1. Using ReactionView® and ReactionProbe ™ : In-Situ Reaction Monitoring with FTIR Spectroscopy

2. Mid-IR Spectroscopy Wavelength range 2.5 to 15 micrometers (µm) Generally use units proportional to frequency (wave number in units of cm -1 ) rather than wavelength 2.5 to 15 µm ≡ 4000 to 600 cm -1 ReactionView® operates at 5000 to 900 cm -1 Absorption of radiation in this region by a typical organic molecule excites vibrational (stretching and bending) and rotational modes. © Remspec Corp. 2013

3. Mid-IR Spectroscopy of Organic Molecules © Remspec Corp. 2013

4. Mid-IR Spectroscopy of Organic Molecules Source: Socrates, 2001 © Remspec Corp. 2013

5. Mid-IR Spectroscopy of Organic Molecules Source: Socrates, 2001 © Remspec Corp. 2013

6. Mid-IR Spectroscopy of Organic Molecules Source: Socrates, 2001 © Remspec Corp. 2013

7. Beer's Law A (ν) = a (ν) bc A (ν) is absorbance at any wavenumber ν a (ν) is absorptivity at ν b is the pathlength c is the concentration of the sample Absorbance is directly, linearly, proportional to concentration. © Remspec Corp. 2013

8. In-Situ Spectroscopy: Requirements Technique can detect chemically meaningful information Robust, transferable calibration Probe can fit into standard reactors Probe is inert Probe can withstand realistic reaction conditions (temperature, pressure) © Remspec Corp. 2013

9. In-Situ Spectroscopy © Remspec Corp. 2013

10. Probe Properties 200 bar>200 to <-100°CHigh Pressure 5 bar>200 to <-100°CHigh Temp. 5 bar60 to -100°CLow Temp. 5 bar60 to -20° CStandard PressureTemperature © Remspec Corp. 2013

11. Chalcogenide Glasses for Mid-IR Arsenic, Sulphur, Selenium, Tellurium Long lengths of sub-0.5 dB/m fiber available Extruded Polycrystalline Materials Silver halide (still experimental and unreliable) Photosensitive, reactive with many metals Hollow Core Fused Silica Silica tubes internally coated with silver and silver halide Good for laser power transmission, but the transmission changes when the fibers are moved. Fiber Materials © Remspec Corp. 2013

12. How Do Fiber Optics Work? Waveguide Structure © Remspec Corp. 2013

13. What is ATR? Attenuated Total Reflectance ATR crystal, or Internal Reflectance Element (IRE) Effect depends on differences in refractive index © Remspec Corp. 2013

14. What is ATR? © Remspec Corp. 2013

15. What is ATR? Approximate penetration depth at each bounce is given by the expression: = wavelength of the radiation, n p = refractive index of the crystal,  = angle of incidence of the light beam, and n sp = ratio of refractive indices of sample and crystal © Remspec Corp. 2013

16. ATR Tip on Fiber Optic Probe © Remspec Corp. 2013

17. ATR Tip on Fiber Optic Probe © Remspec Corp. 2013

18. Transmission Head © Remspec Corp. 2013

19. Transmission Head The Liquid Transmission Head lowers the detection limit to <0.1mM. It is a double-pass transmission cell with a mirror wall. It can only be used in solvents that have low mid- IR absorbance (e.g. hexane,acetonitrile, methylene chloride, THF); suspended solids can interfere with performance. © Remspec Corp. 2013

20. Calibration © Remspec Corp. 2013

21. Calibration © Remspec Corp. 2013

22. Calibration © Remspec Corp. 2013

23. Calibration © Remspec Corp. 2013

24. Fiber Handling Optical fiber is not copper wire. Weak chemical bonds are required for IR transmission. The fiber is packaged to withstand normal careful use and accidental mishandling. Do NOT force things. Avoid coiling the cables -- use a large bend radius when possible. © Remspec Corp. 2013

25. Fiber Handling The ends of the cables and the probe shaft are optically polished. Keep the optical surfaces clean at all times (if necessary, wipe with a cotton bud soaked in isopropyl alcohol or ethanol). Cover the ends when not in use. Take care when inserting the probe shaft into a probe head - - you are mating two optical surfaces. © Remspec Corp. 2013

26. Sampling Heads The Standard ATR Head is available in a range of materials; ZnSe is shown. ATR is ideal for solutions (down to ~0.1%), slurries and semi-solids. Only the liquid phase is sampled; the ATR head does not “see” suspended solids etc. 6 mm OD © Remspec Corp. 2013

27. Sampling Heads Low Temperature Head ATR or Transmission Room temperature to below -100ºC © Remspec Corp. 2013

28. Sampling Heads High Temperature Head Gas cooled (air or nitrogen) ATR or Transmission -100ºC to >200ºC; pressure-tolerant up to 30 bar (available) 15mm OD © Remspec Corp. 2013

29. Sampling Heads High Pressure Head 9/16” HIP or 1/2” Dynisco fittings P > 200 bar ATR or Transmission Gas cooled (air or nitrogen) -100ºC to >200ºC © Remspec Corp. 2013

30. Choosing a Head Standard Head -20ºC < T < 50ºC 0 bar < P < 5 bar Low Temperature Head -100ºC< T < 50ºC 0 bar < P < 5 bar High Temperature Head -100ºC < T < 200ºC 0 bar < P < 5 bar or 0 bar < P < 30 bar High Pressure Head -100ºC < T < 200ºC 1 bar < P < 200 bar © Remspec Corp. 2013

31. ATR or Transmission ATR Liquids Emulsions Suspensions 0.1% < C < 100% Soft Solids Transmission Liquids Gases (1 mm to 5 mm path) 0.001% < C < 0.5% (Liquids) Requires weakly absorbing solvent © Remspec Corp. 2013

32. Choosing an ATR Crystal ZnS Highest sensitivity Cuts off at 950 cm -1 Not resistant to halogenation reagents Good resistance to acid and base ZnSe Less sensitive than ZnS Full spectral coverage Not resistant to halogenation reagents Good resistance to acids and mild bases © Remspec Corp. 2013

33. Choosing an ATR Crystal AMTIR Similar sensitivity to ZnSe Resists acid up to and including fuming sulphuric Dissolves in strong aqueous base Not resistant to halogenation reagents Diamond Less sensitive than ZnSe Low Transmission at 2000 cm -1 Highly chemically resistant Expensive © Remspec Corp. 2013

34. Installation of Standard ATR Head Unscrew the metal end cap. The tip and the PTFE gasket should come off together with the end cap. Gently push the crystal out of the assembly with, e.g. a wooden toothpick. © Remspec Corp. 2013

35. Installation of Standard ATR Head Take a fine point and “screw” the PTFE gasket out from inside the end cap. The gasket is removed and discarded each time the end cap is dismantled. Place a new gasket (beveled side up) over the tip of the replacement crystal. Carefully insert the crystal into the end cap, pointed end first, so that the flat end will be next to the probe tip when the end cap is installed. © Remspec Corp. 2013

36. ReactionView® © Remspec Corp. 2013

37. Installation of Standard ATR Head Replace the Teflon tape in the threads of the probe shaft to ensure a good seal. Good sealing is very important. Leakage of liquids behind the crystal compromises optical performance and can permanently damage the probe tip. Thread the end cap onto the shaft and tighten to a hard “finger tight”. © Remspec Corp. 2013

38. Installation of Low Temperature Head The Low-Temperature Head slides onto the end of the standard Remspec probe. There is an ATR or optical transfer crystal inside the plastic jacket of the head. It is important to seat the crystal securely against the probe end using some spring tension– but be careful not to grind the end of the crystal, as this will diminish its optical performance. © Remspec Corp. 2013

39. Installation of HT and HP Heads After loosening the set screw gently slide the head onto the probe shaft Rotate head to optimize signal Stretch spring a little and tighten set screw © Remspec Corp. 2013

40. Transmission Head Adjustment The path length of the Liquid Transmission Cell is adjustable from <0.5 mm to about 6 mm. Adjustment is made by turning the screw at the end of the cell. Be careful not to drive the screw into the signal- transfer crystal when decreasing the path length. © Remspec Corp. 2013

41. Using OPUS © Remspec Corp. 2013

42. The “Measure” Menu © Remspec Corp. 2013

43. Measurement/Optic © Remspec Corp. 2013

44. Measurement/Acquisition © Remspec Corp. 2013

45. Measurement/Advanced © Remspec Corp. 2013

46. Measurement/Check Signal © Remspec Corp. 2013

47. Measurement/Check Signal © Remspec Corp. 2013

48. Optical Alignment The system comes pre-aligned with locked-down alignment at the interferometer end and a user- adjustable XYZ positioner at the detector end. After moving the equipment or disconnecting the probe, check the alignment. Use OPUS™ to check the signal level. © Remspec Corp. 2013

49. Launch and Detector Optics The X (side to side) and Y (up and down) adjustments are preset at the factory and cannot be changed by the user. The Z (in and out) adjustment is controlled by a screw ring. It may need a small amount of fine adjustment, but should not be over-adjusted. You are moving the probe end in and out of the focal point of the mirror with this adjustment. © Remspec Corp. 2013

50. In-Compartment Launch Optics The X and Y (side-to-side) and the Z (up-and-down) are preset at the factory and should not require to be changed. If a small adjustment is needed:  The XY holding plate is released using the four silver nuts. Do not loosen it too mcuh, just enough to move the optical connector around.  The Z adjustment is released using the silver ring. Adust the Z up and down by gently screwing the black ferrule 1/2 or 1/4 turn at a time.  You are moving the probe end in and out of the focal point of a mirror with these adjustmets. © Remspec Corp. 2013

51. Detector © Remspec Corp. 2013

52. You can sometimes enhance the signal level by very carefully rotating the probe end in the launcher fitting – be careful not to stress the optical cable if you do this. Sometimes, slight asymmetries arise in the packing of the optical fibers in the probe end, and this can lead to variations in the response depending on orientation. Launch and Detector Optics © Remspec Corp. 2013

53. Some Things to Look Out For Keep the cables away from hot objects. Use the align mode when making adjustments so you can tell if your changes are affecting the signal level. © Remspec Corp. 2013

54. Running Experiments: VizIR™ The opening screen shows the Control Panel for mid-IR reaction monitoring. File names and experimental parameters are set on this screen. © Remspec Corp. 2013

55. Setting Parameters Resolution The default value for mid-IR is 4 cm -1, recommended for most organic reaction mixtures. If noise is a particular problem, try 8 cm -1. To change the default resolution, type the number into the box on the screen. © Remspec Corp. 2013

56. Setting Mid-IR Parameters Scans The number of interferometer scans that are combined for each spectrum is a major factor in determining the level of noise and the overall quality of the data you will collect. In general, use the maximum number of scans possible for the time interval required between spectra. Type the number of scans you want into the “Scans” box on the screen (75 – 200 is typical). © Remspec Corp. 2013

57. Setting Parameters Collection Interval When you change the number of scans or the exposure time, VizIR automatically sets the minimum time interval between spectra. You can increase this time but not decrease it. To adjust the time interval, click the Adjust Interval button, set the time in minutes and seconds, then click OK. © Remspec Corp. 2013

58. Setting Parameters File Limits Sets the frequency limits of the spectrum that will be collected. Default mid-IR values: 5000 cm -1 and 900 cm -1 ( the full spectral range that is available from the system). © Remspec Corp. 2013

59. Setting Parameters File Name In the File Name box near the foot of the control panel, type the file name to be used for the new reaction monitoring data set. VizIR saves data from each experiment in Reaction Markup Language, a.reml multifile that can be read by VizIR and ReactionSleuth. All of the spectra are saved in a single file Notes and calculated trandlines are also saved VizIR also saves a GRAMS multifile in.spc format © Remspec Corp. 2013

60. Collecting Data Background Before collecting mid-IR data from a reaction, you must first collect a background spectrum. The reaction data will be “ratio-ed” against this background to give the spectrum of the reactants etc. To collect the background spectrum, make sure the probe is set up correctly, then click the Collect Background button. If you do not change the Background Name, the new background will be saved over the old one – this is usually OK. © Remspec Corp. 2013

61. Collecting Data Mid-IR Background Record the background in air: If you are looking for large spectral changes If the composition will change appreciably during the course of the reaction. If temperature changes during the reaction are likely to alter the spectral response of the solvent (e.g. If the solvent is water) Record the background in the reaction solvent: When you expect only small spectral or compositional changes When you are looking for features that you know are close to solvent features when using a transmission head © Remspec Corp. 2013

62. Collecting Data Typical mid-IR Air Background. The upper and lower display windows become active. © Remspec Corp. 2013

63. Collecting Data Single Scan Check that a appropriate file name has been entered, then click the Single Spectrum button. The trace appears in both Display Windows This feature is useful for collecting a solvent spectrum before the reaction begins. © Remspec Corp. 2013

64. Collecting Data Reusing background If you want to save the solvent spectrum and start a reaction run you can select File/Close/Clear current scan... to use the same background If you select...Completely close file, you will need to collect or load a new background. © Remspec Corp. 2013

65. Collecting Data Multiple sequential scan Type in a new file name in.spc format Check the settings (especially for Number of Scans, Exposure, and Collection Interval) Click the large green button at the top left of the screen, below the Display Menu. © Remspec Corp. 2013

66. Displaying Spectra 3D spectral display in real time Most recent spectra (1 or 5) Trend lines © Remspec Corp. 2013

67. Displaying Spectra Display/Secondary Plot allows you to change the content of the lower display window. The Secondary Plot sub-window includes: 1 or 5 most recent spectra Trend lines of peak intensity versus time © Remspec Corp. 2013

68. Displaying Spectra Spectral Limits Default limits ≡ Data collection limits Select Display/3D Settings or double-click the 3D display for access to the controls for the 3D spectral display. Upper and lower frequency limits have been changed and Applied. © Remspec Corp. 2013

69. Displaying Spectra Rotate first option under the Display Menu Also the default setting Hold left mouse key down and move cursor to rotate 3D display. Do not rotate more than half at urn in either direction. © Remspec Corp. 2013

70. Displaying Spectra Translate Second option under the Display Menu Hold left mouse key down and move cursor slowly up and down, or from side to side © Remspec Corp. 2013

71. Displaying Spectra Zoom Third option under the Display Men Hold left mouse key down and move cursor up or down the screen; the image will “zoom” in or out. © Remspec Corp. 2013

72. Displaying Spectra Stop/Start Updating Display The 3D image reverts to the default view every time a new spectrum is added to the data set. The final option under the Display Menu is “Stop Updating Display”. Data will still be collected, but you will be able to examine the 3D image using the Zoom, Rotate, and Translate options without interruption. When you select “Start Updating Display”, the display will be brought completely up to date. © Remspec Corp. 2013

73. Displaying Spectra Secondary Display Control Most Recent Spectrum is the default All possible choices are accessed at “Secondary Plot” under the Display menu. Most Recent Spectrum Five Most Recent Spectra (waterfall or overlaid) Up to 5 trend lines © Remspec Corp. 2013

74. Displaying Spectra Secondary Display Five Most Recent Spectra Spectra displayed in “waterfall” or overlaid format Updated as spectra are collected Most recent trace at back Useful for picking up the first appearance of a new feature © Remspec Corp. 2013

75. Displaying Trend Lines Secondary Display Trend Lines Start a graph of absorbance versus time (a trend line) at any time during your experiment up to five lines can be displayed at once Data from the entire run will be analyzed and displayed © Remspec Corp. 2013

76. Displaying Trend Lines Secondary Display Trend Lines A number of tools are available. Click Create Simple to access the most commonly used ones. © Remspec Corp. 2013

77. Displaying Trend Lines To generate a simple absorbance/time graph, identify the position of the peak that you want to follow. choose strong, isolated peaks that are expected to change intensity as the reaction progresses you can often pick peaks from the display of the five most recent spectra A simple graph of the absorbance measured at the selected wavelength versus time will often give a good trend line. © Remspec Corp. 2013

78. Displaying Trend Lines Simple Trendlines If you type in a peak position, you will see a preview of the absorbance/time trend at that position. Click Add to put it on the list of lines to be saved. © Remspec Corp. 2013

79. Displaying Trend Lines Peakfinder Visual tool for trendline selection Includes a guide to functional group positions* Displays the most recent spectrum, with any limits you have previously set Wavenumber and Absorbance counters track cursor * Can be customized for specific reactions © Remspec Corp. 2013

80. Displaying Trend Lines Peakfinder Displays the most recent spectrum, with any limits you have previously set Wavenumber and Absorbance counters track cursor Use the cursor to draw a box around a feature to be expanded. © Remspec Corp. 2013

81. Displaying Trend Lines Peak Finder Left-click to select peak position The selected peak wavenumber will be used for the trend line Right-click to Autoscale the display and reset it to full range. © Remspec Corp. 2013

82. Displaying Trend Lines Trendline List You can add as many lines as you like to the list of saved trendlines. Up to five can be displayed at once. Select a tab, then select the line you want. © Remspec Corp. 2013

83. Displaying Trend Lines Trend Line graph of Absorbance Units versus time calculated from the beginning of the data set up to date automatically updated when new spectra are added to the data set © Remspec Corp. 2013

84. Displaying Trend Lines Baseline Correction identify areas of the spectrum that are free from spectral features to give a good baseline position Correction can be added manually or by using Peak Finder. © Remspec Corp. 2013

85. Displaying Trend Lines Baseline Correction single-point correction Choose a wavenumber where there are no peaks Absorbance at that position is subtracted from the absorbance of the chosen peak two-point correction A straight line is calculated between two points that define the baseline Baseline absorbance at the peak position is subtracted from the total peak absorbance © Remspec Corp. 2013

86. Displaying Trend Lines Baseline Correction The 2-point correction uses the peak position and one baseline value. © Remspec Corp. 2013

87. Displaying Trend Lines Baseline Correction In the Peakfinder, select the main trendline peak by double-clicking. Then, select the baseline point and double-click there (repeat at a second baseline position for 3- point correction). © Remspec Corp. 2013

88. Displaying Trend Lines Baseline Correction In many cases, the 2- and 3-point corrections will lead to small differences in the resulting trend line © Remspec Corp. 2013

89. Displaying Trend Lines In some cases, even with baseline correction, the simple graph of peak absorbance versus time does not match the behavior of the peak observed in the 3D display. When the selected peak is part of a group of closely spaced peaks, consider using curve- fitting methods to model a spectral region. © Remspec Corp. 2013

90. Data Handling Saving trend lines Peak fitting Using GRAMS/3D © Remspec Corp. 2013

91. Saved Data Sets You can use VizIR to display and manipulate saved data sets from completed experiments Make sure data collection is not active, or stop the experiment using the red STOP button Select “Close Window” from the File menu Use File/Open to open any saved experiment Saved experiment files will be named [name].reml. A copy of the spectral data will also be saved in.spc format. By default, they are saved in the VizIR\Data directory © Remspec Corp. 2013

92. Saved Data Sets All of the VizIR features can be used with saved data sets © Remspec Corp. 2013

93. Saving Trend Lines Trend lines are set up in the same way as for realtime display The entire data set is used © Remspec Corp. 2013

94. Saving Trend Lines Save Trend Lines Select Data/Trendlines/ Save or File/Save Trendlines Saved as.csv files suitable for import into a spreadsheet. © Remspec Corp. 2013

95. Saving Trend Lines Save Trend Line Easily imported into spreadsheets for further analysis © Remspec Corp. 2013

96. Peak Fitting Simple absorption/time graphs are not always adequate Overlapping peaks Peaks with shoulders If you need to “follow” a diminishing peak down to a level close to baseline noise © Remspec Corp. 2013

97. Peak Fitting © Remspec Corp. 2013

98. Peak Fitting © Remspec Corp. 2013

99. Peak Fitting Peak fit model building is a function that is not available in VizIR™ GRAMS/AI® is used GRAMS/AI® is included with the standard ReactionView™ system, and will have been preinstalled on your computer if purchased from Remspec © Remspec Corp. 2013

100. Peak Fitting Open GRAMS/AI® Use File/Open Trace to open the multifile you plan to use. This is the filename that you chose at the beginning of the experiment, e.g. run01.spc The first spectrum in the file will be displayed. You can display all of the spectra in turn using Page Up/Page Down © Remspec Corp. 2013

101. Peak Fitting Pick a spectrum that shows all of the peaks that you wish to model. Typically, you should model peaks from an early spectrum if a strong peak is disappearing Model from the middle or end of the experiment if a feature is emerging as the reaction progresses. © Remspec Corp. 2013

102. Peak Fitting To set up the model: Display the individual spectrum you want to model using Page Up/Page Down Select the spectral range using View/Trace Limits to set the Left X and Right X values. It is usually unwise to model the entire spectrum; pick the range that is of greatest chemical significance, or where you see changes from spectrum to spectrum In the example, we are going to use the region from 1170-1900 cm -1 © Remspec Corp. 2013

103. Peak Fitting Select Applications/Advanced Processing and take the option Peak Fitting Alternatively, you can select “curvefit.ab” from the Applications/AB Program file selector You will see a warning that Peak Fitting can only be performed on the current subfile. Click OK, and you will see the following screen: © Remspec Corp. 2013

104. Peak Fitting © Remspec Corp. 2013

105. Peak Fitting The Control Panel on the right of the screen gives access to all of the peak-fitting capabilities of GRAMS/AI®. A simple set of steps to build a peak fitting model for use in VizIR™ is outlined below. For a detailed description of the features in GRAMS/AI®, see the GRAMS/AI® manual that was enclosed with ReactionView® © Remspec Corp. 2013

106. Peak Fitting Select the Find tab set the Peak Function to Lorentzian. This determines the mathematical function that will be used to model the peaks in the spectrum. The Lorentzian function better describes the line shape of an IR absorption the the default Gaussian function. © Remspec Corp. 2013

107. Peak Fitting Select the Peaks tab Position the pointer at the top of the first peak and right click A Lorenzian-shaped model peak will appear at that position. Continue to point-and-right-click all the peaks in the range, until a model peak has been created for each. To remove a model peak, select the “Delete” radio button on the Control Panel, then right-click the peak To start over, click the “Clear” button © Remspec Corp. 2013

108. Peak Fitting Select the Iterate tab in the Control Panel. It is usually best to accept the default setting and values here, so simply click the “Run” button. When the iterations are complete, you will see a screen showing the Original Trace and Fitted Trace: © Remspec Corp. 2013

109. Peak Fitting © Remspec Corp. 2013

110. Peak Fitting After inserting model peaks, the “Pk Params” button will become active. Click it, and you will see a list of peaks with their properties. You can edit the properties by highlighting a row and clicking “Edit”. © Remspec Corp. 2013

111. Peak Fitting You may need to fix or limit certain parameters so that they will not be varied during an iteration. For example, set the Low Limit for the height of a peak to 0 (zero) to prevent its value from becoming negative during iteration. Fix or limit the Width of certain peaks to prevent them from “smearing out” during iteration. © Remspec Corp. 2013

112. Peak Fitting To see statistical parameters such as reduced χ 2, click the “Statistics” button on the Control Panel. In many cases, including this example, you will find that the fit is good, but not perfect; the fit may be characterized as a Local Minimum, based on the χ 2 value. You can often improve the fit by using advanced features of the GRAMS/AI® curve- fitting procedure, and you will find complete details on how to do this in the GRAMS/AI® manual. To construct useful trend lines based on peak positions and areas, the procedure described above will usually give quite adequate data. © Remspec Corp. 2013

113. Peak Fitting The peak model must be saved for use in VizIR™. Before saving, you must fix some of the peak parameters, particularly peak position and peak width (at half height). To do this, use the Peak Params./Edit option for each peak. © Remspec Corp. 2013

114. Peak Fitting Save the model for use in VizIR™ Exit the Pk Params dialog Activate the Options Tab Click the “Save” button under “Parameter File”. Save the file in the VizIR/Data directory in the format: [name].crv You can then close out of the Peak Fitting program and close GRAMS/AI®. © Remspec Corp. 2013

115. Peak Fitting In VizIR™, you can use a saved peak-fit model to calculate trend lines for all of the peaks in the model. With a saved multifile from a completed experiment (including the one you used to develop the model). To calculate a real-time trend line for an experiment in progress (the reaction mixture must be similar to the one used to develop the model). You can even open a current multifile while the experiment is running – just minimize VizIR™, open GRAMS/AI, and follow the regular peak-fitting procedure. You can then use the new peak- fitting model to analyze the spectra as they are collected. © Remspec Corp. 2013

116. Peak Fitting Using a Peak Fit model in VizIR™ Select Data/Start PeakFit. You will be prompted for the.crv file that contains the model (this will usually have been saved in the RamIR/Data folder). The program will attempt to fit the model against each of the subfiles in turn. Be patient – the process may take a few minutes if a large multifile has been saved from a experiment. Once the calculation is complete, the results are available for use in creating a trendline. © Remspec Corp. 2013

117. Peak Fitting Select Display/Secondary Plot, and you will see a list of the trendlines that have been calculated and are available for display. When a Peakfit model has been run, the resulting peaks will appear in the list. They are labelled “PF” to distinguish them from other types of trendline. © Remspec Corp. 2013

118. Peak Fitting Trendlines calculated by Peak Fitting, by 2-Point Baseline Correction, and by 1-Point Absorbance versus Time are very similar in most cases. Differences arise if: 2 overlapping peaks vary in different fashion between spectra A peak “disappears” into the baseline © Remspec Corp. 2013

119. Resources Griffiths and De Haseth Fourier Transform Infrared Spectroscopy, Wiley, New York, 2007 (2 nd edition) www.spectroscopynow.com infrared.als.lbl.gov/FTIRinfo.html Socrates, Infrared and Raman Characteristic Group Frequencies: Tables and Charts, Wiley, New York, 2004 www.spectraonline.comwww.spectraonline.com [free library of FTIR, Raman and other spectra provided by Thermo Fisher Scientific, all in the GRAMS.spc format]