• Browse (All)
• Browse A
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.