We have measured some organic samples (fuels) and used kerosene to dilute the samples. When I changed the dilution times, from 1:5 to 1:10, the results are different. For example, for the content of zinc, it is 25 ppm by 1:5 dilution, 27 ppm by 1:10. Is this a big difference? Could you please expain, how can I determine, which is more accurate? I think from sample to sample, the dilution time could be also different. But I have no idea, how to determine it.