When Good Intentions Go Bad - False Positive Microplastic Detection Caused by Disposable Gloves.

Apart from being considered a potential threat to ecosystems and human health, the ubiquity of microplastics presents analytical challenges. There is a high risk of sample contamination during sampling, sample preparation and analysis. In this study, the potential of sample contamination or misinterpretation due to substances associated to disposable laboratory gloves or reagents used during sample preparation, was investigated. Leachates of ten different types of disposable gloves were analysed using Raman microspectroscopy (µ-Raman), Fourier-transform infrared microspectroscopy (µ-FTIR) and pyrolysis-gas chromatography/mass spectrometry (pyr GC/MS). There appeared to be Polyethylene (PE) in almost all investigated glove leachates and with all applied methods. Closer investigations revealed that the leachates contained long-chain compounds such as stearates or fatty acids, which were falsely identified as PE by the applied analytical methods. Sodium dodecyl sulphate, which is commonly applied in microplastic research during sample preparation, may also be mistaken for PE. Therefore, µ-Raman, µ-FTIR and pyr-GC/MS were further tested for their capability to distinguish between PE, sodium dodecyl sulphate and stearates. It became clear, that stearates and sodium dodecyl sulphates can cause substantial overestimation of PE.