*2.6. Evaluation of Procedural Blanks*

Due to the widespread usage of NP-containing substances, including consumer goods, NPs are often present in laboratory environments. These environments are also susceptible to contamination from external sources [5]. Both NPs and their parent compounds, NPEOs, are, therefore, ubiquitous in the environment due to the increasing production volumes of NPs in industry [14]. Special precautions are, therefore, required to prevent contamination during experiments [13]. NP residues were regularly present in the blank samples in this study to ensure that these compounds were not contaminated during the experiment procedure. To minimize contamination during the experiment and to properly control the procedural blank, glassware was mostly used throughout the experiments. Procedural blanks were analyzed to evaluate the analytical methods of the high-fat and low-fat matrices. The analytical procedure was identical to that illustrated above, except for the sample addition. Procedural blanks were analyzed using gas chromatography/mass spectrometry (GC-MS) as described below.
