We have a problem with repeatability of the results. Internal standard (Y) measurements are also unstable, eg for four samples the results are 1.05; 1.04, 1.04, 1.05 but for the next sample the result is 1.89. And I don't know why. Sometimes I have to repeat the sample twice to get the good value of the internal standard. This problem appears also for calibration standards. Mayby I should add that we use the online system for the internal. The second problem is unrepeatability of the results of our samples. For the three replicate from the same sample I got the different concenration (-0.127,0,25 and 4014). This problem appears not everyday but often and always for radial obserwation. Do you have any idea how to deal with these problems? Thank You for your help!