Novel on-tap passive sampling for odorous compounds in drinking water

Abstract

Because taste and odour events in drinking water are often fleeting and unpredictable phenomena, an innovating passive sampler has been developed to trap off-flavour compounds, directly at the tap of the consumer: ARISTOT (Advanced Relevant Investigation Sampler for Taste & Odour at Tap). Each tool is equipped with seven SBSE stir bars, magnetic stirring roads coated with a polydimethylsiloxane (PDMS) phase, allowing the sorption of water organic compounds into PDMS at each tap opening. To study the efficiency of these passives samplers, a private network pilot unit has been created in our laboratory, equipped with four faucets in series, solenoids valves for automation of the system and a mixing chamber, developed to spike drinking water with odourous compounds in order to have homogenous smelling water at each tap. After enrichment, the bars are taken out and are then in-line thermo-desorbed and analysed by gas chromatography coupled with a mass spectrometer. Results showed a high sensitivity of the system, which was able to quickly analyse odourous compounds at the sub ng/L level. A “multishot” method was developed to analyse every molecule trapped on the seven stir bars in only one chromatographic run increasing sensitivity. To follow enrichment of stir bars, loading and unloading were studied and showed a very slight unloading of the stir bar under a clean water flow rate which allowed us to previously spike every stir bar with an internal standard to see analytical variations. The influence of heated water was also investigated and seems to lead to a higher unloading of the stir bar, but according to a qualitative aspect this loss is balanced by the high sensitivity.