Room temperature determination of earthy-musty odor compounds in water using vacuum-assisted headspace solid-phase microextraction

This work proposes non-equilibrium headspace solid-phase microextraction (HSSPME) sampling under reduced pressure conditions for extracting at room temperature two of the most common earthy-musty odor compounds found in water samples (2-methylisoborneol (MIB) and geosmin). MIB and geosmin are semi-volatile compounds with Henry's law constants (KH) close to the threshold values for low KH compounds. Accordingly, non-equilibrium HSSPME sampling under reduced pressure conditions (referred to as vacuum-assisted HSSPME or Vac-HSSPME) increased the volatilization rates of target analytes and resulted in a room temperature HSSPME procedure, eliminating the need for heating the sample as seen in regular HSSPME. Several experimental parameters were studied and optimized (salt content, sample temperature, sample volume, agitation and extraction time). Analytically the method showed good linearity over the concentration range of 5-250 ng L-1 and the limits of detection were 2.5 and 1.7 ng L-1 for MIB and geosmin, respectively. The repeatability of the method expressed as the relative standard deviation was 4.3% for MIB and 8.0% for geosmin. The matrix was found not to affect the extraction. The proposed method was successfully applied to quantify trace amounts of MIB in real tap water samples. Overall, compared to regular HSSPME methods currently in use, Vac-HSSPME sampling eliminated the need for heating the sample and yielded high extraction efficiencies and very good sensitivities at room temperature and without sampling for a longer time.