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### Topic: The Absorbtion Spectrum of Hemoglobin- Need urgent help with some calculations.  (Read 10453 times)

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#### gggggggggg

• Regular Member
•   • Posts: 37
• Mole Snacks: +0/-0 ##### The Absorbtion Spectrum of Hemoglobin- Need urgent help with some calculations.
« on: October 29, 2009, 07:43:59 PM »
Hello, Hope you will be able to lend a hand.

1))The question is asking me to calculate the molar absorption  coefficient  of hemoglobin at the wavelength of maximum absorption which i know is 0.58 from my results. We are told to use the molecular weight of hemoglobin which is 65000  to work this problem. We were also told the absorption of a solution of hemoglobin which was 0.11g/L

My work:   since E=A/Cl   Where E is the absorption coeff. A= Absorption C=concen.   l =1 (constant)

I tried working to find C. I did 0.11/65000 to get 1.6923...E-06 . Then placed the value in the equation above to get E=0.58/my C value to give 3.4272E5.

Problem: Am i doing this right? I feel like i am missing something here. Maybe the units need to be changed around?

2))Another question gives me  the following information : Value of E, Value of absoption and asking me to work out concentration. That part is easy, but in the information it says that "the scientists made a 1 in 1000 dilution  of the patients blood sample.

My question is , how does the dilution come into effect when finding the concentration. It shouldnt right? because concentration stays the same in any dilution? or am i thinking the wrong way

Thank you for your time and consideration guys. Hope you can help.

GG.

#### JGK ##### Re: The Absorbtion Spectrum of Hemoglobin- Need urgent help with some calculations.
« Reply #1 on: October 30, 2009, 10:59:45 AM »
The wording in your text is unclear :

the way it reads is that 0.58 is your calculated molar absorption  coefficient  of hemoglobin at the wavelength of maximum absorption, however from your calculations it is the Absorbance measurement made during the experiment?

"We were also told the absorption of a solution of hemoglobin which was 0.11g/L" Have you told us what it was? Is this the 0.58 value?

If you were working at ~414 nm you're not that far away with your calculated result.

You're wrong about your concentration assumption. If I give you a solution of xg/mL and tell you it is made by diluting a solution of y g/mL by a factor of 100, what is the relationship between x and y?

In your example you've been given a diluted sample and a dilution factor and asked to calculate the concentration before dilution.
Experience is something you don't get until just after you need it.

#### gggggggggg

• Regular Member
•   • Posts: 37
• Mole Snacks: +0/-0 ##### Re: The Absorbtion Spectrum of Hemoglobin- Need urgent help with some calculations.
« Reply #2 on: October 30, 2009, 01:00:41 PM »
The wording in your text is unclear :

the way it reads is that 0.58 is your calculated molar absorption  coefficient  of hemoglobin at the wavelength of maximum absorption, however from your calculations it is the Absorbance measurement made during the experiment?

"We were also told the absorption of a solution of hemoglobin which was 0.11g/L" Have you told us what it was? Is this the 0.58 value?

If you were working at ~414 nm you're not that far away with your calculated result.

You're wrong about your concentration assumption. If I give you a solution of xg/mL and tell you it is made by diluting a solution of y g/mL by a factor of 100, what is the relationship between x and y?

In your example you've been given a diluted sample and a dilution factor and asked to calculate the concentration before dilution.

Hey, thank you for your response. Hope i can clarify what i said in my first post.

Method of experiment:

The absorption of a solution of hemoglobin (0.11g/L) in distilled water was recorded at 20 nm intervals from 340 nm to 540 nm using a spectrophotometer. After plotting my values on a graph of absorption (Y-axis)  against wavelength ( x-axis), i found out (from my graph) that the maximum absorption was at 0.58 at a wavelength of 410nm.

1) The question: Given the molecular weight of hemoglobin being 65000, calculate the molar absorption coefficient of hemoglobin at the wavelength of maximum absorption.

2) For my second part of the question about the dilution, is it right for me to conclude that since the concentration i calculated was with dilution i need to multiply the answer by 1x10^3 ( because the dilution was 1 in 1000)?

Hope i clarified it a bit better.

Thank you again,

GG.

#### gggggggggg

• Regular Member
•   • Posts: 37
• Mole Snacks: +0/-0 ##### Re: The Absorbtion Spectrum of Hemoglobin- Need urgent help with some calculations.
« Reply #3 on: November 01, 2009, 11:55:58 AM »
I wouldnt post this if i didnt have to hand in my work tomorrow, so it is pretty urgent. Can someone please help me out?

Sorry to the moderator, for being impatient.

#### JGK ##### Re: The Absorbtion Spectrum of Hemoglobin- Need urgent help with some calculations.
« Reply #4 on: November 03, 2009, 11:05:27 AM »
1) The question: Given the molecular weight of hemoglobin being 65000, calculate the molar absorption coefficient of hemoglobin at the wavelength of maximum absorption.

Like I said in my original post, you are not that far away from tabulated values with your calculation

2) For my second part of the question about the dilution, is it right for me to conclude that since the concentration i calculated was with dilution i need to multiply the answer by 1x10^3 ( because the dilution was 1 in 1000)?

Yes

Experience is something you don't get until just after you need it.