Quantification of auto-photobleaching effects during Raman measurements for microplastic detection

Fluorescence interference is a common issue when analyzing microplastics with Raman spectroscopy due to the presence of coloring substances such as organic dyes. Various methods have been attempted to mitigate this fluorescent background, with photobleaching being widely used. However, there has been a lack of quantitative studies on the extent of photobleaching at the single-particle level. In this study, we quantitatively analyzed the photobleaching effect by varying microplastic size, dye concentration, and laser intensity, revealing the magnitude of this effect and its dependence on these parameters. Specifically, we analyzed how quickly fluorescence decreases at the single-particle level, considering the photobleaching efficiency of typical organic dyes. Our results show that, under realistic Raman measurement conditions, careful adjustment of these variables can lead to rapid photobleaching of microplastics below a certain size, thereby sufficiently eliminating fluorescence background issues. These insights are crucial for optimizing experimental protocols and streamlining the detection of small colored microplastics in real environmental samples using Raman spectroscopy. [Display omitted] •Fluorescence interference is a common issue when analyzing microplastics using Raman spectroscopy.•There has been a lack of quantitative studies for photobleaching at the single particle level.•Microplastics less than 5 μm could be detected within 27 s through photobleaching.•The fluorescent background can be minimized due to photobleaching by considering values such as plastic size and laser power.