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The world leader in serving science Transmission Techniques Solids.

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Presentation on theme: "The world leader in serving science Transmission Techniques Solids."— Presentation transcript:

1 The world leader in serving science Transmission Techniques Solids

2 2 Solid Transmission Analysis  Pressed Pellet  Mull  Pressed Film  Cast Film IoIo IsIs

3 3 Transmission Analysis  High sample throughput  Qualitative and quantitative analysis  Requires sample preparation  Low cost

4 4 Pressed Pellet  Traditional Technique  Great for powders and solids that can be ground  Uses a solid Matrix to dilute the sample  Pressing a consistent pellet takes PRACTICE KBr Die Kit

5 5 Technique 1) Grind the sample thoroughly to reduce scattering effects (Particle size < 10  m) 2)Mix sample with ground matrix material to obtain the proper ratio (Peak intensity ~ 10%T) 3)Combine sample and matrix in a ratio of ~1:100 4)Carefully transfer mixture to sample holder 5)Press

6 6 Pressing Technique 1) Need to avoid trapping air in the sample matrix so use one of two methods: -Press slowly releasing pressure often to allow compressed air to escape -Run a vacuum line to the sample holder and evacuate before pressing 2)With hand presses, more pressure is better. With hydraulic press, use ~8000psi for 15 seconds 3)Good pellet should be clear

7 7 Matrix Materials  Choose matrix based on properties and spectral range: KBr (40, cm-1) CsI (40, cm-1) Polyethylene (650-50cm-1) KCl ( cm-1) Diamond ( cm-1) For temperature studies and “wet” samples. Reusable  Keep matrix dry if hydroscopic

8 8 Types of Presses  Hydraulic Press Reproducible Easy to use Excellent control Expensive

9 9 Types of Presses  Hand Press Manual Flexible Inexpensive User dependent

10 10 Example Universal Anvil Collar Upper Anvil Hand Held Press

11 11 Alignment  Use sample mount that allows maximum flexibility  Position mount in sample compartment and find interferogram signal  Use laser position to determine approximate height of collar  Loosen sample holder and reposition in x,y and angular planes to maximize signal

12 12 KBr Pellet Trouble Shooting Inadequate pressure Corrected spectrum

13 13 Quantitative Analysis  Can generate acceptable results  Need to measure matrix and sample quantity accurately  Should try to apply same amount of pressure in creating pellet  Reproducible particle size of sample is important

14 14 Mull Suspension  Powders  Waxy materials  Eliminates physical changes from other environments  Easy and inexpensive

15 15 Technique  Grind sample as much as possible  Add a drop of the mulling oil and mix  Continue to add drop wise and mix until mull has approximate consistency of hand cream  Transfer mull to window  Use second window to seal system to avoid contamination.  Universal sample holder provides excellent control

16 16 Mulling Oils Nujol Fluorolube

17 17 Subtracting Mulling Oil  Sample and Spectrum dependent  Only works if mulling oil not totally absorbing  Searching the fingerprint region is a convenient alternative Sample in Nujol Nujol Sample + Residual

18 18 Split Mull Caffeine in Nujol Caffeine in Fluorolube

19 19 Polishing Windows  Important to use clean, polished windows.  Reduces scattering and spectral drift  Easy to do

20 20 Mull Troubleshooting Insufficient sample grinding Sample reground to smaller particle size

21 21 Quantitative Analysis  Can generate good results but it is hard  Need to use peak ratio or internal standard to compensate for changes in pathlength  Must stay away from frequencies where mulling oil could interfere with calculations  Reproducibility of particle size of sample is large factor in error.

22 22 Cast Film  Simple and effective technique  Great for rubbers, plastics, resins and viscous liquids  Dependent on finding a solvent

23 23 Technique  Select suitable solvent and dissolve a small amount of sample  Place drop of sample solution on compatible window or glass slide(create a free standing film)  Drying time varies with solvent and may need additional attention  Be sure to evaporate all the solvent. Pockets may form and the solvent bands will contaminate the sample spectrum

24 24 Solvent Selection (Polarity Index) Polar Non Polar Tetrafluoropropanol (9.3) Water (9.0) Formamide (7.3) Methanol (6.6) Dimethyl Sulfoxide (6.5) Acetic Acid or Acetonitrile or Methyl Formamide (6.2) Pyridine (5.3)) Ethylene Glycol or Acetone (5.4) Nitrobenzene or Cyclohexanone or Methyl Ethyl Ketone (4.5) Chloroform (4.4) Ethyl Acetate or 1-Propanol(4.3) Tetrahyrofuran (4.2) Methylene Chloride (3.4) Ethyl Ether (2.9) Phenyl Ether (2.8) Chlorobenzene (2.7) P-Xylene (2.4) Toluene (2.3) Isopropyl Ether (2.2) Carbon Disulfide (1.0) Cyclohexane (0)Hexane (0)

25 25 Cast Film Trouble Shooting Solvent

26 26 Quantitative Analysis  Can generate good results  Need to dry completely  Inconsistent pathlength causes error  Compensation of pathlength involves peak ratios or internal standards.

27 27 Pressed Film  Quick & Easy  Minimal sample preparation  Great for any samples that melt  Proper equipment gives great quantitative results

28 28 Techniques  Use small amount of sample in sample holder  Choose a low heat setting  Cover sample with flat, non-stick surface  gradually heat to desired temperature and apply pressure until sample softens and thins to desired thickness  If fringing occurs, try matted surface

29 29 Universal Film Maker

30 30 SAMPLE ALUMINIUM FOIL TEMPERATURE CONTROLLER FOR HEATED PLATENS HYDRAULIC PRESS TOP HEATED PLATEN BOTTOM HEATED PLATEN Carver Press

31 31 Temperature Effects  Want hot enough temperature to melt plastic -->create free standing film  Too hot will potentially burn sample (Volatilize) of thermally alter (spectral changes)  Too cool sample will not form thin enough film

32 32 Interference Fringe Constructive interference adds energy to the resultant wave

33 33 Pressed Film Trouble Shooting Interference Fringe

34 34 Calculating Sample Thickness %Transmittance Wavenumbers (cm-1) Thickness= Number ofMaxima 2 (Refractive Index) ( 12  

35 35 Quantitative Analysis  Reproducible sample thickness major advantage  Accurate control of pressure and heat necessary for reproducibility  Thickness of sample should be adjusted so that the frequencies of interest absorb between.3-1 absorbance (50-10%T)


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