Spectrophotometer and It Function

Experiment 1: Spectrophotometer and its function Introduction The spectrophotometer is an instrument that measures the intensity of light. It works by transmitting a narrow beam of light of a designated, specific wavelength through a sample and measures the amount of light absorbed, spectrum, by the sample. This value can be measured because the solute in a solution absorbs a certain amount of light due to its specific characteristics. The difference between the light intensity before and after passing through the sample is the measured value. Through this measurement, the spectrophotometer determines the absorbance of a sample. Since the absorbance of a sample is directly proportional to the amount of solute in a sample, the concentration of a solute can be determined. There are multiple ways in which the absorbance can be calculated: (I) Transmittance (T) refers to the amount of light transmitted through a sample solution. Its formula is:

I represent the incident light whereas I0 represents the energy of light transmitted through the solution. Absorbance (A) represents the amount of light absorbed by a solution which is related logarithmically to transmission by:

(II)

According to Beer Lambert Law, Absorbance, , represents the molar absobtivity coefficient in L mol-1cm-1, a constant for a particular compound, different compound has different molar absorbtivity. , represents the path length in cm (set to 1cm), the path length of the cuvette in which the sample is contained. , represents the concentration of the compound in solution, in mol L-1. This shows that there is a relationship between molar absorptivity, path length and molar concentration in Beer Lambert Law. Furthermore, concentration of a solution can be calculated by using Beer-Lambert Law if its molar absorptivity coefficient is known. The equation that has been rearranged can be used to calculate the molar absorptivity. The equation is:

Besides that, concentration of different compounds in...