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### Topic: spectrophotometry calculations  (Read 10183 times)

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#### pieka

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##### spectrophotometry calculations
« on: January 26, 2010, 06:23:25 AM »
Solution D contains a mixture of ADP and CMP. These compounds both absorb light in the same range of the spectrum and are often found together in biological extracts. The molar extinction coefficients of these compounds are: At 260nm: ADP, 15.4x103; CMP, 7.5x103 litres/mole.cm At 280nm: ADP, 2.5x103; CMP, 13.0x103 litres/mole.cm

If the following optical densities were measured in a 1 cm cuvette:
At 260nm 1.45
At 280nm 1.89

Calculate the concentrations of ADP and CMP in Solution D, explaining the principle involved.

I have no idea how to do this... any suggestions?
thanks

#### deuterium

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##### Re: spectrophotometry calculations
« Reply #1 on: January 27, 2010, 06:17:29 AM »
You must solve system of two equation:

1.45=15.4x103*C1+7.5x103*C2
1.89=2.5x103*C1+13.0x103*C2

C2-concentration of CMP

#### Train

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##### Re: spectrophotometry calculations
« Reply #2 on: January 30, 2010, 09:45:55 AM »
Or alternatively you could plot (absorbance sample/absorbance ADP std) vs. (absorbance CMP std/absorbance ADP std) over many wavelengths to obtain a line with slope (conc. CMP in samle/conc. CMP in std) and intercept (conc. ADP in sample/conc. ADP in std).

#### xoto

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##### Re: spectrophotometry calculations
« Reply #3 on: February 16, 2010, 04:52:15 PM »

#### sc414

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##### Re: spectrophotometry calculations
« Reply #4 on: January 26, 2011, 12:01:59 PM »
Having completed the calculation I was wondering if anyone could clarify my answers. For C1 [ADP] I got a concentration of 25.75um and for C2 [CMP] I got a concentration of 140.5 um. Any feedback would be much appreciatied!

#### cjf30

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##### Re: spectrophotometry calculations
« Reply #5 on: January 26, 2011, 05:41:27 PM »
Having completed the calculation I was wondering if anyone could clarify my answers. For C1 [ADP] I got a concentration of 25.75um and for C2 [CMP] I got a concentration of 140.5 um. Any feedback would be much appreciatied!
I have a deadline for this experiment tomorrow and cannot do the equations for this question. How did you get those figures?
Chaarrs

#### cjf30

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##### Re: spectrophotometry calculations
« Reply #6 on: January 26, 2011, 07:35:17 PM »
Having completed the calculation I was wondering if anyone could clarify my answers. For C1 [ADP] I got a concentration of 25.75um and for C2 [CMP] I got a concentration of 140.5 um. Any feedback would be much appreciatied!
I have a deadline for this experiment tomorrow and cannot do the equations for this question. How did you get those figures?
Chaarrs
OK i figured it out and got 25.76 and 140.4, so virtually identical answers!