The challenge of sample-stabilisation in the era of multi-residue analytical methods: A practical guideline for the stabilisation of 46 organic micropollutants in aqueous samples

Water sample storage and stabilisation may affect data quality, if samples are managed improperly. In this study three stabilising strategies are evaluated for 46 relevant organic micro-pollutants: addition of the biocides (i) copper sulphate and (ii) sodium azide to water samples directly after sampling with subsequent sample storage as liquid phase and (iii) direct solid phase extraction (SPE), stabilising the samples by reducing the activity of water. River water and treated effluent were chosen as commonly investigated matrices with a high potential of biotransformation activity. Analyses were carried out for sample storage temperatures of 4 and 28 °C for water samples stored as liquid phase and for sample storage temperatures of 4, 20 and 40 °C for SPE cartridges. Cooling of water samples alone was not sufficient for longer storage times (> 24 h). While copper sulphate caused detrimental interferences with nitrogen containing heterocyclic compounds, sodium azide proved to be a suitable stabilising agent. The best results could be obtained for SPE cartridges stored cool. Recommendations for samples preservation are provided.