The document discusses the detection and characterization of microplastics using FTIR microscopy, highlighting the environmental impact of plastic pollution. It explains the distinction between primary microplastics, which are raw materials, and secondary microplastics, which form from the degradation of larger plastics. The effectiveness of Shimadzu's FTIR instruments in analyzing microplastics is emphasized through detailed methodologies and results from various samples.

1. Microplastics Detection and
Characterization using FTIR
Microscopy
Shimadzu Scientific Instruments, Columbia, MD

2. Introduction
Plastic pollution is one of the major environmental issues faced at global scale. Interest
in this topics has exponentially increased in the past years. Microplastics are minute
pieces of not easily-degradable plastics with size ranging from few microns to several
millimeters (Figure 1). They are persistent in the environment and can act as sinks for
other contaminants. Hence, they can cause adverse effects to aquatic ecosystems.
Figure 1. Dissection of a dead seabird (left). Some microplastics were found in
the stomach (right)

3. Introduction
Therefore, the hazardous impact of increasing amount of microplastics in aquatic
environments calls for more scientific research to understand their occurrence, effects
and mitigation strategies. The FTIR (Fourier-Transform Infrared) and FTIR microscopy
techniques have shown that they are very powerful techniques to detect and
characterize a variety of microplastics.
In this work, we describe the analysis of primary and secondary microplastics. Primary
microplastics are used as raw materials for industrial polishing and scrubbing agents,
and are already 5.0 mm in size or less before entering the environment. On the other
hand, secondary microplastics are created from the degradation of larger plastic
products once they enter the environment through external processes such as
ultraviolet rays and crush.

4. Instruments and Measurement Parameters
Microplastic detection, characterization and mapping were carried out using Shimadzu
IRTracer-100 FTIR spectrophotometer with AIM-9000 FTIR automated microscope
system and ATR (Attenuated Total Reflectance) accessory (Figure 2). Method
conditions are listed in Table 1.
Figure 2: Shimadzu IRTracer-100 FTIR
spectrophotometer (left) attached to AIM-9000
Infrared Microscope (right)
Instrument
Shimadzu IRTracer-100 and AIM-
9000
Measurement
mode
Transmission
Resolution 4.0 cm-1
Number of
scan
50 times
Aperture size 100 x 100 μm Or 50 x 50 μm
Table 1: Measurement Parameters

5. Analysis of Primary Microplastics
Sample:
Primary microplastics in facial cleanser.
Pretreatment:
Microplastics dispersed in water was suction filtered using
cellulose filter paper (figure 4).
Measurement:
The micro plastic collected on the filter paper was moved to a
diamond cell to measure transmission. Area without plastics was
set as background.
Figure 3. Primary microplastic
sample
Figure 4. Microplastics on cellulose filter paper

6. Analysis of Primary Microplastics
Observation:
From transmission spectra of primary microplastics, we were able to determine that the
sample was a mixture of polyethylene (PE) and cellulose. The presence of cellulose in
the sample was confirmed carrying out appropriate background spectral subtractions to
eliminate spectra from the filter (also cellulose). Spectra are shown in Figure 5.
80010001200140016001800200024002800320036004000
cm-1
10
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30
35
40
45
50
55
60
65
70
%T
80010001200140016001800200024002800320036004000
1/cm
30
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%T
FTIR Measurement
Cellulose
Polyethylene
Figure 5. IR spectra of cellulose (top) and PE (bottom).

7. Analysis of Secondary Microplastics and
Mapping
Sample:
Secondary microplastics in ocean water.
Pretreatment:
Microplastics dispersed in water was suction filtered using PTFE
filter paper (infrared absorption in the vicinity of 1,200 cm-1).
Measurement:
The sample collected on the PTFE filter paper was moved to
diamond cell to measure transmission. PTFE is a convenient filter
for direct measurement although noisy spectra around 1,200 cm-1 is
observed.

8. Observation:
Library matching of spectra (Figure 6) and mapping results (Figure 7) allowed us to
determine the composition of microplastics in the ocean water sample.
Analysis of Secondary Microplastics and
Mapping
Figure 6. Data obtained from the FTIR systems were matched with library database to identify and
quantify microplastics

9. Analysis of Secondary Microplastics and
Mapping
Distribution of PE
(corrected area of 718 cm-1)
Distribution of PP
(corrected area of 2,839 cm-1)
Distribution of PET
(corrected area of 1,724 cm-1)
Visible microscope image
Figure 7. Distribution of types of plastics detected in sample.

10. Conclusion
FTIR and FTIR Microscopy are suitable techniques to detect and characterize
microplastic samples. The ease of use and mapping features provided by these
instruments keep the sample preparation minimum while helping properly identify
the different types of microplastics in real-world samples.

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