Hello,
We have synthesized series of Hydroxyapatite nano-particles.
We are trying to collect UV-Vis DRS spectra using Perkin Elmer - Lamda 750 spectrophotometer using integrating sphere.
But we are getting negative absorbance or Transmission/ Reflection greater than 100% .
We have tried to not apply auto zero but we are geeting weird UV-Vis spectra like attached photograph.
How to solve this error as we have tried for 3-4 times but getting errors in results.
Thank you so much for help
Hello Mrs. Krishna Joshi
I hope that the following papers help you:
https://www.moleculardevices.com/sites/default/files/en/assets/user-guide/br/spectramax-quickdrop-uv-vis-spectrophotometer.pdf
Negative Absorbance Readings Sample measurements read negative absorbance for the following reasons: The absorbance value of the reference is higher than the sample. The reference and the sample are interchanged. The sample is very dilute and close to the absorbance of the reference. The minimum concentration for the micro-volume sample port is 1 ng/µL (dsDNA) The minimum concentration for the 10 mm pathlength standard cuvette port is 0.5 ng/µL (dsDNA).
https://www.researchgate.net/post/What_is_negative_absorbance_and_why_am_I_getting_it
https://www.researchgate.net/post/what_is_meant_by_Negative_absorbance
I think you need to check the concentration of the solution or check the reference solution which you have taken. This is the main reason one can face the negative absorption. If the absorption of the reference solution is higher than the observed solution, it will show the negative absorption.
Dear Krishna Joshi,
The problem usually arises while dealing with low-concentration solutions and that too around lower wavelength regions. To solve this problem you may prepare a solution of higher concentration or utilize a different solvent for the dispersion. Also, make sure to use clean cuvettes for the analysis as the incorporation of other impurities inside and outside of the cuvette surface affects the absorbance abilities. The other important thing is to measure/remove the background absorbance carefully as it also affects the absorbance spectra. You can also remove the negative data if the material under analysis has known absorbance or try to record the data within the expected region as it may not affect the absorbance value by much. (Not ideally suggested)
@ Yash Doshi Thank you so much for reply. It really helped me to understand the problem.
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