Chemometrics-assisted excitation-emission fluorescence spectroscopy for simultaneous determination of ethoxyquin and tert-butylhydroquinone in biological fluid samples

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 p.g mL-1 in plasma and from 6.87 to 20.6 gg mL-1 in urine; TBHQ, from 4.49 to 20.2 ~tg mL-1 in plasma and from 6.73 to 22.4 I.tg mL-l in urine. The recoveries from spiked bi- ological 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.

Insight into synergistic antioxidation mechanisms of butyl hydroxyanisole with common synthetic antioxidants

Butyl hydroxyanisole(BHA) is usually blended with other synthetic antioxidants to improve the antioxidative property due to synergistic antioxidation. However, the synergistic antioxidation mechanisms of BHA with synergists have not been revealed yet. Thus, the antioxidation of BHA with butylated hydroxytoluene(BHT), tert-butylhydroquinone(TBHQ), or propyl gallate(PG) was investigated in the 2,2-azobis(2-amidino-propane) dihydrochloride oxidizing system. The contents of BHA, BHT, TBHQ,PG, and transformation products were measured by high-performance liquid chromatography. Transformation products were identified with liquid chromatography-mass spectrometry and gas chromatography–mass spectrometry. Results showed that synergistic antioxidation occurred between BHA and BHT, TBHQ, or PG. The synergistic antioxidation effect of BHA and BHT was attributed to the regeneration of BHA by BHT. Transformation products of BHA and BHT(compounds 6 and 7, dimers of BHA and BHT) had little contribution due to the relatively low content(<0.6%). The synergistic antioxidation effect of BHA and TBHQ or BHA and PG was attributed to the protective mechanism of TBHQ or PG on BHA. No transformation products were detected of BHA and TBHQ. Transformation products of BHA and PG(compounds 9 and 10, dimers of BHA and PG) had limited contribution due to the relatively low percentage(<7%). Therefore, BHA and BHT performed competitive antioxidation,while BHA and TBHQ or PG performed protective antioxidation.