In a matrix of unknown or ambiguous content, a good approach to determination of an analyte is to use

a. a linear calibration curve method
b. a standard addition method
c. a method of least squares
d. an external standard method

In a matrix of unknown or ambiguous content, a good approach to determination of an analyte is to use a standard addition method.

Option b

When the matrix of a unit varies the analytical sensitivity of the system then one should follow the Standard addition. It is also described as the standard of the practical curve for examples delivered with refined water that is unique from the identical working curve formed up in marsh liquid.

One of the various complex standard addition systems includes appending one or more additions of a normal solution to check aliquots including equal volumes. Each solution is then thinned to a settled volume before measurement.

A consistent volume of the anonymous solvent is supplemented to each of the four volumetric flasks of capacity Vflask. Then a group of rising volumes of the stock solution is added. Eventually, every flask is built up to the point with solvent and blended well.

an external standard method

Explanation:

If other components are present in a solution to be analysed, the components will distort the analyte's signal. This distortion is known as matrix interference or matrix effect, and a solution with a matrix effect would give a different signal compared to a solution containing purely the analyte. Consequently, a calibration curve based on solutions containing only the analyte cannot be accurately used to conclusively determine the analyte's concentration.

A commonly used method in overcoming matrix interferences is standard addition. This procedure involves the addition of known quantities of the analyte (the standard) to the solution of interest and measuring the solution's analytical signals in response to each addition.

If the analytical signal still changes proportionally to the concentration of the analyte in the presence of matrix effects, a calibration curve can be obtained based on simple linear regression and used to determine the analyte.

a corroding iron, if that's one of your choices