Scanning Electron Microscopy as a tool to detect and quantify microscopic physical hazards in bottled mineral waters

Abstract

This work aims to investigate the presence of microscopic foreign materials in bottled mineral waters and suggest the use of Scanning Electron Microscopy (SEM) as a suitable technique for counting foreign matter. Eight samples of mineral water were obtained, and 100 mL subsamples were filtered through membranes, which were then dried, coated with platinum, and observed under SEM. Areas of 21,025 μm² were analysed, and the particles present were counted. Variance analysis was carried out, and the Regwq test was applied to compare the counting averages. Samples of the dirt particles were imaged at different magnifications. The analysis of variance revealed high significance among the samples, indicating substantial differences between them. The averages followed a stratification pattern and were estimated with great precision, suggesting that the subdivision into 10 count groups and the extrapolation to 100 mL volume is a reliable estimate for the count of particles filtered in this volume of water. It was shown that SEM was a suitable instrument for counting and observing foreign matter and dirt in samples of bottled natural mineral waters, especially when their dimensions are too small to be detected by conventional methods.