Výběr z aplikací infračervené spektrometrie Ján Pásztor, Nicolet CZ s.r.o.

Transcription

1 Výběr z aplikací infračervené spektrometrie Ján Pásztor, Nicolet CZ s.r.o.

2 Fourier Transform Infrared Spectroscopy Introduction Electromagnetic radiation Vibrational spectroscopy Instrumentation Interferometry The Fourier Transform

3 Electromagnetic Spectrum x-rays visible near-ir microwave ultraviolet mid -IR far-ir radio waves Wavenumbers nuclear electronic vibrational rotational transitions Wavelength in microns

4 Harmonic Vibrations The vibration of a diatomic molecule can be approximated by the vibration of a spring R e -DR R e R e +DR The wavenumber of the vibration equals: 1 k 2x m c m with m= 1 m 2 m 1 + m 2

5 Quantized harmonic, anharmonic h/2p (k/ k/m).( M).(ν+1/2)

6 Selection Rules for Infrared Activity The frequency of the light must be identical to the frequency of the vibration (resonance) The dipole of the molecule must change during the vibration The direction of the dipole change must be the same as the direction of the electric field vector

7 Dipole Change To absorb energy, the dipole must change when the transition occurs The intensity of the absorption is proportional to the magnitude of the dipole change Cl H N N

8 %T Molecular Vibrations Bending Twisting + - C C C C C Stretching Deformation cm- 1

9 Polyatomic Molecules The spectrum becomes more complex as the number of bonds increases Functional groups Fingerprint region Wavenumbers (cm -1 ) 1000

10 Energy Frequency Non-linear Triatomic Molecule (H 2 O) 3 normal vibrations (3N-6) Coupling of vibrations bending (1595 cm - 1 ) E E 1 E symmetric stretching (3657 cm - 1 ) E 2 asymmetric stretching (3756 cm - 1 )

11 Fixed Rotations in a Lattice (-CH 2 ) Since the atoms are fixed in a skeleton, more bending vibrations occur scissoring (~1463 cm - 1 ) twisting (~1300 cm - 1 ) - + CH 2 rocking at 720 cm -1 wagging (~1280 cm - 1 ) + +

12 Overtones Occur close to INTEGER MULTIPLES Of FUNDAMENTAL Bands. For example: C-H Overtones Will Occur Near: First Overtone 2960 cm -1 (C-H Stretch) * 2 = 5920 cm -1 Second Overtone 2960 cm -1 (C-H Stretch) * 3 = 8880 cm -1 The intensity of the absorption depends on the degree of anharmonicity and gets weaker with increasing overtones

13 Combination Bands COMBINATION Bands Appear Near The Sum Of Two Or Three FUNDAMENTAL Bands For Example: A C-H Combination Will Occur Near 2960 cm -1 (C-H Stretch) cm -1 (C-H Bend) = 4420 cm -1

14 Absorbance (Log 1/R) NIR spectrum 0.5 Combination st Overtone 0.2 2nd Overtone rd Overtone Wavelength (nm)

15 Sources, Beamsplitters and Detectors

16 Source, Beamsplitter, and Detector Combinations Depend on Application

17 FT-IR System

18 Wave Interactions (Interference) In-phase Constructive interference + = Out-of-phase Destructive interference + =

19 Michelson Interferometer-1 Interferometer Fixed mirror BF BM l 0 -l Moving mirror Beamsplitter IR Source BF = BM Path difference = 0 Detector

20 Michelson Interferometer-2 Interferometer Fixed mirror BF BM l 0 -l Moving mirror Beamsplitter IR Source BF = BM - 1/8 Path difference = 1/4 Detector

21 Michelson Interferometer-3 Interferometer Fixed mirror BF l 0 -l Moving mirror BM Beamsplitter IR Source BF = BM - 1/4 Path difference = 1/2 Detector

22 Michelson Interferometer-4 Interferometer Fixed mirror Moving mirror 0 - Beamsplitter IR Source Detector

23 Voltage Signal at the Detector 0 1 / 4 1 / 2 3 / 4 Path difference

24 Volts Volts The Interferogram One Wavelength Many Wavelengths Data Points Data Points

25 Sampling the Interferogram Source He-Ne laser

26 Dynamic Alignment Fixed mirror Beamsplitter Moving mirror x 0 -x Laser diodes He-Ne laser R X Y

27 Dynamic Alignment Advantages Better short term stability Better long term stability Better spectral line shapes

28 Fast Fourier Transformation Interferogram FFT Spectrum V o l t s Data Points E m i s s i v i t y Wavenumbers

29 Transmission Spectrum Data Points Volts Data Points Volts Wavenumbers Emissivity Wavenumbers Emissivity bkg: FFT sam: FFT Wavenumbers Transmittance Ratio

30 Summary Advantages of FT-IR Instruments Multiplex advantage (Felgett s) All wavelengths are measured simultaneously Throughput advantage (Jacquinot s) Higher energy throughput (larger apertures) Precision advantage (Connes ) Internal calibration is derived from He-Ne laser (precision = 0.01 cm -1 )

31 Technique Choice Analytical goals Quantitative Qualitative Sample dependent factors Size Chemical makeup of sample Optimization

32 Sampling Techniques and Applications Transmission Attenuated Total Reflectance - ATR Diffuse Reflectance DRIFTS Gas Analysis Semiconductor Oil Analysis GC/FT-IR TGA/FT-IR Mobile/Portable FT-IR

33 Advances in Accessory Design Automatic set-up of system parameters and experiment Rugged, permanently aligned, plug & play design On-line help and tutorials Design for fast purge Operation integrated with spectrometer and software Automatic tests ensure proper accessory operation System checks ensure high quality spectra are collected

34 Transmission Analysis Requires sample preparation Proper pathlength required Strong absorbers - short pathlength Weak absorbers - long pathlength Solids, liquids, gases Qualitative analysis Quantitative analysis Maximum sensitivity Low cost

35 Analysis of Antioxidant Levels in Lubricating Oil The peak at 3651 cm -1 was used to quantify the antioxidant butylated hydroxy toluene (BHT) in the poly-a-olefin (PAO) lubricant

36 Attenuated Total Reflectance Versatile and non-destructive technique for infrared sampling Requires minimal or no sample preparation Useful for surface characterization

37 Considerations for ATR Analysis d p = 2p n atr (sin 2 q) - [ ] 1/2 ( ) 2 n sample n atr Refractive index of ATR and sample Pathlength requirements Spectral range of interest Phase of sample: solid, liquid, gel Chemical properties Hardness of sample

38 Attenuated Total Reflectance ATR Single Bounce vs Multi-bounce Plunger Crystal Cap Penetration depth up to two microns Crystal IR Beam ZnSe Internal Reflection Element Small sampling area Use for strong absorbers Solid samples Broad sampling area provides greater contact with the sample Use for weak absorbers or dilute solutions

39 Properties of ATR Crystals ATR Spectral Range (cm-1) Refractive Index Depth of Penetration (µ) (at 45º & 1000 cm-1) Material Uses Good for most samples. Germanium 5, Strong absorbing samples, such as dark polymers. Silicon 8,900-1,500 & Resistant to basic solutions. AMTIR 11, Very resistant to acidic solutions. ZnSe 15, General use. Good for most samples. Diamond 30, Extremely caustic or hard samples.

40 Analysis of Fibers Using Single Bounce ATR No sample preparation Non-destructive to the sample Shallow depth of penetration good for dark polymers

41 Identifying Fiber Threads Inside An Automotive Hose

42 ATR Summary Ease-of-use Rapid qualitative and quantitative analysis No sample preparation Multiple crystals for various sampling needs Best technique for condensed phase samples

43 Diffuse Reflectance (DRIFTS) A multi-modal technique Specular Reflectance Diffuse Specular Reflectance True Diffuse Reflectance Kubelka-Munk equation Absorbance-like results F(R ) = (1-R ) 2 2R = K S R = reflectance with infinite depth K = molar absorption S = scattering coefficient

44 Compound Parabolic Concentrator Independent of sample height Reduces sample packing effects Minimizes front surface reflection (specular component) Efficient high throughput collection optics Sample positioned below optics No damage to optics from sample spills CPC Design Input / output optics CPC Powder sample cup

45 DRIFTS Analysis of Pharmaceutical Powders

46 Lo g( 1/R) Lo g( 1/R) Lo g( 1/R) DRIFTS Analysis of Pharmaceutical Powders 0.5 Ibuprofen Powder 0.4 Analytical Goal 0.3 Naproxen Sodium Powder Simplified sample preparation Identification of key ingredients Ps eudoephedrine H Cl Powder Wav enumbers ( cm- 1)

47 Benefits of Diffuse Reflectance Good choice for dilute powders Analysis of non-reflective materials Minimal sample preparation

48 FT-IR Gas Analyzer Detects pollutants CO, NOx, HC NH 3, HCN, N 2 O Nexus Gas Analyzer 2 meter gas cell MCT-A detector Detection limits less than 1 ppm 0.09 cm -1 resolution

49 NO x Reduction in Diesel Exhaust Diesel engines are run lean, i.e. with excess air during combustion Naturally low hydrocarbon and CO emissions but high NO and NO 2 emissions Urea with catalyst can reduce NO and NO 2 However, concern is that HCN is generated

50 Abs HCN Emissions Urea injection reduced NO and NO 2 and can be tuned to minimize HCN generation HCN 97 ppm in exhaust HCN 0.6 ppm in exhaust HCN standard cm

51 Semiconductor Wafer Analysis Semiconductor devices are manufactured on silicon wafers, using successive layers of metals and insulators Many devices are produced from each wafer. As many as 300 Pentium TM like devices, or more than 800 memory chips, can be produced from a single 8 or 12 diameter wafer

52 Semiconductor Analysis The samples were analyzed using the Nicolet ECO 3000 Samples were scanned in transmission (silicon is transparent to infrared radiation)

53 Si-H Variation

54 Conclusion Hydrogen concentration can effect the dielectric constant in these films Customer was able to identify a heating problem with the wafer platen in the deposition system, based on the shape of the center region of the profile After adjusting the temperature parameters in the system, uniform films were produced and device yields reached 98%

55 Approaches for Lubricant QC Total Process Checking Incoming ingredient testing Base oil and add-pack lot consistency Blended product analysis Additive levels Outgoing product verification Assure product correct for shipment Used Oil Analysis Engine Monitoring Edible Oil Analysis Product Consistency

56 Integra Oil Analysis

57 Spectral Regions of Interest for Used Oil 0.8 Water Nitro Sulfate A bs 0.7 Carboxyl Fuel o r b a nc e Soot Glycol 0.2 Phosphate Anti-wear Wavenumber

58 Polymer Additive Identification by GC/FT-IR Reverse Engineering Customer wants to deformulate competitive product Product is complex polymer with several additives GC analysis alone was inconclusive Infrared spectroscopy was necessary for identification of additives

59 Nicolet Nexus GC/FT-IR System

60 Polymer Additives by GC/FT-IR Real-Time Display 8 cm-1 Resolution 0.74 sec/spectrum

61 GC/FT-IR Peak Identification

62 TGA/FT-IR Rubber Gasket Characterization High pressure and temperature application Gasket from backup supplier fails TGA only reveals small difference TGA/IR reveals compositional differences

63 TGA/FT-IR System TGA FT-IR spectrometer TGA/IR interface OMNIC Series software

64 TGA/IR Data of Rubber Gaskets 8 cm -1 resolution DTGS detector 10.0 sec time resolution OMNIC Series software

65 TGA/IR Spectra of Rubber Gasket Samples

66 Library Search Results

67 Mobile and Portable Infrared Analysis Incident Preparedness and Response (IPAR) First Responders Fire Fighters Clandestine Lab Investigators WMD/CST US Army/US Navy

68 Implementation Mobile system offers full sampling flexibility in a small footprint Expandability and flexibility AC power necessary GLP or 21 CFR Part 11 software tools Portable system offers rapid setup and simplicity of operation Compact, integrated, transportable system Flexible power sources - AC, 12 volt or battery Laptop computer compatibility via USB

69 Mobile Solution Full laboratory capability in a small footprint Dynamic Interferometer alignment Rugged--Sealed and desiccated or Purgeable Smart accessories ease sample preparation Full OMNIC capability IR Microscope ready GLP, Validation 21 CFR Part 11 Compliance tools

70 Hazardous Sample Analysis Accessory Smart Golden Gate Diamond ATR Natural Type IIa diamond Diamond brazed to tungsten carbide disk Top plate removable for glove box loading Sample anvil isolates sample from environment Extremely easy-to-use and simple decontamination

71 Absorban ce Hazardous Materials Analysis 0.14 Mustard HD Wav enumbers (cm-1)

72 Conclusions - Sampling Techniques Thermo Electron FT-IR spectrometers provide a broad range of analytical solutions We develop new sampling technologies based upon your sampling needs Speed, resolution and sensitivity of our systems can be tuned to your experiment Let us know how we can help solve your analytical problems

73 Human Hair Analysis Verify the fiber to be consistent or inconsistent with hair from the suspect FT-IR microscope w/ ATR objective

74 Absorbance Surface Analysis of Hair ATR, excellent surface analysis tool Maximizes surface response Hair without Hairspray Hairspray on Hair Wavenumbers (cm-1) 1000

75 Absorbance Surface Analysis of Hair Difference FT-IR bands consistent with PVA hair spray ATR microscopy - surface sensitive, non-destructive Subtraction Result: Hairspray on hair - hair PVA from Library Wavenumbers (cm-1) 1000

76 Fiber from Crime Scene Fiber Diameter - 20 microns ATR Objective Sample Area - 7 microns

77 Micro ATR Fiber Spectrum micron diameter fiber by Micro-ATR 1.4 A b s o r b a n c e

78 Paint Chip Analysis Automotive Paint Identification Multilayered, microns each Redundant Aperturing Required

79 View-Thru Aperturing - 15x15 microns No Apertures Lower Aperture Both Apertures Analyze!

80 Paint Spectra Grey Layer - 25 microns thick Red Layer - 17 microns thick Clear Layer - 25 microns thick A b s o r b a n c e Wavenumbers (cm-1)

81 NIR Spectroscopy Advantages Easier Remote sampling No sample preparation Glass is transparent Quick data collection Disadvantages Difficult or impossible to interpret spectra More complex to develop methods Difficult to add extra compounds to a sample ID method

82 SabIR Near-IR Fiber Optic Accessory

83 Absorbance NIR Fiber Optic Sampling 1.0 Aspirin Tablet in Packaging Wavenumbers (cm-1) 6000

84 Absorbance Polyvinyl Chloride / Vinyl Acetate Copolymers PVC100 PVC/AC 90/10 PVC/AC 87/13 PVC/AC 81/ Wavenumbers (cm-1)