In chemical analysis, matrix refers to the components of a sample other than the analyte.^[1] The matrix can have a considerable effect on the way the analysis is conducted and the quality of the results obtained; such effects are called matrix effects.^[2] For example, the ionic strength of the solution can have an effect on the activity coefficients of the analytes.^[3][4] The most common approach for accounting for matrix effects is to build a calibration curve using standard samples with known analyte concentration and which try to approximate the matrix of the sample as much as possible.^[2] This is especially important for solid samples where there is a strong matrix influence.^[5] In cases with complex or unknown matrices, the standard addition method can be used.^[3] In this technique, the response of the sample is measured and recorded, for example, using an electrode selective for the analyte. Then, a small volume of standard solution is added and the response is measured again. Ideally, the standard addition should increase the analyte concentration by a factor of 1.5 to 3, and several additions should be averaged. The volume of standard solution should be small enough to disturb the matrix as little as possible.

[edit] References

1. ^ International Union of Pure and Applied Chemistry (1989). "Matrix (in analysis)". Compendium of Chemical Terminology Internet edition.
2. ^ ^{a b} F. W. Fifield, P. J. Haines. Environmental Analytical Chemistry. Blackwell Publishing, 2000, p. 4-5. ISBN 0632053836.
3. ^ ^{a b} Harris, D. C. Quantitative Chemical Analysis, 4th ed. Freeman, 1995, pp.194, 404. ISBN 0716725988.
4. ^ International Union of Pure and Applied Chemistry (1989). "Matrix effect". Compendium of Chemical Terminology Internet edition.
5. ^ Marco Aurelio Zezzi Arruda. Trends in Sample Preparation. Nova Publishers, 2006, p. 15-18. ISBN 1600211186.