Pulsed splitless injection and the extent of matrix effects in the analysis of pesticides

The applicability of pulsed splitless injection to the gas chromatographic analysis of pesticide residues in fruit and vegetables has been evaluated. 22 pesticides belonging to different chemical classes, including those know n to be liable to matrix induced response enhancement, were selected for th e study. The parameters of pressure pulse have been tested for optimum perf ormance of injection. Application of the pressure pulse was found to decrea se matrix effects during analyses of real samples. Further decline of matri x effects was obtained using higher sample injection volumes. The installat ion of a deactivated retention gap was necessary to obtain good peak shapes with injection volumes exceeding 1 mu L of sample. Up to 4 mu L was then i njected without peak distortion and consequent loss of resolution. Using 4 mu L pulsed splitless injection, matrix effects were almost completely elim inated even at very low concentration levels of analytes. The highest matri x effects observed for tested compounds at the lowest concentration level t ested were in the range of 110-122%.