Full working needed and all formulas used. A justification is needed of why that
ID: 558342 • Letter: F
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Full working needed and all formulas used. A justification is needed of why that is the right answer. Will give thumbs up for correct answers. 2. In Dr. Holland's lab, a fluorescent molecule called calcein is used as a drug substitute in drug-release experiments. To measure the concentration of the drug in a solution, the fluorescence (a particular type of light emission) is measured with a spectrofluorometer. A spectrofluorometer works in a similar manner as a spectrophotometer, except instead of measuring absorbance it measures fluorescence. A standard curve measured with the spectrofluorometer is shown below. If the concentration in the sample is increased, initially the fluorescence intensity will also increase. At a concentration of 9 g/ml, the fluorescence intensity peaks at 225 units. If the concentration is further increased, the sample beingsa reversible process known as quenching and the amount of fluorescence coming from the sample decreases 250 200 150 100 50 0 10 20 30 40 50 60 70 Calcein Concentration (g/ml) a. If you are given an unknown sample and measure a fluorescence intensity of 150 units, what are the possible calcein concentrations? b. What additional experiments could you do with this sample to determine which concentration it was when it was first given to you?Explanation / Answer
Analysis of calcein
The calibration curve is drawn using solutions of known concentration
a. If the unknown sample of calcein gave a fluorescent intensity of 150 units,
by looking at the calibration curve,
The possible concentration values corresponding to 150 units are = 2.5 ug/ml and 16 ug/ml
b. The initial concentration of calcein in the sample can also be determined by calcium ion determination technique. Here, the intensity of calcium ion in solution is recorded proportional to the amount of calcein in solution and then the unknown solution intensity if measured. The data from the calibration curve lets us calculate concentration of calcein in the original solution.
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