P167

Improving the sustainability of trace element analysis through plastic vial re-use

The amount of plastic waste generated in the laboratory is becoming concerning. Plastic waste arises from uncertainties about cross-contamination when reusing plastic vials, given the sensitivity of some instruments. It thus becomes necessary to establish sustainable cleaning practices that eliminate cross-contamination and allow the reuse of plastic vials in trace analysis laboratories.

This study compares the effectiveness of various cleaning reagents (distilled water, deionised water, 5% nitric acid (HNO₃), and detergent followed by distilled water) in removing residual trace elements from polypropylene vials (Falcon® tubes).  Each tube was filled with a 1 mgL^-1 multi-element solution for 72 hours, then washed uniformly with each reagent. The same washing protocol was repeated four times. The tubes were filled with 2% HNO₃ to stand for 24 hours at room temperature before an aliquot was analysed by inductively coupled plasma mass spectrometry (Agilent 7700X). The effects of 5, 10, 25, and 50% (v/v) HNO₃ concentrations on Falcon tubes over six weeks were also investigated by analysing cut segments of the tubes using ATR-Fourier transform infrared (FTIR) spectroscopy and scanning electron microscope (SEM).

The results indicated that washing Falcon® tubes effectively reduced residual trace element concentrations, albeit no reagent consistently outperformed the others. Different elements varied in removal efficiency (e.g. residual cadmium concentration was <0.03 μg L^-1, while residual copper concentration was up to 3 μg L^-1 after one rinse). Although washing was insufficient for reuse in trace element research with ICP-MS analysis, the tubes could be repurposed for less sensitive applications, such as flame atomic absorption spectrometry in a teaching laboratory. FTIR spectra showed no significant changes in the plastic vials, but SEM images indicated increased brittleness with higher acid concentrations and longer exposure times.  This means the integrity of the falcon tubes after acid exposure remains unchanged. This further established that the polypropylene plastic vials can be reused to reduce plastic waste generation from the laboratory.