A novel method applying simple, rapid, effective and inexpensive excitation-emission matrix (EEM) fluorescence spectroscopy coupled with second-order calibration method for simultaneous determination of ethoxyquin (EQ) and tert-butylhydroquinone (TBHQ) contents in biological fluid samples was developed. After a simple data preprocessing that was to insert zeros below the first-order Rayleigh scattering, the second-order calibration method based on the alternating normalization-weighed error (ANWE) algorithm was used to deal with EEM data. Via the introduced "second-order advantage", the individual con- centrations of the analytes of interest could be obtained even in the presence of uncalibrated interferences. The experimental concentration ranges for the analytes were as follows: EQ, from 4.58 to 20.6 g mL 1 in plasma and from 6.87 to 20.6 g mL 1 in urine; TBHQ, from 4.49 to 20.2 g mL-1 in plasma and from 6.73 to 22.4 g mL-1 in urine. The recoveries from spiked biological fluid samples were in the ranges of 92.8%-106.2% for EQ and 94.6%-107.2% for TBHQ. These results demonstrate that the three-dimensional EEM fluorescence with second-order calibration method is a powerful tool for obtaining both EQ and TBHQ quantitative results in plasma and urine samples, and could be applied to more complex matrices.
The effectiveness of traditional Chinese medicine (TCM) against various diseases urges more low cost, speed and sensitive analytical methods for investigating the phamacology of TCM and providing a theoretical basis for clinical use. The potential of second-order calibration method was validated for the quantification of two effective ingredients of Schisandra chinensis in human plasma using spectrofluorimetry. The results obtained in the present study demonstrate the advantages of this strategy for multi-target determination in complex matrices. Although the spectra of the analytes are similar and a large number of interferences also exist, second-order calibration method could predict the accurate concentrations together with reasonable resolution of spectral profiles for analytes of interest owing to its 'second-order advantage'. Moreover, the method presented in this work allows one to simply experimental procedure as well as reduces the use of harmful chemical solvents.
Xiao-Hua Zhang, Hai-Long Wu, Jian-Yao Wang, Yao Chen, Yong-Jie Yu, Chong-Chong Nie, Chao Kang, De-Zhu Tu, Ru-Qin Yu State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082, PR China
