Full set of Notes with Fill-Ins - San Jose State University

Chem 155 Unit 1 Page 45 of 316Spike Recovery Validates Sample Prep.To do a spike recovery analysis, one takes replicatesamples and to a subset of them adds a spike ofanalyte before the sample prep begins. So, forexample, one could take four vitamin tablets, anddivide them into two groups of two. To one group onecould add some Fe, say half the amount originallyexpected. For example, if there is supposed to be 15mg of iron in the tablet, one could spike two sampleseach with 5 mg of iron and leave two unspiked.Acids etc.digestfilterDilute to100 mLvolumeAnalyze 140ppm14.0 mgfoundSampleSample+ 5.00mg spikedigestfilterDilute to100 mLvolumeAnalyze 187ppm18.7 mgfound18.7-14.0 = 4.7 mg of spike found: spikerecovery percent = 4.7 / 5.00 94%What does this say aboutour sample preparationmethod?We may be losing about6% of the analyte duringsample prep.Page 45 of 316