3.2.2. Total RGB values
The relationships derived from the combination of the total RGB
data, may provide additional valuable information not available from the individual values [15]. These were calculated both in
terms of intensity (ITOTAL = IR + IG + IB) and absorbance (ATOTAL
= AR + AG + AB) and related to methamphetamine concentrations
and are illustrated in Fig. 5. It was found that the sensitivity of the
total values was higher than those of the individual values
(0.56 0.03 a.u. mL mg1 compared to 0.23 0.1 a.u. mL mg1 for
the red channel), but covered the same linear range (0.1–
2.5 mg mL1).