From Tap Water to Marine Organisms: a Micro-Spectroscopic Approach - - PowerPoint PPT Presentation

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From Tap Water to Marine Organisms: a Micro-Spectroscopic Approach to Micro-Plastic Characterization

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Name Abbreviation Expanded Polystyrene EPS Polypropylene PP Polyethylene PE Acrylonitrile-butadiene-styrene ABS Polystyrene PS Polyamide (Nylon) PA Polymethyl methacrylate PMMA Polycarbonate PC Cellulose Acetate CA Polyvinyl chloride PVC Polyethylene terephthalate PET Polytetrafluoroethylene PTFE

• A micro-plastic is a small piece of plastic
• How small?
• 5 mm to 1 micron
• Common micro-plastics
• PE, PP, PET
• Sources
• Primary
• Particles designed to be small (ie: cosmetic

microbeads)

• Secondary
• Formed from the breakdown of larger items

Micro-Plastics – What are they?

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1) Synthetic fibers in the wash 2) Tire dust 3) Paints 4) Secondary microplastics 5) Synthetic fibers in the air 6) Microbeads - primary

Where Does It Come From

https://orbmedia.org/stories/Invisibles_plastics/multimedia

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• Ubiquitous
• Found in so many places
• Environmental Impact?
• Aquatic life
• Food Chain
• Water Supply
• Bottled Water
• Fish & Seafood
• Consumer Products
• Injectable pharmaceuticals

Why the concern?

• 8 million tons of plastic makes it’s

way to the ocean

• 250K tons are micro-plastics

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EVERYWHERE! Studies have found micro-plastic in

• Marine environment
• Food grade salt
• Bottled water
• Tap water
• Seafood and meat
• Human stool
• Blood contamination
• Injectables
• …

Where Is It Found

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• Technique used to identify material

depends on:

• Particle Size
• Information Required
• Identity
• Particle Size
• Size Distribution
• Number of particles to be analyzed
• Common questions
• How much (Load)?
• What type (Identity)?
• Which dimension/shape (sizing)?
• Identity of plastic is related to:
• Source
• Potential Toxicity
• Some plastics contain endocrine disruptors
• Others have the potential to be vectors for

toxins (oleophilic polymers)

Characterization of Micro-Plastics

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• FTIR and Raman are commonly used to identify

plastics

• Both are non-destructive
• Both can be used to identify microscopic particles
• The choice depends on the particle size and the

information required

• 5mm to 0.1mm (macro sampling techniques)
• 100µm to 10µm (both FTIR and Raman microscopy)
• 10µm to 1µm (Raman microscopy is probably required)

FTIR and Raman Spectroscopy

Poly ethy lene

0.0 0.2 0.4 0.6 0.8 1.0 Abs

Poly propy lene

0.0 0.2 0.4 0.6 0.8 1.0 Abs 1000 1500 2000 2500 3000 3500 Wavenumbers (cm-1)

IR Spectra of polyethylene and polypropylene

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• Particle sizes below 100 microns require

micro-spectroscopy

• To visualize the sample
• To focus the spectrometer beam to a suitably

small size

• Microscopy has two benefits
• The ability to measure small particles
• The ability measure multiple particles

automatically

• Both FTIR and Raman are available in

microscope configurations

Focus on Particles below 100 microns: Micro-Spectroscopy

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• Single point
• Only a single point is collected
• Multiple-point
• Many discrete particles are analyzed in

sequence

• Discrete point mapping
• Imaging
• Contiguous data points are acquired to provide

a chemical map of an area

Data Collection Options

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• Exfoliant microbeads obtained from person

care formulation

• Beads are 100-25 microns in size
• Using and IR microscope equipped with an

ATR objective, the particles were identified as polyethylene

• Simple ‘point-and-shoot’ analysis

Single Point Analysis: Microbeads – Only Practical for a Small Number of Particles

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Generic Workflow for Sampling & Analysis of Micro-Plastics

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• Typically after sampling and pre-treatment micro-plastics end up as suspensions
• Particles are isolated by filtration
• The choice of filters is important for subsequent spectroscopic analysis
• Filter material should allow for direct analysis of the particles without significant interference
• Typically many particles are observed but only a small fraction are micro-plastics
• Minerals
• Biological organic material
• Etc.
• Manually sorting through and isolating micro-plastic particles is time consuming

Sample Preparation for Micro-Spectroscopy Analysis

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Choice of Filters – Some Common Filter Types

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Example of Filtration Apparatus Using Silicon Filters

silicone gasket hole Si Filter PTFE gasket Bottom Middle Top

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After Particles Have Been Isolated on a Suitable Filter

Proceed to Spectroscopic Analysis: Discrete Particle Analysis or Spectroscopic Imaging

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Discrete Particle Analysis First Step – Collect a Visual Image of the Filter and Particles

• Sample: Filtered bottled water 500 ml
• Silicon filter
• 8 mm diameter circular area (defined by

gasket)

• Visual mosaic image constructed from many

individual fields of view

• Visible Image (contrast) is important because

visible image is used to select particles and determine particle size

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Defining Particles for Analysis – Remember Only a Small Fraction are Micro-Plastics

Sensitivity Size

• Visual Contrast is used to define particles for

analysis

• Adjustments to the sensitivity defines what is

selected as a particle

• Size parameters limits the size of the

particles considered for analysis

• Proceed to automated collection of spectral

data from all the selected particles to identify particle material types

• FTIR and Raman Microscopy

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• Raman Microscopy
• Collect Raman spectra from selected

particles

• Filter contributions can be subtracted out as

required

• Search libraries to identify particles
• Report particle identities along with size and

shape information derived from the visual image analysis

Spectral Data Collection: Identifying Particles - Workflows for FTIR and Raman

• FTIR Microscopy
• Collect spectra from selected particles
• Transmission or Reflection
• Automatically adjusts aperture to fit with

particle size

• Collect a series of backgrounds with

corresponding apertures

• Generate infrared spectra from all the

particles

• Search libraries to identify particles
• Report particle identities along with size and

shape information derived from the visual image analysis

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• 5

5 10 15 20 25 30 35 40 45 50 55 60 Int 1000 1500 2000 2500 3000 Raman shift (cm-1)

# Spectrum Position X,Y (µm) Identified Component Name Area (µm^2) Length (µm) Width (µm) 994 #0994 X,Y=1162,7289 Polypropylene, Isotactic 1032 78 16 Particle # 994 Library spectrum of polypropylene

Example of Identified Micro-Plastic Particle

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Example: Tabulated Results of the Particle Analysis (Raman)

Spectrum Position X,Y (µm) Identified Component Name Area (µm2) Length (µm) Width (µm)

#0349 X,Y=4075,1656 Polyethylene 1727 56 39.3 #0823 X,Y=1406,5406 Poly(Ethylene Terephthalate) 229 16.6 16.6 #0833 X,Y=2197,5672 Poly(Ethylene Terephthalate) 25403 316.8 102.1 #0957 X,Y=1422,7059 Poly(Ethylene Terephthalate) 390 22.1 22.1 #0036 X,Y=118,218 Poly(Tetrafluoroethylene) 10424 199.1 66.6 #0246 X,Y=2957,1103 Poly(Tetrafluoroethylene) 673 30.4 28.2 #0304 X,Y=7914,1476 Poly(Tetrafluoroethylene) 275 19.4 18.1 #0481 X,Y=8702,2555 Poly(Tetrafluoroethylene) 1551 57.5 34.3 #0534 X,Y=365,3010 Poly(Tetrafluoroethylene) 405 22.3 22.3 #0810 X,Y=6955,5268 Poly(Tetrafluoroethylene) 329 27.6 15.1 #0925 X,Y=40,6827 Poly(Tetrafluoroethylene) 306 22.1 17.6 #0976 X,Y=924,7129 Poly(Tetrafluoroethylene) 734 33.2 28.2 #1063 X,Y=6737,7969 Poly(Tetrafluoroethylene) 222 19.4 14.6 #0477 X,Y=760,2542 Polyisoprene 22560 355 80.9 #0555 X,Y=8396,3093 Polypropylene, Isotactic 168 16.6 12.9 #0750 X,Y=6687,4717 Polypropylene, Isotactic 604 35.9 21.4 #0994 X,Y=1162,7289 Polypropylene, Isotactic 1032 77.9 16.9 #0646 X,Y=1593,3709 Polystyrene 12997 156.4 105.8 #0365 X,Y=3193,1743 Polystyrene 275 19.4 18.1 #0580 X,Y=6208,3224 Polystyrene 390 22.3 22.3

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Summary of Micro-Plastics Identified from Bottled Drinking Water

• A majority of the particles present were not micro-plastics
• Some micro-plastics are better identified by Raman and some are better identified by FTIR
• Selection rule differences (dipole moment vs. polarization), fluorescence issues with Raman, particle size considerations, etc.
• Some of the features selected as particles were just features on the surface of the filter (scratches, etc.)
• Some of the particles were not Raman or FTIR active materials
• There were particles present other than micro-plastics
• Protein, cellulose, beta carotene, talc, silica, calcium carbonate, etc.

Type of Micro-Plastic FTIR (total particles – 801) Raman (total particles 1065) PTFE

5 9

Polyester (PET)

3 3

Polystyrene Not observed

3

Polypropylene

3 3

Long chain hydrocarbon material (search result not sufficient for positive identification)

2 1

Polyethylene

2 1

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Spectroscopic Imaging of Micro-Plastic Particles

FTIR & Raman Microscopic Imaging of Filters and Particles

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FTIR Imaging Example: Silicon Filter – Bottled Drinking Water

• Area Imaged: 8975 µm x 9050 µm
• Linear Array Detector: 16 element,

25 x 25 µm2 pixels

• 130680 spectra total
• Transmission through silicon filter

FTIR Transmission Image The red areas in the image show areas blocked by the sample holder

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Example of Micro-Plastic Particles: Poly(tetrafluoroethylene) (PTFE)

PTFE

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Example of Micro-Plastic Particles: Poly(butylene terephthalate)

0.00 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.10 0.11 0.12 0.13 0.14 0.15 0.16 0.17 0.18 Absorbance 1000 1500 2000 2500 3000 3500 Wavenumbers (cm-1)

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Example of Non Micro-Plastic Particles: Protein Particles

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Raman Imaging Analysis of Microplastics in Venice

• Lagoon Beach Sand / Sediment sample
• Pellestrina, Venice
• Sample preparation:
• Remove sand by settling
• Remove heavy particles
• Treated with hydrogen peroxide to

remove organic matter

• Image: Result of final filtration

Image from Google™ Maps

• M. Rocchia, I. Ruff and A. Vianello

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Particles on Filter: Raman Imaging

• Experimental Conditions
• Laser wavelength: 532nm
• Laser power: 5mW
• Acquisition rate: 200 spectra/sec
• Selected Regions analyzed
• 22 regions chosen

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Particles on a Filter: Raman Imaging

Polypropylene Polyethyleneterephthalate

In total, 6 different plastics identified including; PP, PET, LLDPE, PET, PVC

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v Micro-plastics are ubiquitous and are present in water, food, medicines, and living organisms v The wide distribution of micro-plastics along with the sizable quantities raises concerns v While the toxicity of most polymers is probably low it does warrant evaluation and consideration v To understand the sources and to evaluate the impact it is necessary to identify the types of plastics v FTIR and Raman microscopy are uniquely suited for this task and allow for distinguishing micro- plastic from the multitude of other possible particle materials present in many samples. v Whether it involves single point analysis, discrete point particles analysis, or spectroscopic imaging both FTIR and Raman microscopy provide an effective way of identifying micro-plastic particles

Summary

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Micro-Plastics Website

www.thermofisher.com/microplastics