AN EVALUATION OF SOLID-PHASE MICROEXTRACTION FOR ANALYSIS OF VOLATILE ORGANIC-COMPOUNDS IN DRINKING-WATER

Solid-phase microextraction (SPME) has been applied to the quantitative analysis of 60 volatile organic compounds (VOCs) in drinking water, Equilibration curves for the partitioning of the VOCs between the fiber coating and fortified water obtained at 20, 50, and 80 degrees C are found between the theoretical curves for completely agitated and non-agitated samples, Two important factors for the amount adsorbed by the SPME fiber coating are the extraction time and the fiber coating/water distribution coefficient, K-FW. Both depend on the sample temperature, but in a counteracting manner: Increasing the temperature shortened the equilibration times, especially for the heavier VOCs, but also lead to lower K-FW values, and consequently a lower sensitivity of the method. K-FW values are determined for 33 of the VOCs at 40, 60, and 80 degrees C and the heats of adsorption, -Delta H, are calculated, The nature of the adsorption is found to be exothermic which explains the decreasing sensitivity of the method with increasing temperature, Detection limits were typically from 20 ng/l to 200 ng/l, except for the very light VOCs with which detection difficulties were encountered, For all of the VOCs the linear range extended from the lowest concentration at which they were actually detected to at least 5 mg/l, The precision, 3% average standard deviation when an internal standard was used, was satisfactory for most quantitative routine analysis, SPME was also applied to head-space (HS) analysis of drinking water through the coupled equilibrium between water/head-space/fiber coating, HS-SPME is demonstrated to have shorter equilibration times than SPME directly from the water and equal sensitivities, except for the very light VOCs, Water samples from a drinking water plant contaminated in the low mu g/l range with 1,1,1-trichloroethane, trichloroethene and tetrachloroethene were analyzed, There seems to be a reasonable agreement between results obtained by SPME and purge & trap, It is concluded that SPME has a great potential for drinking water analysis.