Your approach seems reasonable if you have a priori defined acceptance criteria that meet the needs of your assay. You say that matrix components may be left within the sample after TCA stipping and column, so in that case, selectivity may be a good parameter to assess. So, you would want to know whether your assay works in multiple different lots (individuals) of matrix rather than just a single lot. Blank, low QC and high QC spikes in 6 to 10 individual lots of matrix is usual. Also, you might consider inter assay precision and accuracy as you may just get lucky with the first plate.
hope it works!