Analysis of malachite green and crystal violet in fish with bilinear model

A new method for the simultaneous analysis of malachite green (MG) and crystal violet (CV) in fish samples has been developed. In the presence of thiocyanate, the second order data of MG or CV obtained from the spectra of MG or CV in a series of water–ethanol mixed solvents with various ethanol volume fractions could be expressed as the combination of two bilinear data matrices. With the bilinear model, the second order spectra data of mixtures containing MG and CV those coexist with interferents could be analysed using the second order calibration algorithms, and the simultaneous determination of MG and CV in fish samples could be achieved. The algorithms were based on residual bilinearisation (RBL) and unfolded partial least-squares/residual bilinearisation (U-PLS/RBL) respectively. The method has been successfully used to determine simultaneously MG and CV in some fish samples with satisfactory results.