(in analytical chemistry) The combined effect of all components of the sample other than the analyte on the measurement of the quantity. If a specific component can be identified as causing an effect then this is referred to as interference.
See: matrix (in analysis)
Source: PAC, 1989, 61, 1657. 'Nomenclature for automated and mechanised analysis (Recommendations 1989)' on page 1660 (https://doi.org/10.1351/pac198961091657)
(in surface analysis) Effects which cause changes in Auger-electron, photoelectron, secondary ion yield, or scattered ion intensity, the energy or shape of the signal of an element in any environment as compared to these quantities in a pure element. (a) Chemical matrix effects: changes in the chemical composition of the solid which affect the signals as described above. (b) Physical matrix effects: topographical and/or crystalline properties which affect the signal as described above.
Source: PAC, 1979, 51, 2243. 'General aspects of trace analytical methods—IV. Recommendations for nomenclature, standard procedures and reporting of experimental data for surface analysis techniques' on page 2247 (https://doi.org/10.1351/pac197951112243)