Analyzing for a Single Analyte

Prepare the standards. Be as accurate as possible since any concentration error in the standards is carried through as error in the predicted concentrations of the unknown samples. 

Take two aliquots of each sample and obtain separate spectra of them. In theory, these two spectra should be identical because they were obtained with the same sample, instrument, sampling accessory, and experimental conditions. 

Subtract these two spectra using a subtraction factor of one, obtaining a subtraction result called a residual. Look closely at the residual. Two spectra of the same sample should be identical, and should give a residual 

FIGURE 5.5 Spectral residuals obtained by subtracting two spectra of the same sample. Top No sample features are seen, just noise and a COj peak. Bottom Sample spectral features are present. 

Examine the spectra and choose a band whose height or area changes with concentration. 

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