Wavelength concentration (x axis) absorbance (y axis) 305 2.40 100um or 1.00 x 1
ID: 706707 • Letter: W
Question
Wavelength concentration (x axis) absorbance (y axis)
305 2.40 100um or 1.00 x 10^-4
305 1.18 50um or 5.0 x 10^-5
305 .60 25 um or 2.5 x 10^-5
305 1.08 ????
Use a spreadsheet program (such as Open Office Calc or Microsoft Excel) to create an x-y plot (called a "scatter" plot in many programs) of the absorbance (y-axis) vs concentration (x-axis) of the three known standards. In this plot, be sure to enter the concentration values in Molarity instead of the micro-Molar values listed on the pipette in the lab window (you need to move the decimal six places to the left). The plot should appear linear. If the plot is not linear, either your absorbance values are incorrect or your spreadsheet plot is set up incorrectly. Report below the slope and y-intercept of the best fit line to these data. slope y-intercept Since all the samples had the same pathlength of 1.00 cm, the Beer- Lambert equation indicates that the slope of your plot of A vs concentration will be the molar absorptivity, e, of EDMAB (in Mcm 2) at the absorption maximum. Note - the value obtained should be significantly greater than 10,000 M1cm1.Explanation / Answer
Beer's law is given by A= ebC
where A is absorbance, e is molar extinction coefficient, b is path length =1 cmand C is concentration.So the theoretical equation is y(A)= m(b)*x(C)
So for finding the slope and intercept, one has to draw the plot of A ( y -axis) vs C ( x-axis).
um=10-6M, the data is converted to M by dividing the concentration by 106.
since C represents concentration in uM, y-axis should be Absorbance and x axis need to be concentration. the data is given need to be changed for x and y-axis.
from the plot, molar extinction coefficient= 23924/M.cm
when A=1.08,
1.08=23924*Concentration
concentration in M= 1.08/23924=4.51*10-5 M
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