New technique using stir bar sorptive extraction and gas chromatography/mass spectrometry analyses off-flavours in drinking water at subnanogram-per-litre levels
Agilent Technologies has announced an analytical technique to characterise odourous compounds in drinking water at subnanogram-per-litre levels (down to 0.1ng/l).
This new approach can help water companies control taste and odour problems in their water supplies and has been successfully used to identify a variety of off-flavour problems in drinking water systems near Paris.
Complaints received by water companies are most often due to bad tastes and odours in drinking water, particularly from the presence of chlorine and earthy or musty smelling compounds. Identifying these compounds in water has been an analytical challenge because they can cause odour even at extremely low concentrations - a problem for conventional analytical methods such as closed-loop stripping analysis, purge and trap, and solid phase micro-extraction.
This new technique combines Agilent gas chromatography/mass spectrometry (GC/MS) with stir bar sorptive extraction (SBSE) from Agilent's German partner, Gerstel. SBSE is based on sorption rather than adsorption, and is a highly sensitive, simple and fast alternative to traditional extraction methods.
To validate this approach, chemists from Anjou Recherche in Saint-Maurice, France analysed water samples spiked with six odourous organic compounds: 2-methylisoborneol (MIB); geosmin; 2,4,6-trichloroanisole; 2,3,6-trichloroanisole; 2,3,4-trichloroanisole; and 2,4,6-tribromoanisole.
The combination of GC/MS and SBSE enabled quantification of these compounds at the subnanogram per litre level, under or near their odour thresholds.
Using this method, the chemists were able to extract and analyse more than 20 samples a day.
The scientists also applied this method to real-world samples taken from three different locations around Paris: the outlet of a treatment plant, a water tank and at consumer homes.
The approach showed a strong correlation between flavour profile analysis, MS analysis, and olfactometric detection.
In addition to the target compounds, it was possible to identify unknown odouous compounds at very low levels much more rapidly than possible using conventional techniques.
Further information is available by requesting Agilent application note 'Stir bar sorptive extraction: A new way to extract off-flavour compounds in the aquatic environment', Agilent publication number 5988-8900EN.
This note is available without charge from any Agilent sales office or its website (link below).
