4 Impact and Fate of Microplastics in the Riverine …
107
4.5.1 FT-IR Analysis
A simple combination of stereomicroscopy and Fourier-transformed infrared (FTIR) spectroscopy can lead to under or over estimation of MPs due to limitation of
identification technique between natural and synthetic polymer or non-detection of
transparent plastic particles (Song et al. 2015). MPs identification with standard
FT-IR requires visual pre-sorting of potential plastic particles with limitations of
prolonging time requirement and error occurrence. Recently, with development of
FT-IR combined with microspectoscopy (i.e., µ-FT-IR), the identification of very
small-sized MPs (few micrometre) has become possible due to improvement of spatial resolution (Harrison et al. 2012; Löder et al. 2015). In contrast to standard FT-IR
machine, µ-FT-IR with focal plane array detectors does not require pre-sorting of
MPs with advantages of high throughput analysis of the environmental samples
(Harrison et al. 2012; Löder et al. 2015; Tagg et al.2015). Currently, plastic particles
more than 10–20 µm size could be identified using this technique (Rist and Hartmann 2018). The only disadvantage of the FT-IR based system is that it has very
limited scope for plastics with unknown chemical compositions. The absorbance or
transmittance bands of pure plastic materials are included in the library, and they
are matched with the extracted plastic materials to detect the chemical composition.
Thus, it becomes very difficult to identify unknown plastic fragments from environmental samples, as the FT-IR bands of plastics may change due to the degradation on
the plastic surface (Song et al. 2015). Figure 4.6 depicts the infrared spectrum of PE
which shows characteristics band of stretching and bending vibration of –CH 3 and
–CH 2 at 2850–3000 cm
−1 and 1350–1480 cm
−1 , respectively, whereas the biotically
(Aspergillus niger)-degraded PE shows the small bands at 1715 and at 940 cm
−1 corresponding to the ketonic carbonyl group and alkene group (Raghavan and Torma
1992).
Fig. 4.6 Infrared spectrum of polyethylene film (A), abiotically degraded PE film and biotically
(Aspergillus niger) degraded PE film
107
4.5.1 FT-IR Analysis
A simple combination of stereomicroscopy and Fourier-transformed infrared (FTIR) spectroscopy can lead to under or over estimation of MPs due to limitation of
identification technique between natural and synthetic polymer or non-detection of
transparent plastic particles (Song et al. 2015). MPs identification with standard
FT-IR requires visual pre-sorting of potential plastic particles with limitations of
prolonging time requirement and error occurrence. Recently, with development of
FT-IR combined with microspectoscopy (i.e., µ-FT-IR), the identification of very
small-sized MPs (few micrometre) has become possible due to improvement of spatial resolution (Harrison et al. 2012; Löder et al. 2015). In contrast to standard FT-IR
machine, µ-FT-IR with focal plane array detectors does not require pre-sorting of
MPs with advantages of high throughput analysis of the environmental samples
(Harrison et al. 2012; Löder et al. 2015; Tagg et al.2015). Currently, plastic particles
more than 10–20 µm size could be identified using this technique (Rist and Hartmann 2018). The only disadvantage of the FT-IR based system is that it has very
limited scope for plastics with unknown chemical compositions. The absorbance or
transmittance bands of pure plastic materials are included in the library, and they
are matched with the extracted plastic materials to detect the chemical composition.
Thus, it becomes very difficult to identify unknown plastic fragments from environmental samples, as the FT-IR bands of plastics may change due to the degradation on
the plastic surface (Song et al. 2015). Figure 4.6 depicts the infrared spectrum of PE
which shows characteristics band of stretching and bending vibration of –CH 3 and
–CH 2 at 2850–3000 cm
−1 and 1350–1480 cm
−1 , respectively, whereas the biotically
(Aspergillus niger)-degraded PE shows the small bands at 1715 and at 940 cm
−1 corresponding to the ketonic carbonyl group and alkene group (Raghavan and Torma
1992).
Fig. 4.6 Infrared spectrum of polyethylene film (A), abiotically degraded PE film and biotically
(Aspergillus niger) degraded PE film