Validation of the SPME-GC / MS method for determination of Methyl Tert-Butyl Ether and its degradation products in ground water

Abstract

Methyl tert-butyl ether (MTBE) is a fuel oxygenate widely used in Paraguay as well as in many South American countries as octane enhancers to replace toxic additives that have been phased out of gasoline. In several European countries was founded in groundwater due to leaking of gasoline tanks in the ground. Validation of the analytical method was performed for MTBE and its bi-products of degradation as tert-butyl alcohol (TBA) y tert-butyl formate (TBF) by solid phase micro-extraction and gas-chromatography coupled with mass spectrometer (SPME-GC/MS) using standard validation procedures. This method is still under development including the cooling of the extraction fiber. Under this study, the fiber temperature was 21-25oC. Other parameters evaluated were: specificity, linearity, sensitivity, detection limit, accuracy, including an evaluation of the veracity and precision. 5mL of sample with 1,8g of NaCl added as matrix modifier, extracted with continuous steering at 35ºC for 30 minutes. A linear calibration curve was plotted over the range of 0-200 ?g/L for MTBE. The lineal r2 of the method were 0.9991 -0.9925 and 0.9992 for MTBE, TBA y TBF respectively, with relative standard deviation of 0.5 to 6.6%. The Lower Detection Limits obtained were 0.009?g/L for MTBE; 0.029?g/L for TBA and 0.010?g/L TBF. Accuracy was evaluated with veracity and precision in conditions of repeatability and reproducibility obtaining recoveries between 100.4 y 106.8% with relative standard deviation up to 6.4%. In addition temperatre range, ie. 21-25ºC, showed to be appropriate. This method fulfill validation criteria within the levels of concentration, offered high sensitivity and selectivity enough for bioanalytical investigation and thus is adequate for routine use in the analysis of these analytes in drinking water and groundwater.