Fourier transform infrared spectroscopy coupled with multivariate calibrationfor determination of carmine and rhodamine B levels in lipstick

Carmine is a natural colorant allowed to be used in cosmetics, while rhodamine is nonallowable. For some reason, carmine may be substituted with rhodamine to get economic profits. Therefore, some analytical methods are proposed and developed. This study developed fourier transform infrared (FTIR) spectroscopy in conjunction with utilizing multivariate calibration to determine carmine (CAR) and rhodamine B (RHB) levels in lipstick samples. Lipstick samples were placed directly into an attenuated total reflectance (ATR) crystal and scanned in the 4,000-650 cm-1 wavenumber range. The CAR and RHB levels were also determined using HPLC to be used as actual values. Partial least squares regression (PLSR) was used to stimulate the correlation between actual CAR and RHB values and predicted FTIR values. Based on optimization in terms of the selection of wavenumbers region, for CAR and RHB prediction modeling, absorbance values at wavenumbers of 1,357-673 cm-1 were used. The developed methods, besides having high validity, are rapid and exclusive of extensive solvents with minimum sample preparation; therefore, this technique is environmentally friendly