> In total nearly 2000 microplastic particles > 100 um were extracted from all of the filters, with nearly 1000 (~50%) being further analyzed by FTIR. Obtained FTIR spectra were compared to libraries of known spectra in order to confirm and identify the polymeric content of the particles. All particles analyzed were either best matched to a polymer, plastic additive or known plastic binder providing additional supporting evidence that Nile Red selectively adsorbed to microplastic particles within the bottled water. With this spectroscopic confirmation, it can be concluded that on average each bottle of water contains at least 10.4 MPP/L (Table 2).
[...]
> Given the limitations of the lab, particles < 100 um (the so-called ‘NR tagged particles’) were not able to be confirmed as polymeric through spectroscopic analyses (FTIR &/or Raman spectroscopy). However, in testing of various stains and dyes that could be employed for microplastic detection and analysis within environmental samples with a greater potential for misidentification and false positives (i.e., sediments and open-water environmental samples) both Maes et al. (2107) and Erni-Cassola et al. (2017) concluded that Nile Red (NR) was very selective, especially within the time scales of incubation employed, and could be used for the rapid detection of microplastics without the need for additional spectroscopic analysis. To be sure that is why this stain was employed for this study. Additionally FTIR analysis was done on fluorescing particles >100 um and every particle analyzed was confirmed to be polymeric. Even further, NR is well-established to selectively adsorb to hydrophobic (‘water-fearing’) materials and, as such, will not adsorb to the only contents reasonably expected to be within bottled water, water &/or its mineral components.
https://orbmedia.org/sites/default/files/FinalBottledWaterRe...
> In total nearly 2000 microplastic particles > 100 um were extracted from all of the filters, with nearly 1000 (~50%) being further analyzed by FTIR. Obtained FTIR spectra were compared to libraries of known spectra in order to confirm and identify the polymeric content of the particles. All particles analyzed were either best matched to a polymer, plastic additive or known plastic binder providing additional supporting evidence that Nile Red selectively adsorbed to microplastic particles within the bottled water. With this spectroscopic confirmation, it can be concluded that on average each bottle of water contains at least 10.4 MPP/L (Table 2).
[...]
> Given the limitations of the lab, particles < 100 um (the so-called ‘NR tagged particles’) were not able to be confirmed as polymeric through spectroscopic analyses (FTIR &/or Raman spectroscopy). However, in testing of various stains and dyes that could be employed for microplastic detection and analysis within environmental samples with a greater potential for misidentification and false positives (i.e., sediments and open-water environmental samples) both Maes et al. (2107) and Erni-Cassola et al. (2017) concluded that Nile Red (NR) was very selective, especially within the time scales of incubation employed, and could be used for the rapid detection of microplastics without the need for additional spectroscopic analysis. To be sure that is why this stain was employed for this study. Additionally FTIR analysis was done on fluorescing particles >100 um and every particle analyzed was confirmed to be polymeric. Even further, NR is well-established to selectively adsorb to hydrophobic (‘water-fearing’) materials and, as such, will not adsorb to the only contents reasonably expected to be within bottled water, water &/or its mineral components.