# Methods of Analyzing Microsized Plastics in the Environment
## 1 Introduction  
Plastics are resin products that are molded and processed by applying heat or pressure. In general, they refer to synthetic resins which are easy to synthesize and have light but complex properties. Additionally, it is possible to enhance their suitability for their purpose of use through plastic-related chemicals (PRCs), such as whitening agents, plasticizers, antioxidants, and surfactants, which are added during synthesis [1, 2]. The usage of plastic and the amount of plastic waste thrown away have rapidly increased because it is easy to transform plastic into various shapes [1, 3, 4, 5]. In particular, the amount of plastic waste has recently risen due to the use of masks to prevent the spread of COVID-19 [6]. Microplastics are also produced during the use of plastic products. The formation of microplastics has also increased because they are also found in discarded waste [7]. Microplastics, synthetic organic polymers with a size of 5 mm or less, are classified as primary and secondary microplastics. Primary microplastics are those made at the appropriate size from the beginning for use as microplastics, such as those in face wash and beads. Secondary microplastics form after larger pieces of plastic naturally decompose due to UV light, waves, and wind or due to wear or waste while being used [5, 8, 9]. Once microplastics are introduced into the environment, they are difficult to remove. Plastic undergoes degradation into micro sizes due to physical influences (e.g., wind or rain), chemical influences (e.g., ultraviolet radiation from sunlight or corrosion), and through biodegradation (e.g., microorganisms) mechanisms [10]. Moreover, it is distributed over wide areas by waves and wind because it is light. Microplastics are ubiquitous from near shore areas to the middle of the sea, from sea level to the bottom, and from the subtropicalseas to the poles [11; 12]. It has been reported that plankton, which lie on the lowestropic level in the marine ecosystem, ingest microplastics as food. Plankton are then eaten by predators higher up the food chain. It was confirmed that microplastics were also accumulated in plants, water, and honey [13; 14]. As such, microplastics accumulated from lowerropic levels eventually accumulate in humans, the highest predator [15; 16]. Since humans consume both animals and plants, the amount of microplastics accumulating in the body through food is increasing. The toxicity of microplastics accumulating in the body has not yet been clearly reported. However, there are studies that show their tendency to cause chronic inflammation; therefore, we believe that the toxicity of microplastics should be evaluated after further research is conducted on this [17]. Ingested microplastics also reduce in size through the digestive process [18]. In addition, heavy metals and organic pollutants accumulate on the surface of microplastics and move together, increasing environmental pollution [19]. Studies monitoring microplastics require reliable and comparable standardized sampling and analysis methods [20; 21]. Additionally, studies on the toxicity and body accumulation of microplastics require appropriate methods for analyzing microplastics qualitatively and quantitatively. However, analytical methods for microplastics are currently in the development stage, and a standardized method has not yet been determined [22]. The procedure for analyzing microplastics from environmental samples consists of extraction, separation, identification, and quantification [23]. It is generally possible to classify large microplastics in size range of 1-5 mm with the naked eye. However, studying the wide size range of microplastics and their harmful biological effects requires quantification to the smallest possible size, including nanoscale plastics. In addition, it is difficult to organize analysis results through characteristics, such as size, shape, color, and polymer type, because microplastics are produced from various types of plastics synthesized for each purpose.