**A.4 Results**

For each replicate, the number of particles at a given volume is given by the sum of the particles collected on all the filters used for that sample (main solution and washing water).

#### **A.4.1 Note**

For more accurate results, we suggest counting the number of fibers on each section of the filter to avoid losing the count of overlapping fibers.

Zoom in and break the image into square sections to cover the entire filter, and then, manually count the microparticles in each of the sections and the number of fibers on each section of the filter.

The same procedure can be used to identify the chemical composition of microfilaments. As an alternative to manual counting, it is possible to perform automatic counting of microplastics with the software of the optical instrument.

#### **A.4.2 Calculation**

$$\text{N\text{\textquotedblleftfil\textquotedblright}\text{\textquotedblright}\text{\textquotedblleft}1\text{\textquotedblright}\text{\textquotedblleft}1\text{\textquotedblright}\text{\textquotedblleft}\text{\textquotedblleft}\text{\textquotedblright}\text{\textquotedblleft}\text{\textquotedblleft}\text{\textquotedblleft}\text{\textquotedblleft}\text{\textquotedblright}\text{\textquotedblright}\text{\textquotedblleft}\text{\textquotedblleft}\text{\textquotedblleft}\text{\textquotedblright}\text{\textquotedblright}\text{\textquotedblright}\text{\textquotedblleft}\text{\textquotedblleft}\text{\textquotedblleft}\text{\textquotedblleft}\text{\textquotedblleft}\text{\textquotedblleft}\text{\textquotedblleft}\text{\textquotedblleft}\text{\textquotedblleft}\text{\textquotedblleft}\text{\textquotedblleft}\text{\textquotedblleft}\text{\textquotedblleft}\text{\textquotedblleft}\text{\textquotedblleft}\text{\textquotedblleft}\text{\textquotedblleft}\text{\textquotedblleft}\text{\textquotedblleft}\text{\textquotedblleft}\text{\textquotedblleft}\text{\textquotedblleft}\text{\textquotedblright}\text{\textquotedblright}\text{\textquotedblright}\text{\textquotedblright}\text{\textquotedblleft}\text{\textquotedblleft}\text{\textquotedblleft}\text{\textquotedblleft}\text{\textquotedblleft}\text{\textquotedblleft}\text{\textquotedblleft}\text{\textquotedblleft}\text{\textquotedblleft}\text{\textquotedblleft}\text{\textquotedblleft}\text{\textquotedblleft}\text{\textquotedblleft}\text{\textquotedblleft}\text{\textquotedblleft}\text{\textquotedblleft}\text{\textquotedblleft}\text{\textquotedblleft}\text{\textquotedblleft}\text{\textquotedblleft}\text{\textquotedblleft}\text{\textquotedblright}\text{\textquright}\text{\textquright}\end{}\text{\textquotedblright}\end{\text{\textquotedblleft}}\text{\textquotedbl$$

where N° filaments means number of filaments obtained by automatic or manual counting as sum of filaments counted on filters.

NOTE: samples have been prepared with an initial volume of 500 ml. Tables (Test Report) show how the data shall be entered for each sample analyzed:


#### **A.4.3 Identification of Fibers by μ-FTIR and μ-Raman**

The operative conditions of identification and analysis of microfilaments can be optimized both with μ-FTIR and μ-Raman instrument (full mapping and/or particle by particle). FTIR can be carried out using different kinds of detectors (single detector, line array dector, focal plane array (FPA) detector).

#### **A.4.4 Measure of microplastic fibers lengths**

Moreover, the measurements of the microplastic fiber lengths and diameters can be carried out with


*Round Robin Test on Microplastic Counting and Identification Method DOI: http://dx.doi.org/10.5772/intechopen.109757*



**Table 4.**

*Example of test report to have for each sample.*

*Advances and Challenges in Microplastics*
