Reference no: EM133142276

Experiment - The spectrofluorometric determination of acetylsalicylic acid in an aspirin tablet and an Infrared Spectroscopic study of Aspirin

Determination of acetylsalicylic acid in an aspirin tablet

Obtain an aspire' tablet from the technician If the tablet has a sample number or batch number, record it Record the brand name or manufacturer of the tablet if its made available to you Weigh the tablet on an analytical balance with the tablet in either a sample vial or or a polythene weighing boat.

 Place the tablet in a clean, dry mortar Use a clean pestle to grind the tablet into a powder.

Data Analysis (report on the proforma) -

Plot a calibration graph of fluorescence intensity against acetylsalicylic acid concentration. For each data point add error bars to show the 99 % confidence interval on the fluorescence reading. If these are too small to be visible this should be stated alongside your graph. Using the excel template provided perform linear regression analysis. You will need not only the slope and intercept of the linear lit but also the uncertainty in the y-estimate of the slope.

Calculate the amount of acetylsalicylic acid in the solution and in the original weighed tablet (mean and 95% confidence interval). The standard deviation of the concentration of the unknown depends not only on the standard deviation of the triplicate fluorescence readings for the unknown but also or the error in the slope of the calibration curve and on the closeness of the unknown measurement to the centre o' the calibration range. Use the excel template provided to calculate the confidence interval in the concentration of the aspirin sample and propagate this through to the value for the mass in the original tablet.

Compare the calculated mass of acetylsalicylic acid in the tablet with the expected result listed on the packaging, and comment on the value obtained.

Determine the limit of detection using both the blank measurements and intercept of the calibration graph.

Confirm that the fluorescence response is linear over the calibration range or, if necessary, identify the linear range. An easy way to check for linearity is to examine the residuals are these randomly scattered or are they negative for high and low concentrations and positive for intermediate values, implying a slight curvature towards the concentration axis at high concentrations? Also use a computer to perform linear regression or the data set and to compare the R² value when using all data points to that when the highest concentration is omitted. If omitting the maximum data point improves (increases) R² that implies the highest data point has a deviation from linearity.

Questions (answer on the proforma) -

Sketch an energy level (Jablonski) diagram and use this to explain the difference between the processes studied in UV-visible absorption, fluorescence and phosphorescence spectroscopes.

Attachment:- Experiment File - The spectrofluorometric.rar