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Q: What does the negative absorbance show?
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What is difference between specific absorbance and absorbance interms of spectroscopy?

specific absorbance- it is absorbance in a solution containing one gm of substance in 100 ml solvent in 1cm shell. so it is having a difference with absorbance which is negative logarithm of incident light to the transmitted light. divya.chakraborty@gmail.com


What is the specific absorbance of hypericin?

Hypericin salts are red in organic solvents and show a typical absorbance at 590 nm, which is useful to quantify hypericin in the drug extracts


Is wavelength or absorbance the dependent variable?

"absorbance"Since in the experiment, you probably choose the wavelength, then measure the absorbance (absorption?, the absorbance is the dependent variable.


What is the purpose of the blank?

Blank Sample in Spectrophotometry is used to measure the absorbance of light without sample. It is subtracted from the total absorbance for measurement of Absorbance from a sample's absorbance.


Why acetone show absorbance at 280nm?

Acetone exhibits absorbance at 280nm due to the presence of its carbonyl group (C=O), which is associated with a peak in the ultraviolet-visible spectrum at that wavelength. The absorbance at 280nm is a characteristic feature of the electronic transitions within the molecular structure of acetone.


Why is absorbance not measured directly?

Absorbance is not measured directly because it represents the amount of light absorbed by a sample and is proportional to the concentration of the absorbing species. By measuring absorbance, we can infer information about the concentration of the species in a sample. Absorbance is typically measured using a spectrophotometer, which quantifies the amount of light that passes through a sample relative to a reference.


What is the different between primary absorbance and secondary absorbance in fluorescence?

in primary light absorbed by outer molecule while in secondary re-absorbance occurs


What is the specific absorbance of aspirin?

The specific absorbance of a substance like aspirin refers to its unique ability to absorb light at a specific wavelength. To find the specific absorbance of aspirin, you would need to measure its absorbance at a specific wavelength using a spectrophotometer.


What is baseline in uv?

In UV spectroscopy, the baseline refers to the horizontal line at zero absorbance on the absorbance axis. It represents the reference point for measuring the absorbance of the sample. The baseline should be stable and noise-free to ensure accurate measurement of the absorbance of the sample.


What do negative uv absorbance readings mean?

Negative UV absorbance readings typically indicate a baseline offset or error in the measurements. This can be due to factors such as improper blank correction, instrumental noise, or a sample preparation issue. Troubleshooting these factors and ensuring proper calibration can help correct negative absorbance values.


Why spectophotometer gives negative value?

A spectrometer can provide absorbance information in a number of ways.. For example transmissivity can be given as a percentage value. The absorbance is often represented on a log scale. It may be calculated by: A = -log10(I/I0) Since incident light intensity must be greater than detected light intensity, Absorbance technically can't be negative. However, a spectrometer must be zeroed before each use to provide a baseline. If a material which is contaminated or otherwise inappropriate is used to zero the spectrometer, it may give a bad baseline, and thus a sample may appear to give negative absorbance. The 'blank' which was used to zero the spectrometer would have had higher absorptivity than the sample. Another instance in which you may get negative absorption could be fluorescence. If your material is excited by light, it can emit light at a different frequency. Detecting at this frequency may produce negative absorption. Similarly, 'upconversion' by certain porphyrins may also cause emission at certain wavelengths.


What is the abbreviation for Absorbance?

A