Which of the following descriptions about standard addition and internal standards are NOT correct?

a) Internal standard is useful when the matrix in the unknown is complicated.
b) Standard addition could be a single standard addition or multiple standard additions to an unknown solution.
c) Standard addition is useful when the matrix in the unknown is complicated.
d) Internal standard is used when instrument response varies from run to run.

a) Internal standard is useful when the matrix in the unknown is complicated.

b) Standard addition could be a single standard addition or multiple standard additions to an unknown solution.

d) Internal standard is used when instrument response varies from run to run.

Explanation:

(a) Internal standard is useful when the matrix in the unknown is complicated.This statement is not correct as only Standard addition is used in case when the matrix of the unknown is complicated.

b) Standard addition could be a single standard addition or multiple standard additions to an unknown solution. This statement is not correct.

d) d) Internal standard is used when instrument response varies from run to run. This statement is not correct.  If the instrument response varies from run to run then. it can be mistake of various other manual and instrumental parameters. This statement is not correct

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explanation:

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