Stable isotope labeled internal standards are widely used in mass spectrometry. Isotopic interference between signals of the internal standard and the analyte, however, causes nonlinear calibration, which limits the dynamic range and produces inaccurate assessments of analyte concentration.
Application of two equations to mass spectrometry expands the range of analysis by generating a more accurate fit and correcting the inherent bias for many analyte/internal standard pairs. This process allows for corrections to nonlinear data, enabling the use of analyte/internal standard combinations that would otherwise be impractical. This approach removes much of the difficulty associated with use of stable labeled internal standards, such as labeling, isotope effects, and cost.