Apparent content curves: new analytical applications

Characterisation of quaternary mixtures by the apparent content curves method: identification of tocopherols in vegetable oils

“…However, for a mixture of three compounds (A+I 1 +I 2 ), Q varies with the nature of the compounds and with the relative concentrations of the two compounds considered as interferents [7]. So, in ternary mixtures, Q permits knowledge of this relationship between the concentrations:…”

“…So, the Q parameter can be used for the qualitative analysis of a sample with a limited number of components. In this way, the procedure was applied in previous work for the identification of amphetamines [9,10] and the determination of the ratio of two compounds present in ternary mixtures [7]. The identification of compounds is carried out from tabulated values of Q and slopes and the procedure has the advantage that it is not necessary to prepare calibration solutions.…”

“…From these curves, several strategies that allow the identification of spectral interferences [6] and the quantification of an analyte in binary [5], ternary [7] and multicomponent [8] samples have been developed.…”

Ultraviolet and Light Absorption Spectrometry

“…Chemometrics have been widely applied in the area of multicomponent determination and include a comparative study involving a genetic algorithm, simulated annealing, and stepwise elimination as methods for wavelength selection (274); the use of apparent content curves for the analysis of mixtures such as fluorescein-eosine-acridine and methyl red-methyl orangecresol red (275) and theophylline in antiasthmatic pharmaceutical products (276); and the application of the H-point standard additions method for the determination of mixtures of phenol, o-cresol, 4-chlorophenol, and 3,4-dichlorophenol (277), and also mixtures of phenol, 4-chloro-2-nitrophenol, 2,4-dichlorophenol, and 2,4,6-trichlorophenol (278). Other multicomponent analysis systems have employed zero-crossing and derivative quotient spectra with standard divisor and numerical methods MULTI and PLS for the resolution of binary and ternary mixtures of acetylsalicylic acid, caffeine, and thiamine (279); polynomial approximation and nonlinear transformation of the wavelength axis for the analysis binary mixtures of dyes (280); Fourier to orthogonal function coefficients to provide exact compensation of any component in binary mixtures (281); modified multiwavelength K-factor spectrophotometry for the analysis of ternary mixtures of sodium diclofenac, chloropheniramine, and paracetamol (282); and the introduction of a damping factor into the p-coefficient matrix in order to reduce the "abnormality" of normal simultaneous equations to effect the analysis of multiple vitamin B components in pharmaceutical samples (283).…”