[SOLVED] CEGR338 Morgan State UV Vis Spectroscopy Lab Assignment

5. UV-Vis Spectroscopy5.1 Introduction

Objective

Review basic analytical chemistry skills, including solution making, transferring and linear diluting. Understand the error involved and error propagation.

Materials:

Methylene Blue C16H18ClN3S, MW 319.85.Also called Swiss blue. One gram dissolves in about 1000 ml of water. Peak absorption at 369 nm

5.2 Create Calibration Curve from standard solutions

Procedures:

  1. Weigh 500mg dye on electric balance
  2. Dissolving all the solid dye in beaker
  3. Transfer all the solution into a 500ml volumetric flask
  4. Fill up the volumetric flask to the tick mark
  5. Prepare standard solutions of 500, 200, 100, 50 and 20 ppm from 1000 ppm stock

page26image2773393264
page26image2773393584

solution

Table 5-1 Preparation of standard solutions

PPM

page26image2773404256

STD

Stock

page26image2815052576

DI water

Total Volume

20

0.2

page26image2814948992

9.8

page26image2814948208

10ml

50

0.5

9.5

10ml

100

1

page26image2814985040

9

page26image2814985744

10ml

200

2

8

10ml

500

5

page26image2814945136

5

10ml

  1. Vortex vial to complete mix
  2. Transfer Standard solutions to cuvette

26

  1. Measure the transmissivity at a peak measure three times and make a note of your results in your lab notebook
  2. Create calibration curves from data.
    Table 5-2 Absorbance of standard solutions

PPM

Wavelength

Absorbance

1

2

Average

20

page27image2815008528 page27image2815007488 page27image2814920784

50

100

200

page27image2816535536 page27image2816520752 page27image2816521792

500

1 0.8 0.6 0.4 0.2 0

UV/VIS

page27image2816508304
page27image2816508624
page27image2816508880
page27image2816509136
page27image2816509456
page27image2816509776
page27image2816510032

0 50 100 150 200 250 300 350 400 450 500

Concentration (ppm)

Figure 5-1 Calibration curve from standard solutions

5.3 Two steps of a serial dilution and measure the concentrations of unknown samples

  1. Pour about 11 ml unknown concentration of methylene blue solution from the bottle to your vial
  2. Dilute the dye solution 10 fold by using pipettes : Pipette 1 ml above sample solution to your vial
  3. Fill the solution to 10 ml
  4. Transfer Standard solutions to cuvette
  5. Measure absorbance of each

27

Absorbance

page28image2815313680

Figure 5-2 Serial Dilution of unknown samples Table 5-3 Absorbance of unknown samples

Instrument Use

  1. Power on instrument (switch is on left side).
  2. Turn on monitor and double-click ‘Cary win UV’
  3. Instrument will run through a start-up check for about 1 minutes.
  4. In the toolbar frame, select the ‘Concentration’ icon.
  5. In dialog box, enter wavelength 369 nm.

Serial Dilution

Absorbance

page28image2815253360page28image2815263616

Wavelength

page28image2815254240

1

page28image2815283056

1/10

page28image2815282816page28image2815245728

1/100

Sample 1

page28image2773424816page28image2773420624 page28image2773431424page28image2773437040page28image2773434208page28image2773439408 page28image2773441360 page28image2773442256

Sample 2

Sample 3

page28image2815935424 page28image2815940528page28image2815932976 page28image2775410160

a.

b.

  1. Clicka. b.
  2. Click
  3. Click
  4. Click

Choose Abs (absorbance).

Replicate is 2on ‘Standard’.

unit : mg/L

number of standard and concentration of standard solutionon ‘Sample’ and enter sample number
‘OK’
on Zero icon after insert Blank cuvette into UV slot.

  1. Fill cuvette 3⁄4 with standard samples and cleaning cuvette surface with chem wipes.
  2. Place cuvette in the slot.
  3. Click ‘Start’
  4. Record Abs(absorbance)
  5. Drawing standard graph
  6. Fill cuvette 3⁄4 with unknown samples and cleaning cuvette surface with chem wipes.
  7. Place cuvette in the slot.
  8. Click ‘Start’
  9. Record concentrations

28

Lab report requirement

o Calculate solution concentration by ppm for all solutions
o Discuss source of data errors
o How do you improve your skill to get better accuracy and precision of solution makingo Describe the key steps of the experiment
o Attach all the original data and spectrum

[opskill_register_order]

"Looking for a Similar Assignment? Order now and Get a Discount!

Hey, wait!You Don't want to miss this offer!

Before you go, let us offer you a 20% discount coupon for your next purchase.