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

Solid-phase microextraction (SPME) has been applied to the quantitativ e analysis of 60 volatile organic compounds (VOCs) in drinking water, Equilibration curves for the partitioning of the VOCs between the fibe r 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/wate r distribution coefficient, K-FW. Both depend on the sample temperatur e, but in a counteracting manner: Increasing the temperature shortened the equilibration times, especially for the heavier VOCs, but also le ad to lower K-FW values, and consequently a lower sensitivity of the m ethod. 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, Dete ction limits were typically from 20 ng/l to 200 ng/l, except for the v ery light VOCs with which detection difficulties were encountered, For all of the VOCs the linear range extended from the lowest concentrati on at which they were actually detected to at least 5 mg/l, The precis ion, 3% average standard deviation when an internal standard was used, was satisfactory for most quantitative routine analysis, SPME was als o applied to head-space (HS) analysis of drinking water through the co upled equilibrium between water/head-space/fiber coating, HS-SPME is d emonstrated to have shorter equilibration times than SPME directly fro m the water and equal sensitivities, except for the very light VOCs, W ater samples from a drinking water plant contaminated in the low mu g/ l range with 1,1,1-trichloroethane, trichloroethene and tetrachloroeth ene were analyzed, There seems to be a reasonable agreement between re sults obtained by SPME and purge & trap, It is concluded that SPME has a great potential for drinking water analysis.