Can I Determine Unknown Sample Concentration Using Absorption Spectroscopy?

[sukanyasv]

Hi

I'm trying to measure the concentration of a sample dissolved in water. I'm using the spectrometer USB4000 which directly gives me the absorbance value. Using beer-lambert law is there a way i can determine the unknown sample concentration from this measurement? I have the values 'A' and 'l' for the law. can someone throw some light on this??

 

[Andy Resnick]

I think you need to have at elast two measurements of the absorbance with different thicknesses. There are cells for this- a rectangular cross section, so you do two readings with the cuvette rotated 90 degrees.

 

[sir-pinski]

Yes, it is possible to determine the concentration of an unknown sample using absorption spectroscopy. The Beer-Lambert law states that the absorbance of a sample is directly proportional to its concentration and path length. Therefore, by measuring the absorbance value and knowing the path length, you can calculate the concentration using the equation A = εcl, where A is the absorbance, ε is the molar absorptivity of the sample, c is the concentration, and l is the path length. You will need to know the molar absorptivity of the sample, which can be determined experimentally or found in literature. Additionally, it is important to ensure that the sample is within the linear range of the instrument, as deviations from the Beer-Lambert law can occur at high concentrations. Overall, absorption spectroscopy is a reliable method for determining the concentration of a sample and can provide accurate results when used properly.