chemical analysis Analytical chemistry studies and uses instruments and methods to separate, identify, and quantify matter. In practice, separation, identification or quantification may constitute the entire analysis or be combined with another method. Separa ...

, matrix refers to the components of a sample other than the

analyte An analyte, component (in clinical chemistry), titrand (in titrations), or chemical species is a substance or chemical constituent that is of interest in an analytical procedure. The remainder of the sample is called the matrix. The procedure ...

of interest. The matrix can have a considerable effect on the way the analysis is conducted and the quality of the results are obtained; such effects are called matrix effects.F. W. Fifield, P. J. Haines. ''Environmental Analytical Chemistry''. Blackwell Publishing, 2000, p. 4-5. . For example, the

ionic strength The ionic strength of a solution is a measure of the concentration of ions in that solution. Ionic compounds, when dissolved in water, dissociate into ions. The total electrolyte concentration in solution will affect important properties such a ...

of the solution can have an effect on the activity coefficients of the analytes.Harris, D. C. ''Quantitative Chemical Analysis'', 4th ed. Freeman, 1995, pp.194, 404. . The most common approach for accounting for matrix effects is to build a

calibration curve In analytical chemistry, a calibration curve, also known as a standard curve, is a general method for determining the concentration of a substance in an unknown sample by comparing the unknown to a set of standard samples of known concentration. ...

using standard samples with known analyte concentration and which try to approximate the matrix of the sample as much as possible. This is especially important for solid samples where there is a strong matrix influence.Marco Aurelio Zezzi Arruda. ''Trends in Sample Preparation''. Nova Publishers, 2006, p. 15-18. . In cases with complex or unknown matrices, the standard addition method can be used. In this technique, the response of the sample is measured and recorded, for example, using an

electrode An electrode is an electrical conductor used to make contact with a nonmetallic part of a circuit (e.g. a semiconductor, an electrolyte, a vacuum or a gas). In electrochemical cells, electrodes are essential parts that can consist of a varie ...

selective for the analyte. Then, a small volume of

standard solution In analytical chemistry, a standard solution (titrant or titrator) is a solution containing an accurately known concentration. Standard solutions are generally prepared by dissolving a solute of known mass into a solvent to a precise volume, or by ...

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.

Matrix effect

Matrix enhancement and suppression is frequently observed in modern analytical routines, such as GC, HPLC, and ICP. Matrix effect is quantitated by the use of the following formula: :

ME = 100  \left ( \frac \right )

where A(extract) is the peak area of analyte, when diluted with matrix extract. A(standard) is the peak area of analyte in the absence of matrix. The concentration of analyte in both standards should be the same. A matrix effect value close to 100 indicates absence of matrix influence. A matrix effect value of less than 100 indicates suppression, while a value larger than 100 is a sign of matrix enhancement. An alternative definition of matrix effect utilizes the formula: :

ME = 100  \left ( \frac \right ) - 100

The advantages of this definition are that negative values indicates suppression, while positive values are a sign of matrix enhancement. Ideally, a value of 0 is related to the absence of matrix effect.

References

{{Analytical chemistry Analytical chemistry

Matrix effect

See also

References