From Beer-Lambert law, Absorbance = Ecl. As the concentration of the solution increases, the absorbance increases as well. The absorbance for 5.0x10-6 of p-np is 0.372 while that of 5.0x10-5 of p-np is 1.019 showing that absorbance increased by 3 times(Table 1). This can be rationalized by the fact that there is more protein in solution, hence more light from the spectrophotometer is absorbed. Conversely, as concentration decreases, there is less protein to absorb light and hence less absorbance. Absorbance is also affected by pathlength. AS pathlength increases, absorbance increases. This is because light passes through more proteins, hence more light is absorbed. The results fail to demonstrate that trend since for the same concentration of p-np, a change of pathlength from 11 to 21mm results in a decrease in absorbance from 0.900 to 0.480 (Table 1). This error may have been from scattering of light due to particulates in the sample, changes in refractive index at high analyte concentration, stray light or shifts in chemical equilibria as a function of concentration (University of Adelaide, 1999). Extinction coefficient is not affected by concentration and pathlength. It is unique to a particular wavelength. However, this is not supported by Table 1 showing fluctuations in the value of the extinction coefficient. This may be due to some experimental errors as mentioned before.
The absorption spectrum shows where substances absorb the best wavelength of light. The absorption spectrum for p-np has a maximum absorption of 400nm (Graph 1). It is described of as a curve with a maximum with a particular range for each solution measured. An absorption spectrum can be used to identify compounds by first finding the maximum wavelength, absorbance and hence plug those values in the Beer-Lambert equation so as to find the extinction coefficient which is unique to each compound. If the 2.5x10-5 p-np solution is used, the shape of the curve is expected to be the same with...