Self-test 4.4C

An analyst intended to determine the repeatability of the method. He analyzed a food sample by LC-MS. He carefully homogenized the sample in a blender and took a subsample. With the subsample he carried out sample preparation (consisting of extraction, precipitation and centrifugation). As a result he obtained a clear solution. He transferred it into a 100 mL volumetric flask and filled it up to the mark with the mobile phase. He analyzed 10 aliquots of this solution during the same day and calculated the repeatability as standard deviation of the results.

An analyst intended to determine the trueness of the method. He analyzed a food sample by LC-MS. He carefully homogenized the sample in a blender and divided it into 10 subsamples and added a known amount of standard solution in each subsample. With the subsamples he carried out sample preparation (consisting of extraction, precipitation and centrifugation). As a result he obtained a clear solutions that he diluted to 1 mL with mobile phase. He analyzed all samples during the same day and divided the mean analyte amount detected by the analyte amount added to the sample.