# Concentration Calculation From UV Vis Absorbance

## Concentration Calculation From UV Vis Absorbance

Absorbance (a.u.)

Molar Absorptivity (L/mmol.cm)

Cell Length (cm)

Results

mmol/L

For Molar Absorptivity Calculator: Click Here...

#### Calculation Tutorial:

**STEP1:**Open the absorbance graph of the solution, which is obtained from the UV Vis spectroscopy. Raw HTML

**STEP2:**Now zoom on the peak for which you want to calculate the concentration and note down the Absorbance value. Raw HTML

**STEP3:**Now enter the measured absorbance value (eg. 0.84) into the "Absorbance of Solution" column of the calculator; also enter the value of "Molar Absorptivity" (eg. 19400) of that material from the literature survey and "Solution Cell Length" (eg. 1 cm) in the next columns. You should get the calculated results of the band gap in the "Calculated Result" field.

**NOTE:** For accuracy you can make a solution for known concentration and enter the values of "Absorbance of Solution", "Solution Cell Length" and "Known Concentration of Solution" in the given columns. You should get the value of "Molar Absorptivity" from the calculator.
Then enter the value of "Molar Absorptivity" in the above calculator and find the exact concentration of solution from the above calculator, Please use this calculator
https://instanano.com/wp/characterization/theoretical/concentration-to-molar-absorptivity-calculator/

**Theory Behind Calculations:**
Calculations are based on the Beer's Lambert law given by:
A = ε l c
Where A = Absorbance of solution at a particular wavelength; ε = Molar Absorptivity; l = Length of Solution Cell; and c = Concentration of Solution (mol/dm3)

## Post a Comment

very useful and helpful

ReplyDeletehow to calculate molar absorptivity is it the slope value of the calibration curve how can the absorptivity of different strengths of the same solution with different absorbance show the same value of absorptivity for all ( simultaneous equation method of uv spectrophotometry of multicomponent analysis)

ReplyDeleteYou have to prepare 3-5 concentration of the same solution and then take the absorbance, {mind it, the max concentrated solution' absorbance must be below 1. Then plot a linear curve of absorbance at lamda(max) vs concentration. the slop of the plot would be molar absorptivity with a unit of Lmol-1cm-1

Deletehello! how do I convert absorbance to g/L?

ReplyDeleteafter determining the molar (∈) absorptivity of the solution as Lmol_1cm_1. you can get the concentration from any absorbance by C=A/∈ in mol/L then by multiplication with the MW you will get conc in g/L.

Deletehow to calculate molar absorptivity ?

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ReplyDeleteconcentration of what is needed in the calculation of molar absorptivity

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ReplyDeletei did not get the rate constant equation calculation from UV graph.

ReplyDeletei have 4-nitrophenol concentration decreases interms of absorbance, how i need to take those absorbance values interms of concentration for rate constant calculation