In compared to the value of 0.962757712 for

In this experiment, both
methods produced results within a +/-10% margin of error from the expected
acetaminophen concentration, which is in line with current pharmacological
guidelines. However, the standard addition method (SA) produced a result for
acetaminophen concentration that was 2.7% lower than the result produced by the
calibration curve (CC) method. As both results fall within the +/-10% error
allowed by pharmacological guidelines, determining which method gave the more
accurate result would require further research with a greater (n > 3) number
of repeat readings and, particularly for the standard addition method, a
greater number of non-sample values. However, from the R2 value
alone, the CC method appears to have given data which conforms more accurately
to the linearity expected with an R2 value of 0.965022738 compared to the value of 0.962757712
for the SA method, a small but relevant difference.

the results by this experiment appear to suggest that the CC method was of
higher reliability and, if the tablet was indeed of 500 mg acetaminophen as
stated on the packaging, greater accuracy, the SA method is in fact considered
in analytical terms to be more reliable and more accurate. This is due
primarily to the presence of matrix effects, also known as multiplicative
interferences, which give rise to biased results as a consequence of an altered
calibration function.

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effects may impact results via two primary routes: a translational effect,
which alters the intercept of a calibration function and may manifest in all
calibration methods, and a rotational effect, which alters the slope but does
not manifest in SA methods. The rotational effect arises from interference produced
by non-analyte substances present in the test solution but not in the standard which
may attenuate or amplify the analyte signal. In the case of this experiment, although
the mechanically macerated tablet was added to a solution and the undissolved
bindings agents removed via filtration, other non-acetaminophen
impurities may have remained which could have impacted the amplitude of the DPV
signal recorded for the sample in a way which would not have occurred in the
standard solutions. Unlike CC methods which do not include the test solution in
comparative measurements, SA methods overcome this rotational effect by including
the same volume of test solution in each standard addition and hence overriding
any impact non-analyte substances may have on the amplitude of the analyte
signal. Both CC and SA methods, however, are vulnerable to translational matrix
effects as stated above due to translational effects being independent of
analyte concentration.

methods do have their limitations, particularly regarding the use of
extrapolation which is widely assumed to degrade the precision of the result
when compared to the use of interpolation in CC methods, although this
assumption has been challenged in recent years.i
Standard addition also assumes true linearity of the analytical calibration over
the whole relevant concentration range, and that a small volume of standard solution
does not alter the matrix composition of the test solution, both of which would
require experimental and statistical verification in a research environment. The
use of a calibration curve also assumes linearity but has the additional
benefit of multiple standard comparisons, thereby reducing random errors in
preparing and reading the standard solutions as they are averaged over several
standards. This benefit could obviously be implemented for SA procedures
by increasing the number of additions tested.



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