Fourier transform infrared spectroscopy

Characterization of the potential microplastics in the products was important to confirm their composition and beneficial to understanding the physical and morphological characteristics. Further, quantification of microplastics was carried out to estimate the microplastic emission per product usage. A stereomicroscope (Inskam315-W wifi digital microscope) was used to take images of the microbeads and microplastic presence in the samples. Then images were analyzed using Image J software to understand the size, shape, and color of the microplastics [23 (link)]. FT-IR (Fourier Transform Infrared) spectroscopy (Bruker – Alpha) was carried out to identify the composition of extracted microplastics. The Attenuated Total Reflection (ATR) method was used to characterize the potential microplastics and used an open-source spectrum library to identify the polymer type [24 (link)]. To increase the accuracy of the analysis at least 03 particles from each brand were used. However, in some products, some particles were hard to isolate. In that case, the extract was carefully scraped off the filter paper and checked for composition. Fig. 1 illustrates the process applied in this study for microplastic identification.Fig. 1

Flowchart of microplastic identification.

Fig. 1

2-Methylimidazole (2.5 M, Sigma-Aldrich) was prepared in water and mixed with streptavidin-HRP (5 μg/ml, Thermo Scientific), polyacrylic acid (0.2 M, Sigma-Aldrich) and zinc nitrate hexahydrate (0.5 M, Sigma-Aldrich) at 25 °C under stirring condition. After incubation for 30 min, the suspension was centrifuged at 500 g and washed with phosphate-buffered saline (PBS). The as-synthesized hybrid HRP@ZIF-8 nanoparticles were characterized for their hydrodynamic diameter and zeta potential through dynamic light scattering analysis (Zetasizer Nano ZSP, Malvern). 3 × 14 measurement runs were performed at room temperature. Z-average diameter, zeta potential and polydispersity were analyzed. For every measurement, the auto-correlation function and polydispersity index were monitored to ensure sample quality for size and surface charge determination. Powder X-ray diffraction was performed in the 2θ range 5–50 ° at a scanning rate of 2 °/min on an X-ray diffractometer (Bruker D8 Advanced) with a Cu-Kα radiation at 40 kV and 40 mA. Fourier transform infrared spectroscopy (Bruker) was performed at an attenuated total reflectance unit in the range of 500–3500 cm⁻¹.