TABLE OF CONTENTS As previously discussed (Chapter 2), much of the work in analytical chemistry involves the manipulation of weights and volume measurements. Frequently, calculations are concerned with concentrations; as in:
The amount (weight) of a component in a unit weight or a unit volume of the sample.
The amount of the component in a unit volume of solution.
Most instrumental methods of analysis do not give an absolute measure of the concentration of the component we are determining ( i.e. the analyte ). Usually instruments can give only a comparative measurement. We have to compare the response of the instrument (perhaps a meter reading) to a sample solution with the response it shows to solutions of known concentrations. The solutions of known concentrations that we use to calibrate the response of the instrument are the standard solutions for the determination.
It is important that the standard solutions are made very accurately, or the results of the analysis cannot be accurate. It is also important that the other constituents in the solutions are as similar as possible in all the standard solutions, blank solutions and sample solutions. These other constituents make the solution matrix . If the solution matrices are not similar, the instrument may not respond consistently to different concentrations of the analyte.
Of course it is not possible to make all the solution matrices identical, because we cannot know all that is in the sample solutions. However, if the sample extract or digest solutions are in 1 M...
