Graphs were constructed with the relative response on the y axis and the corresponding concentrations in logarithmic scale on the x axis, as suggested Huber [42] to verify that all used points are within the corresponding linear dynamic range. These graphs (Fig. 3, Fig. 4, Fig. 5 and Fig. 6) showed that the method is linear within the response range of 95 to 105% and it is within the linear range for all pesticides studied. The points found to be outside the linear range of 95 to 105% were excluded from the analytical curve.