Working with ATR-FTIR (Attenuated Total Reflectance - Fourier Transform Infrared) spectroscopy for microplastic studies is a powerful analytical technique that can provide valuable insights into the types of polymers in environmental samples. Here are some tips and resources to help you with interpreting peaks, finding spectral libraries, and recommended literature:

Interpreting Peaks

Finding Spectral Libraries

Recommended Literature

General Tips

• Practice: The more spectra you analyze, the better you will become at interpreting them.
• Collaboration: Engage with the scientific community. Collaborating with experts or joining forums can provide additional support and insights.
• Software: Familiarize yourself with the software that comes with your instrument. Many software packages have built-in tools for peak identification, library searching, and spectral manipulation.

Remember, the field of microplastic research is rapidly evolving, and staying up-to-date with the latest literature and techniques is crucial. Good luck with your PhD studies!

To interpret ATR-FTIR spectra for identifying polymers, familiarize yourself with key peaks associated with common polymers, such as polyethylene (PE) and polypropylene (PP), and focus on both group frequencies (above 1500 cm⁻¹) and fingerprint regions (below 1500 cm⁻¹). Normalize and baseline-correct your spectra for improved accuracy. For spectral libraries, consider resources like the NIST Chemistry WebBook, Sigma-Aldrich FTIR Spectra, and the FTIR Spectral Database for Organic Compounds (SDBS). Recommended literature includes "Introduction to Infrared and Raman Spectroscopy" by Barbara H. Stuart and "Infrared Spectroscopy: Fundamentals and Applications" by J. Coates, along with research articles like Jung et al. (2017) for practical insights. Engaging with online forums and attending hands-on training sessions can further enhance your skills in ATR-FTIR spectroscopy for polymer studies.

Detecting small microplastics down to 1.3 μm using large area ATR-FTIR

Yuanli Liu a,b,c,d,*, Stephan Lüttjohann e, Alvise Vianello a, Claudia Lorenz a, Fan Liu a,

Jes Vollertsen a

a Department of the Built Environment, Aalborg University, Thomas Manns Vej 23, 9220 Aalborg, Denmark

b College of Environmental and Biological Engineering, Putian University, Putian 351100, China

c Fujian Provincial Key Laboratory of Ecology-Toxicological Effects and Control for Emerging Contaminants, Putian University, Putian 351100, China

d Key Laboratory of Ecological Environment and Information Atlas, Fujian Provincial University, Putian 351100, Fujian, China

e Bruker Optics GmbH & Co. KG, Rudolf-Plank-Straße 27, 76275 Ettlingen, Germany

A R T I C L E I N F O

Keywords:

LAATR

ZnSe

Ge

Microplastics

Spectroscopy

A B S T R A C T

Large area attenuated total reflectance-Fourier transform infrared spectroscopy (LAATR-FTIR) is introduced as a

novel technique for detecting small microplastics (MPs) down to 1.3 μm. Two different LAATR units, one with a

zinc selenide (ZnSe) and one with a germanium (Ge) crystal, were used to detect reference MPs < 20 μm, and

MPs in marine water samples, and compared with μ-FTIR in transmission mode. The LAATR units performed well

in identifying small MPs down to 1.3 μm. However, they were poorly suited for large MPs as uneven particle

thickness resulted in uneven contact between crystal and particle, misinterpreting large MPs as many small MPs.

However, for more homogeneous matrices, the technique was promising. Further assessment indicated that there

was little difference in spectra quality between transmission mode and LAATR mode. All in all, while LAATR

units struggle to substitute transmission mode, it provides additional information and valuable information on

small MPs.

1. Introduction

Microplastics (MPs) have gained much attention over the last decade

or so (Thompson et al., 2004), and thousands of studies have been done

to investigate the distribution, source, and fate of MPs to better understand

their potential threat (Bank and Hansson, 2019; Li et al., 2018;

Simon-S´anchez et al., 2022; Wang et al., 2021). Studies have revealed

that the presence of microplastics (MPs) in aquatic environments can

have adverse impacts on ecosystems (Ding et al., 2022b), including

potential implications for human health (Blackburn and Green, 2021),

highlighting the importance of understanding the occurrence of MPs in

natural and anthropogenic environments. However, a lack of harmonization

of methods and quality control procedures makes the comparison

among studies extremely challenging, hampering the scientific community

from obtaining a more comprehensive understanding of such

multifaceted pollutants (Cui et al., 2022; Ding et al., 2022a; Liu et al.,

2021).

The methodologies for detecting MPs have undergone significant

technological advancements, moving from simple visual inspection to

complex chemical detection (Fahrenfeld et al., 2019; Hidalgo-Ruz et al.,

2012; K¨appler et al., 2018). Fourier Transform Infrared Spectroscopy

(FTIR) is by far the most widely used chemical detection technology,

providing information about the chemical bonds of the analyzed material

(Cowger et al., 2020; Valls-Conesa et al., 2023). The FTIR spectra

can be compared to reference libraries for identification (Gaffney et al.,

2012), which are typically commercially available or custom-built for

specific purposes. There are three signal acquisition modes commonly

used for the detection of MPs, mostly depending on the size range of the

particles targeted: attenuated total reflectance (ATR) (Cowger et al.,

2020; Veerasingam et al., 2021), transmission (K¨appler et al., 2015;

L¨oder et al., 2015), and reflectance (Harrison et al., 2012; Vianello et al.,

2013). ATR-FTIR is routinely used to analyze larger particles (>300 μm)

mainly because of particle’s thickness and surface irregularity (Chand

et al., 2022; Liu et al., 2019). It requires limited sample preparation and

allows the analysis of thick and irregularly shaped materials producing

high-quality spectra not influenced by the thickness of the particle.

However, this approach requires a manual pre-sorting of putative MPs,

after which each particle is analyzed by ATR-FTIR, resulting in a long

analysis time. Smaller particles (