Analysis and Characterization of Microplastics through Vibrational Spectroscopic Techniques for Environmental Monitoring

The pinnacle of technological advancements, especially plastic, has become one of the greatest environmental challenges that the earth has ever dealt with. In the face of ground-breaking versatility, plastic litter has marked its presence from the highest peaks to the deepest points in the oceans. Microplastics (MPs) are plastic particles with a size of less than 1 mm along their longest dimension, originating from a wide array of sources. The current public awareness of MP pollution is based on a huge amount of scientific research completed and published over the last fifteen years, which has just recently been highlighted by the media. It's been a protracted process that began with isolated examinations carried out by researchers who were ordinarily working in various fields of study but recognised the threat's potential. MPs are not traditional chemical contaminants, but rather a complex array of manmade detritus made up of various sizes, polymers, chemical additives, and sorbed pollution. The MP study is still in its infancy stage since it continues to be hampered by a lack of defined protocols and methodologies for investigating MPs in the laboratory. The use of MPs in laboratory research necessitates precise particle characterization to link the impacts of microplastics to their characteristics. To understand microplastic transit, deposition, and toxic effects, it is vital to distinguish between MP particles and those that are not. This thesis has primarily focused on the application of a new technology for analyzing MPs, based on Near-Infrared Spectroscopy (NIRs). As revealed by the bibliometric analysis of characterizing MPs by Fourier-Transformation Infrared Spectroscopy (FTIR) and Near-Infrared Spectroscopy, NIRs have only lately been applied, notably in the form of the miniaturized spectrometer (NIRs). Although NIR spectroscopy has been used as a standard tool for online quality assurance in food manufacturing and pharmaceuticals for decades, its ability to analyse microplastics in various environmental matrices has only recently been recognized. The workflow of this thesis begins with the use of handheld MicroNIR to analyse urban plastic garbage and construct an in-house NIR spectrum library, showcasing the usage of portable technology in the recycling sector. Because most libraries are constructed with virgin polymers, spectral shifts caused by MPs degradation are frequently missed. As a result, a new, more durable library searching algorithm capable of dealing with the difficulty of comparing degraded MPs to pristine polymer references was necessary. The second section discussed the significance of using reference materials in MP research and compares three techniques for producing MPs for research laboratories. This work will make it easier to comprehend the morphologies of MPs produced from the same parent particle using diverse techniques in a short period, allowing MP research to accelerate. The third section is based on the proof-of-concept study to analyse mixtures of microplastics through a handheld Near-Infrared Spectrometer. Given that, this study has proven the possibility of a portable tiny near-infrared spectrometer (MicroNIR) paired with chemometric methodologies for the measurement of secondary MPs mixes created at a laboratory scale for the first time. Extraction and purification are followed by identification and quantification in the MP analysis. The extraction of MPs from any environmental matrix is the most important phase since it is controlled by the matrix type and microplastic's size, shape, and density. As a result, the extraction technique should be tailored to the type of matrix under consideration. Following this idea, a comprehensive description of microplastic extraction processes distinguished by environmental matrix is offered at the end of this thesis in the form of a review. With concluding remarks, the final chapter gives a glimpse into the study's future prospects.