Interferents

Interferents are substances present in a sample that alter the measurement of a target analyte, leading to inaccurate results. Interference can be chemical, physical, or biological in nature and can affect accuracy, precision, limits of detection, or quantification. Interferents may act by absorbing or scattering signal, reacting with reagents, or changing the sample matrix in ways that bias the analytical readout.

In analytical chemistry and clinical laboratories, interference is a common concern across many methods. Interferents can be endogenous, such as bilirubin, lipids, or hemoglobin in blood, or exogenous, including medications, dietary components, or environmental contaminants. They may co-elute with the analyte in chromatography, absorb at the same wavelength in spectroscopic measurements, or cause nonspecific binding or cross-reactivity in immunoassays.

Examples of interferents by method include: in immunoassays, heterophile antibodies or high-dose hook effects; in spectrophotometry, substances that strongly absorb at the measurement wavelength or cause turbidity; in chromatography, matrix components that co-elute with the analyte or suppress/enhance signal; and in mass spectrometry, isobaric species and matrix effects that alter ionization efficiency. Molecular techniques can be affected by inhibitors that impede enzymatic reactions.

Mitigation strategies emphasize method validation and quality control. Approaches include interference testing during method development, sample pretreatment and cleanup, chromatographic or spectral separation, use of internal standards or matrix-matched calibration, dilution, standard addition, and alternative analytical methods. Clear documentation of known interferents is essential for accurate interpretation of results.