2. Methodology
2.6 Statistical evaluation of ARVs using SERS
Raman bands arising from the anti-HIV medication were selected and evaluated using statistical methods with the aim of comparing, calibration and analytical sensitivities and limit of detection for selected functional groups present. Each of the above parameters was evaluated using their corresponding mathematical equations that are well-published in literature.
The calibration sensitivity was calculated from plotting the peak area against the sample concentration. A linear equation was derived from the plot along with a R2 values which were used to determine the quality of the fit. The resulting equation was
๐ = ๐๐ + ๐๐๐ (1) where S is the signal (peak area), m is the slope or calibration sensitivity and Sbl is the signal from the blank sample. The calculations began with recording the standard error of the mean sm for each selected peak provided by the instrumental software and using that value to calculate the standard deviation s using the following equationwhere N is the number of replications for each sample group
๐ = ๐ ๐
โ๐
The calibration sensitivity and the standard deviation values were used to calculate the analytical sensitivity as follows
๐พ = ๐/๐ ๐
where m is the slope from equation 1 and ss is the standard deviation of the measurements. The limit of detection was determined by using the average values of the blank signal ๐๐๐ and the corresponding standard deviation sbl with a standard multiple k (valued at 3) using the equation.
๐๐ = ๐๐๐ + ksbl
The slope from equation 1 is then used to determine cm, the lowest detectable concentration or limit of detection from the equation.
๐ถ๐ =๐๐โ ๐๐๐ ๐
From these equations, comparisons between the API and API were made possible to determine the efficiency of the sensors across the analytes [38] .
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