A suitable reference species must b

A suitable reference species must be available for the internal standard method to compensate for errors. The reference species must not have unique interferences different from the analyte. There must be no analyte contamination in the materials used to prepare the internal standard. Also, both species must be present in concentrations that are in the linear portions of their calibration curves. Because of the difficulty in finding an appropriate internal standard species, the internal standard method is not as commonly used as some other error-compensating methods.