Dilution bioanalytical validation

In the study on indinavir in human plasma [21], two sample pretreatment methods, i.e., dilution of urine and LLE with MTBE, two chromatographic systems, i.e., with low and high capacity factor, and the use of ILIS and ANIS were compared. It was concluded that the potential effect of co-eluting unseen endogenous species should be evaluated during method development and validation of bioanalytical LC-MS methods. 

Validation of bioanalytical methods requires experiments to assess accuracy, precision, limit of detection, limit of quantitation, range, linearity, selectivity, and sample stability (23). The sample preparation step has a great impact on all these parameters. The extraction efficiency must be experimentally determined by comparison of extracted samples to unextracted standards (24,25). The unextracted standards, because of interference, must be diluted in saline or the mobile phase rather than plasma. 

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