Closing the gap between small and smaller:
Towards an analytical protocol for the detection of Micro- and Nanoplastic in freshwater systems
.
Svenja M. Mintenig
1,2, Patrick S. Bauerlein
2, Albert A. Koelmans
3,4, Stefan C. Dekker
1, Annemarie P. van Wezel
1,2.
s.m.mintenig@uu.nl
RESEARCH GAPS
• Unharmonized sampling, extraction and identification methods generate data of different quality and resolution
• Numerous studies perform visual sorting of MP, with a size limitation of 300 µm. Often no spectroscopic or thermo-chemical polymer identification is conducted
• Actual occurence of NP in environmental samples has not been proven yet
Faculty of Geosciences Copernicus Institute of Sustainable Development
STUDY OBJECTIVE
Development of an analytical protocol, consistently determining sizes and polymer types of all plastics from environmental samples.
Thereby a special focus is on the unknown NP- fraction.
1 Copernicus Institute of Sustainable Development, Environ. Science, Utrecht University (NL)
2 KWR – Watercycle Research Institute, Nieuwegein (NL)
3 Aquatic Ecology and Water Quality Management Group, Wageningen University (NL)
4 IMARES – Institute for Marine Resources & Ecosystem Studies, Wageningen UR (NL)
ANALYTICAL PROTOCOL
Micro-FTIR
(Nicolet iN10, ThermoFisher)
• Fourier- Transform Infrared Microscopy
• MP enriched on aluminum oxide (Anodisc) filter are identified by chemical mapping
• Five fields (35 % of the filter area) are mapped with a spatial pixel resolution of 20 x 20 µm, resulting in a measuring time of 7 hours (Figure 1)
500 µm
Field Flow Fractionation (FFF, Postnova)
.
• Separation of NP due to differences in size
• 2 working modes (normal and steric): Reversal of fractionation order for particles larger than 500 nm (Figure 2)
A prior filtration step is necessary to guarantee a sufficient separation
• Coupled detectors: Determination of sizes (MALS) and concentrations (UV-Vis)
BACKGROUND
Nowadays microplastic (MP) can be found in almost all environmental habitats. Degradation and fragmentation lead to smaller particles. Recently the actual fragmentation of polystyrene into nanoplastic (NP) was proven experimentally (Lambert & Wagner 2016).
However, sampling and identification methods are still under development, consequently information on quantity, quality and fate of especially small NMP are limited.
Fig. 1:
Surfacewater sample from lake IJsselmeer (NL) enriched on Anodisc filter, the visual picture of one measuring field and the chemical map (integrated from 1480- 1430 cm-1, Loeder et al 2015). Identification of polymers through library reconciliation• Crossflow filters (Fresenius Medical Care) with a pore size of about 50 nm
• The used system was originally developed for the concentration of rare microorganisms (Veenendaal & Brouwer-Hanzens 2007)
Pyrolysis GC- MS (GSG- Mess & Analysengeräte)
"
pure
"water
Hemoflow
Enzymatic Purification Density Separation 5
0,5
50
20
mm mm
nm
µm
visual sorting FTIR- ATR
Fig. 2:
Principle of the Asymmetrical Flow- FFF. Particles of a heterogeneous sample are fractionated according to size. A successful fractionation for PS particles of 50 – 500 nm size was conducted (black). A coupled MALS detector determines particles sizes, revealing a distortion if 1000 nm PS beads (green) would be injected simultaneously.CONCLUSION
• MP (20- 500 µm) is identified by micro-FTIR without manual particle handling
• NP with a size of 25- 500 nm are successfully fractionated by FFF
• Single plastic types in an environmental matrix can be determined by Pyrolysis GC-MS
Lambert, S. and Wagner M. (2016). "Characterisation of nanoplastics during the degradation of polystyrene." Chemosphere
Löder, M. G. J. et al. (2015). "Focal plane array detector-based micro-Fourier-transform infrared imaging for the analysis of microplastics in environmental samples." Environmental Chemistry
Veenendaal, H.R. and Brouwer-Hanzens, A.J. (2007). "A method for the concentration of microbes in large volumes of water." Techneau
Fig. 3:
The pyrogram (black) of the surfacewater sample from lake IJsselmeer (50 nm – 500 µm) showing the characteristic signals of polyethylene (PE, red) at a mass of 82.9 – 83.4.Flow
FFF
Cross- FlowMALS
350 µm
0.002 0.5 20 500 5000 µm
nano- micro- meso-/macroplastic
FFF micro-FTIR manual sorting SIZE
Pyrolysis-GC-MS IR-spectroscopy IDENTIFICATION
normal mode steric mode
5 10 15 20 25 30 35
50 nm
100 nm
200 nm
500 nm
Detector signal
time (min)
1000 nm
fraction 50 nm - 20 µm fraction 20 – 500 µm
PE:PP, 86 µm
PE, 120 µm
PE, 145 µm
OUTLOOK
• Further optimisation of settings for individual analytical techniques
• Protocol- validation for drinking, surface and treated waste water samples
• Usage of the FFF for the determination of nano- fragmentation for various plastics as a consequence of UV- exposure
• Size fractions are identified by pyrolysis coupled to GC-MS
• Using the characteristic fingerprint of individual polymer types for their identification in environ- mental samples (Figure 3)
• A database, including 6 polymer types was created and needs to be extended
0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9
1250 1750
2250 2750
3250
RT:0.00 - 59.00
0 5 10 15 20 25 30 35 40 45 50 55
Time (min) 0
2 4 6 8 10 12 14 16 18 20 22 24 0 2 4 6 8 10 12 14 16 18 20 22 24
Relative Abundance
48.07
41.78
51.55
45.44
38.96 45.02
48.43 46.21 31.64 35.43
39.68 27.60
43.57
7.18 13.81 23.28
31.39 35.28
12.16 15.96 18.67 22.78 27.23
0.57 1.35 2.745.64 8.35 8.87 16.08 20.87 25.80 31.18 32.44 38.38
48.29 51.14
56.23
45.29
42.12
48.67 19.89
9.03 45.70
39.26 42.57 38.75
35.19 56.93
35.74
18.27 31.38 31.99 57.64
27.98 25.53
16.26 42.68 45.84
48.78 29.87
14.08 32.17
0.160.59 5.396.52 7.42 11.24 20.91 24.69 32.56 35.9038.08 41.33 43.86 46.23 48.93
NL:
7.38E7 m/z=
82.90000- 83.40000 MS p20160301a _160301114 007
NL:
2.54E8 m/z=
82.90000- 83.40000 MS p20160211_
01
m/z:
82.9- 83.4
m/z:
82.9- 83.4
0 10 20 30 40 50 time (min)
Relative Abundance
Absorbance
wavenumbers cm-1
Absorbance
0.25 0.2 0.15
0.1 0.05
0
