MP analysis by FTIR spectroscopy. From From macro macro scale analysis to micro scale imaging-ftir. State of the art and future perspectives. Alvise Vianello Vianello, Jes Vollertsen Aalborg University, Denmark
1 µm The size range and the analytical techniques for MP analysis 100 µm 10 µm 1000 µm Increasing uncertainty 5000 µm Optical microscopy µ ATR FTIR (single point analysis of particles on a filter) Increasing uncertainty Possibly down to a few μm (not proven) ATR FTIR (particles hand picked, analyzed on bench) Imaging μft IR using filters, windows, or slides IR Molecular Spectroscopy Macro Raman (particles hand Imaging μraman possible method, not well proven picked, analyzed on bench) NIR (pre sorting, bench analysis) Hy Spec. Imaging NIR (not well proven) TDU Pyr GC/MS; TED GC MS
Spectroscopic techniques for MP analisys Infrared (IR) molecular spectroscopy is the most used instrumental technique to identify polymers particles in environmental samples (28 studies Hidalgo Ruz et al., 2012) Wavenumber (cm 1) Electromagnetic spectrum 109 GAMMA RAYS 10 6 Most used IR spectroscopy! 107 108 10 5 X RAYS 10 3 10 4 ENERGY DECREASE WAVELENGHT INCREASE NEAR IR 14000 IR region 0,7µm 0.16 0,95 NIR 0.15 0.14 0.13 105 ULTRAVIOLET (UV) 10 2 4000 104 10 1 500 103 0,85 0,80 0,75 1 10 20µm 0,80 0,55 0,60 0,50 Intensity Absorbance Absorbance 0,65 0,45 0,40 0,35 0,40 0.06 0,35 0.05 0,30 0,25 0.04 0,25 0,20 0,20 0,15 0,30 0,15 0.02 0,10 0,10 0.01 0,05 0,05 4700 4600 4500 4400 4300 Wavenumbers (cm-1) 4200 4100 4000 Raman 0,65 0,45 107 106 Wavelenght (µm) 105 500µm 0,70 0,55 RADAR, RADIO, TELEVISION WAVES 20 Micrometers 0.10 0.03 104 0,75 0,50 10 1 FAR IR 0.11 0.07 103 Wavenumbers (cm 1) 0,60 0.08 1 MICROWAVES 102 0,70 0.09 10 INFRARED (IR) MID IR 2,5µm 102 FT-IR 0,90 0.12 106 VISIBLE 1010 ENERGY INCREASE WAVELENGHT DECREASE 10 3 10 2 3500 3000 2500 2000 Wavenumbers (cm-1) 1500 1000 500 3500 3000 2500 2000 1500 Raman shift (cm -1) 1000 500
FT-IR spectroscopy FT-IR Vibrational spectroscopy which relies on the interaction (mostly absorption) of IR light with matter (sample). IR beam IR Active molecular specific bonds VIBRATIONS IR ABSORPTION (I0).. if there is a Δ in the molecular electric dipole moment Energy absorption IR vibrations are characteristic for each chemical bond, they "occupy" precise regions of the IR spectrum (specific wavenumbers ranges) Identification of a wide range of substances (organic and inorganic) IR Spectrum H2O FT-IR Spectrum 1,0 0,9 O H Stretching 0,8 0,7 Absorbance I<I0 (I) H O H Bending 0,6 0,5 0,4 0,3 0,2 0,1 4000 3500 3000 2500 2000 1500 1000 500 Wavenumbers (cm-1)
Quick overview of the IR vibration normal modes Direction Symmetry Radial Latitudal Longitudal Symmetrical stretching Scissoring Wagging Antisymmetrical stretching Rocking Twisting Symmetric Antisymmetric
FT-IR spectrometer Michelson Interferometer Sample chamber Detector Light measured by detector Interferogram Data collection and management Mobile mirror Fourier Transform Mirror position (mm) Single beam 4.0 Interface Computer 3.5 3.0 Single Beam 2.5 Beamsplitter 2.0 1.5 1.0 0.5 Fixed mirror Sample 0.0-0.5-1.0 3500 3000 2500 2000 Wavenumbers (cm-1) 1500 1000 Background FTIR spectrum Source 0,95 PE 0,90 0,85 0,80 0,75 0,70 Absorbance 0,65 0,60 0,55 0,50 0,45 0,40 0,35 0,30 0,25 0,20 0,15 0,10 0,05 4000 3500 3000 2500 2000 Wavenumbers (cm-1) 1500 1000 500
FT-IR for MP analysis MP identification according to their characteristic IR spectra (highly specific IR absorption, distinct band patterns in FT IR spectra) Sample preparation Dependent by the signal aquisition mode. A a clean up step is suggested to remove organic matter; sample must be dried (H 2 O absorbs in FT IR) FT IR analysis ATR (Macro/µ) Diffuse Reflection Trans Reflection Transmission ATR crystal Sample IR beam I 0 to detector I IR beam Diffuse component Sample I 0 IR beam Specular component to detector I Transmitted component Sample Gold coated slide I 0 IR beam Sample I Transmission window to detector LMPPs 5 1mm; SMPPs (1mm 300μm) SMPPs (300μm 5μm) MALMÖ, NOVEMBER 8 th 2017
Analysis of Large MP by ATR-FTIR spectroscopy FTIR analysis of pre sorted Large MP (5000 500/300 µm particles) 0.20 FTIR Spectrometer + ATR Sample spectrum Ref. spectrum Spectrum analysis Abs 0.15 0.10 0.05 Polypropylene: Match = 98.53 % 0.20 Abs 0.15 0.10 0.05 Spectrum collection 4000 3500 3000 2500 2000 Wavenumbers (cm-1) 1500 1000 500 Advantages Good FT IR spectra from massive and rough samples Diamond ATR, no issues with silicates or hard materials Drawbacks Manual analysis (time consuming) Particle size limitation (500/300 μm)
Analysis of Small MP by FTIR spectroscopy: µft-ir μft-ir Analysis of MP directly on filter/ IR slide/ir windows IR Microscope FTIR Spectrometer Cassegrain objective Single point μft-ir Analysis Microscopic inspection of the sample (filter, petri dish, etc.) Analysis of selected single particles by FTIR choosing the right beam size (µatr; Reflection; Transmission) µftir spectrum from a single MCT detector µft-ir-imaging analysis Analysis of the spatial distribution of the component materials in a sample FTIR imaging systems contain multi element detectors, producing IR images (each pixel contains an IR spectrum)
Source globar Interferometer IR Objective scheme Detector Reflection Cassegrain Objective Single MCT detector Linear array detector µft-ir Mirrors Sample Mirrors Transmission FPA detector Cassegrain Condenser MALMÖ, NOVEMBER 8 th 2017
µft-ir-imaging spectroscopy for Small MP analysis µft-ir-imaging Powerful and versatile analytical technique for spectrochemical imaging Analysis of the spatial distribution of the component materials in a sample FTIR imaging systems contain multi element detectors, producing IR images (each pixel contains an IR spectrum) at relative hi speed. The array detector allows to collect up to 16,000 pixels/spectra simultaneously and has therefore enabled the FT IR microscopy to become also an imaging technique. Visible Image IR Image Filtered IR Image
µft-ir-imaging spectroscopy for MP analysis (Linear array vs Focal Plane array detectors) Linear array 2 linear arrays of 16 MCT detectors Slower than FPA High spatial resolution ( 10 µm) Spectral range 4000 800 cm-1 FPA detector (32x32 up to 128x128 MCT detectors) Faster than Linear Array Best spatial resolution ( 5 µm or more) Spectral range 4000 900 cm-1 Focal Plane array
FPA-µFT-IR-Imaging spectroscopy for Small MP analysis Visible Image IR Map 70 Row = 146 Col = 111 %T 60 1332.050-154.692 50 40 Spectral range Image filter 30 20 1714.910 2624.178 FTIR spectrum (PBT) 1262.750 3035.053 3700 3600 3500 3400 3300 3200 3100 3000 2900 2800 2700 2600 2500 2400 2300 2200 2100 2000 1900 1800 1700 1600 1500 1400 1300 1200 1100 1000 900 Wavenumbers (cm-1)
FPA-µFT-IR-Imaging spectroscopy for Small MP analysis Powerful and versatile analytical technique for spectrochemical imaging Sample (10 mm diameter) scan velocity up to 4,5h (128x128 FPA) 2 3 scans per day Huge amount of data (Many GB!) to process Multiple issues in data handling and managing Most of FT IR imaging softwares are not reliable for the MP analysis A lot of clicking Inaccurate analysis!
FPA-µFT-IR-Imaging spectroscopy for MP analysis: First example of automatic pipeline (AWI) Data aquisition from FPA µft IR Imaging FTIR Data processing by Opus Macro Image analysis (Python Script) Open source/freeware software MP identification, quantification and image analyis (particle size distribution) Based on a commercial FTIR software Primpke et al., 2017
A dedicated MP analysis software First steps in developing a dedicated software for FPA Imaging data analysis MPHunter Software written by Jes Vollertsen using RAD Studio (Embarcadero Delphi IDE) RAD Studio: an object oriented programming environment allowing easy construction of user friendly interfaces preserving fast computational speed.dmd (Agilent) and.dx (Bruker) file conversion to MPHunter software file format (.spe) Managing of FPA data from different FPA detectors (e.g. 64x64 and 128x128) Friendly User Interface (FT IR software like ) Extremely light application around 5 MB! MALMÖ, NOVEMBER 8 th 2017
How does it works? Load a pre converted mosaic Load reference spectra from a library (file.txt) Select one or more ref. spectra (we hope to use it with many ref. spectra ) Load the filters (to use afterwards) Select the spectral range (up to 4 ranges at the same time here just 3750 860 cm 1) Heat map Control Panel Ranges Ref. Library Filters
How does it works? Pearson s Correlation Coefficient analysis Removing noise using filters Mark particles as MP Measure dimensions Save MP Display the found MP
...To summarize... FTIR is the most promising analytical technique for MP analysis (ID, quantification) Macro ATR FTIR is suitable for Large MP analysis, giving reliable results, but it is manual and time consuming Other IR techniques (like Hy Spec NIR and Macro Raman) has to be tested to automatize Large MP analysis Imaging μft IR is the most suitable technique for Small MP analysis, avoiding manual pre sorting A full automatization (or semi automatization) of the data analysis is important to increase the accuracy and precison of the analysis AWI automatic pipeline is the first example of fully automatized MP data analysis (very important step) AAU MPHunter is another example of semi automated software for MP analysis, user friendly and customizable A better automatization is required to make MPHunter more reliable and eventually get rid of the clicking nightmare Interface MPHunter with AWI Automatic Pipeline for MP analysis, creating a freeware program for MP data analysis MALMÖ, NOVEMBER 8 th 2017
Thank you av@civil.aau.dk MALMÖ, NOVEMBER 8 th 2017